Re: [time-nuts] Terrestrial GPS

[Bob kb8tq]

Hi

But, by their nature, not useful for timing or precision navigation. They are 
simply
a solution to the “feed you coupons at the mall” issue. Since they run as an 
independent 
system (they have their own ID’s) the direct “pollution” issue on a GPSDO is 
eliminated. 
You still have the previously mentioned receiver dynamic range questions.

Bob

> On Mar 15, 2018, at 5:26 AM, Leo Bodnar  wrote:
> 
> Such system already exists, is called IMES, uses L1 band and is supported by 
> standard Ublox 8 firmware.
> 
> http://gpsworld.com/wirelessindoor-positioningopening-up-indoors-11603/
> 
> Leo
> 
> 
>> From: Stewart Cobb 
>> Peter Reilley suggests a backup to GPS using terrestrial transmitters. This
>> idea has been around since the early days of GPS
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Re: [time-nuts] Need a Watch Recommendation

[Bob kb8tq]

Hi

The most common way to pull the 32KHz signal off of a watch is via a tuned 
microphone. At least that’s the way we did it in production. A watch crystal 
*can* (but usually doesn’t) move > 100 PPM with temperature. When things 
are set up, assumptions are made about “your” temperature environment. If
the watch is off temperature vs the assumptions, it will not keep good time. 

Some numbers:

10 seconds a month is 3.8 ppm
120 seconds a month is 46 ppm 

The temperature curve is parabolic so *usually* temperature will result in a
slow watch. If the “target” set point is 10 seconds fast, you would need to 
be right at 50 ppm off to loose two minutes a month. 

If you take a look a the previous numbers on trim range on the trimmer. A 
trimmer that will do +/- 25 ppm is “adequate” for setting the watch in 
production.
It’s not good enough (by a factor of 2) to take care of a 2 minute / month 
timing 
error. 

Just for the record, I don’t think I have *ever* owned a quartz watch that was 
off by more than a 15 seconds per month. I’ve owned cheap ones and expensive
ones. They all have done pretty well. The fancy ones *have* done better ….

Bob



> On Mar 15, 2018, at 11:51 AM, Dana Whitlow  wrote:
> 
> Most of the quartz watches I've owned were off by about 1-2 minutes per
> month,
> which I consider inexcusable.
> 
> Agreed, the mechanical trimmer is rather problematical, but I'd sure like
> to see
> *something *that the sophisticated user can tweak at home. Measurement of
> the
> current rate error is probably not much of a problem; I once tried seeing
> the
> 32kHz signal in the watch by capacitive coupling to the face, and could
> detect
> the signal.  I just tried a token attempt on my current watch and failed,
> but it
> was a crude, unshielded attempt by merely laying a 'scope probe against the
> watch face.  I was being severely jammed by the local 1230 kHz AM station.
> Anyway, the idea is to observe the signal's phase drift while triggering
> the 'scope
> from a trusted 1PPS source.
> 
> So now all that's needed is an alternate way for trimming the watch's
> frequency
> without opening the case.  There must be a way...
> 
> Dana
> 
> 
> On Thu, Mar 15, 2018 at 8:13 AM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> 
>>> On Mar 15, 2018, at 1:33 AM, Dana Whitlow  wrote:
>>> 
>>> I concur with Bill.  And even if one keeps tabs on the current watch
>> error,
>>> as is the usual practice by celestial navigators, once that error reaches
>>> or exceeds more than a minute the process frankly gets more clumsy and
>>> error prone.  And if a watch drifts in time very rapidly, one loses faith
>>> in its
>>> ability to coast at a known rate between checks against WWV, which
>>> opportunities are not always available when one wants, due to
>>> propagation issues.
>>> 
>>> Whatever happened to the quartz watches with trimmer capacitors
>>> for setting the rate?
>> 
>> Trimmer caps to set watch crystals are problematic. They are a source of
>> error
>> as well as a set mechanism. You bump this or that and the trimmer moves.
>> They
>> also cost money to buy and install properly (no flux in-between the plates
>> …).
>> Once that is all done you need a way to set them in the factory. Back in
>> the day,
>> yes, we hat line workers who did that sort of thing. We also sold the
>> crystal in the
>> watch module (not the whole module) for $2 once upon a time.
>> 
>> How close do you want to set it? In our case, the set was supposed to be <
>> 0.5
>> ppm of the target. Ideally you needed a design that would do a small
>> fraction
>> of a ppm in a typical situation.
>> 
>> If the trimmer is a normal device, you get about 120 degrees of travel for
>> the
>> useful part of the tuning curve. A tune range of 30 ppm for the crystal
>> and another
>> 20 ppm for the other parts would not be unusual. Even taking the 0.5 ppm
>> number,
>> you are into 120 / 100 = 1.2 degrees sort of set on that little trimmer.
>> 
>> Bottom line: They went away because they weren’t good enough and they were
>> to expensive …. Setting a modern “shoot the chip” register based module is
>> way
>> more accurate and reliable. It’s silicon so the cost is whatever sand is
>> selling
>> for ….
>> 
>> Bob
>> 
>>> 
>>> And radio controlled?  No way!
>>> The process is to delicate and marginal to rely upon.  Give me a
>>> good stable free-running watch any day.
>>> 
>>> I don't like the solar watch concept mainly because on

Re: [time-nuts] Need a Watch Recommendation

[Bob kb8tq]

Hi


> On Mar 15, 2018, at 1:33 AM, Dana Whitlow  wrote:
> 
> I concur with Bill.  And even if one keeps tabs on the current watch error,
> as is the usual practice by celestial navigators, once that error reaches
> or exceeds more than a minute the process frankly gets more clumsy and
> error prone.  And if a watch drifts in time very rapidly, one loses faith
> in its
> ability to coast at a known rate between checks against WWV, which
> opportunities are not always available when one wants, due to
> propagation issues.
> 
> Whatever happened to the quartz watches with trimmer capacitors
> for setting the rate?

Trimmer caps to set watch crystals are problematic. They are a source of error
as well as a set mechanism. You bump this or that and the trimmer moves. They
also cost money to buy and install properly (no flux in-between the plates …). 
Once that is all done you need a way to set them in the factory. Back in the 
day,
yes, we hat line workers who did that sort of thing. We also sold the crystal 
in the
watch module (not the whole module) for $2 once upon a time. 

How close do you want to set it? In our case, the set was supposed to be < 0.5 
ppm of the target. Ideally you needed a design that would do a small fraction
of a ppm in a typical situation. 

If the trimmer is a normal device, you get about 120 degrees of travel for the 
useful part of the tuning curve. A tune range of 30 ppm for the crystal and 
another
20 ppm for the other parts would not be unusual. Even taking the 0.5 ppm number,
you are into 120 / 100 = 1.2 degrees sort of set on that little trimmer. 

Bottom line: They went away because they weren’t good enough and they were
to expensive …. Setting a modern “shoot the chip” register based module is way
more accurate and reliable. It’s silicon so the cost is whatever sand is 
selling 
for ….

Bob

> 
> And radio controlled?  No way!
> The process is to delicate and marginal to rely upon.  Give me a
> good stable free-running watch any day.
> 
> I don't like the solar watch concept mainly because one sometimes
> has to go for weeks without an opportunity to expose his watch to
> direct sunlight (or some indoor equivalent) for the requisite period
> of several hours.
> 
> Yesterday I was reading the manual for the Citizen ECO series,
> and that thing requires far too much effort and complication to keep
> it working and on time.  A good watch must simply work, with no
> maintenance beyond occasional battery replacements (and possible
> gland replacement at battery-change time), and accurately enough
> that the time need never be reset between battery replacements.
> 
> I use an old quartz diving watch I bought just under 10 years ago,
> (brand no longer distinguishable), which has never drifted more than
> about 30 sec (usually less) between battery replacements, and I never
> take it off between batteries except when compelled to do so at TSA
> checkpoints.  Aside from its LCD's failing I'd be happy to use if forever,
> but it's getting awfully hard to read these days.
> 
> Dana
> 
> 
> 
> On Wed, Mar 14, 2018 at 10:54 PM, Bill Byrom  wrote:
> 
>> On Wed, Mar 14, 2018, at 6:53 PM, Dr. David Kirkby wrote:
>>> What is the most demanding task one would use a wrist watch for?
>> 
>> It depends on your job or hobby.
>> 
>> During the Apollo 13 rocket burn before their emergency re-entry, Jack
>> Swigert used a wrist watch to time the retrorocket burn which was
>> manually controlled by Jim Lovell. Their normal capsule chronometer was
>> inoperative. This was mostly a differential (time interval) timing
>> measurement.
>> If you needed to determine your location (longitude) and all you had
>> was a wristwatch and a sextant (and software or a table with certain
>> information), the accuracy of the distance calculation would depend on
>> the absolute time accuracy of the watch. At the equator the longitude
>> error due to time error is (40,075.16 km/day) / (86,400 sec/day) =
>> 463.8 m/sec.
>> Amateur astronomers need to know time accurate to about a second or
>> better for accurate osculation observations.
>> Amateur Radio nets and phone, Skype for Business, or WebEx conference
>> calls usually start pretty close to the scheduled time. In some cases
>> people start wondering if the organizer is delayed after about 15 to
>> 30 seconds.--
>> Bill Byrom N5BB
>> 
>> 
>> 
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Re: [time-nuts] Need a Watch Recommendation

[Bob kb8tq]

Hi

Yes, but will it display TimeNuts emails on the face of the watch? 

Better hope it’s a top poster it does :) …. scrolling through a lot of text is 
sort of non-functional on the Apple Watch. 

Bob

> On Mar 14, 2018, at 9:58 PM, Jean-Louis Oneto  wrote:
> 
> The half dial in 02:00 with "S M T W T F S" looks like a weekday indicator to 
> me.
> Best regards,
> Jean-Louis 
> 
> 
> 
> 
> Envoyé depuis mon appareil mobile Samsung.
> 
>  Message d'origine 
> De : Jeremy Nichols  
> Date :14/03/2018  22:40  (GMT+01:00) 
> A : Discussion of precise time and frequency measurement  
> Objet : Re: [time-nuts] Need a Watch Recommendation 
> 
> Nice but lacks "day” feature (has “date”). I don’t normally care whether
> it’s the 22nd or the 23rd but it’s nice to know whether it’s Tuesday or
> Wednesday. YMMV, of course.
> 
> Jeremy
> 
> On Wed, Mar 14, 2018 at 1:57 PM Achim Vollhardt 
> wrote:
> 
>> Dear Don and all,
>> no mentioning of the Seiko Astron GPS Solar?
>> 
>> http://www.seiko-astron.com/
>> 
>> 73s
>> Achim DH2VA
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>> 
> -- 
> Sent from my iPad 4.
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Re: [time-nuts] Terrestrial GPS

[Bob kb8tq]

Hi

There *are* multiple different things that get tagged as “WiFi location” 
services.
One is a passive approach. They look at what your device can “see” and guess
your location. Another is an active approach. You are logged on to a WiFi system
and they try to back track your location though a trace route. I believe the 
initial
comment was related to the passive system.

Why does this stuff matter? 

Well, as you stroll around the mall with big piles of cash bulging in your 
pockets, 
the store you just passed wants to send you a coupon to drag you into the 
store. 
They feel the need to do this *after* (but not long after) you stopped and 
looked 
in the window. If you are on the floor above or the floor below the store … no
coupon. 

Doing this with timing based navigation (like GPS) is a bit tricky. You need to 
get
things sync’d good enough for < 3 M accuracy in a space with a lot of 
multi-path. 
Setting up a bunch of basestations that are sync’d to a few ns might seem 
simple, 
but it’s not. Without that sort of timing accuracy, they need to guess where 
you 
are by other means. 

All of this is independent of the issues regarding “do I want this to happen”. 
Diving
into that part heads even further off subject for this list …..

Bob

> On Mar 14, 2018, at 2:47 PM, Jeremy Nichols  wrote:
> 
> Apparently the database in my area is poor. Another location I am sometimes
> found in is *Fremont*, almost 100 miles southeast. Fremont most frequently
> shows up as the "closest store" when I am looking at (for example) hardware
> store web sites.
> 
> Jeremy
> N6WFO
> 
> 
> On Wed, Mar 14, 2018 at 10:15 AM Bob kb8tq  wrote:
> 
>> Hi
>> 
>> WiFi based location can be pretty good or it can be a real joke. It all
>> depends on
>> how good the database happens to be and how many stationary WiFi setups you
>> can “see”. I’ve had it pop up with locations that are off by many miles.
>> ISP’s
>> feed you IP addresses via DHCP and the “on net” numbers are rarely visible
>> to
>> the casual passerby. , They likely are depending on other information
>> (like SSID
>> surveys from vehicles).
>> 
>> Bob
>> 
>>> On Mar 13, 2018, at 11:15 PM, Bill Byrom  wrote:
>>> 
>>> Have you noticed that your mobile devices (smartphone, iPad, tablet PC,
>>> laptop PC) can often know your location when you inside a  building
>>> shielding you from GPS satellites (or producing multipath confusing the
>>> GPS receiver)? Here is a quick test you can do if you have a PC with no
>>> GPS receiver but with WiFi capability:
>>> Start up a browser and go to http://maps.google.com (which redirects to
>>> https://www.google.com/maps/...) with a WiFi connection. Near the lower
>>> right of the screen you should see the + - zoom buttons, and above these
>>> a target icon. Click that target icon. If asked, enable location
>>> finding. You may also need to enable your browser to release location
>>> information.  In my case, I am now sitting near the middle of my house
>>> and the laptop Windows 10 PC Google Maps locator places my location on
>>> the street adjacent to my house, about 25 meters or so from my actual
>>> location. My iPhone iOS map shows my location more closely (inside my
>>> house) and it very accurately shows the location of the minivan I parked
>>> in the driveway several hours ago (as "parked car").  My iPad also shows
>>> my location within my house.
>>> How do these devices know your location without GPS? Several methods are
>>> used to produce a hybrid positioning system[1]:(1) Your IP address from
>> your ISP. This gets me within a few km of my
>>>   location. See: https://www.iplocation.net/(2) WiFi positioning
>> system[2] - This makes use of databases which
>>>   contain the geographic location of WiFi access points. The data is
>>>   collected by methods such as comparing the GPS receiver location
>>>   reports of mobile devices with the signal strength of access
>> points.(3) Cellular radio location - Various techniques allow accurate
>>>   mobile phone tracking[3]. The signal strength and propagation
>>>   delay from cellular base stations allow moderately good
>>>   determination of location.
>>> If you are in an area without GPS receiver coverage, your mobile device
>>> or PC can determine the time using various techniques:(1) Crystal
>> oscillator for short-term time stability.
>>> (2) NTP: https://en.wikipedia.org/wiki/Network_Time_Protocol
>>> (3) Cellular timing - cellular phone networks require very accurate
>>>   timing of the RF signals.
>>&

Re: [time-nuts] Terrestrial GPS

[Bob kb8tq]

Hi

WiFi based location can be pretty good or it can be a real joke. It all depends 
on 
how good the database happens to be and how many stationary WiFi setups you
can “see”. I’ve had it pop up with locations that are off by many miles. ISP’s
feed you IP addresses via DHCP and the “on net” numbers are rarely visible to
the casual passerby. , They likely are depending on other information (like SSID
surveys from vehicles). 

Bob

> On Mar 13, 2018, at 11:15 PM, Bill Byrom  wrote:
> 
> Have you noticed that your mobile devices (smartphone, iPad, tablet PC,
> laptop PC) can often know your location when you inside a  building
> shielding you from GPS satellites (or producing multipath confusing the
> GPS receiver)? Here is a quick test you can do if you have a PC with no
> GPS receiver but with WiFi capability:
> Start up a browser and go to http://maps.google.com (which redirects to
> https://www.google.com/maps/...) with a WiFi connection. Near the lower
> right of the screen you should see the + - zoom buttons, and above these
> a target icon. Click that target icon. If asked, enable location
> finding. You may also need to enable your browser to release location
> information.  In my case, I am now sitting near the middle of my house
> and the laptop Windows 10 PC Google Maps locator places my location on
> the street adjacent to my house, about 25 meters or so from my actual
> location. My iPhone iOS map shows my location more closely (inside my
> house) and it very accurately shows the location of the minivan I parked
> in the driveway several hours ago (as "parked car").  My iPad also shows
> my location within my house.
> How do these devices know your location without GPS? Several methods are
> used to produce a hybrid positioning system[1]:(1) Your IP address from your 
> ISP. This gets me within a few km of my
>location. See: https://www.iplocation.net/(2) WiFi positioning system[2] - 
> This makes use of databases which
>contain the geographic location of WiFi access points. The data is
>collected by methods such as comparing the GPS receiver location
>reports of mobile devices with the signal strength of access points.(3) 
> Cellular radio location - Various techniques allow accurate
>mobile phone tracking[3]. The signal strength and propagation
>delay from cellular base stations allow moderately good
>determination of location.
> If you are in an area without GPS receiver coverage, your mobile device
> or PC can determine the time using various techniques:(1) Crystal oscillator 
> for short-term time stability.
> (2) NTP: https://en.wikipedia.org/wiki/Network_Time_Protocol
> (3) Cellular timing - cellular phone networks require very accurate
>timing of the RF signals.
> It would be hard to place terrestrial transmitters on the GPS satellite
> frequencies without dynamic range and other problems, and of course
> someone could use this technique to jam GPS reception in an area. But
> several terrestrial geolocation and timing dissemination systems have
> been proposed, and some limited deployment has been 
> achieved.https://en.wikipedia.org/wiki/NextNav
> http://www.nextnav.com/technology
> http://esatjournals.net/ijret/2013v02/i04/IJRET20130204031.pdf
> https://spectrum.ieee.org/tech-talk/telecom/wireless/us-master-clock-keepers-test-ground-alternative-to-gps--
> Bill Byrom N5BB
> 
> 
> 
> On Tue, Mar 13, 2018, at 5:17 PM, Stewart Cobb wrote:
>> Peter Reilley suggests a backup to GPS using terrestrial
>> transmitters. This> idea has been around since the early days of GPS. The 
>> terrestrial
>> transmitters were called "pseudo-satellites", or "pseudolites"
>> for short.> The big problem with this idea is that the GPS signal format has
>> a narrow> dynamic range. The signal strength from a terrestrial
>> transmitter varies> widely (inverse square law) from positions near the 
>> transmitter to
>> positions far away. The variation in any practical system is
>> larger than> the GPS signal format can handle. This is called the "near-far
>> problem".> For an extensive discussion of the pseudolite concept, including 
>> the
>> near-far problem, see my dissertation. You can find it with a
>> web search> for my full name and the word "pseudolites".
>> 
>> Cheers!
>> --Stu
>> _
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> and follow the 
>> instructions there.
> 
> 
> Links:
> 
>  1. https://en.wikipedia.org/wiki/Hybrid_positioning_system
>  2. https://en.wikipedia.org/wiki/Wi-Fi_positioning_system
>  3. https://en.wikipedia.org/wiki/Mobile_phone_tracking
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger --> GPS Issues

[Bob kb8tq]

Hi

> On Mar 12, 2018, at 9:54 AM, Peter Reilley  wrote:
> 
> Reading this paper makes one wonder if there are other improvements that
> can be made to increase the robustness against jamming, software bugs, solar 
> events
> or hostile attacks to the GPS system
> 
> A suggestion:
> 
> Create a parallel terrestrial GPS system.   This would be a system of GPS 
> transmitters
> mounted on cell phone towers.   They would masquerade as GPS satellites (but 
> unusually low
> and stationary).   It would be ideal if they could have unique identifiers 
> and be integrated
> into the GPS receivers timing and location calculations as any other 
> satellite.   If there
> is no room in the existing ID space then the terrestrial node would take over 
> the ID of
> a satellite that is below the horizon.   When the satellite reappeared the 
> terrestrial node
> would simply take over a different below the horizon satellite's ID.

If it takes over the ID of an existing satellite, it also takes over the 
ephemeris and almanac 
information for that satellite. There is only a *very* finite amount of “data 
space” in the transmissions
for that stuff. 

Simple answer - it would have to be an independent system. You need a unique 
almanac for it
and unique ID numbers for the stations. 


> 
> Such a system could be built out as needed.   It may not require any 
> alterations to existing
> GPS receivers.   It would not disrupt the operation of the existing satellite 
> constellation.
> It would protect against attacks on the satellite system by either a human 
> enemy or a natural
> one, the sun.
> 
> Each node need not contain an accurate time source like a cesium standard.   
> They could
> derive timing from a neighbor.  

If you do that, you make your backup system *very* open to attack. Spoof one 
and all the 
rest tracking it follow ….


> Cesium reference nodes would be periodically placed around the
> system.   Timing derivations would be more accurate since the distances would 
> be much closer and
> thereby encounter less environmental disturbance.

Only if you distributed a *lot* of very good clocks *and* monitored them the 
same way as you 
monitor a GPS sat. Since they are all low to the ground, that would take a 
*very* different 
setup for monitoring. 

> 
> GPSDO units would prefer such close and stationary references vs distant 
> moving ones.

Ummm …… er ….. not so much. A GPSDO simply locks up to “all in view”. 
Unless you 
tell it to reject a sat, it uses it. To the degree that there is a rejection 
process (TRAIM), it 
looks at the group solution. If the “majority time” looks ok … off we go. 

==

The idea of using cell tower signals for timing was at the heart of a couple of 
systems. The gotcha 
turned out to be that not all tower operators are created equal. Unless you 
have direct control
over the gear ( = you own and operate it) there is no way to keep it “correct”.

If you are going out to buy up a bunch of cell tower space, that is quite 
expensive. There are
other *much* less expensive ways to create an independent system. In fact, we 
already have
several alternate systems (Glonass and Galileo and BeiDou). They are already 
available (or will
soon be available) in the data stream of a lot of GPS modules. Working out what 
to do with
them is less complex than adding a “something else” system.

Bob


> 
> Pete.
> 
> On 3/11/2018 5:26 PM, Magnus Danielson wrote:
>> Hi Andy,
>> 
>> On 03/11/2018 08:40 PM, Andy Backus wrote:
>>> Thank you for your posting, Magnus.
>>> 
>>> Your information is very interesting.
>>> 
>>> Do you mind saying a little more about the "incident" on 26-JAN-2016?  I 
>>> don't find reference to it in the link.  And my own TE plot for then shows 
>>> no obvious disturbance.
>>> 
>>> Thanks.
>> Please read this:
>> https://rubidium.dyndns.org/~magnus/papers/GPSincidentA6.pdf
>> 
>> In short, the GPS to UTC time correction polynomial got screwed up.
>> 
>> I got email from NASA, ended up having to call NASA HQ and got invited
>> to Washington DC to present before the US PNT advisory board.
>> 
>> Among the stranger things I've done in my life, but it was fun.
>> 
>> Cheers,
>> Magnus
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

If you pick the “right” STM board, it can handle processing up around 
a megasample. It’s internal ADC’s are more of an issue than the sample
rate. You can only do just so well on harmonics with a 12-ish bit ADC.
Even if you go crazy and get one with a display, they still are pretty cheap.

Bob

> On Mar 11, 2018, at 6:13 PM, Attila Kinali  wrote:
> 
> On Sun, 11 Mar 2018 14:41:23 -0500
> Dana Whitlow  wrote:
> 
>> I'll have to take a look around to see if there isn't something cheap that
>> can run
>> standalone so I don't have to tie up (or wear out) a whole PC for the
>> acquistion
>> process.
> 
> Blub... I should the whole mailsorry about that.
> 
> How about this: get a uC board (e.g. STM32discovery), replace
> the crystal with a 10MHz input from your frequency reference.
> Use the on-chip 12bit (really just 6bit) ADC to sample the
> sine wave from your mains. Do phasor measurement in software.
> 
> Probably any sampling frequency between 200Hz and 1kHz should
> do the job, Which is slow enough so you can still handle the
> samples with the uC alone and don't need any fancy DSP.
> 
> 
>   Attila Kinali
> 
> -- 
>   The bad part of Zurich is where the degenerates
>throw DARK chocolate at you.
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

Cute !!

It certainly beats firing up an R-392 to see if you can get a tick from WWV…

Bob

> On Mar 11, 2018, at 5:42 PM, Tom Van Baak  wrote:
> 
>> “Back in the day” we used WWV and the kitchen clock for that sort of thing……
> 
> Bob,
> 
> Yes, not much has changed. I use multiple methods to measure 60 Hz in order 
> to gain confidence in the results. Besides the picPET, I've used a commercial 
> TrueTime TFDM (Time/Frequency Deviation Meter) and also a plain old kitchen 
> clock (synchronous motor, wall clock).
> 
> Example: I took photos of the kitchen clock precisely 30 seconds after each 
> quarter hour. Here's the short animated GIF of that run; you can see how the 
> wall clock wanders from 0 to 5 seconds ahead of the UTC reference clock (seen 
> in the background):
> 
> http://leapsecond.com/pages/tec/mains-clock-ani.gif
> 
> For alert readers: the +/- 1 second jitter in the reference clock is due to 
> drift and latency in the PC scripts used to trigger the photo capture. Also 
> sunrise (Pacific time) can be seen in the background starting about 1300 UTC.
> 
> /tvb
> 
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

“Back in the day” we used WWV and the kitchen clock for that sort of thing……

Bob

> On Mar 11, 2018, at 8:32 AM, Tom Van Baak  wrote:
> 
> Bob,
> 
> Correct, measuring mains frequency to a couple of digits is not hard. What 
> makes an interesting challenge is to monitor mains, "kitchen clock", phase 
> drift. And to do it with cycle accuracy; no slips. Note that to measure down 
> to 1 cycle over 1 day is 0.2 ppm. Over a month, 6 ppb, and over a year, 
> 5e-10. So the numbers add up and you see why we use atomic standards or GPS 
> or even NTP as a long-term reference for this.
> 
> Your measurement system needs to have short- and long-term stability ~10x 
> better than:
>http://leapsecond.com/pic/mains-adev-mdev-gnuplot-g4.png
> 
> Again, that's not asking a lot. But it makes a really fun project. Much of 
> what you ever need to know about time & frequency metrology can be done by a 
> student with $10 in parts and a 60 Hz outlet.
> 
> /tvb
> 
> p.s. Yes, it's very early here on the west coast, but I had to check how 
> badly my WWVB clocks handled DST a few hours ago.
> 
> - Original Message - 
> From: "Bob kb8tq" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Sunday, March 11, 2018 4:53 AM
> Subject: Re: [time-nuts] Recommendations for Mains Power Monitor / Logger
> 
> 
> Hi
> 
> So, how good is “good enough?”. My first attempt ran a counter with a 1 us 
> period resolution. 
> (remember, it was tube based …). That turned out to be major overkill in 
> terms of line frequency
> measurement. 60.123 Hz is doing pretty well in terms of line frequency. Even 
> to get that level, you 
> will be doing a bit of filtering (or you are  just watching the last two 
> digits pop around randomly). 
> 
> Your typical time base in a PC is good to a few hundred ppm. That’s giving 
> you an error in the 
> fourth digit of your measurement. With a bit of luck, your sound card 
> timebase may be 5X 
> more accurate than your system clock. (or it may be worse …) it depends a bit 
> on how fancy
> your audio setup is. 
> 
> Adding NTP to your PC will correct for any long term errors. In a rational 
> environment it should 
> get you into the “few ppm” range short term and zero error long term. 
> 
> A GPS gizmo will get you into the parts per billion (or better) range. It 
> might be 100’s of ppb, but it’s
> still *way* better than your CPU clock. The usual auction sites have lots of 
> candidates in the sub $50
> range.There are also places that are happy to sell you shields with GPS 
> devices on them.
> 
> A fancier yet solution is a GPSDO. We are well into overkill at this point. 
> The advantage to using
> one is that it may be the time / frequency standard for your entire lab 
> setup. You are up in the 
> $100 to $500 range for most of them. They will get you into 10’s or 100’s of 
> parts per trillion. 
> 
> There are indeed *lots* of different time sources you could use. The number 
> of alternatives is 
> *much* larger than what’s on the list above.
> 
> Bob
> 
>> On Mar 10, 2018, at 11:46 PM, Tom Van Baak  wrote:
>> 
>>> I've done some Googling and have found any number of designs.
>> 
>> Pat,
>> 
>> 1) Safety. I usually use a low voltage step-down transformer. This gives 
>> isolation and safety. Anything from 3 VAC to 24 VAC is fine.
>> 
>> 2) Trigger. There are dozens of schematics on the web for capturing the 
>> zero-crossing of a low-voltage sine wave. You can easily go overboard on 
>> this. Or just keep it simple and feed the signal through a resistor directly 
>> into a microprocessor input. The internal clamping diodes do their thing. A 
>> Schmitt trigger input is helpful but not necessary depending on how your 
>> software makes the measurement.
>> 
>> 3) Timebase. Given the long-term accuracy of mains (seconds a day, seconds a 
>> year) you don't need an atomic timebase. If you collect data for a couple of 
>> days any old XO will be fine. If you plan to collect data for months you may 
>> want a OCXO. Most of us just use cheap GPS receivers.
>> 
>> 4) Measurement. There are many ways to measure the signal. You can measure 
>> frequency directly, as with a frequency counter. You get nice data but it 
>> may not be perfect long-term due to dead time or gating effects in the 
>> counter.
>> 
>> So what most of us do is measure phase (time error) instead. One way is to 
>> make time interval measurements from a given mains cycle to a GPS 1PPS tick 
>> or vice versa, from each GPS/1PPS tick to the very next

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

So, how good is “good enough?”. My first attempt ran a counter with a 1 us 
period resolution. 
(remember, it was tube based …). That turned out to be major overkill in terms 
of line frequency
measurement. 60.123 Hz is doing pretty well in terms of line frequency. Even to 
get that level, you 
will be doing a bit of filtering (or you are  just watching the last two digits 
pop around randomly). 

Your typical time base in a PC is good to a few hundred ppm. That’s giving you 
an error in the 
fourth digit of your measurement. With a bit of luck, your sound card timebase 
may be 5X 
more accurate than your system clock. (or it may be worse …) it depends a bit 
on how fancy
your audio setup is. 

Adding NTP to your PC will correct for any long term errors. In a rational 
environment it should 
get you into the “few ppm” range short term and zero error long term. 

A GPS gizmo will get you into the parts per billion (or better) range. It might 
be 100’s of ppb, but it’s
still *way* better than your CPU clock. The usual auction sites have lots of 
candidates in the sub $50
range.There are also places that are happy to sell you shields with GPS devices 
on them.

A fancier yet solution is a GPSDO. We are well into overkill at this point. The 
advantage to using
one is that it may be the time / frequency standard for your entire lab setup. 
You are up in the 
$100 to $500 range for most of them. They will get you into 10’s or 100’s of 
parts per trillion. 

There are indeed *lots* of different time sources you could use. The number of 
alternatives is 
*much* larger than what’s on the list above.

Bob

> On Mar 10, 2018, at 11:46 PM, Tom Van Baak  wrote:
> 
>> I've done some Googling and have found any number of designs.
> 
> Pat,
> 
> 1) Safety. I usually use a low voltage step-down transformer. This gives 
> isolation and safety. Anything from 3 VAC to 24 VAC is fine.
> 
> 2) Trigger. There are dozens of schematics on the web for capturing the 
> zero-crossing of a low-voltage sine wave. You can easily go overboard on 
> this. Or just keep it simple and feed the signal through a resistor directly 
> into a microprocessor input. The internal clamping diodes do their thing. A 
> Schmitt trigger input is helpful but not necessary depending on how your 
> software makes the measurement.
> 
> 3) Timebase. Given the long-term accuracy of mains (seconds a day, seconds a 
> year) you don't need an atomic timebase. If you collect data for a couple of 
> days any old XO will be fine. If you plan to collect data for months you may 
> want a OCXO. Most of us just use cheap GPS receivers.
> 
> 4) Measurement. There are many ways to measure the signal. You can measure 
> frequency directly, as with a frequency counter. You get nice data but it may 
> not be perfect long-term due to dead time or gating effects in the counter.
> 
> So what most of us do is measure phase (time error) instead. One way is to 
> make time interval measurements from a given mains cycle to a GPS 1PPS tick 
> or vice versa, from each GPS/1PPS tick to the very next mains cycle. Either 
> way you get about sample per second. If you're in search of perfection it 
> gets a bit tricky when the two signals are in a coincidence zone.
> 
> The other approach is not to use a frequency or time interval counter at all. 
> Instead you timestamp each cycle, or every 60th cycle. Unix-like systems have 
> this capability. See Hal's posting. I use a picPET, a PIC microcontroller 
> that takes snapshots of a free-running decimal counter driven by a 10 MHz 
> timebase (OCXO or GPSDO).
> 
> The advantage of the timestamp method is that you don't ever miss samples, 
> you can time every cycle (if you want), or throw away all but one sample per 
> second or per 10 seconds or per minute, etc. And best of all, timestamping 
> avoids the hassles of the coincidence zone.
> 
> 5) CPU. A plain microcontroller, or Arduino, or R-Pi can be used. Or if 
> you're on Windows and have a native or USB serial port try this simple tool 
> as a demo:
> 
>http://leapsecond.com/tools/pctsc.exe
>http://leapsecond.com/tools/pctsc.c
> 
> 6) An assortment of mains links:
> 
> http://leapsecond.com/pages/mains/
> http://leapsecond.com/pages/mains-cv/
> http://wwwhome.cs.utwente.nl/~ptdeboer/misc/mains.html
> http://leapsecond.com/pages/mains/mains-adev-mdev-gnuplot-g4.png
> http://leapsecond.com/pages/tec/mains-clock-ani.gif
> http://leapsecond.com/pages/ac-detect/
> http://leapsecond.com/pic/picpet.htm
> http://leapsecond.com/pic/pp06.htm
> 
> 7) Final comments.
> 
> It is tempting to worry about the design, as they are so many out there on 
> the web. Which is best? What are the pitfalls? What about noise immunity? 
> What about precision and accuracy? My recommendation is not to over-think 
> this. Just throw something together and see what you've got. Most of the work 
> is with handling the data you get, doing the math, making plots, etc. If 
> after the first day you see odd-

Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Bob kb8tq]

Hi

The most basic question is - what do you have already? My first adventure with 
line monitoring was with a vacuum tube based counter. It was what I just 
happened 
to have. 

One basic need is something to monitor against. GPS is a pretty cheap option if 
you
have nothing already. 

Rather than guessing from there …

Bob

> On Mar 10, 2018, at 5:53 PM, Patrick Murphy  wrote:
> 
> All this talk of varying mains power frequency aberrations has me
> curious what is happening in my own back yard here in Tulsa in the
> USA. Can some recommend a reasonable "introductory level" solution for
> this? (As a fledgling Time-Nut, those two words were hard to say.😀)
> At the least I would like to watch voltage and frequency, with a
> configurable monitoring and logging interval. I can provide precise
> timing as needed for synchronization and time-stamping. Expanded
> ability to also monitor amperage, various power factors, etc is a plus
> but not required at this point.
> 
> I've done some Googling and have found any number of designs. What I
> can't tell is how well they work. I am pretty handy with my hands and
> do not at all mind a DIY solution.
> 
> So what do the Oracles say?
> 
> Thanks!
> 
> -Pat
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Re: [time-nuts] GPS L2 CNAV health reporting changes

[Bob kb8tq]

Hi

The Trimble empire here (NetRS’s and NetR8) seem to be reasonably happy with 
everything. 
I haven’t dug into any of the data. They all show L2C tracking along like 
normal. 

Bob

> On Mar 8, 2018, at 9:23 PM, J. Grizzard  wrote:
> 
> I got a message from the Swiftnav support folks yesterday (I have a piksi 
> multi amongst my little fleet of GPSen) because they had an emergency 
> firmware patch to their kit because of a change in the L2C signal was giving 
> them issues. (Props to them for getting a firmware update out in ~12 hour, 
> too)
> 
> After a little bit of inquiring, it looks like what happened is that 
> yesterday, the L2 CNAV message started marking all of the L1 signals as 
> unhealthy. If a device actually listens to this health signal (apparently 
> their GPS did), suddenly most GPS satellites become unusable (with the only 
> remaining ones being ones that aren't transmitting an L2C signal).
> 
> (According to NANU 2014039, you shouldn't be using those health indicators, 
> though it does also say that the L1 health indicators would all indicate 
> "healthy", so this seems to be a departure from their stated plan.)
> 
> Anyhow, probably doesn't affect anyone here, but I thought it was 
> interesting. Sadly, I can't see what's actually being transmitted, since my 
> only pieces of kit that can decode L2C are my piksi (which won't give me raw 
> NAV/CNAV, and they apparently have zero interest in adding that 
> functionality), and the Novatel OEM628 that I picked up off eBay last year 
> ... which crashes every 20 or 30 minutes if I ask it to decode L2C. Argh.
> 
> (Maybe u-blox's upcoming kit will be affordable(ish) and have good raw CNAV 
> output... I can hope, right?)
> 
> -j
> 
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Re: [time-nuts] Ultra low power RTC

[Bob kb8tq]

Hi

> On Mar 7, 2018, at 6:33 PM, Mike Cook  wrote:
> 
> 
>> Le 7 mars 2018 à 11:10, Attila Kinali  a écrit :
>> 
>> On Tue, 6 Mar 2018 21:57:32 -0500
>> Bob kb8tq  wrote:
>> 
>>> Assuming you are going to run it off a battery. What’s the self discharge
>>> rate on a reasonable battery? 
>> 
>> With supply currents below 100nA you can assume that you are likely
>> to be limited by the self-discharge using coin sized LiMnO2 cells
>> (e.g. a CR2032 is specced in the order of 100-300nA self-discharge).
>> For the smaller cells, you have to check which one is larger, but
>> they are of the same order of magnitude.
> 
> This is interesting. When you talk of self discharge, is there any way of 
> harnessing that. Is that what the chip manufactures are doing?

Self discharge = current flowing through the internal elements of the cell 
(plus 
other long term degradation effects).

Bob

> 
>> 
>> 
>>  Attila Kinali
>> -- 
>> It is upon moral qualities that a society is ultimately founded. All 
>> the prosperity and technological sophistication in the world is of no 
>> use without that foundation.
>>-- Miss Matheson, The Diamond Age, Neil Stephenson
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> 
> "The power of accurate observation is commonly called cynicism by those who 
> have not got it. »
> George Bernard Shaw
> 
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Re: [time-nuts] Ultra low power RTC

[Bob kb8tq]

Hi

Ok, so energy harvesting from Lazy Bob in his arm chair makes a button cell 
look like a giant power source ….. 

You likely aren’t going to win any ADEV competitions with that oscillator. They
did go to a *lot* of effort to squeeze out that last nano watt.

Bob

> On Mar 7, 2018, at 11:47 AM, Tom Van Baak  wrote:
> 
>> Since we don’t often *need* the smallest cell made *and* we’re probably 
>> talking lifetime of the cell….. does 22 na vs 33 na matter?
> 
> It gets even more amazing ...
> 
> "A 1.5 nW, 32.768 kHz XTAL Oscillator Operational From a 0.3 V Supply"
> https://web.northeastern.edu/ecl/wp-content/uploads/2016/12/xtal.pdf
> 
> /tvb
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Re: [time-nuts] Ultra low power RTC

[Bob kb8tq]

Hi

I’ve designed watch guts (long ago). It was at a time that you used 
an analog (motor) movement if you wanted really low power. The CMOS
/ LCD’s of that era were power hogs by comparison. 

What you can put in a small / thin  watch isn’t what you would use on a 
RTC board. My suspicion is that the leakage from a number of sources will 
indeed dominate the actual power consumption in a random build
sort of application. (At least compared to 10’s of nano amps of power
into the chip). 

Bob

> On Mar 7, 2018, at 11:03 AM, Attila Kinali  wrote:
> 
> On Wed, 7 Mar 2018 08:27:00 -0500
> Bob kb8tq  wrote:
> 
>> Since we don’t often *need* the smallest cell made *and* we’re probably 
>> talking lifetime of the cell….. does 22 na vs 33 na matter?
> 
> Not really. It starts to matter when you are space limited and don't
> have space for a CR2032.
> 
> At this level, though, every tiny bit of leakage matters. Finger prints,
> dust, humidity, FR4... Going below 1µA in current consumption is like
> going below 10^-12 in frequency stability, suddenly 1M is a low resistance.
> 
>> Based on the previous data on the chip, I think I would just run the crystal
>> all the time. 
> 
> The the watches (quartz with analog dials) I have run >5 years
> on their batteries, an I am pretty sure they don't have a CR2032.
> And at least one of them must have a TCXO.
> 
> 
>   Attila Kinali
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Ultra low power RTC

[Bob kb8tq]

Hi

Since we don’t often *need* the smallest cell made *and* we’re probably 
talking lifetime of the cell….. does 22 na vs 33 na matter?

…. hmmm ….

CR2032 ( which is the smallest I would use) is rated at 0.22 AH. 

A nano amp for a year is about 8 uA hours a year. 

So 30 na for 20 years is 0.005 AH 

Indeed, the self discharge of the cell (or life or whatever you want to call it)
will probably get you before the 30 na drain will. 

Based on the previous data on the chip, I think I would just run the crystal
all the time. 

Bob

> On Mar 6, 2018, at 11:22 PM, Mark Sims  wrote:
> 
> Probably 20+ years for a lithium coin cell... basically the shelf life of the 
> cell.  I have a card of 24 year old CR-2032's that are still above 3V, and no 
> sign of leakage.
> 
> BTW, never handle a coin cell (particularly in watch applications) with your 
> fingers... your grubby fingerprints are rather conductive and can discharge a 
> cell surprisingly quickly.   
> 
> Also note the clock chip has 512 bytes of RAM in it.
> 
> 
> 
>> Assuming you are going to run it off a battery. What’s the self discharge
> rate on a reasonable battery? 
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Re: [time-nuts] HP 107BR Ski Question

[Bob kb8tq]

Hi

The oscillators were tested and sorted at the end of the manufacturing line. 
Everything got
checked for aging. It’s not clear that everything got detail tested for ADEV. 
The suspicion is that 
they did enough ADEV to get the few tight(er) spec units they needed. 

Next layer is that these tests were done a *long* time ago. The characteristics 
of OCXO’s do change
with time. What was once a tight spec unit may not be so today. What was once a 
bit noisy may be
quieter now. 

I would not worry a lot about the different dash numbers on decades old 10811’s.

Bob

> On Mar 6, 2018, at 11:57 PM, Perry Sandeen via time-nuts  
> wrote:
> 
> List,
> In getting documentation together for my HP 107BR I discovered the manuals I 
> was able to aquire were for prefix 333.
> My unit prefix is 708.  Does anyone have that prefix schematics or an errata 
> sheet?  Or does the 708 prefix just designate another factory run?
> TIA
> Perrier
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Re: [time-nuts] Ultra low power RTC

[Bob kb8tq]

Hi

Assuming you are going to run it off a battery. What’s the self discharge
rate on a reasonable battery? 

Bob

> On Mar 6, 2018, at 8:34 PM, Attila Kinali  wrote:
> 
> On Tue, 6 Mar 2018 22:59:34 +
> Mark Sims  wrote:
> 
>> Sparkfun is selling an interesting RTC clock chip board. 
>> It draws 22 nA.  It has a rather novel clock generator...
>> a tuning fork crystal disciplines an RC oscillator every few minutes.
>> They claim 3 minutes per year drift.
> 
> *Sigh* There are a couple of things wrong with that description.
> 
> 1) The part is from Microcrystal, so you can believe the specs
> they publish with high confidence. This also means this is probably
> the exact same chip you will find in Swiss quartz watches.
> (Microcrystal is part of the Swatch group and the main supplier
> of 32kHz oscillators and electronics for the Swiss watch industry)
> 
> 2) The 22nA is the _typical_ consumption in auto-cal mode.
> Max (the number you should design with) is 32nA. Keep in
> mind this number is for the chip alone, no external connection.
> It also includes the implicit condition that all input pins are
> at valid voltage levels. If a pull up/down resistor is too weak
> (because you tried to safe a few more nA) it will result in
> pins being driven by leakage currents, possibly reaching invalid
> voltage levels, which in turn will cause shot-through currents
> through the input stages, increasing the power consumption 10 fold
> at least, 1000 fold easily.
> 
> 3) The current ratings are at 25°C. Going higher means also
> an increase in power consumption. How much, is not specified.
> 
> 4) The 3minutes per year number comes from the +/-3ppm first year
> aging. This is, as usual, at 25°C and is on top of the typ. +/2ppm
> time accuracy. So, the real accuracy is more like 5min after the first
> year... when running from Xtal all the time!
> Which has a typ. 60nA/max 80nA current spec!
> Taking temperature into consideration, assuming something in the order
> of 10 minutes per year is probably more realistic... if you stay
> close to 25°C. The quadratic nature of the temperature dependence
> for tuning fork X-cut crystals causes high deviations pretty quickly
> (In one of the devices I designed, the 10ppm spec of the crystal
> suddenly became 300ppm when taking the whole temperature range at
> which it had to operate into consideration)
> 
> 5) The precision of the auto-cal mode is not specified. It can be
> litterally anything. Especially considering that the datasheet
> talks about using it "several hours at Backup Supply Voltage," 
> i.e. as an emergency measure when the normal power supply is lost.
> 
>   Attila Kinali
> 
> -- 
>   The bad part of Zurich is where the degenerates
>throw DARK chocolate at you.
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Re: [time-nuts] My Favorite Watch

[Bob kb8tq]

Hi

Most (as in the center of the distribution) afordable  watches are calibrated 
to run fast. 
There is info on this in the archives. A pretty typical target is 10 seconds a 
month.  Yes,
we used that as a target back in the 70’s but it’s still pretty common. You 
have to get 
lucky to find one that is dead on time. 

Some math:

2,592,000 seconds in a month. 1 second is about 0.4 ppm.

Your typical watch crystal moves about 20 PPM over 0 to 50 C. 

The curve is a parabola with a tolerance on the inflection point.

So 10 seconds a month comes out to around 4 ppm. With the temperature out 
around 
20 ppm, you need a fairly stable / consistent environment to hit even that sort 
of number.

Yes, you could play compensation games, but doing so only works to the degree 
that
the crystal matches some ideal curve. ( = you get a pretty limited gain with 
low cost crystals
and no testing). 

Bob

> On Mar 6, 2018, at 3:02 PM, al wolfe  wrote:
> 
> My Timex Indiglo looses about a second a month. I think that's pretty good
> for a <$30 watch I got at Walmart.
> 
> Al
> 
> 
> Virus-free.
> www.avast.com
> 
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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Re: [time-nuts] u-blox F9

[Bob kb8tq]

Hi

Looking at the press release, this is sort of the next step in the process that 
got us
the NovaTel GPS units on eBay as ex-Uber surplus. If they can come up with a 
$1,000
board that replaces the NovaTel $5,000 unit, they have a product …. Will we see 
a 
$100 LEA-9T with the chip in it? Only time will tell. My guess would be not any 
time soon….

Bob

> On Mar 6, 2018, at 5:20 AM, Magnus Danielson  
> wrote:
> 
> Hi,
> 
> It seems that u-blox now have an interesting chip coming, according to
> the press-release it has L1/L2/L5 and GPS, GLONASS, GALILEO and BEIDOU
> capability, with RTK support as an option.
> 
> As I have suggested before, the precision would fit the purpose of
> identifying which lane a care is in, something they make explicit
> reference to as a use scenario.
> 
> As for timing support not much is known, but it is interesting.
> 
> https://www.u-blox.com/en/press-releases/u-blox-announces-u-blox-f9-robust-and-versatile-high-precision-positioning-technology
> 
> Cheers,
> Magnus
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Re: [time-nuts] Z3801A OCXO manual trimming

[Bob kb8tq]

Hi

Assuming you can break the EFC lead to the OCXO, you aren’t going to damage 
anything 
inside by feeding the EFC line with +/- 5V. If you are going to tear open the 
OCXO, the line
will need to be pulled anyway. Without knowing what they drive the EFC line 
with, it’s hard to
know if the driver on the line would be happy with a back fed voltage. Best to 
be careful ….

Bob

> On Mar 6, 2018, at 3:30 AM, gandalfg8--- via time-nuts  
> wrote:
> 
> 
> 
> 
> 
> Crazy thought.Could you just force a DC offset into the EFC assuming the
> internal varicap is not out of range.
> It would be simply adding a resistor to pull up or down to see if you can
> get a bit of pull and allow the dac to move back in range a bit. Its a band
> aid.
> I know its sort of crazy. But ripping the oven apart really is no fun at
> all.
> Regards
> Paul
> WB8TSL
> 
> 
> 
> **
> 
> Not really such a crazy thought, I've done this on a Trimble-Nortel NTGS50AA 
> where the original 34310-T oscillator had "aged" beyond the 3 to 6 Volt EFC 
> range.
> 
> On a unit that was refusing to lock the oscillator was removed and confirmed 
> to require an EFC voltage of approx 6.5 Volts for an output frequency of 10 
> MHz. As other tested samples of this oscillator, although admittedly not 
> many, required around 4.5 volts there does remain the possibility of an 
> actual internal fault but it did test on the bench as otherwise ok.
> 
> Using a simple unity gain level shifter based on a few resistors and a TL071 
> op amp, just because there was one to hand, the EFC voltage from the control 
> circuit was shifted 2 Volts high and the unit then behaved as expected.
> 
> The effects of temperature, supply variation, etc on the modified circuit 
> were not investigated as this was only a short term test but it certainly 
> looked to be a viable proposition, to the extent that rather than fit a 
> replaccement 34310-T that board was fitted with SMB connectors using the pads 
> provided to keep as a test bed.
> 
> Nigel GM8PZR
> 
> 
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Re: [time-nuts] Z3801A OCXO manual trimming

[Bob kb8tq]

Hi

The control range should be +/- 5V if I remember correctly. If it’s not, the
only other standard would be 0-5V. There is zero logic in running a wider
swing mod to an OCXO at a lower EFC range. 

It indeed sounds like the DAC has trouble. 

Bob

> On Mar 6, 2018, at 1:24 AM, Mark Sims  wrote:
> 
> I'm not sure what the Z3801A uses for EFC range.   Heather uses the EFC 
> relative command to report the EFC setting.  That command reports values from 
> -100% to 100%.   There is a command that reports the DAC input in counts, but 
> nothing documented that shows volts/count.
> 
> Since the DAC is at -2V with a 99+% DAC setting, it looks like the DAC 
> circuit has issues, or power supply problems.   I think the DAC circuit is a 
> 16 bit DAC with 4 more bits of resolution created by dithering the DAC inputs.
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Re: [time-nuts] Z3801A OCXO manual trimming

[Bob kb8tq]

Hi

Either tear into the OCXO or go shopping for a new(er) GPSDO. The
Z38xx devices all had a lot more in common with each other than they
did differences. The OCXO design changed from the 10811 to various
more modern designs. The disciplining process seems to have remained
pretty much the same over the years. 

Bob

> On Mar 5, 2018, at 11:21 AM, Joe Hobart  wrote:
> 
> 
> Thank you, Hal, for these links and to others for your comments.
> 
> Setting the oven temperature on a turning point appears tedious.  Perhaps 
> there
> is enough range in the frequency adjustment to put the oscillator back on
> frequency - or close enough for the EFC to be effective.  If not, I may have 
> to
> adjust the temperature, but time is limited.
> 
> Some measurements with the EFC disconnected and a calibrated frequency 
> counter:
> 
> .815  KHz  at Z3801A turn on
> 
> .9984 KHz  highest frequency seen (temperature overshoot)
> 
> .9947 KHz  approximate final frequency
> 
> The EFC does have wide range; it can almost pull the 5.3 Hz offset onto 
> frequency.
> 
> Thanks again,
> Joe, W7LUX
> 
> 
>> Does the oscillator have an adjustment?  If so, is this somewhat accessible
>> without destroying the assembly?  Are there pictures of the oscillator
>> assembly?
> 
> https://www.realhamradio.com/GPS-oven-journey.htm
> 
> https://www.realhamradio.com/z3801a-turning-point.htm
> 
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Re: [time-nuts] WWV or Net Clock controlled oscillator

[Bob kb8tq]

Hi

A very normal way to get the 60 Hz into the clock chips is to pull it off
of something like the 24V transformer winding. They run through a resistor
over to a limiter circuit to turn the sine wave into a square wave. That
square wave heads into the input pin on the clock chip. Some “quality time”
spent working out what’s what on the pc board should allow you to find 
the relevant section of the board. 

Once you find the right stuff, it should be as simple as opening up a 
resistor and running a jumper wire to the right spot on the board. Feed
the wire with your new 60 Hz square wave out of Tom’s PICDIV. The
“mods” should be very reversible and not a threat to the longevity of
the DCBI. 

Bob

> On Mar 5, 2018, at 9:17 AM, D. Resor  wrote:
> 
> The unit has an external switching power supply which provides 5+ VDC.  In 
> addition there is a 24VAC transformer which provides the power for the bell 
> solenoids.  This where the AC reference is "sampled"  I cannot completely cut 
> out the AC transformer as it is essential to other operations of the DCBI.
> 
> A lot to study.
> 
> 
> Donald R. Resor Jr. T. W. & T. C. Svc. Co.
> http://hammondorganservice.com
> Hammond USA warranty service
> "Most people don’t have a sense of humor. They think they do, but they 
> don’t." --Jonathan Winters
> 
> 
> 
> -Original Message-
> From: time-nuts  On Behalf Of Tom Van Baak
> Sent: Sunday, March 04, 2018 3:02 PM
> To: Discussion of precise time and frequency measurement 
> Subject: Re: [time-nuts] WWV or Net Clock controlled oscillator
> 
> Donald,
> 
> Possible solutions to your 60 Hz mains problem:
> 
> 1) If you don't want to open or hack the clock controller in any way consider 
> using a "online" UPS. Typically the synthesized 60 Hz AC output is quartz 
> controlled.
> 
> 2) Make your own low-power 60 Hz AC/DC/AC power supply -- using a quartz, or 
> ovenized quartz, or GPSDO or NTP-based timebase. How many watts do you need? 
> How many seconds per week is your limit?
> 
> 3) Open the clock controller and locate the wire that gets the 60 Hz timing; 
> probably from a low voltage winding of the transformer. Then cut the wire and 
> feed your own precise digital 60 Hz instead.
> 
> 4) You mentioned "the 60Hz reference can be switched out". In that case what 
> is the time source? What frequency? Based on a cheap quartz xtal? If so, 
> perhaps it's easier to replace that instead of messing with 60 Hz.
> 
>> I was trying to locate a cost effective clock reference which can be 
>> synchronized from either WWV, request the correct time from a net 
>> server or possibly GPS.  It then needs a clock referenced output of 60Hz.
> 
> Can you be more specific about this requirement? Generating a precise 60 Hz 
> is a different problem from knowing what the current local date / time is.
> 
> /tvb
> 
> - Original Message -
> From: "D. Resor" 
> To: "Time Nuts List" 
> Sent: Sunday, March 04, 2018 2:30 AM
> Subject: [time-nuts] WWV or Net Clock controlled oscillator
> 
> 
>> Hello,
>> 
>> 
>> 
>> My first post here. I found this group's user group page while researching a
>> source for either a WWV, GPS or Network referenced oscillator.
>> 
>> 
>> 
>> The devices/equipment which I was able to find didn't  seem to fit the
>> requirements.
>> 
>> 
>> 
>> What I have is a Maas-Rowe DCB1 (Digital Chronobell Series 1) clock
>> controller.  
>> 
>> Seen here:
>> http://hammondorganservice.com/downloads/images/carillon/TempleCitySDADCB1a.
>> jpg
>> 
>> 
>> 
>> The system can be heard playing the Westminster Chimes and striking 12 noon
>> here:
>> 
>> 
>> 
>> https://www.youtube.com/watch?v=Ij5c6RqGhn0
>> 
>> 
>> 
>> 
>> 
>> It can be programmed to play Westminster sequences and/or music selections
>> using Maas-Rowe real struck chromatically tuned bell rods.
>> 
>> 
>> 
>> This unit is installed in Southern California Edison area.  The problem is,
>> this unit receives its clock reference from the 60Hz AC line to keep it in
>> sync.  Up until a few years ago this worked very well.  Now, Edison's 60Hz
>> line frequency is all over the place and this clock unit now gains 30
>> seconds and/or more a week which makes it difficult to keep it synchronized.
>> 
>> 
>> 
>> The 60Hz reference can be switched out by the use of dip switches, however
>> that setting isn't much better.
>> 
>> 
>> 
>> I was trying to locate a cost effective clock reference which can be
>> synchronized from either WWV, request the correct time from a net server or
>> possibly GPS.  It then needs a clock referenced output of 60Hz.
>> 
>> 
>> 
>> Does such a thing exist?
>> 
>> 
>> 
>> Thank You
>> 
>> 
>> 
>> 
>> 
>> Donald R. Resor Jr. T. W. & T. C. Svc. Co.
>> 
>> http://hammondorganservice.com
>> Hammond USA warranty service
>> "Most people don't have a sense of humor. They think they do, but they
>> don't." --Jonathan Winters
>> 
>> 
>> 
>> ___
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>> To u

Re: [time-nuts] Need a Watch Recommendation

[Bob kb8tq]

Hi


> On Mar 5, 2018, at 1:38 AM, Don Murray via time-nuts  
> wrote:
> 
> Hello Time Nuts...
> 
> 
>  
> After 6 years of no troubles, in sync with WWV any
> hour of the day, flawless transfer between
> standard and daylight time my Stauer Titanium
> Atomic wristwatch bite the dust a year ago.
>  
> Since then, Stauer has sent me three replacements,
> each with some type of problem.  
>  
> So it looks as if I am in need of a new wristwatch,
> which will give me some kind of time accuracy.
>  
> So, Time Nuts...  any suggestions or recommendations?

If you want to stick with WWV, the Citizen “Ecco Drive” (solar) WWVB 
watches are a pretty good option. Until I caved in to the wonders of
a cell phone on my wrist, I used them for many years. Nothing to fuss 
with. No battery to die on you. Always keeps the right time. Available 
in titanium. The only drawback is the limited number of styles they
make it in. You may or may not see one you like the looks of. 

Bob

>  
> TNX
>  
> 73
> Don
> W4WJ
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Re: [time-nuts] Z3801A OCXO manual trimming

[Bob kb8tq]

Hi

> On Mar 4, 2018, at 10:30 PM, Joe Hobart  wrote:
> 
> 
> Mark,
> 
> When I press "D" Lady Heather replies:
> 
> Manual disciplining not supported by this receiverpress ESC
> 
> 
> Questions about the Z3801A:
> 
> Does the oscillator have an adjustment?  If so, is this somewhat accessible

Yes, if you dig deep enough

> without destroying the assembly?

Depends on how good you are at ripping into things 

>  Are there pictures of the oscillator assembly?

I believe there are in the archives

> 
> Is there an adjustment for temperature?

Yes, by changing the select resistor 

>  Is this accessible?

Yes, once you have the inside oven board out of the enclosure. Accessible is a 
relative term. I would not dig that deep. Others on the list seem to be happy 
going
that far into the assembly. 

Bob

> 
> Thanks,
> Joe, W7LUX
> 
> 
> Lady Heather has a command that lets you set the DAC voltage.  It's in the "D"
> menu.   Depending upon the firmware, you may need to disable disciplining 
> first
> (also in the "D" menu).  If the DAC  command works to change the OCXO freq,  
> the
> osc EFC and DAC are probably OK.  If it does not, I'd suspect the DAC or the
> osc EFC input... or perhaps your firmware does no support the DAC setting 
> command.
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Re: [time-nuts] While we are talking about Z3801's

[Bob kb8tq]

Hi

Basic troubleshooting: 

Check the regulator output voltages and repair as needed.

Basic serial troubleshooting:

Bring up a terminal program, loop back the serial with a jumper, see if you 
have 
a connection. 

If you do, issue basic commands, see what happens. 

Switch to likely baud rates repeat basic commands. 

If still nothing, put a scope on the RX output of the serial chip in the 3801. 
Do the same 
for the TX input of the same chip. 

…… dig on in from there. 

Bob

> On Mar 4, 2018, at 9:22 PM, Hal Murray  wrote:
> 
> 
> wpxs...@gmail.com said:
>> Hal, I can't communicate with it. That has been gone for a while now. 
> 
> I assume it worked at some point.  Did talking to it stop working at the same 
> time the frequency stopped tracking?  If so, I'd guess the CPU inside has 
> stopped working and isn't setting the DAC correctly.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] LT1016 as a pulse shaper...

[Bob kb8tq]

Hi

Having tried to do these measurements a lot of ways ….. the TimePod makes it 
*very*
easy. The ability to get phase noise and ADEV “all at once” is part of it. The 
ability to 
handle a wide range of input levels with minimal degradation is a also part of 
the why.
The software makes it easy for lazy Bob … a big plus ….

Bob

> On Mar 4, 2018, at 8:32 PM, Bruce Griffiths  
> wrote:
> 
> Since I have a Timepod all that I'd need would be a board that had SMA inputs 
> and outputs with provision for an LC L network to  step up the input if 
> necessary plus an RLC network on the output something like in the attachment.
> 
> If one doesnt have a Timepod or equivalent a low noise phase detector will 
> suffice for the noisier sources. An adjustable phase shift network is 
> required to achieve quadrature between the LO (driven directly from the 
> splitter) and the RF input (driven by the DUT output).
> 
> The required phase shift adjustment range could perhaps be reduced by using a 
> quadrature hybrid to split the test source instead of a standard splitter. 
> The output of the phase detector is low pass filtered and amplified and fed 
> to a high resolution ADC such as a sound card.
> 
> Bruce
> 
>> 
>>On 05 March 2018 at 13:59 Hal Murray  wrote:
>> 
>>Bruce Griffiths  said:
>> 
 
>>>If I had a suitable PCB board for it I would do the measurement 
>>> properly.
>>> 
 
>>What would a suitable board look like and/or what sort of gear do you 
>> need to
>>measure PN?
>> 
>>--
>>These are my opinions. I hate spam.
>> 
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Re: [time-nuts] LT1016 as a pulse shaper...

[Bob kb8tq]

Hi

The “best” way to measure phase noise will always be a “that depends” sort of 
thing. One
pretty darn good way to check noise on any amplifier is to use something like a 
TimePod. 
You use a power splitter and a pretty good source. First you check your TImePod 
(or whatever)
for floor. You then stick the amp in one leg. You re-measure phase noise (or 
ADEV). Assuming 
it comes up above the previous floor, you have your number for the device. If 
it does not come
up above the previous floor, you need a different test set. 

Bob

> On Mar 4, 2018, at 7:59 PM, Hal Murray  wrote:
> 
> Bruce Griffiths  said:
>> If I had a suitable PCB board for it I would do the measurement properly.
> 
> What would a suitable board look like and/or what sort of gear do you need to 
> measure PN?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Z3801A OCXO manual trimming

[Bob kb8tq]

Hi

> On Mar 4, 2018, at 1:13 PM, Joe Hobart  wrote:
> 
> My Z3801A failed about a year ago (there was a warning the electronic 
> frequency
> control was nearing a limit).
> 
> Symptoms (most from GPS Control and Lady Heather:
> 
>   Frequency about 1E-8 low
> 
>   Time Invalid  (many hours off)
>   Date 6 months old
>   DAC 99.9969 percent
>   Life 72K Hours
> 
> Lady Heather shows the following as OK:
> 
>   ROM, RAM, OSC GPS, Power, EEPROM, Antenna, Discipline, 5 satellites
> 
> GPS Con shows the following:
> 
>   EFC: ERR
>   No time display
>   Outputs Invalid
> 
> Only the front panel power light is lit.
> 
> This suggests either the crystal has aged or the heater temperature has 
> drifted
> slightly.  I hear/read that opening the oscillator is difficult.  Is there a
> usable adjustment?
> 
> What have others done to restore operation?  Is it time to consider a 
> different
> time & frequency standard?

With enough effort and enough time spent troubleshooting, you probably can 
fix the beast. You might have to swap out the OCXO, but that’s still just a 
repair
process. The bigger question is indeed how much work to put in. 

The basic approach is to fire up a counter and get into the EFC voltage line.
Swing it to both limits and see what the frequency does. That will give you 
an idea if it’s the OCXO or if it’s the DAC side of things. 

The 3801 was made for a while. Some are hitting 20 years old at this point. 
Mine seem to eat power supply components from time to time. One of these
days, whatever it is that pops the fuse will do more damage. 

Back when the 3801 hit the surplus market there really was not a whole lot
else to look at. These days, we’re hip deep in a whole range of units sourced
mostly from “China Electronic Salvage Inc”.  Who knows …. maybe one day
there will be another TimeNuts TBolt “sale”…..

Bob


> 
> Thanks,
> Joe, W7LUX
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Re: [time-nuts] Z3801A OCXO manual trimming

[Bob kb8tq]

Hi

Heater failure is pretty easy to spot. You will be *way* off frequency. No need 
for a 
GPSDO in your counter to see if it’s out by 0.0001 Hz. You should be > 20 Hz low
in frequency. Since there *are* multiple heaters, there are some odd 
combinations
in a 3801. Your inner heater can be dead, but the outer heater still works. The 
unit
will look like it’s warming up but doing so *really* slowly. 

Based on seeing a lot of 10811’s and a lot of modern OCXO’s, a crystal that 
ages out
is pretty rare. The “something else” category is way more likely when diving 
into one
that is off frequency. That wasn’t always true so you can go back far enough in 
time 
(like into the 60’s) and find units that have aged out. They also aged out in 
the first 
ten years after they left the factory. Things got a lot better over the years 
in terms of
long term precision crystal aging ….

Bob

> On Mar 3, 2018, at 10:12 PM, Tom Holmes  wrote:
> 
> Bob...
> 
> Interesting point about the heater not working vs the XTAL having drifted too 
> far. Mine has the same symptoms as the others reported (EFC at the end of its 
> rope) but have not tackled it yet, figuring I'd have to dismantle the whole 
> thing. Certainly troubleshooting a non-operating heater would be much more 
> pleasant.
> 
> Thanks for that insight.
> 
> Tom Holmes, N8ZM
> 
> -Original Message-
> From: time-nuts  On Behalf Of Bob kb8tq
> Sent: Saturday, March 03, 2018 2:07 PM
> To: Tom Curlee ; Discussion of precise time and 
> frequency measurement 
> Subject: Re: [time-nuts] Z3801A OCXO manual trimming
> 
> Hi
> 
> First off some basics about OCXO’s.
> 
> In a single oven design, you have a heater that warms up the entire crystal 
> and the guts of the oscillator. It is on all the time and 
> it gets things up to a temperature that makes sense for a given crystal. It 
> can be adjusted based on manufacturing data or by 
> trial and error to match the characteristics of that crystal. 
> 
> In a double oven design, you have two ovens that are on all the time. One 
> heats up the other one. They both work together to
> achieve the end result. The gain of one adds to the gain of the other to give 
> an improved result. On some double ovens, the 
> entire heat range of the inner oven is only 10’s of degrees ….
> 
> In a boosted oven, you have a second heater to get things going when it is 
> very cold. This is an unusual approach and rarely 
> seen. Its normally easier to just design a bit more power into the main oven 
> circuit. In a boosted design, the boost heat goes
> away in normal operation at typical temperatures. In normal operation, the 
> gain of the boost circuit does not count. 
> 
> SO ….
> 
> The oscillator in the Z3801 is a boosted 10811. It is boosted to allow them 
> to hit a spec of -40C on the unit. At the time it was
> designed, there was talk about mounting these things in un-heated boxes 
> outdoors. After they got a bit further into all the 
> details of the designs … that part went away. The spec still hung around long 
> enough to apply to very early designs. 
> 
> The net result is that you can pretty much destroy the outer heater stuff and 
> the oscillator will work fine. There is no need 
> for it in a typical lab. There are some alarm triggers that need to be wired 
> “ok” when you do so. The details are in the archives. 
> 
> But …
> 
> Best guess if your unit is at max EFC = the “real” heater on the 10811 has 
> quit working. To get at that, you will need to dig 
> into the guts of the unit. Given the massive EFC on the Z3801 version of the 
> oscillator, it would take a crazy amount of aging
> to hit limit.
> 
> Bob
> 
> 
>> On Mar 3, 2018, at 1:37 PM, Tom Curlee  wrote:
>> 
>> Since the Z3801A is being discussed, I thought I'd ask about an issue I'm 
>> having with my unit.  I use my Z3801 as my working lab standard for the 
>> usual pieces of RF test equipment.  In the past year or so I've had the unit 
>> drop out of lock and go into standby mode.  Resetting/cycling power would 
>> bring it back into lock for a while, but it generally got worse and now 
>> stays in hold over mode.  LH (thanks Mark Sims!!) reports that everything is 
>> operating normally except that the it has a PLL unlock.  The one highly 
>> suspicious item is that the DAC is at 99.996902% - full output.
>> The unit shows it has over 94.5K hours run time, so I suspect that the OCXO 
>> has aged to the point that the EFC can't pull it into lock.  I disassembled 
>> the OCXO to see if it had a trimmer capacitor like the standard 10811 units. 
>>  After removing the outer case and foam insulation, I see that the outer 
>> heater is o

Re: [time-nuts] 50 ohm drivers

[Bob kb8tq]

Hi

We have gone over CMOS 50 ohm line driving a bunch of times. Check the archives 
for all
of the various opinions. A quick summary:

If you are driving CMOS, the output swing does not have to hit 99% of the 
supply. You
can do a pretty good job with gates in parallel and no source termination. 

If you want both source and load termination *and* want 5V p-p on the load, you 
will
need a 10V p-p source. Good luck if that source ever gets tied to a “normal” 
CMOS 
input. Something made from 2N3904’s and 2N3906’s is probably your best bet 
(along 
with dual supplies) if *really* want to do this.

Source termination (open load) is the low power approach. Cable reflections are 
minimized
and you don’t use a lot of power.

===

If all you are after is sine wave signals, a pair of gates running on 5V will 
give you 20 dbm 
without a lot of effort. There aren’t many applications in the timing world 
that need more
power than that. 

Bob

> On Mar 3, 2018, at 9:17 PM, David C. Partridge 
>  wrote:
> 
> Brice said:
> 
>> . Some fast CMOS devices (esp clock drivers) have an output R close to 50
> ohms as they are intended to drive 50 ohm source terminated transmission
> lines.
> 
> Any in particular that you'd recommend?   I need to drive a 50ohm line and a
> single gate inverter doesn't have the grunt to do so ...
> 
> Thanks
> David
> 
> 
> 
> 
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Re: [time-nuts] LT1016 as a pulse shaper...

[Bob kb8tq]

Hi

If you are simply dealing with 10 MHz sine waves (as many of us are). 

— and —

It’s a “matched” application ( = you know the level / the source and converter 
are tied together) 

— and —

You don’t mind an L network to match increase the Vpp when it goes to the gate

— and —

Once the performance of the circuit is better than any source you can drive it 
with, you 
don’t care. ( = you only care if it degrades the signal) 

You can do a very good job with a biased CMOS gate. Running at 5V (or even 
better 5.5) 
will out perform 3.3V. They are dirt cheap. They are easy to solder down in 
SOT-23 packages. 
They are reasonably robust in terms of overload. They perform pretty well when 
under driven
by modest amounts. They have nice short delay paths.

What’s not to like :)

Bob



> On Mar 3, 2018, at 4:34 PM, Bruce Griffiths  
> wrote:
> 
> Ideally one should use a Collins style optimised cascade of increasing 
> bandwidth and gain limiting stages. The LTC6957 with its selectable input 
> stage bandwidth has a performance that is comparable with the Holzworth sine 
> to CMOS "amplifier" which is better than any comparator by itself. If the 
> amplitude of the input signal is large enough (i.e. input slew rate seen by 
> the gate is large enough) the performance of a single CMOS gate can be very 
> good. However the performance of current CMOS gates degrades in this 
> application with input frequencies of 100MHz and above.
> 
> Measuring the PN performance of CMOS gates used as sine to CMOS converters is 
> on the todo list.
> 
> Bruce
> 
>> 
>>On 04 March 2018 at 06:38 "David C. Partridge" 
>>  wrote:
>> 
>>You might consider using MC74VHC1GT14 or MC74VHC1G14 (Schmitt trigger 
>> inverting buffers) depending on the exact voltage levels.
>> 
>>They are fast (74AC logic fast) single gate devices in SC70 (SOT-353) or 
>> SOT23-5 case and can drive 25mA output if needed.
>> 
>>I've seen documents saying that using fast logic gates can result in 
>> lower jitter/phase noise. Bruce - do you know ?
>> 
>>David
>> 
>>-Original Message-
>>From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Ulf 
>> Kylenfall via time-nuts
>>Sent: 03 March 2018 17:08
>>To: Discussion of Precise Time and Frequency Measurement
>>Subject: [time-nuts] LT1016 as a pulse shaper...
>> 
>>Gentlemen,
>>I have so far been using LT1016 as a pulse shaper and also whenever I 
>> needed toconvert a sine wave into TTL Logic levels. Some hysteresis and all 
>> the decouplingand layout precautions as recommended by LT.
>>Are there any similar or better alternatives out there that could be 
>> usedthat would provide lower jitter and that are less expenceive?
>>Ulf Kylenfall
>>SM6GXV
>> 
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Re: [time-nuts] Z3801A OCXO manual trimming

[Bob kb8tq]

Hi

First off some basics about OCXO’s.

In a single oven design, you have a heater that warms up the entire crystal and 
the guts of the oscillator. It is on all the time and 
it gets things up to a temperature that makes sense for a given crystal. It can 
be adjusted based on manufacturing data or by 
trial and error to match the characteristics of that crystal. 

In a double oven design, you have two ovens that are on all the time. One heats 
up the other one. They both work together to
achieve the end result. The gain of one adds to the gain of the other to give 
an improved result. On some double ovens, the 
entire heat range of the inner oven is only 10’s of degrees ….

In a boosted oven, you have a second heater to get things going when it is very 
cold. This is an unusual approach and rarely 
seen. Its normally easier to just design a bit more power into the main oven 
circuit. In a boosted design, the boost heat goes
away in normal operation at typical temperatures. In normal operation, the gain 
of the boost circuit does not count. 

SO ….

The oscillator in the Z3801 is a boosted 10811. It is boosted to allow them to 
hit a spec of -40C on the unit. At the time it was
designed, there was talk about mounting these things in un-heated boxes 
outdoors. After they got a bit further into all the 
details of the designs … that part went away. The spec still hung around long 
enough to apply to very early designs. 

The net result is that you can pretty much destroy the outer heater stuff and 
the oscillator will work fine. There is no need 
for it in a typical lab. There are some alarm triggers that need to be wired 
“ok” when you do so. The details are in the archives. 

But …

Best guess if your unit is at max EFC = the “real” heater on the 10811 has quit 
working. To get at that, you will need to dig 
into the guts of the unit. Given the massive EFC on the Z3801 version of the 
oscillator, it would take a crazy amount of aging
to hit limit.

Bob


> On Mar 3, 2018, at 1:37 PM, Tom Curlee  wrote:
> 
> Since the Z3801A is being discussed, I thought I'd ask about an issue I'm 
> having with my unit.  I use my Z3801 as my working lab standard for the usual 
> pieces of RF test equipment.  In the past year or so I've had the unit drop 
> out of lock and go into standby mode.  Resetting/cycling power would bring it 
> back into lock for a while, but it generally got worse and now stays in hold 
> over mode.  LH (thanks Mark Sims!!) reports that everything is operating 
> normally except that the it has a PLL unlock.  The one highly suspicious item 
> is that the DAC is at 99.996902% - full output.
> The unit shows it has over 94.5K hours run time, so I suspect that the OCXO 
> has aged to the point that the EFC can't pull it into lock.  I disassembled 
> the OCXO to see if it had a trimmer capacitor like the standard 10811 units.  
> After removing the outer case and foam insulation, I see that the outer 
> heater is one of the thin printed circuit serpentine heaters on what I think 
> is Kapton.  That would need to be peeled off of the case to either get to the 
> hole for the trimmer (if there is one) or to remove the cover for the inner 
> case.
> What I don't understand is the purpose of what looks like another coil or 
> heater wrapped around the Kapton printed circuit heater stuck to the inner 
> case.  This second coil/heater is 2 layers of 1/8" thick red foam wrapped 
> completely around the inner case, with fine copper wires wrapped over each 
> layer.  At least I think there are wires on each layer.  This whole second 
> heater is taped down and I don't want to dig any further until I know a bit 
> more about what I'm doing or find that there isn't a trimmer on the double 
> oven 10811 oscillators.
> Any ideas on the purpose of the outer heater (or whatever it is)?  Does the 
> double oven 10811 have a manual trimmer that I can adjust to bring the 
> oscillator back to the center of the EFC range?  Assuming that I can manually 
> adjust the OCXO back into adjustment range, will there be any issues with the 
> Z3801 performance, things like phase noise, short term stability, etc?
> Any suggestions will be most appreciated.
> Thanks,
> Tom
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Re: [time-nuts] Microsemi up for sale?

[Bob kb8tq]

Hi

There’s a big chunk of sales under the “not semiconductor” side of Microsemi.  
It may
not be big compared to an $8 billion sell price, but it’s not a trivial part of 
the company. 
Exactly what happens to things like the 5071 … we’ll see …..

How the sales policies of one or the other  company impact the new combine 
after a deal 
is always a bit unclear.  It may be a few years before that all gets worked 
out. Not all 
mergers get sorted on the first day. Their statement about $300 Million savings 
in the
third year might suggest a slow-er approach to consolidation. 

Bob

> On Mar 3, 2018, at 12:45 PM, Forrest Christian (List Account) 
>  wrote:
> 
> There is an announcement of the impending purchase on the Microchip website.
> 
> From my perspective this is a good thing as I've been eyeing some of the
> microsemi semiconductor products for some time for use in various designs
> of mine and this is likely to make those products easier to incorporate due
> to the microchip sales policies.
> 
> Not sure how this will work for the finished products they sell as
> historically microchip has only been a semiconductor maker.  It wouldn't be
> surprising to see microchip divest themselves of the assembled product
> line.  I know microchip has divested themselves of small portions of
> acquired businesses in the past when they didn't fit their roadmap.
> 
> 
> 
> On Mar 3, 2018 8:48 AM, "ewkehren via time-nuts"  wrote:
> 
>> The manager many not know but the market does and there have been
>> announcements and the stock is up and for the day the fifth most active of
>> all US markets. At 2 pm #2Bert Kehren
>> 
>> 
>> Sent from my Galaxy Tab® A
>>  Original message From: "Richard (Rick) Karlquist" <
>> rich...@karlquist.com> Date: 3/3/18  9:30 AM  (GMT-05:00) To: Discussion
>> of precise time and frequency measurement , Anders
>> Wallin  Subject: Re: [time-nuts] Microsemi
>> up for sale?
>> I asked the CBT manager at Microsemi about this
>> rumor and he disavowed any knowledge of this.
>> He told me they were making 8 a week (not clear
>> if this is just 5071A's, or includes replacement
>> CBT's).  I don't remember the production ever
>> being anywhere near this level.  The reason
>> for the relatively brisk sales is that the risk
>> of GPS spoofing means that various military and
>> 3 letter agencies need to own dedicated 5071's.
>> With a large installed base of 5071's, there will
>> be a guaranteed market for replacement tubes.
>> The US government considers the 5071A to be of
>> great strategic importance and would be certain
>> to "encourage" its continued production in case
>> of any business reorganization.
>> 
>> When we designed the 5071A twenty five years ago,
>> it seemed that there were two safe bets:
>> 
>> 1.  Working Cs standards (outside the lab) would
>> obsoleted by what HP called "smart clocks" running
>> off of GPS.
>> 
>> 2.  Magnetic state selection, as used in the 5071A,
>> would be replaced by optical pumping.  Len Cutler
>> was heartbroken that HP/Agilent management wouldn't
>> fund this effort.
>> 
>> It turns out that, even now in 2018, optical pumping
>> is not ready for prime time in a working standard
>> because the lasers drift over time.  The 5071A's
>> claim to fame is that you turn it on and it just
>> works ... until it runs out of cesium.  That is
>> another reason the 5071A isn't going away any time soon.
>> 
>> Rick Karlquist N6RK
>> Member: 5071A design team
>> 
>> On 3/3/2018 1:22 AM, Anders Wallin wrote:
>>> Just a change to the last part of the name then ;)
>>> https://www.ft.com/content/10192a2a-1d99-11e8-956a-43db76e69936
>>> "semi" -> "chip"
>>> 
>>> 
>>> On Sat, Jan 27, 2018 at 1:27 AM, Clint Jay  wrote:
>>> 
 Perhaps of interest to the list
 
 https://www.theregister.co.uk/2018/01/25/microsemi/
 
 --
 Clint.
 
 *No trees were harmed in the sending of this mail. However, a large
>> number
 of electrons were greatly inconvenienced.*
 ___
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 mailman/listinfo/time-nuts
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>>> ___
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>> mailman/listinfo/time-nuts
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>>> 
>>> 
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Re: [time-nuts] Setting Z3801 date

[Bob kb8tq]

Hi


> On Mar 2, 2018, at 5:05 PM, Hal Murray  wrote:
> 
> Thorbjørn Pedersen said:
>> Try this:
>> Disconnect antenna.
>> Power off / power on.
>> Set date correctly. (You have the commands?)
>> Connect antenna.
>> Let it survey and stabilize
> 
> That's what I remember.
> 
> The first problem is that the Z3801 doesn't accept dates after 2007.  It 
> gives an E-222 error.  (I forget the text, it's something like out-of-range.) 
> I didn't search for the exact cutoff.  I just edited the year and tried 
> again, so it's somewhere in 2007 or 2008.
> 
> The second problem is that I'm using an "antenna challenged" setup.  So it 
> takes a while to latch on to the satellites.
> 
> But I tried again.  This time, I set it to 2007 and after waiting long 
> enough, GPS got synced and time jumped to the correct time.
> 
> Thanks for the poke.
> 
> ---
> 
> Then I shifted to the KS-24361
> 
> It doesn't complain about the dates it doesn't like.  It just doesn't do 
> anything with them.
> 
> It takes dates after 2007.  I forget the exact break point.
> 
> But when the GPS syncs up, it jumps to 1998.  ??  Sigh.

Even with newer hardware, there are still weird date issues. The simple 
fact that these GPSDO’s keep on running at all is a bit amazing. 

Best to simply use the PPS from the GPSDO and get the date / hours /
minutes / seconds tag  info by some other means. Let that “other means” 
sort out leap seconds and all the other nonsense that is likely to tie things 
in knots. 
We do have a GPS week zero coming up soon ….

Bob


> 
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Efratom 105243-003 10MHz OCXO

[Bob kb8tq]

Hi

Pretty good bet that if it’s a 100K termination it’s a square wave output.
The highest impedance you typically see on a sine wave is about 1K ohms. 
Even that is pretty rare on OCXO’s. 

Bob

> On Mar 2, 2018, at 2:07 PM, David C. Partridge 
>  wrote:
> 
> Does anyone know the specs for the 10MHz output of this?   I'm looking at a
> board using it that is terminating it with a 100kOhm resistor to ground.
> 
> Yeah I know, probe it with a scope - the catch is that the equipment is
> currently well disassembled so I can't do that so easily ...
> 
> Is the output of this beast 0-5V square wave?
> 
> Dave
> 
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Re: [time-nuts] FRK

[Bob kb8tq]

Hi

Judging from the date codes on some of the parts, I’d guess that 
your FRL-L is from 1982. I’m only looking at a few parts that came 
through well enough in the picture to read (and that have what look 
like rational date codes …).

Bob

> On Feb 27, 2018, at 5:30 AM, Attila Kinali  wrote:
> 
> On Mon, 26 Feb 2018 20:04:56 -0800
> "Tom Van Baak"  wrote:
> 
>> Bert's M100 Rb teardown photos are now here:
>> 
>> http://leapsecond.com/bert/m100.htm
> 
> For those, who would like to see the rest of M100/FRK,
> I just took pictures of my FRK-L that was sitting on my
> desk for way too long:
> 
> http://time.kinali.ch/Efratom_FRK-L/
> 
> Yes, there are only the pictures of the four PCBs from outside.
> I didn't want to take the FRK further appart, as that would
> require a soldering iron, and I really should be doing something
> else.
> 
>   Attila Kinali
> 
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Allan variance by sine-wave fitting

[Bob kb8tq]

Hi

Yet another reason to nuke the battery and the A2 board. 

It is amazing just how small a signal can mess things up at the levels involved 
in
a good frequency standard. The old “when in doubt, throw it out” mantra may be
a good one to keep in mind relative to a lot of add on features…. how much does
a PIC-DIV pull compared to the 1 pps section of one of these old beasts (Cs or 
Rb)? 

Lots to think about. 

Bob

> On Feb 26, 2018, at 2:20 PM, Tom Van Baak  wrote:
> 
>> at telling you it was sitting on top of a power transformer. It didn’t 
>> matter a lot
> 
> I did ten runs of various standards that were within a couple of meters of 
> the bench; the TimePod did not move the entire time. Each standard had a 
> different looking PN plot, so I'm pretty sure the 120 Hz spur we see is the 
> 5065A itself, not something in the lab.
> 
> File http://leapsecond.com/tmp/2018b-Ralph-2-pn.png is attached.
> 
> Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What 
> do you think that is? On a hunch I opened the front panel and reset the 
> blinking amber battery alarm lamp, and voila, that noise went away. Makes 
> sense when you think of the power variations associated with a blinking 
> incandescent lamp.
> 
> /tvb
> 
> - Original Message - 
> From: "Bob kb8tq" 
> To: "Tom Van Baak" ; "Discussion of precise time and 
> frequency measurement" 
> Sent: Monday, February 26, 2018 7:00 AM
> Subject: Re: [time-nuts] Allan variance by sine-wave fitting
> 
> 
> Hi
> 
> One of the TimePods that I had access to in the past was particularly good
> at telling you it was sitting on top of a power transformer. It didn’t matter 
> a lot
> which instrument the power transformer was in. For some weird reason it
> was a good magnetometer at line frequencies. I never bothered to send it
> back for analysis. Simply moving it onto the bench top (rather than stacked 
> on top of this or that) would take care of the issue.
> 
> As far as I could tell, it was just the one unit that had the issue. None of 
> the
> others in the fleet of TimePods seemed to behave this way. Given that they
> normally are very good at rejecting all sorts of crud and ground loops, it 
> was 
> somewhat odd to see. 
> 
> Bob
> 
>> On Feb 26, 2018, at 7:13 AM, Tom Van Baak  wrote:
>> 
>>> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?
>> 
>> The ADEV wiggles aren't visible with normal tau 1 s measurements. But since 
>> the TimePod can go down to tau 1 ms, when I first measure a standard I like 
>> to run at that resolution so effects like this show up. Once that's done, 1 
>> ms resolution is overkill.
>> 
>> In this case it appears to be power supply noise. Attached are the ADEV, PN, 
>> and TDEV plots.
>> 
>> The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing 
>> at 60 Hz. When integrated these cause the bumps you see in the ADEV plot. 
>> It's best seen as a bump at ~4 ms in the TDEV plot.
>> 
>> Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 
>> Hz.
>> 
>> /tvb
>> <5065a-adev.png><5065a-pn.png><5065a-tdev.png>
> 
> <2018b-Ralph-2-pn.png>___
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Re: [time-nuts] Allan variance by sine-wave fitting

[Bob kb8tq]

Hi

One of the TimePods that I had access to in the past was particularly good
at telling you it was sitting on top of a power transformer. It didn’t matter a 
lot
which instrument the power transformer was in. For some weird reason it
was a good magnetometer at line frequencies. I never bothered to send it
back for analysis. Simply moving it onto the bench top (rather than stacked 
on top of this or that) would take care of the issue.

As far as I could tell, it was just the one unit that had the issue. None of the
others in the fleet of TimePods seemed to behave this way. Given that they
normally are very good at rejecting all sorts of crud and ground loops, it was 
somewhat odd to see. 

Bob

> On Feb 26, 2018, at 7:13 AM, Tom Van Baak  wrote:
> 
>> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?
> 
> The ADEV wiggles aren't visible with normal tau 1 s measurements. But since 
> the TimePod can go down to tau 1 ms, when I first measure a standard I like 
> to run at that resolution so effects like this show up. Once that's done, 1 
> ms resolution is overkill.
> 
> In this case it appears to be power supply noise. Attached are the ADEV, PN, 
> and TDEV plots.
> 
> The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing 
> at 60 Hz. When integrated these cause the bumps you see in the ADEV plot. 
> It's best seen as a bump at ~4 ms in the TDEV plot.
> 
> Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 Hz.
> 
> /tvb
> <5065a-adev.png><5065a-pn.png><5065a-tdev.png>___
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Re: [time-nuts] Beware the Casio WaveCeptor analog watch

[Bob kb8tq]

Hi

I’ve had the Citizen “Atomic” analog watches for quite a few years. The solar 
powered
versions have gotten a bit better over the years. They nave never had a “hand 
slip” 
problem that I have noticed.

Bob

> On Feb 25, 2018, at 6:52 PM, Skip Withrow  wrote:
> 
> Hello Time-Nuts,
> 
> For many years I owned a Casio WaveCeptor digital watch and like it a
> lot.  The down side was that the battery had to be replaced every few
> years.  And since I had worn it for many years, the plastic case and
> crystal had taken quite a beating.  Finally, the pin holder that
> secures the band broke - end of watch (except as a 'pocket' watch).
> 
> So, I went out and bought a solar powered analog version of the
> WaveCeptor (and vowed not to take it caving).  However, several months
> ago I needed to take an action at an exact time (not ebay) which was a
> miserable fail.  I found that the watch was over a minute off.
> 
> I went back and explored the watch manual and found that there is a
> procedure to sync the minute and second hands.  I did this and after
> syncing to WWVB all was good.
> 
> Now, a couple of months later I needed the precise time again.
> However I checked my watch before hand and found that it was 8 seconds
> off.  Ahrg!
> 
> It appears that the stepper motor position of the second and minute
> hands can be jarred out of sync with normal wear bumps and shocks.
> The trouble is you don't know when it happens (unless you check your
> watch against a trusted source often).
> 
> Now I'm seriously considering buying a solar version of the digital
> watch to get rid of the problem.
> 
> Regards,
> Skip Withrow
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Re: [time-nuts] Replacement Backup Battery for 5065A?

[Bob kb8tq]

Hi

One very practical option: Pull the battery and don’t replace it. When the unit
next comes out of storage, run it on a very normal UPS. The battery was
a fine idea back in the era when this gear was newly designed. These days,
the better option is an external “bulk” backup. 

If you are going to run 24/7/365, the charger circuit in all of these gizmos (HP
liked battery backup …..) is not the best for long term battery survival. It’s 
not
awful, but it’s not what you would do today. If the unit goes into storage most 
of 
the time, batteries really don’t like that very much either. 

Bob

> On Feb 25, 2018, at 2:41 PM, Stan  wrote:
> 
> With all this recent 5065A talk I decided to pull mine out of storage and 
> fire it up. After a little time to let everything warm up and settle in, I'm 
> happy to report that it's working just fine!
> 
> My 5065A has the battery backup option, and the battery is the original one 
> (1420-0066, Energy Sales p/n ES710, 25.2V 1.4 Ah). Not surprisingly, the 
> battery is quite dead. Does anyone any insight about installing a more modern 
> battery (SLA or NiMH, perhaps) that will fit in the battery compartment in 
> the 5065A?
> 
> I've looked at a few small 12V/2.2Ah SLA batteries that are physically small 
> enough that I should be able to fit a couple in the enclosure and connect 
> them in series to get 24 volts out, but I want to wait until either I have 
> assurance from someone with more experience than I that this will actually 
> work, or a better idea about a more suitable replacement.
> 
> Thanks,
> Stan
> 
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Re: [time-nuts] Replacement A9 boards for the HP 5065A

[Bob kb8tq]

Hi

Teflon is the traditional “best of the best” for integrator caps. Simply 
finding 
any plastic cap  (other than a motor start device) up around 5 uf is not that 
easy 
these days.  As mentioned by PHK, being sure it is what it’s supposed to be ….
good luck. 

Bob

> On Feb 24, 2018, at 6:45 PM,   wrote:
> 
> Hi,
> 
> I'm working to make some replacement A9 boards for the HP 5065A to the
> new style schematic.
> 
> Will share the Gerber file when done.
> 
> The integrator capacitor is a 1986 vintage TRW 5.0ufd 50V 10% .42"DX1.0"L
> axial.
> 
> Of course it has an HP part number and no manufactures #.
> 
> Any guess as to what type it is?
> 
> Polycarbonate, polypropylene, ???
> 
> Just wanting to find a good modern replacement for its use. (Integrator
> with a 50ms time constant.)
> 
> Thanks,
> 
> Corby
> 
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Re: [time-nuts] Curious, how many t-nuts have 5065A

[Bob kb8tq]

Hi

The “pickup only” part of the deal would be a bit of an issue for some of us :)

Bob

> On Feb 24, 2018, at 5:46 AM, George Atkinson via time-nuts 
>  wrote:
> 
> There is one on UK ebay at the moment but its not being given away. From the 
> one partial photograph it looks a bit rough.
> 
> https://www.ebay.co.uk/itm/HP-5065A-Rubidium-Frequency-Standard/183057846558?
> 
> Robert G8RPI.
> 
>> 
>>On 24 February 2018 at 10:02 John Miles  wrote:
>> 
 
>>>Hi
>>> 
>>>Well, if anybody else is “giving away” 5065’s I’d certainly be 
>>> willing to
>>>“accept”
>>>one :)
>>> 
>>>Bob
>>> 
 
>>Be careful what you wish for. :) The unit Pete is talking about is a 
>> 1969-era model, in nice overall shape but with the usual bad capacitors on 
>> the oven controller board. The lamp oven winding should be about 50 ohms 
>> cold, but is closer to a dead short. It will take a LOT of work to restore 
>> to working condition.
>> 
>>The failed controller ran long enough to smoke a 1.5-ohm 1W resistor, 
>> 1N400-something diode, and eventually the 1A line fuse ( 
>> http://www.ke5fx.com/5065A_A11_sm.jpg ). Needless to say the lamp PCB looks 
>> like something out of Fukushima. It'll need to be rebuilt from scratch after 
>> rewinding the heater.
>> 
>>Seriously -- anyone with a 5065A who hasn't checked/replaced the caps on 
>> A11, don't let this happen to you. They aren't making any more of these 
>> puppies. If the caps on that board are original, don't bother to check them, 
>> just replace them, as Luciano suggests at 
>> http://www.timeok.it/hp5065a-corner-3/. No need for exotic parts, just put 
>> in whatever you have that is somewhere close to the original values.
>> 
>>Not a bad idea to verify the ESR of the new parts you're installing as 
>> well.
>> 
>>-- john, KE5FX
>>Miles Design LLC
>> 
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Re: [time-nuts] Curious, how many t-nuts have 5065A

[Bob kb8tq]

Hi

Well, if anybody else is “giving away” 5065’s I’d certainly be willing to 
“accept”
one :)

Bob

> On Feb 23, 2018, at 10:25 PM, Pete Lancashire  wrote:
> 
> Wow, don't know why but more than I expected. I no longer do, but if the
> person who I gave it to wants and is on TN can.
> 
> -pet
> 
> On Fri, Feb 23, 2018 at 6:23 PM,  wrote:
> 
>> Hi,
>> 
>> My current Tally of  "Known" HP 5065A is 120 units!
>> 
>> Cheers,
>> 
>> Corby
>> 
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Re: [time-nuts] HP 5065A super

[Bob kb8tq]

Hi

> On Feb 23, 2018, at 6:17 PM, jimlux  wrote:
> 
> On 2/23/18 1:33 PM, Bob kb8tq wrote:
>> Hi
>>> On Feb 23, 2018, at 4:23 PM, Attila Kinali  wrote:
>>> 
>>> Hoi Bob,
>>> 
>>> On Thu, 22 Feb 2018 21:58:09 -0500
>>> Bob kb8tq  wrote:
>>> 
>>>> The same nickel plating effect gets into a lot of things. If you are 
>>>> shopping for very
>>>> low IMD connectors, nickel plating is out. Things get non-linear (to a 
>>>> very slight
>>>> degree) when it is present. If -180 db is the goal for those spurs, you 
>>>> might only
>>>> hit -120 db with the nickel connectors …..
>>> 
>>> Interesting. About what frequency range are you talking?
>> UHF up into microwaves. It was part of a lecture back when I was in school … 
>> I
>> assume the basic physics hasn’t changed since then :)
> 
> 
> Passive intermodulation distortion? What is the physics... hysteresis curves 
> in the magnetization of the nickel is what I would suspect.
> 

It turns out that the nickel’s really awful magnetic properties at RF get it 
into all sorts
of problems. More or less, the issue is the non-linear field response in the 
vicinity
of the nickel. You go from “reasonable skin depth” to “don’t go there” in zero 
distance
when you hit the nickel plating. Past that it gets a bit complicated and it was 
a very long
time ago ….

Bob



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Re: [time-nuts] HP 5065A super

[Bob kb8tq]

Hi

> On Feb 23, 2018, at 4:23 PM, Attila Kinali  wrote:
> 
> Hoi Bob,
> 
> On Thu, 22 Feb 2018 21:58:09 -0500
> Bob kb8tq  wrote:
> 
>> The same nickel plating effect gets into a lot of things. If you are 
>> shopping for very 
>> low IMD connectors, nickel plating is out. Things get non-linear (to a very 
>> slight 
>> degree) when it is present. If -180 db is the goal for those spurs, you 
>> might only
>> hit -120 db with the nickel connectors …..
> 
> Interesting. About what frequency range are you talking?

UHF up into microwaves. It was part of a lecture back when I was in school … I 
assume the basic physics hasn’t changed since then :)

Bob


> 
>   Attila Kinali
> 
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Chinese made eBay antenna breakdown.

[Bob kb8tq]

HI

> On Feb 22, 2018, at 8:46 PM, John Green  wrote:
> 
> I didn't mean to imply that all Chinese made products are garbage. But,
> some of them are. And, has been said, that is because people want to pay
> the absolute lowest prices for stuff. The company I recently retired from
> has a long history with Chinese competition. We had a product that had but
> one American competitor. We thought, foolishly, that being a low cost item
> with a modest annual sales volume, he wouldn't have to worry about foreign
> competition. We didn't take into account our main customer who would slit
> your throat over a tenth of a cent. It wasn't long before we began seeing
> competing products from China. At first, they either did what was cheapest
> without regard for RF concerns, or they copied us exactly. However, in
> recent years, I have seen Chinese products that show the result of some
> real engineering talent. In some cases, they are better than ours. These
> are parts that are molded in plastic, and the foreign competition certainly
> knows a lot more about molding than we do. Their parts are cosmetically
> superior to ours in almost every instance. Lately, I have suggested that we
> obtain some of these products and copy them. That is what it has come to.
> I noticed that the enable input is tied to the voltage input. I thought
> that it may have seen too high a voltage, but the specs say it should be
> able to take 20 volts.

Enable tied to Vin is pretty much “the way it’s done” with a lot of linear 
voltage regulators. I have never seen a failure traced back to an enable 
over-voltage. 

I *do* believe that the bypass caps could be the problem. I’ve seen it before.
Tired Old Bob grabs the reel of 0.047uf devices rather than the 0.47 parts
when he loads the pick and place …. It happens all over the world. 


> So, I don't really see any reason it should have
> failed. I will put a new 3.3 volt regulator in and see if I can get it to
> work. I want to do comparisons to other antennas. The rest of the circuitry
> looks OK to me.

You might try feeding it a regulated 3.3V and see if the beast works or not. 

Bob


> There is one SAW bandpass filter per band. Not like the Trimble, but should
> work fine for my purposes.
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Re: [time-nuts] HP 5065A super

[Bob kb8tq]

Hi

The same nickel plating effect gets into a lot of things. If you are shopping 
for very 
low IMD connectors, nickel plating is out. Things get non-linear (to a very 
slight 
degree) when it is present. If -180 db is the goal for those spurs, you might 
only
hit -120 db with the nickel connectors …..

Bob

> On Feb 22, 2018, at 9:15 PM, jimlux  wrote:
> 
> On 2/22/18 12:29 PM, Leo Bodnar wrote:
>> Here is ENIG fact that is not widely known at the moment but which some 
>> might find useful.
>> I could not understand why I get better TDR and insertion loss results from 
>> solder-mask covered microstrip transmission lines than from otherwise 
>> identical microstrips on the same substrate with soldermask removed and, 
>> therefore, covered with ENIG.
>> Gold can't be bad, right? As it turns out, even gold coin has two sides to 
>> it.
>> I have found that Shlepnev and McMorrow conducted extensive research and 
>> published data, some of which is presented here 
>> http://www.simberian.com/Presentations/NickelCharacterizationPresentation_emc2011.pdf
> 
> the ever useful http://www.microwaves101.com/ site has an excellent 
> discussion of this under the "skin effect" heading.
> 
> 
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Re: [time-nuts] Teardown of Chinese made eBay GPS antenna.

[Bob kb8tq]

India

> On Feb 22, 2018, at 5:37 PM, Van Horn, David 
>  wrote:
> 
> 
> "Some  of you are to young to remember when Javanese products were considered 
> junk same storyBert Kehren"
> 
> I've lived through Japan, Taiwan, and now China.  Who's next?  😊
> 
> 
> 
> 
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Re: [time-nuts] Teardown of Chinese made eBay GPS antenna.

[Bob kb8tq]

Hi

As mentioned in another post, the part does claim to have thermal limit
built in. They appear to pulse test them at 150 ma and 16V so there is
indeed *something* that would suggest operation at 12V would be ok. 
I’d guess that the thermal regulation spec applies up to 16V and past that
you are on your own…..

I’d take a look at the bypass caps on the regulator. Looking back at the 
original test data, it may have simply gone unstable at the higher voltage.
A 0.1 uf on the input and 0.47 uf on the output seem to be the minimums. 

Bob

> On Feb 22, 2018, at 2:48 PM, John Green  wrote:
> 
> For those who have been following the saga of the Chinese made, eBay
> purchased antenna that failed, I may have an answer as to why it failed.
> I had to destructively disassemble it. I just could not get it apart any
> other way. I used a Chinese version of a Dremel tool with a metal saw
> blade. After making a huge mess with plastic particles everywhere, it
> revealed a circular FR4 board with two patch antennas mounted, one atop the
> other. I assume the smaller one to be the L1, and the larger to be L2. This
> part looks almost identical to the Trimble Microcentered antenna I worked
> on recently. On the back side of this is a metal shield  about 3 by 3
> inches soldered to the circular FR4 board. I switched to a abrasive wheel
> and took off some of the solder holding the shield to the board. Then,
> using a small screw driver, I went around the shield breaking the solder
> loose. The shield off revealed that the coax goes to some capacitors that
> couple RF out and through an inductor with some capacitors to ground and
> finally to a SOT23-5 package labelled LK33. This appears to be a Micrel
> MIC5203 3.3 volt regulator. It is shorted on the input side. I believe that
> putting anything over 7.5 volts on the input exceeded the power dissipation
> rating and caused it to fail. I plan on wiring up a more robust 3.3 volt
> regulator in its place and trying again. It looks like I will be able to re
> solder the shield back. The watertight integrity is gone for good. I think
> I can find a plastic box I can mount it in so I can at least experiment
> with it. I have sent a message to the seller detailing my findings. The
> Micrel part lists a 20 volt maximum input voltage, so in theory at least,
> this might have worked, and there might be some of these out there that
> don't fail.
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Re: [time-nuts] HP 5065A super

[Bob kb8tq]

Hi

The control loop (of which A9 is a part) ultimately locks the OCXO in the 5065 
to the Rb 
transition. Gain in the control loop suppresses the noise of the OCXO, making 
it’s ADEV
better than it would have been stand alone. 

Ok so far? Bob’s not off the tracks (yet)? 

The various processes that create ADEV (or whatever you want to call it) on the 
OCXO 
could be translated back to an “equivalent EFC noise” number at various 
frequencies. 
More or less, assume an ideal OCXO and blame all the problems on some little 
noise
source in series with the EFC line. Very much like blaming all the noise in an 
op amp on
the input stage. 

Still ok (if a bit unconventional) ? 

At this point one should be able to sum the magic EFC noise with op amp noise 
or whatever
else you are worried about and compare their magnitudes. If one is 1/100th of 
the other 
then maybe it’s not the thing to worry about. Yes, you could carry it on 
through the various 
control loop equations and get things even more correct. 

No, I haven’t done all of this, but it seems to be a way to come up with a 
fairly detailed answer
to “what’s good enough” in the control loop, 

Bob

> On Feb 22, 2018, at 9:04 AM, Charles Steinmetz  wrote:
> 
>> Ais the LT1793 the best choice the time constant is 0.05 seconds with a 
>> 10 K resistor and 5 uF Capacitor
>> Bshould we add resistors and decoupling on the + - 15 volt op amp 
>> supplies
>> CGold plating the edge connecter,  does any one know a reasonable 
>> source, or is doing it at home an option and if yes, how best way to do so.
> 
> A.  The 1793 is a good choice.  You should look at the LT1012 also.  The 
> headlines on the 1793 datasheet suggest it is significantly quieter than the 
> 1012.  HOWEVER: you are particularly interested in frequencies well below 
> 10Hz, and due to an extremely low 1/f noise corner, the 1012 is actually 5x 
> quieter than the 1793 between 0.1 and 10 Hz (0.5uV for the 1012 p-p vs. 2.4uV 
> p-p for the 1793).  The 1012 can also be overcompensated, which could be a 
> significant advantage in this application.  [Note that the 1793 has lower 
> input current noise than the 1012, but that is irrelevant in the HP circuit 
> because of the relatively low impedances at the op-amp inputs.  Because of 
> that, the input voltage noise dominates the total noise.]
> 
> B.  If you do this, the decoupling has to be good down through at least 
> milliHz, maybe even microHz.  That would require capacitors in the 1F range 
> with suitable decoupling resistors (100 ohms or below).  The op amp is fed by 
> dedicated +/- regulators, so you'll get the best result by just using the 
> lowest-noise regulators available.  That means the LT3042 for V+.  You will 
> have to pore through datasheets to find the lowest-noise negative regulator 
> available today (as above, paying particular attention to the noise specs 
> below 1Hz).
> 
> C.  You normally just tell the board house to plate the edge fingers. It is 
> not outrageously expensive.  OR, here is another, heretical suggestion:  I 
> have designed a number of plug-in daughterboards using ENIG finish on the 
> whole board, including the edge fingers.  *NOTE* this is an "off-label" use 
> of ENIG finish.  The board house I used for the first batch of ENIG-plated 
> fingers (ITEAD Studio) gave me very robust plating, so I have continued to 
> use them for boards with ENIG-plated edge fingers.
> 
> I tested a number of the cards over more than 100 insertion-removal cycles, 
> and viewed under magnification there was very little wear and absolutely no 
> nickel or copper showing ("ENIG" stands for "electroless nickel immersion 
> gold," meaning the copper is coated first with nickle and then with gold.  
> The boards I've tested have not worn through the gold even after >100 
> insertion-removal cycles -- way, way more than any plug-in board is likely 
> ever to see.)
> 
> *NB:*  ENIG plating varies widely from one board house to another, and very 
> likely varies somewhat from one batch to another at any particular board 
> house, so YMMV!!!  I've done a dozen or so projects with ENIG-plated fingers 
> using ITEAD Studio, and have been very pleased with the results each time.
> 
> Charles
> 
> 
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Re: [time-nuts] LED instead of discharge lamp for Rb vapor cell standards

[Bob kb8tq]

Hi


> On Feb 22, 2018, at 8:22 AM, Attila Kinali  wrote:
> 
> On Wed, 21 Feb 2018 18:10:17 +
> "Poul-Henning Kamp"  wrote:
> 
>>> So the Rb85 "notch" filter might not get rid of all the unwanted light
>>> and some of this might depopulate the excited state of the Rb87
>>> that are in the RF cavity.
>> 
>> I have a hard time seeing how you can not get worse S/N that way.
> 
> 
> Well, the question is how much? Keep in mind that an Rb lamp is
> anything but a clean light source. 

The point is that it’s clean where it matters. It does not dump a bunch of
energy into the transitions that you want to avoid.

Bob

> 
>> If you want to do it with a LED, I think it needs to be a stabilized
>> LED-Laser.
> 
> The problem with a Laser is that you need to lock it to the
> right line. This requires either some significant change to the
> electronics of the Rb standard, or an additional vapor cell and
> some optics to lock it to that cell. Neither is trivial (apparently,
> according to the papers I've read, not difficult, but I don't trust
> that until I have tried myself).
> 
>   Attila Kinali
> 
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] LED instead of discharge lamp for Rb vapor cell standards

[Bob kb8tq]

Hi

There are a number of papers on LED / Laser excitation of Rb cells (and 
other gas cells). They go back quite a ways. The gotcha (as pointed out 
in PHK’s post) is that you need to stabilize the LED source. Doing that is 
a bit complex. Doing that so that the result beats a gas lamp is a bit more 
involved than just getting it working. Part of the problem is that there are 
a number of transitions you can hit and you only want the “right” one. The
next layer is the signal to noise once you get on the right transition 

Based on the examples I have seen on my bench, the ADEV of a typical 
laser based unit is not super duper compared to Corby’s modified units. 
In defense of the designers, they normally are targeting small size rather 
than super stability. That’s what the market wants to buy …. If you are 
spending tens (or hundreds) of millions of dollars, you focus on a product 
you can sell a lot of. 

Bob

> On Feb 21, 2018, at 12:49 PM, Attila Kinali  wrote:
> 
> Moin,
> 
> Has anyone ever tried using a LED instead of a discharge lamp for Rb 
> standards?
> There are quite a few and very cheap 780nm IR LEDs available. They usually
> have a line width in the order of 20nm to 50nm (FWHM). This means that they
> still need the Rb85 filter, but they would not produce all those spectral 
> lines
> that the discharge lamp has, thus one could get rid of the (not so cheap)
> optical filter that Corby uses for the super-5065. 
> 
> The one thing I am not sure about is the filter efficiency of Rb85.
> Because now the light isn't two discrete lines from the Rb87 lamb
> of which one needs to be masked, but a continuous and wide spectrum.
> So the Rb85 "notch" filter might not get rid of all the unwanted light
> and some of this might depopulate the excited state of the Rb87
> that are in the RF cavity.
> 
> As a side-effect, you also get easier regulation of the light intensity
> of the LED, thus potentially less instability due to light-shift variation.
> Beside the LED operation being much simpler than that of a discharge lamp
> and overall less heat dissipation.
> 
>   Attila Kinali
> 
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] The "NAKED" 5065A optical unit

[Bob kb8tq]

Hi

Indeed very cool pictures.

If the lamp is like most gas bulb lights, there is indeed a “strike voltage” 
required
to get things going (or an RF excitation). There inevitably is some temperature 
dependence as well. A constant current driver might be the better bet.

Bob

> On Feb 20, 2018, at 4:30 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message , cdel...@juno.com writes:
> 
>> Here is a PIX of the optical unit from a 5065A totally removed from the
>> shield assembly.
> 
> Nice!
> 
>> Left to right:
>> 
>> Lamp assy
>> lamp oven cylinder
>> lamp reflector/convection block/diffuser
>> Rb85 filter cell
> 
> It looks like there is a square filter of some kind
> between the reflector and the filter cell ?
> 
> I've been thinking a little bit more about power for the lamp assembly.
> 
> Since I have the lamp on the bench-supply I am going to plot lamp
> voltage vs. photo-I because it looks like a threshold rather than
> a linear relationship.
> 
> If that is the case, I think it will make sense to give the lamp
> its own adjustable voltage regulator (LM317), so the power can be
> reduced to what is optimal/necessary without having to take the
> lamp apart and change a resistor.
> 
> A 1R resistor between the 22-30V supply and the LM317 will make it
> easy to monitor lamp current, and a 300mA short-circuit protection
> is a nice bonus.
> 
> If need be, the regulator could start out at 20V and drop to something
> lower in a matter of minutes.
> 
> Actually, now that I think about it, I should try to measure if it
> is gives better stability if I drive the lamp with constant current,
> constant power, constant voltage or constant photo-I...
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Looking for some Frequency Electronics info....

[Bob kb8tq]

Hi

If it works like the unit that replaced it, it has a level detect on the 
external
input that rejects signals below some threshold. It either locks up to the 
internal
standard or to the external input. All of the outputs are in the 7 to 13 dim 
range
when operating. 

The fault circuit looks at the OCXO warmup indicators as well as things like 
PLL out of range to pop the fault light. It should have timers to qualify all 
of 
this stuff. 

There also *may* be an option to pass the external standard through to the
low frequency output connector ( = no PLL on the low frequency). It depends
a bit on which application it was going into. 

Bob

> On Feb 19, 2018, at 11:35 PM, Arthur Dent  wrote:
> 
> Some time ago bought one on Ebay for under $50 just because it looked
> interesting. It isn't a prototype but most of the FEI units probably
> had limited production. It seemed to be more complicated than I
> expected it to be but if I understood it better it would make more
> sense.
> 
> The 10Mhz board is enabled/disabled by the int/external switch. The
> 10Mhz output and EFC from this oscillator board are connected to the
> interface board. I believe that these 2 boards and the switch/connector
> on the back allow you to use the internal 10Mhz oscillator to output
> 10Mhz and send 10Mhz on (perhaps a connector marked J4) to a comparator
> board. If I recall this part of the unit should work independant of
> the other boards.
> 
> The comparator board is probably a PLL that compares its 10Mhz input
> with its 100Mhz input and outputs an EFC voltage to the 100Mhz
> oscillator. the 100MHz oscillator output goes to the amplifier board
> with two 100Mhz outputs on the back panel. There is also a 100Mhz
> signal that goes back to the PLL board so the 100Mhz is locked to
> the 10Mhz oscillator or an external input (if I remember correctly).
> 
> There are also other wires that control the light and other stuff
> but I didn't trace them out and my unit seems to work as intended.
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Re: [time-nuts] Rubidium for HP 53131A

[Bob kb8tq]

Hi

Be careful about air flow. Those counters have heat issues even in the stock 
configuration.
The Rb is a bit of a power hog so it heats up as well. Not saying it won’t 
work, only that
you need to be sure the air is moving in the right places.

Bob

> On Feb 19, 2018, at 4:18 PM, Skip Withrow  wrote:
> 
> Hello Time-Nuts,
> 
> A while back I acquired an HP 53131A, and a bit later added one of the
> Chinese knock-off 3GHz prescalers.  Makes for a nice counter except
> for the very poor standard timebase.  So, While researching the Option
> 010 and finding how outrageous the prices are running I found an
> Option 010 DIY project.  It occurred to me that I could just
> substitute a Symmetricom X72 rubidium oscillator for the ovenized
> OCXO.
> 
> It came out really nice (and is much better than an Option 010 - at
> least for anything over 10-100 seconds).  I have a header so that I
> can calibrate the oscillator over the serial port (a one-time exercise
> I imagine).  And I added a LOCK indicator in one of the removable
> plugs right above the reference BNCs on the back panel.  Both the
> oscillator and the LOCK light are powered from the always on +12V so
> there is no warmup when the counter is turned on and the LOCK
> indication works when the counter is powered off.  And since the fan
> runs 24/7 I'm not too worried about the X72 overheating.
> 
> All the extra hardware is mounted on a simple 'L' shaped aluminum
> plate that bolts where the Option 010 mounts to the chassis side rail.
> I used a 16-pin flat cable that plugs directly into the 53131A main
> board.  The only modification that was made to the stock counter was
> to drill the hole in the plastic plug for the LOCK light.
> 
> Now the Reference Out can also be used to drive other devices as well
> (with reasonable accuracy).
> 
> Relatively easy project that can be assembled in a weekend .
> 
> Pictures are attached.
> 
> Skip Withrow
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Re: [time-nuts] Symmetricom 58532A GPS Antenna : Launch3 Surplus

[Bob kb8tq]

Hi

One of the other variables in all this is the type of coax you use. The “best 
stuff” is flooded with silicon goop that is an absolute mess to deal with. 
It also will have a jacket on it that withstands UV better than the typical 
stuff. You may or may not need the UV protection, but you get it anyway. 

No, this will not help the innards of the antenna. Water (and salt and whatever 
..)
moves both ways from the connector. 

Bob

> On Feb 18, 2018, at 12:19 PM, Angus via time-nuts  wrote:
> 
> 
> Hi,
> 
> The problem is that because of the type and position of the connectors
> on so many of the Trimble, Novatel, etc., antennas, it's practically
> impossible to seal them with something easily removed like self
> amalgamating tape. Antennas like the 58532A make life a lot simpler by
> hiding the connector up a tube.
> 
> The idea seems to be that nickel plated brass TNC connectors are all
> that's needed, but it's not that simple - particularly for coastal or
> marine use. 
> In fairness, even a lot of manufacturers of dedicated marine gear
> vastly underestimate where water can get to and what damage it will do
> - at least they did back in the 1990's when I was working with that
> stuff. It could take a very long time (if ever) for them to be
> convinced that what works in their nice little environmental test
> chamber could possibly fail out in the big bad world!
> 
>> However, for the past 10 years or so I have been using double wall 
>> adhesive lined heat shrink tubing. My local electronics and electrical 
>> supplies carry this product and it is not that expensive. This I find 
>> both quicker to install, neater, more reliable, and much easier to 
>> remove than the rubber tape followed by vinyl tape method.
> 
> I was not convinced about adhesive lined heat shrink when I tried it
> since it usually didn't seem to bond well enough to withstand bending,
> although I've not tried the newer types. It probably wasn't the
> premium quality tubing Adrian mentioned either.
> The PIB based self amalgamating tapes had to be well taped up and did
> not like oil, but the EPDM and PE ones we used were less sensitive
> although they still needed to be taped up.
> 
> Since I wanted to be able to swap them easily, I eventually got some
> Amphenol ARC TNC connectors for the GPS antennas, but still chickened
> out of using the heat shrink supplied and went for self amalgamating
> tape instead for sealing the crimp. I really should try the unused
> heat shrink on something to see how it does.
> 
> Angus.
> 
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Re: [time-nuts] GPS Talking Clock

[Bob kb8tq]

Hi


> On Feb 17, 2018, at 11:01 PM, Nick Sayer via time-nuts  
> wrote:
> 
> It’s been a while since I’ve posted here, but I’ve had a bunch of irons in 
> the fire. I’m working on adapting my GPSDO to the ECS ECOC-2522, which the 
> manufacturer claims has a short term ADEV in the low -12s, but I haven’t 
> gotten it doing that well yet.

At least on this data sheet: 

https://www.ecsxtal.com/store/pdf/ECOC-2522.pdf 


They don’t say much of anything at all about ADEV. OCXO’s in the little 
packages are rarely super stars when it comes to ADEV.

Bob



> 
> But one thing that is ready (well, electronically it is - I’m still working 
> on the laser cut case for it) is my GPS Talking Clock.
> 
> The story is that I called the USNO time number at midnight on New Year’s 
> Day, but the wife noted that it was the wrong time zone. That got me 
> thinking, and I wound up designing a GPS driven simulacrum.
> 
> It’s an ATXmega32E5 with the usual Venus838 timing module and a µSD card 
> slot. The card is loaded with audio samples that the 32E5 plays back through 
> its DAC. I got double-buffered DMA to work to feed the DAC, so audio playback 
> is a largely background task. I just have to fill the buffer with the next 
> block from the file every ~30 ms or so. The ticks and beeps are generated 
> from an on board 1 kHz source and are turned on by a PPS ISR, so they’re as 
> accurate as possible. The whole thing is basically as accurate as an aural 
> clock can be - the latency induced by the speed of sound has far more impact 
> than anything else.
> 
> While the audio is turned off, the clock can also do Westminster Quarters (or 
> any other chime you wish to load in).
> 
> The µSD card is FAT formatted and the audio sample files are easy to make 
> with ‘sox’ (raw, 1 channel, 8 kHz, 16 bit little-endian, unsigned), so 
> there’s no reason you can’t substitute my voice with your own, or make your 
> own chimes.
> 
> It’s available at https://www.tindie.com/products/nsayer/gps-talking-clock/
> 
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Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi

I think you probably will have to move up to around $500 or so (and 
still shop pretty hard) to find a Zephyr Geodetic 2 in excellent condition. 
A Novatel 703 Pinwheel would also be on the list of things to watch for. 

If you find a proper (L1 / L2 / L5 ) GNSS receiver with a pps out in working 
shape for $500, go for it. They tend to be quite a bit above that price. Most
of what is in the $400 to $1000 range are L1 / L2 GPS only devices. Even
with them, finding one that will do timing is a bit tough. 

Bob

> On Feb 17, 2018, at 3:07 PM, Trevor N.  wrote:
> 
> It's still extremely rare to see a low-priced used triple-frequency
> antenna on ebay. For less than US$300 I've only spotted extremely
> beat-up Zephyr Geodetic Model 2s and a few Leica AX1203+ GNSS (only
> the "+GNSS" model is triple-frequency) (there is one up right now).
> 
>  I've seen at least one Zephyr 2 listing that had a picture of a
> Zephyr 1 attached (look for the bigger bump in the top center on the
> model 2).
> 
> I have yet to see a triple-frequency receiver for under $500
> 
> 
> John Green wpxs472 at gmail.com wrote:
>> Just so people don’t get to down on eBay antennas:
>> 
>> I have gotten some deals on eBay I just couldn't have gotten elsewhere.
>> That is a nice looking antenna. A bit pricey for my budget. I thought just
>> north of $100 for a used Leica choke ring job was about it. The Trimble
>> antenna I got recently had issues, so I got it cheap and fixed the
>> mechanical problems. I think I have one of those HP timing antennas I have
>> heard mentioned here. I need to dig it up. I think I also have a PC Tel
>> model around somewhere. I still haven't gotten the top off that Chinese
>> made one that bit the dust at 12 volts. I need to get it apart somehow. I
>> think it can probably be repaired. I can at least let the seller know what
>> went bad.
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Re: [time-nuts] Hemisphere Antenna PCB

[Bob kb8tq]

Hi

I think I’d wait for the next batch of “new old stock” telecom L1 only GPS 
antennas to show up. I’d bet they will be roughly the same price. At least 
with them you also get the enclosure. 

They do show up in various conditions at various prices:

https://www.ebay.com/itm/Panasonic-VIC100-GPS-L1-Active-Antenna-CCAH32ST03-with-Mounting-Bracket/263031184915?hash=item3d3de15e13:g:KO8AAOSw-89ZPHeq
 


https://www.ebay.com/itm/Lot-of-2-Panasonic-VIC100-GPS-L1-Active-Antenna-CCAH32ST04-W-Pole-Mount-Bracket/323048812645?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D48419%26meid%3D97afb35c12c949eea12f3722cb123e00%26pid%3D15%26rk%3D3%26rkt%3D6%26sd%3D263031184915%26itm%3D323048812645&_trksid=p2047675.c15.m1851
 


https://www.ebay.com/itm/PCTEL-GPS-L1-26dB-TIMING-ANTENNA-KIT-GPS-TMG-26N-W-Mount-Kit/263472818898?epid=2256151071&hash=item3d58342ad2:g:KU0AAOSw8gVX3BPx
 


https://www.ebay.com/itm/PCTEL-GPS-26dB-Outdoor-Antenna-GPS-TMG-26N/282719724915?epid=2256151071&hash=item41d368a573:g:J~0AAOSwI8lZ~MMh
 



Bob

> On Feb 16, 2018, at 9:03 PM, Gregory Beat  wrote:
> 
> These Hemisphere GNSS 500-1210-004# antenna / pre-amp boards (bulk, bare) with
> no outdoor fiberglass enclosure appear to be same size used in A21 model.
> Good for experimenter.
> https://hemispheregnss.com/Products/Products/Peripherals/a21e284a2-antenna-135
> Hemisphere GNSS is HQ in Scottsdale, AZ
> 
> Seller has eight (8) on the auction.
> eBay auction: 142354760357
> 
> greg, w9gb
> Sent from iPad Air
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Re: [time-nuts] eBay GPS antennas

[Bob kb8tq]

Hi

Part of the issue with Glonass is the accuracy of the datum. It *can* be used
for navigation and timing. It’s best to use it stand alone. Survey a location 
that is specific to it’s datum and then lock the module into timing mode. Don’t 
try to run with a GPS survey as your location.

All that said, still not encouraging. 

Bob

> On Feb 16, 2018, at 2:49 PM, Gary E. Miller  wrote:
> 
> Yo Bob!
> 
> On Fri, 16 Feb 2018 13:47:24 -0500
> Bob kb8tq  wrote:
> 
>> Reports to date on Glonass have not been encouraging.
> 
> I have been testing position accuracy lately on a self contained u-blox
> 8 with built-in antenna supposedly GLONASS capable.  I write a Python
> script to selectively enable GLONASS and GALILEO over GPS.
> 
> All figures below are rough averages.
> 
> Typically, with one particular GPS, in one particular spot, it gives a
> CEP(50) of 10 feet.
> 
> Enable GLONASS and that worsens to 24 feet.  After about a minute the
> u-blox rejects all the GLONASS, that have good SNR, and the CEP(50)
> drops back to normal.
> 
> Enable GALILEO and CEP(50) improves to 6 feet.  And stays that way.
> 
> So be sure to enable GALILEO in your GPS and disable GLONASS.
> 
> Also note: the passband of GALILEO is technically the same as GPS, but
> has more energy at the edges.  Some GPS antennas cut it a little close
> and hurt GALILEO performance.
> 
> RGDS
> GARY
> ---
> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
>   g...@rellim.com  Tel:+1 541 382 8588
> 
>   Veritas liberabit vos. -- Quid est veritas?
>"If you can’t measure it, you can’t improve it." - Lord Kelvin
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Re: [time-nuts] eBay GPS antennas

[Bob kb8tq]

Hi

A full blown choke ring antenna is a pretty big heavy gizmo. That said, 
yes indeed, some shipping charges are insane. 

Bob

> On Feb 16, 2018, at 1:51 PM, Wes  wrote:
> 
> On 2/16/2018 11:31 AM, Stewart Cobb wrote:
>> ...
>> 
>> For example, any AeroAntenna whose part number starts with "AT2775" is a
>> dual-frequency L1/L2 GPS antenna. AT2775-42 is a near-survey-grade antenna,
>> and one of them is available right now (item 263500294711) at a starting
>> bid of $20, after expiring yesterday with no bids at $25.
> ...
> 
> Look out for the shipping charge.
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Re: [time-nuts] eBay GPS antennas

[Bob kb8tq]

Hi

Well, the interesting point about Glonass timing is that it is independent of 
the 
GPS empire. Galileo is another independent time source. Running a GPSDO
linked to each one would let you inter-compare the time from each of them. 
Indeed I would *guess* that Galileo would do pretty well. Reports to date on 
Glonass have not been encouraging. It still might be interesting to do. Once
Furuno releases the Galileo firmware, one of the Opus 7 based devices should
be able to run each of them. uBlox or some of the others would also do the 
same thing. 

Bob

> On Feb 16, 2018, at 1:31 PM, Stewart Cobb  wrote:
> 
> FYI, Antcom and AeroAntenna are two manufacturers of high-quality
> American-made GPS / GNSS antennas. Antcom's datasheets are confusing to
> read, and AeroAntenna hides theirs behind a customer-login barrier, so most
> of eBay doesn't know exactly what they are. This means that good antennas
> are often available cheap.
> 
> For example, any AeroAntenna whose part number starts with "AT2775" is a
> dual-frequency L1/L2 GPS antenna. AT2775-42 is a near-survey-grade antenna,
> and one of them is available right now (item 263500294711) at a starting
> bid of $20, after expiring yesterday with no bids at $25.
> 
> Several other AT2775 antennas are on eBay for under $200. Any of these
> would be excellent for time-nut purposes.
> 
> IMHO, Glonass coverage is not useful for precision timing. If you don't
> have a good enough antenna installation to get continuous GPS coverage,
> you're not really doing precision timing. If you are getting continuous GPS
> coverage, Glonass doesn't add anything.
> 
> Disclaimer: I have no relationship to either company mentioned, other than
> previously being a satisfied customer of both companies. I have no
> connection to any sales currently listed on eBay.
> 
> Cheers!
> --Stu
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Re: [time-nuts] Furuno GT-8031 breakout board

[Bob kb8tq]

Hi

Even more exciting, some of the “M12 like” devices are close, but not exact 
copies of the
M12 command set. Your GPSDO may be fine with the differences on this device, 
but not
so happy with the differences on some other device. 

Bob

> On Feb 16, 2018, at 12:50 PM, Mark Sims  wrote:
> 
> No, the Tbolt does not have a separate receiver board... plus its' GPS is 
> rather special... the RF chain is locked to the OCXO so it does not produce 
> any sawtooth error.
> 
> The Lucent KS firmware expects the GPS to support the older 6/8 channel 
> messages.   The newer 12 channel  messages are different.
> 
> BTW, I just did a Motorola M12 to Adafruit pinout board.  The M12 form factor 
> and pinouts are also used by a lot of other timing receivers.  Why Adafruit?  
> Because it is breadboard friendly,  has enough pins for all the signals that 
> one expects,  and my GPS to RS-232 adapter board has an Adafruit connector on 
> it.
> 
> 
> 
>> Never having opened my TBolt, are the GT-8736 boards of use to replace the 
>> aging and partly deaf receiver in that? Or for a KS-24019?
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Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi

Just so people don’t get to down on eBay antennas: 

https://www.ebay.com/itm/Antcom-Active-L1-L2-Choke-Ring-Antenna-Item-123GM1215A-XT-1-AUTOFARM-AGLEADER/302630180910?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
 
<https://www.ebay.com/itm/Antcom-Active-L1-L2-Choke-Ring-Antenna-Item-123GM1215A-XT-1-AUTOFARM-AGLEADER/302630180910?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649>

Was indeed brand new in box. The pictures don’t quite give credit to the 
branding
on the antenna. It was shipped directly from the outfit that put the great big
letters on it. Price was a bit less than eBay would have you think, but still a 
bit
more than the ones from China. No idea if they will be selling any more. 

An L1 / L2 choke ring is a much better bet pattern wise than the patch 
antennas. It also is a
great big heavy monster of a thing to mount somewhere ….

On the down side, like a lot of what you see, it’s GPS only. At least by spec, 
it will 
not pass the full Glonass L1 or L2  bands. That may be why it turned up as 
“brand new but 
we’re unloading it”.  What the passband *really* looks like ….. we’ll see ….

Bob

> On Feb 14, 2018, at 12:23 AM, Bill Hawkins  wrote:
> 
> Learned tonight that J. P. Morgan got his start by buying 25 K defective
> rifles for %3.50 each and selling them to the Army for $25 each. You
> have no reason to trust a listing.
> 
> Bill Hawkins
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
> kb8tq
> Sent: Tuesday, February 13, 2018 12:04 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] eBay GPS antenna test.
> 
> Hi
> 
> 
>> On Feb 13, 2018, at 12:06 PM, Clint Jay  wrote:
>> 
>> Agreed but stock numbers on boxes and packets  are usually Arabic 
>> numerals or a barcode. It's also possible the seller used a stock 
>> image which can be copied and pasted into Google web search to track 
>> down the maker or at least a distributor who has data.
> 
> The seller did post a number of images for the part that was listed. The
> gotcha is that the part that arrived is not labeled the same way as the
> part that was listed.
> Since the device also has issues, the big question is if it has any
> connection to the part in the listing at all. 
> 
> The seller seems to have been doing GPS stuff for a while. He also has a
> very good approval rating. My guess is: this isn't the first time he's
> seen a bump in the road. I'd bet he's got the ability to check this and
> that out to see what is what. 
> The seller *does* matter when you buy this stuff. That's true no matter
> what you are getting. No matter how good they are, problems do come up.
> The question is always how well they address them. We tend to dump
> pretty hard on these guys. I'm not sure that's always warrantied. 
> 
> Bob
> 
> 
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

As with any antenna mods, the issue isn’t so much doing them as proving that
what you did had this or that effect. A lot of what you are paying for on the 
fancy
antennas is the fact that indeed they went through some sort of validation 
process
on top of the design process. 

An equally valid point is that the standard “telecom” antennas likely are no 
great
thing for low angle multi path either. That is one of several reasons we tend 
to 
like cranking up the elevation mask on our TBolts. 

If you are going for the “I want something that does it all” approach. You 
would want
an antenna that does at least L1 / L2 / L5 and covers the GPS and Glonas parts 
of 
the bands. So far, those have not shown up as $100 new in box items ….. Given
that the price of gear covering all of that is still “a bit high” (even as a 
home brew 
SDR), I’m not sure it matters a whole lot at this point. 

Bob

> On Feb 15, 2018, at 9:13 AM, jimlux  wrote:
> 
> On 2/15/18 6:04 AM, Bob kb8tq wrote:
>> Hi
>> There are a number of reasons to believe that these antennas are worse
>> than the typical “telecom GPS” antenna for L1 only duty driving a TBolt.
>> If you are going to do L1 / L2 work with something like a NetRS, then indeed
>> you will need a dual band antenna. These (the $99 ones)  are the lowest cost
>> “new in box” L1 / L2 antennas that I have seen. One would *guess* that their
>> close to horizon multi path rejection is not quite as good as a Trimble 
>> Zephyr,
>> a Novatel Pinwheel, or a choke ring. The ones from China
>>  also don’t cost $1800 to $6000 when new either …
> 
> 
> one could probably improvise something that serves as a choke ring, or 
> elevation fence.  The infamous JPL Helibowl is pretty simple, and has pretty 
> good rejection of signals near the horizon.
> 
> See, e.g. Page 143 in GPS/GNSS Antennas, by Rao.  (I found it on google
> 
> https://books.google.com/books?id=nL-YFWLQrPIC&pg=PA143&lpg=PA143&dq=helibowl+antenna&source=bl&ots=U-7Y3TMIQw&sig=D4xZVMmv73XkCAH_8KkMegMnxX4&hl=en&sa=X&ved=0ahUKEwjbjLGTjKjZAhVM7WMKHdYPC5sQ6AEIMTAB#v=onepage&q=helibowl%20antenna&f=false
> 
> Oddly, it cites to C.Y Cheng, Numerical Electromagnetic Modeling of a Small 
> Aperture Helical-Fed Reflector Antenna, Masters thesis, Ohio University, Aug 
> 1998.
> 
> Good luck finding that one on-line
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Re: [time-nuts] Team of physicists repeats tvb Project GREAT

[Bob kb8tq]

Hi

> On Feb 15, 2018, at 9:03 AM, jimlux  wrote:
> 
> On 2/14/18 6:51 PM, Tim Lister wrote:
>> On Feb 14, 2018 19:47, "Chris Caudle"  wrote:
>> On Wed, February 14, 2018 7:06 pm, jimlux wrote:
>>> At substantially more expense, and with an experimental lattice clock,
>> Does that schematic figure in the paper imply that the "transportable"
>> strontium and ytterbium clocks are built into trailers instead of the
>> traditional rack enclosure?
>> Actually now that I look more closely it looks like maybe two trailers.
>> Doesn't seem like something that Jim is going to be flying any time soon.
>> Yes. From the Nature article text:
>> "The transportable 87Sr lattice clock is (compared with laboratory clocks)
>> designed to be compact, with robust optical parts12
>> . The physics
>> package is less than 0.6 m3 in size, and we use laser breadboards with
>> mechanical stress-resistant fibre couplers21
>> . All
>> components except the reference cavity of the interrogation laser are
>> rigidly mounted in a car trailer (size 2.2 m × 3 m × 2.2 m), and vibration
>> isolation is provided by rubber dampers. The trailer interior is
>> temperature stabilized, while the small volume of the trailer hinders air
>> exchange and generates hot spots with more than 10 K temperature rise.
>> However, the optics and the physics package are placed apart and shielded
>> from these and are stable to within 0.4 K after an initial temperature rise
>> of about 1 K. The transportable ultrastable reference cavity for the clock
>> interrogation lasers is rigidly mounted to endure transport12
>> . It was placed
>> next to the trailer to avoid its performance being degraded by vibrations
>> induced in the trailer’s air conditioning system. The vibration amplitudes
>> in the trailer are a factor of ten larger than under typical laboratory
>> conditions, leading to a corresponding increase in clock instability. A
>> reference resonator with lower acceleration sensitivity or an active
>> feed-forward system may in the future remedy this inconvenience22
>> ."
> 
> 
> We have discussed the desirability of suitable caves for operation of high 
> quality clocks many times on this list.
> Clearly this is another instance.

Search the archives for “swimming pool full of mercury” for one go around on 
this.

Bob



> 
> With respect to flying such things in space - this is the continual challenge 
> - DSAC (the trapped mercury ion clock) was a couple of benches in a special 
> time keeping lab when I first saw it, oh, a decade ago?. It will fly later 
> this year and it's probably about the size of an airplane carry-on.
> https://www.jpl.nasa.gov/missions/deep-space-atomic-clock-dsac/
> 
> Cold Atom Laboratory basically takes several optical benches operated by a 
> team of post-docs that makes Bose Einstein Condensates (BEC) and turns it 
> into a box the size of a dorm refrigerator that goes "ping" when you press a 
> button and makes a BEC (in either Rb or K, as you choose).
> 
> https://coldatomlab.jpl.nasa.gov/mission/
> 
> Just as a rule of thumb, I've found that it takes about 10-20 times the cost 
> to get from "benchtop prototype"(TRL 5) to "flyable unit" (TRL 6), as it cost 
> to get from idea to benchtop prototype.
> 
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

There are a number of reasons to believe that these antennas are worse
than the typical “telecom GPS” antenna for L1 only duty driving a TBolt. 
If you are going to do L1 / L2 work with something like a NetRS, then indeed
you will need a dual band antenna. These (the $99 ones)  are the lowest cost 
“new in box” L1 / L2 antennas that I have seen. One would *guess* that their
close to horizon multi path rejection is not quite as good as a Trimble Zephyr,
a Novatel Pinwheel, or a choke ring. The ones from China
 also don’t cost $1800 to $6000 when new either …

Bob

> On Feb 15, 2018, at 4:31 AM, Christoph Kopetzky  wrote:
> 
> Moin,
> are in the meantime any experiences with these gps antennas from the china 
> seller (ms_geo)?
> I found two type of them from the same seller:
> 
> 1) 
> https://www.ebay.com/itm/High-Precision-L1-L2-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-antenna/162718512935?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
>  
> <https://www.ebay.com/itm/High-Precision-L1-L2-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-antenna/162718512935?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649>
> this one is the 3.3 - 18 V version with 5 dB antenna gain and 42 dB LNA gain 
> for  appr. 100 US$
> 
> and 
> 
> 2) 
> https://www.ebay.com/itm/High-Precision-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-machine-control-antenna/162710405447
>  
> <https://www.ebay.com/itm/High-Precision-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-machine-control-antenna/162710405447>
> this one has 3.3 - 10 V  voltage requirement and nearly the same gain values 
> but 85 US$ 
> 
> Does anyone have one oth them up and running?
> 
> Are they much more better as a Symmetricom 58532A antenna ore the puck head 
> variant?
> 
> If yes I would give it also a try but the shipment time from goods from china 
> are very high. Here to Germany there are timeframes from four to eight weeks 
> normal. :(
> 
> But the price 
>  -
> Chris
> Am 13.02.2018 um 03:05 schrieb Bob kb8tq:
>> Hi
>> 
>> Sitting here casually reading the data sheets for some of the modern Trimble
>> survey receivers - they have gone to 7.2V (just below your 7.5V trigger 
>> point) 
>> as an antenna supply voltage. 
>> 
>> Who knows what that might imply relative to this antenna. 
>> 
>> Bob
>> 
>>> On Feb 11, 2018, at 12:44 PM, John Green  
>>> <mailto:wpxs...@gmail.com> wrote:
>>> 
>>> They have issued a refund. The seller said that my antenna was defective.
>>> This is kind of a strange outfit. They are in Russia selling Chinese goods,
>>> shipped from China.  Since I don't have to return it, I will disassemble it
>>> to see what went bad. I replied that if he could assure me that it would
>>> work on 12 volts, I might order another.
>>> ___
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>>> and follow the instructions there.
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Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi


> On Feb 13, 2018, at 12:06 PM, Clint Jay  wrote:
> 
> Agreed but stock numbers on boxes and packets  are usually Arabic numerals
> or a barcode. It's also possible the seller used a stock image which can be
> copied and pasted into Google web search to track down the maker or at
> least a distributor who has data.

The seller did post a number of images for the part that was listed. The gotcha 
is
that the part that arrived is not labeled the same way as the part that was 
listed.
Since the device also has issues, the big question is if it has any connection 
to
the part in the listing at all. 

The seller seems to have been doing GPS stuff for a while. He also has a very
good approval rating. My guess is: this isn’t the first time he’s seen a bump 
in 
the road. I’d bet he’s got the ability to check this and that out to see what 
is what. 
The seller *does* matter when you buy this stuff. That’s true no matter what you
are getting. No matter how good they are, problems do come up. The question
is always how well they address them. We tend to dump pretty hard on these 
guys. I’m not sure that’s always warrantied. 

Bob

> 
> On 13 Feb 2018 16:18, "Bob kb8tq"  wrote:
> 
>> Hi
>> 
>> That can be a bit harder if the labels are all in Chinese. Maybe posting
>> pictures of the label? That way those (not I) who can read Chinese might
>> spot something that allows a search to proceed.
>> 
>> Bob
>> 
>>> On Feb 13, 2018, at 11:06 AM, Clint Jay  wrote:
>>> 
>>> Sounds like a drop shipping operation, they've found a supplier in China
>>> who is willing to send goods either in plain wrapping without any
>> supplier
>>> name or the name of the agent who's selling it. It can be useful to
>> Google
>>> anything that looks like a part number on the packaging, you'll often
>> find
>>> the main wholesaler or even the manufacturer.
>>> 
>>> On 13 Feb 2018 15:48, "John Green"  wrote:
>>> 
>>>> Bob wrote:  Sitting here casually reading the data sheets for some of
>> the
>>>> modern Trimble
>>>> survey receivers - they have gone to 7.2V (just below your 7.5V trigger
>>>> point)
>>>> as an antenna supply voltage.
>>>> 
>>>> Who knows what that might imply relative to this antenna.
>>>> 
>>>> After getting my refund, I sent the seller a message saying that I would
>>>> buy another if he could assure me it would work at 12 volts. He replied
>>>> that he needed to get his hands on a couple and do some testing first.
>> The
>>>> antenna that I received seems to be different to the one pictured in the
>>>> eBay listing. At least the labels are different. I get the feeling he is
>>>> kind of a third party dealing with someone in China who is wholesaling
>>>> antennas made by someone else. Who really knows what spec. these are
>> made
>>>> to, or by who. In my former place of employment, we made an SMB
>> terminator.
>>>> Basically, a 75 ohm resistor soldered across the pins of an SMB
>> connector,
>>>> then molded in black plastic. We bought the connectors from a Chinese
>>>> supplier who supplied them in individual plastic bags. We had to cut the
>>>> parts out of the bags before processing, which added a labor step. We
>> tried
>>>> to get the supplier to sell them to us packaged in bulk, but they
>> refused.
>>>> We decided that they were actually buying them from someone else and
>> just
>>>> doing a passthru. The connectors themselves would change from time to
>> time,
>>>> which caused problems in molding, and sometimes caused the electrical
>>>> performance to degrade. Getting parts to reliably meet a specification
>> from
>>>> China can be a problem. I can't even imagine the issues that could arise
>>>> when you try to source an assembly, or completed product.
>>>> 
>>>> <https://www.avast.com/sig-email?utm_medium=email&utm_
>>>> source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>
>>>> Virus-free.
>>>> www.avast.com
>>>> <https://www.avast.com/sig-email?utm_medium=email&utm_
>>>> source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>
>>>> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>>>> ___
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>>>> To u

Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi

That can be a bit harder if the labels are all in Chinese. Maybe posting
pictures of the label? That way those (not I) who can read Chinese might
spot something that allows a search to proceed. 

Bob

> On Feb 13, 2018, at 11:06 AM, Clint Jay  wrote:
> 
> Sounds like a drop shipping operation, they've found a supplier in China
> who is willing to send goods either in plain wrapping without any supplier
> name or the name of the agent who's selling it. It can be useful to Google
> anything that looks like a part number on the packaging, you'll often find
> the main wholesaler or even the manufacturer.
> 
> On 13 Feb 2018 15:48, "John Green"  wrote:
> 
>> Bob wrote:  Sitting here casually reading the data sheets for some of the
>> modern Trimble
>> survey receivers - they have gone to 7.2V (just below your 7.5V trigger
>> point)
>> as an antenna supply voltage.
>> 
>> Who knows what that might imply relative to this antenna.
>> 
>> After getting my refund, I sent the seller a message saying that I would
>> buy another if he could assure me it would work at 12 volts. He replied
>> that he needed to get his hands on a couple and do some testing first. The
>> antenna that I received seems to be different to the one pictured in the
>> eBay listing. At least the labels are different. I get the feeling he is
>> kind of a third party dealing with someone in China who is wholesaling
>> antennas made by someone else. Who really knows what spec. these are made
>> to, or by who. In my former place of employment, we made an SMB terminator.
>> Basically, a 75 ohm resistor soldered across the pins of an SMB connector,
>> then molded in black plastic. We bought the connectors from a Chinese
>> supplier who supplied them in individual plastic bags. We had to cut the
>> parts out of the bags before processing, which added a labor step. We tried
>> to get the supplier to sell them to us packaged in bulk, but they refused.
>> We decided that they were actually buying them from someone else and just
>> doing a passthru. The connectors themselves would change from time to time,
>> which caused problems in molding, and sometimes caused the electrical
>> performance to degrade. Getting parts to reliably meet a specification from
>> China can be a problem. I can't even imagine the issues that could arise
>> when you try to source an assembly, or completed product.
>> 
>> > source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>
>> Virus-free.
>> www.avast.com
>> > source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>
>> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>> ___
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>> mailman/listinfo/time-nuts
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>> 
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Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi

China does a lot of things through a marketplace process. Lots of guys with
piles of this or that. Any sort of product you get in (to them) small volume 
likely goes through this kind of arrangement. Buying OCXO’s and other 
timing gear is every bit as vulnerable to the “this one today, something 
different tomorrow” process that results. 

This sort of process is also vulnerable to the “grabbed the wrong box” problem.
The good ones are in this box and the others are in that box. I’m in a hurry 
and ….

It’s well worth remembering that we *are* (or should be)  paying a very low 
price 
for most of this stuff. It is unfortunate that paying a higher price does not 
seem to guarantee a better outcome. 

Bob

> On Feb 13, 2018, at 8:00 AM, John Green  wrote:
> 
> Bob wrote:  Sitting here casually reading the data sheets for some of the
> modern Trimble
> survey receivers - they have gone to 7.2V (just below your 7.5V trigger
> point)
> as an antenna supply voltage.
> 
> Who knows what that might imply relative to this antenna.
> 
> After getting my refund, I sent the seller a message saying that I would
> buy another if he could assure me it would work at 12 volts. He replied
> that he needed to get his hands on a couple and do some testing first. The
> antenna that I received seems to be different to the one pictured in the
> eBay listing. At least the labels are different. I get the feeling he is
> kind of a third party dealing with someone in China who is wholesaling
> antennas made by someone else. Who really knows what spec. these are made
> to, or by who. In my former place of employment, we made an SMB terminator.
> Basically, a 75 ohm resistor soldered across the pins of an SMB connector,
> then molded in black plastic. We bought the connectors from a Chinese
> supplier who supplied them in individual plastic bags. We had to cut the
> parts out of the bags before processing, which added a labor step. We tried
> to get the supplier to sell them to us packaged in bulk, but they refused.
> We decided that they were actually buying them from someone else and just
> doing a passthru. The connectors themselves would change from time to time,
> which caused problems in molding, and sometimes caused the electrical
> performance to degrade. Getting parts to reliably meet a specification from
> China can be a problem. I can't even imagine the issues that could arise
> when you try to source an assembly, or completed product.
> 
> 
> Virus-free.
> www.avast.com
> 
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

Sitting here casually reading the data sheets for some of the modern Trimble
survey receivers - they have gone to 7.2V (just below your 7.5V trigger point) 
as an antenna supply voltage. 

Who knows what that might imply relative to this antenna. 

Bob

> On Feb 11, 2018, at 12:44 PM, John Green  wrote:
> 
> They have issued a refund. The seller said that my antenna was defective.
> This is kind of a strange outfit. They are in Russia selling Chinese goods,
> shipped from China.  Since I don't have to return it, I will disassemble it
> to see what went bad. I replied that if he could assure me that it would
> work on 12 volts, I might order another.
> ___
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

Well, good news / bad news I guess. The seller is at least responding to your
input. They also did not come back with something about “there is no voltage
spec”. It’s quite possible that they are the 5th person in a chain of sellers 
and
a substitution got made (unknown to them) at seller 3. 

I’d hook up a power supply, a current meter and a couple of clip leads. Shoot a
cell phone picture at 5V and one a second one at 10V. That’s all it should 
take. 
If you have more than one DVM, that would make things even more clear. 

Bob

> On Feb 11, 2018, at 9:07 AM, John Green  wrote:
> 
> I opened a "Not as listed" case and heard back from the seller. They said
> that the antenna is definitely 3.3 to 18 volts and have sold several that
> are in operation. They wanted to know specifically how I tested the
> antenna, why I thought it shorted, and if I actually ever hooked it to a
> GPS receiver. I answered as best I could but haven't heard anything
> further. eBay seems to like pictures or videos. Though problematic, I
> suppose I could take some pictures. I offered to do so in my response to
> the seller. They do seem a bit more responsive to buyer complaints than in
> previous years. I recently ordered a 64 Gb micro SD card from a US based
> seller. I got a message from eBay stating that they had removed the listing
> but that everything should be OK. I never received the SD card, and after a
> month, checked PayPal and saw that I had been charged for it. I contacted
> eBay and they refunded my money the next day.
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

Ok, the antenna in the pictures on the listing *does* have labeling in English 
and it sure looks like it says 3.3 to 18V on the antenna. Certainly you have 
(and the rest of us may soon have) a case for “not as shown” in terms of 
what you got (and we get).

Bob

> On Feb 9, 2018, at 9:31 PM, John Green  wrote:
> 
> Bob wrote:
> Is it labeled 3.3 to 18V on the antenna?
> 
> No, the writing on the antenna is all Chinese. The specs published on eBay
> state that it is.
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Re: [time-nuts] Symmetricom 58532A GPS Antenna : Launch3 Surplus

[Bob kb8tq]

Hi

There are tapes designed for waterproofing things like coax connectors.

Bob

> On Feb 9, 2018, at 7:41 PM, Hal Murray  wrote:
> 
> 
> li...@philpem.me.uk said:
>> Generally speaking, you can seal most RF connectors quite nicely with a few
>> layers of self-amalgamating tape and a layer of PVC tape over the top of
>> that (to protect from UV). 
> 
> Many years ago, I picked up a chunk of scrap the local cable TV installer had 
> left on the ground underneath the utility pole out in front of my house.  It 
> was a chunk of industrial strength shrink wrap with a layer of goop on the 
> inside.
> 
> Is that stuff available in small quantities?  Would the antenna withstand the 
> necessary heat?
> 
> How do hams seal antenna connectors?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

Is it labeled 3.3 to 18V on the antenna?

Bob

> On Feb 9, 2018, at 4:43 PM, John Green  wrote:
> 
> To those who doubted that the antenna was actually a 3.3 to 18 volt design,
> it seems you were correct. Today, I hooked it up to a variable power supply
> and slowly raised the DC voltage fed to the antenna. It began to pull
> current at about 2.9 volts and at 3.3 volts, took about 40 mA. I continued
> to slowly raise the voltage. At about 7.5 volts, the current suddenly
> dropped to 10 mA. At just below 12 volts, it suddenly increased to 80 mA
> and the supply went into current limit. I increased the current limit to
> 130 mA and repeated the exercise. Everything went as above until I reached
> 12 volts and the current went to 130 mA and the supply went into current
> limit. Lowering the voltage didn't lower the current. I disconnected it,
> waited a minute, and tried again. Yep, shorted. It would have worked well
> with the T bolt, but would have blown anyway if I tried to use it with my
> 12 volt supply and bias T. I guess I will get inside it somehow to see if
> it can be repaired. My first attempt ended in failure. I guess I need a
> bigger screwdriver with which to pry the top off. I am going to contact the
> seller and tell them it was not as advertised. I kind of doubt that will
> get me anything, but it won't hurt to try. There is a saying about
> experience being a cruel teacher. You get the results first, and the lesson
> after. Oh well.
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Re: [time-nuts] Does a frequency counter locked to GPS need to "warm up"?

[Bob kb8tq]

Hi

It depends a *lot* on the frequency counter. An old style “just count the 
number of
edges” device should be good to go pretty fast. One of the “fry an egg on it” 
interpolating 
counters that get into the 20 ps range may well need some time to stabilize. If 
you 
are doing ADEV runs, a couple hours of warmup would be a good idea.

Bob

> On Feb 8, 2018, at 2:33 AM, Chris Wilson  wrote:
> 
> 
> 
>  08/02/2018 07:31
> 
> Does  a  frequency  counter  connected  to a permanently running (Trimble 
> Thunderbolt) GPS
> disciplined frequency standard need to warm up after switch on before 
> readings settle?
> Just curious, thanks.
> 
> -- 
>   Best Regards,
>   Chris Wilson.
> mailto: ch...@chriswilson.tv
> 
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Re: [time-nuts] Anyone have experience with this antenna?

[Bob kb8tq]

Hi

They probably have a group of people on staff to go out and dry them off after 
it rains …. :)

Indeed, there are a lot of pictures of heated enclosures for antennas. The 
debate over the
dielectric properties of the coverings goes back a long way. There are notes in 
the standard
databases for the antennas that came with optional covers. They have a separate 
data file
for the “with cover” and “without cover” versions. The discussion here is 
pretty much an 
replay of how the conversation has gone over the years. There is indeed a group 
of people
who (quite rightly) suggest that it’s not a big deal in most cases. 

Bob

> On Feb 7, 2018, at 10:07 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message <875e4bc6-32c3-4724-afcd-086553ae5...@n1k.org>, Bob kb8tq writes:
> 
>> Water wise, one might note the large piles of snow sitting on my antennas at 
>> the moment. Yes, I 
>> could go knock it off, but somehow it just keeps coming back. Weird how 
>> winter works …. There
>> is no perfect solution. 
> 
> Somebody at BIPM told me that their antennas were heated and thermostatically
> kept at constant temperature.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Anyone have experience with this antenna?

[Bob kb8tq]

Hi

It’s not the end stops that are the issue. It’s the wall of the pipe. If the 
dimensions in 
the sketch are roughly correct and you scale it to the dimensions of the eBay 
antenna,
that is a big tall pipe. Indeed “nothing overhead” would mitigate part of the 
issue. That magic
line runs roughly along Hadrian’s Wall in the UK. I’d bet that 80 degrees 
overhead would still be
an issue. 

Again, this is an extreme case and not the typical cover for a GPS antenna. 

Water wise, one might note the large piles of snow sitting on my antennas at 
the moment. Yes, I 
could go knock it off, but somehow it just keeps coming back. Weird how winter 
works …. There
is no perfect solution. 

Bob

> On Feb 7, 2018, at 3:59 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message 
> , Michael 
> Wouters writes:
> 
> One thing about Bo's pipe radome which is worth pointing out is that
> like me he is on 56 degrees north latitude, which just so happens to
> mean that we have no GPS satellites passing directly overhead.
> 
> I can't remember the exact dimensions of the "hole" we look up into,
> but eyeballing Bo's sketch, I think the endstop might just never
> get in the way of any actual signals.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Receiving the MSF time signal on cheap radio modules

[Bob kb8tq]

Hi

Back in the era of VLF disciplined oscillators, carrier phase was the preferred 
approach. 
Getting that to work with 100% AM modulation took some effort ….

Bob

> On Feb 7, 2018, at 2:13 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message 
> , 
> "Deirdre O'Byrne" writes:
> 
>> MSF disciplined oscillator?! I don't trust these receivers to any better
>> than about the 20ms mark, so such a disciplined oscillator would have quite
>> a long integration time!
> 
> It's actually more complicated and better than that.
> 
> The low-pass filter dominates, so the falling flank at second N
> depends on the pulsewidth at second N-1.
> 
> I can't remember the numbers I got when I "sorted" DCF77 pulses depending
> on the previous pulse being short or long, but it was a fair bit better
> than 20ms.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] eBay GPS antenna.

[Bob kb8tq]

Hi

If you spend some “quality time” with the pictures in the listing, the antenna
is indeed labeled “operating voltage 3.3 to 18V”. Yes, I find that a bit 
incredible.
If there is nonsense being generated, it’s not by the person listing the 
antenna 
on eBay.  My guess would be that the automotive world has pushed some odd
semiconductor outfit to tool up a regulator that does what’s needed.

Bob

> On Feb 6, 2018, at 4:03 PM, John Green  wrote:
> 
> I kind of have to believe the specs. The two survey grade antennas I
> already have, a Leica and a Trimble, both have regulators in the preamp
> sections. The Leica has an 8 volt one and the Trimble has a 5 volt one. I
> intend to hook it up to a variable supply and watch the current as I
> increase voltage. If it has a regulator, the current should stabilize at an
> input voltage just above what the internal preamp operates at. If not, it
> should continue to rise. I am tempted to pry it apart, even if it risks
> damage just so I can see for myself what they are using for the preamp
> stages.
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Re: [time-nuts] Receiving the MSF time signal on cheap radio modules

[Bob kb8tq]

Hi

> On Feb 6, 2018, at 3:48 PM, Deirdre O'Byrne  wrote:
> 
> Tom,
> 
> Thanks for the feedback!
> 
> On 6 February 2018 at 20:29, Tom Van Baak  wrote:
> 
>> 
>> 2) Not all decoding errors are equal. Since this is a time code instead of
>> arbitrary binary data you can use the internal structure of the data to
>> your benefit.
>> 
> 
> As I said to Poul-Henning, that is the next level of error detection, which
> also has application in error correcting some of the "almost-right" signals.
> 
> 
>> 3) A side-effect of your data set is that you can track performance of the
>> oscillator inside the logic analyzer: convert the 700k GPS timestamps into
>> interval, find and replace the 4 glitch lines with 2 lines of 1.000150, and
>> then use Stable32 or TimeLab to plot. I used a 10 minute running average to
>> reduce the 50 us quantization noise. Note the mean frequency of your
>> timebase is 152 ppm low.
> 
> 
> I made it out to be 152.2ppm, which is kinda disappointing. But the signal
> analyser cost very little, and you get what you pay for.
> 
> I have not yet wrapped my head around how to create ADEV plots, so thanks
> for your work on that - it's interesting to see that (presumed) initial
> thermal effect.
> 
> 
>> Over 8 days this results in a cumulative sampling error of 105 seconds. If
>> your decoding algorithms are relative instead of absolute this won't be a
>> problem. OTOH, you may be able to use your decoding process to detect this
>> drift and then compensate for it in software. You have the beginnings of a
>> MSF-Disciplined-Oscillator project.
>> 
> 
> MSF disciplined oscillator?! I don't trust these receivers to any better
> than about the 20ms mark, so such a disciplined oscillator would have quite
> a long integration time!

Once upon a time, that *was* how people did disciplined oscillators. Part of the
answer to “how?” is that their target accuracies were not as tight as what we 
now
think of as normal. 

Bob


> 
> Thanks again.
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Re: [time-nuts] Receiving the MSF time signal on cheap radio modules

[Bob kb8tq]

Hi

If you look at the papers for the “new” WWVB format, there are plots of where 
the
MSF issues are likely to be the greatest. Since both signals are phase and 
amplitude
 shifted by propagation effects, you will not get stationary nulls. You simply 
get zones
where the reception is tough. 

Bob

> On Feb 6, 2018, at 5:57 PM, Hal Murray  wrote:
> 
>> Since MSF *is* on 60 KHz, you do indeed get dead spots.
> 
> If the two signals are not encoded identically, there should be an 
> interesting signal when one of the transmitters is off and the other is on.  
> Has anybody looked for that sort of pattern?
> 
> Is there a map of the dead spots?  Any time-nuts live in/near one?
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Receiving the MSF time signal on cheap radio modules

[Bob kb8tq]

Hi

> On Feb 6, 2018, at 4:19 PM, Poul-Henning Kamp  wrote:
> 
> 
> In message 
> , 
> "Deirdre O'Byrne" writes:
> 
>> With a blame algorithm in place it should be possible to recover these 
>> signals.
> 
> Yes, easily.
> 
> At distance MSF is significantly harder to receive than DCF77.
> 
> One of the reasons is that USA also operates two 60kHz transmitters
> also very precisely on frequency, so there are areas of the world
> where the three signals cancel and areas where they reinforce
> each other.

I believe we only have one transmitter on the air at 60 KHz in the US. The 
Japanese do indeed operate multiple transmitters on the same frequency 
( 40 KHz). There have been a number of proposals to set up a second US
transmitter. The last time I noticed them beating the drum for one, it was 
going to be at 40 KHz rather than 60 KHz. The proposal pretty much died 
yet again ….

Since MSF *is* on 60 KHz, you do indeed get dead spots. There probably is an
interesting plot of locations that have issues with both the 40 KHz and 60 KHz
transmissions due to simply being in the wrong place. 

Bob

> 
> I tried to model this many years ago, but I don't trust the result,
> somebody with better HF-propagation chops than me should look at it.
> 
> In addition to that problem, switch-mode designers seems to just
> *love* 60 kHz, and at least here in Denmark there is a lot more
> "hash" around 60 kHz than 77.5 kHz.
> 
> Finally, the modulation scheme of MSF is a bit on the overengineered
> side, which makes pulse discrimination needlessly hard - as you have
> also found out.
> 
> The big advantage of the blame algorithm is that since it is so
> tolerant of missing pulses, you can be throw everything away which
> isn't 100% clearcut.
> 
> If you look at the top of the dcf77.c file, you can see how I did
> that for DCF77, but the complex modulation of MSF needs a much
> more complex state engine there.
> 
> Finally, many of the small "clock-receivers", like the one you use,
> are optimised for battery-life and therefore they use very resonant
> filters, often crystal-filters, and heavy low-pass after demodulation,
> and that trows away a LOT of information which would be useful to
> have to discriminate the pulses.
> 
> If you go for the SDR approach, you will have much more information
> available, and can use much more well-behaved filters to detect the
> pulses, and one added advantage of carrier-tracking is that the
> power-modulation is carrier-synchronous, which makes them much
> easier to spot.
> 
> So really:  Get yourself an 1MSPS ADC chip and go that route instead.
> 
> (In theory, certain modern sound-cards should be usable for this if
> you can rip out their low-pass filters.  Havn't tried.)
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Anyone have experience with this antenna?

[Bob kb8tq]

Hi

Since we are talking about an L1 / L2 antenna here, a reasonable assumption 
would be that the target is something better than an “average result”. If you 
construct 
a cover out of a piece of PVC pipe (as shown in the original drawing), your 
worst 
case path has a foot or so of PVC in it compared to a best case path with well 
under
a tenth of an inch. That’s going to give you a bit of variation ….. Add some 
dirt or water
or ice to the equation and who knows what the result might be. 

Bob

> On Feb 6, 2018, at 3:45 PM, Michael Wouters  wrote:
> 
> I can see why the geodetic community would worry about antenna phase centre
> variation when a radome is installed but is it really an issue in timing
> applications? The few papers I've read suggest PCVs of less than 10 mm, or
> equivalently, 30 ps. This is at the level of precision available from
> post-processed, carrier phase time-transfer but  invisible in the 1 pps
> coming out of your receiver, even with a good sawtooth correction. Am I
> missing something?
> 
> Cheers
> Michael
> 
> On Wed, 7 Feb 2018 at 4:14 am, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> There are “cell site” specific GPS antennas on the market. Panasonic has
>> had one out
>> for quite a while. I’m sure there are several others.
>> 
>> One issue with doing any sort of “cover” for a precision antenna is
>> distorting it’s pattern.
>> Plastic (or whatever you use) will have different properties than air. A
>> path through a blob
>> of “not air” will change the effective path length. That impacts the
>> timing and thus the
>> navigation solution. If you are worried about 2mm sort of pattern
>> accuracy, things get
>> tricky. Early on, there was a big “throw out the radomes push when this
>> was first noticed.
>> 
>> Bob
>> 
>>> On Feb 6, 2018, at 6:15 AM, Bo Hansen  wrote:
>>> 
>>> Hi
>>> 
>>> Besides the RF characteristics it may also be worth considering the
>> quality of the plastics used. Over time water ingress may become an issue.
>> Fours years after the installation of a CN brand antenna, sourced locally
>> so probably not counterfeit either, we had to replace it at OZ7IGY
>> www.oz7igy.dk
>>> 
>>> RF wise 42 dB of gain IS an issue. Again at OZ7IGY, with 12 carriers in
>> the air especially 13 cm and 23 cm, blocking and IMD were an issue before
>> we mounted a BPF. I have taken apart the above mentioned antenna, a
>> Motorola antenna and an eBay "hockey puck" antenna. The best design was
>> clearly the Motorola one because it had a BPF after the pre-amp - probably
>> because it was designed by RF competent people too. Each of the other ones
>> had two FETs/MMICs in series and then a BPF. Of cause if no nearby carriers
>> are in the air it may be less of an issue.
>>> 
>>> So designing a really good antenna and pre-amp may be a business
>> opportunity. There are many hi IP3 MMICs available designed for GPS and the
>> like purposes. SAW BPFs with <1 dB loss are available fairly cheap so one
>> before the FET/MMIC with a 1 dB NF is the way to go. A DIY radome using
>> standard materials from any hardware shop is attached.
>>> 
>>> Bo, OZ2M
>>> 
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Re: [time-nuts] Receiving the MSF time signal on cheap radio modules

[Bob kb8tq]

Hi

If you want to get even more “nutty", look at the “seed” that you likely 
already have 
for the computation. In this day and age, you probably know what day / month / 
year it is. 
Since you might not (say) know the hour, you have a +/- 1 day sort of tolerance 
on that. It rolls 
into month and year in some cases. The seed adds complexity, but probably makes
things more robust. 

If the purpose is to “always be right” then retaining a seed probably improves 
things. 

The flip side is (of course) “what if I’ve been lied to?”. That applies with or 
without a seed. 
Heading off into a situation where you never (re)lock could be one result. How 
long do you go before 
you decide to try something else? 

One cute thing is that this stuff is (in general) not very compute intensive. 
If data past the 
minute tick is being looked at, you probably can afford to run multiple 
parallel solutions (even 
on a < $5 MCU). 

Lots of zigs and zags ….

Bob

> On Feb 6, 2018, at 2:37 PM, Poul-Henning Kamp  wrote:
> 
> 
> In message 
> 
> , "Deirdre O'Byrne" writes:
> 
>> I've been trying to see if I could design a decoding algorithm that
>> would be more noise-tolerant than the algorithms I've seen out in
>> the wild.
> 
> You can: I baptised it "the blame algoritm".
> 
> The trick is not to try to accept pulses as valid but to try to
> throw out pulses which are impossible.
> 
> Imagine you have a 120 second long shift-register, and you feed
> your received pulses into it.
> 
> Then try brute force, for every one of the newest 60 positions if
> that can be the start of a minute or not, by testing all the
> constraints you can think of, and there are surprisingly many.
> 
> Some are obvious, the bits encoding the hour cannot contain "39",
> but that is a remarkable weak filter that seldom kicks in.
> 
> A much stronger filter is that the bits encoding the hour must be
> the same as in the previous minute *unless* minutes were 59 in the
> previous minute *and* zero in this minute.
> 
> If you count it up, that is a strong and very peculiar relationship
> on all the hour-bits and all the minutes-bits and if even one single
> of them are wrong, you can definitively discard that theory for the
> start of the minute.
> 
> A similar thing holds for the date bits, the time in the
> previous minute must be 23:59:59 and in this 00:00:00 for
> there to be any difference between the dates, and even
> then, only a small number of possible changes in the date
> bits are valid.
> 
> If you look in http://phk.freebsd.dk/phkrel/NTPns.20080902.tgz
> you will find a file called dcf77_blame.c with my code,
> here is a couple of the simpler tests:
> 
>/* LSB of minutes must be different from previous minute */
>j = ip->shiftprev[(offset + 21) % 60];
>if (j * ip->shiftreg[(offset + 21) % 60] > 0)
>FAIL((why, " 0"));
> 
>/*
> * If the LSB of minutes was '1' in previous minute
> * the next higher bit must have changed, if it was
> * a '0' it must not.
> */
>if (j *
>ip->shiftreg[(offset + 22) % 60] *
>ip->shiftprev[(offset + 22) % 60] > 0)
>FAIL((why, " 1"));
> 
> When using this algorithm, missing pulses is almost a
> non-issue up to around 40% of them missing, and even
> in an enviroment like that, it is not uncommon to see
> the algorithm lock on to the minute in about 34 seconds
> and know the full time in less than 3 minutes.
> 
> If you make your pulse width discriminator *really* selective,
> which you might as well, you can "blacklist" disproved
> minute positions for the next many minutes as the
> risk of a '1' and '0' being confused is close to zero.
> 
> That will get you minute lock, even with 70%-90% missing
> pulses, in a matter of minutes if you use a longer
> shift register.
> 
> I did a parallel prototype for MSF, but I didn't need it
> so I never completed it, not sure I have it around any
> more.
> 
> I should really write an article about that code...
> 
> Poul-Henning
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Symmetricom 58532A GPS Antenna : Launch3 Surplus

[Bob kb8tq]

Hi

That’s likely a “better” antenna for a TBolt-only setup than the L1 / L2 gizmo 
that
we have been chatting about. Why? 

1) if it’s still $25 it would be ~ 1/4 the price

2) it has a pretty good filter built into it. 

3) it’s designed for continuous outdoor use  (connector is well shielded etc)

4) It’s smaller and easier to mount 

Lots to like.

Bob

> On Feb 6, 2018, at 2:45 PM, Gregory Beat  wrote:
> 
> https://www.febo.com/pipermail/time-nuts/2015-October/094105.html
> In 2014 and 2015 Launch3 Telecom offered NOS Symmetricom 58532A GPS Antennas 
> at a good price ($25 each) to time-nuts members  These were surplus (>750), 
> never used, due to mobile/cellular company merger over decade ago.  Looks 
> like they still have some.
> https://www.launch3telecom.com/symmetricom/58532a.html
> Symmetricom 58532A GPS Antenna -- Data-sheet
> http://www.microsemi.com/document-portal/doc_view/133381-58532a
> Launch3Telecom.com
> 27 Daniel Road
> Fairfield, New Jersey 07004
> ===
> 
> Sent from iPad Air
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Re: [time-nuts] Anyone have experience with this antenna?

[Bob kb8tq]

Hi

The microwave trick is fine for working out if it is a lossy material. 
Unfortunately 
what gets you in this case is more than just loss. A coax cable has core 
material 
that will (usually) do quite well in a microwave. None the less, the delay 
through 
the coax is different than through air ( = the coax has a velocity factor). 

Bob


> On Feb 6, 2018, at 12:25 PM, Bo Hansen  wrote:
> 
> Hi
> 
> Indeed a radome may distort the antenna pattern. In teh case of DIY projects 
> the trick that most can apply is to take a piece of the radome material and 
> put it into a microwave own.  If it doesn't get hot it is OK for most DIY 
> cases.
> 
> Infinion have some nice GNSS MMICs e.g. BGA924N6 
> http://demo.21dianyuan.com/infineon/download/download_down/id/40/type/cn 
> 
> 
> Bo

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Re: [time-nuts] Anyone have experience with this antenna?

[Bob kb8tq]

Hi

There are “cell site” specific GPS antennas on the market. Panasonic has had 
one out 
for quite a while. I’m sure there are several others. 

One issue with doing any sort of “cover” for a precision antenna is distorting 
it’s pattern. 
Plastic (or whatever you use) will have different properties than air. A path 
through a blob
of “not air” will change the effective path length. That impacts the timing and 
thus the 
navigation solution. If you are worried about 2mm sort of pattern accuracy, 
things get 
tricky. Early on, there was a big “throw out the radomes push when this was 
first noticed.

Bob

> On Feb 6, 2018, at 6:15 AM, Bo Hansen  wrote:
> 
> Hi
> 
> Besides the RF characteristics it may also be worth considering the quality 
> of the plastics used. Over time water ingress may become an issue. Fours 
> years after the installation of a CN brand antenna, sourced locally so 
> probably not counterfeit either, we had to replace it at OZ7IGY www.oz7igy.dk
> 
> RF wise 42 dB of gain IS an issue. Again at OZ7IGY, with 12 carriers in the 
> air especially 13 cm and 23 cm, blocking and IMD were an issue before we 
> mounted a BPF. I have taken apart the above mentioned antenna, a Motorola 
> antenna and an eBay "hockey puck" antenna. The best design was clearly the 
> Motorola one because it had a BPF after the pre-amp - probably because it was 
> designed by RF competent people too. Each of the other ones had two 
> FETs/MMICs in series and then a BPF. Of cause if no nearby carriers are in 
> the air it may be less of an issue.
> 
> So designing a really good antenna and pre-amp may be a business opportunity. 
> There are many hi IP3 MMICs available designed for GPS and the like purposes. 
> SAW BPFs with <1 dB loss are available fairly cheap so one before the 
> FET/MMIC with a 1 dB NF is the way to go. A DIY radome using standard 
> materials from any hardware shop is attached.
> 
> Bo, OZ2M
> 
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Re: [time-nuts] eBay GPS antenna.

[Bob kb8tq]

Hi

There is no need for something this exotic for L1 only reception. It *is*
nice to have Glonass L1, but that’s about the extent of how fancy you 
need to go. 

As noted in another post, the preamp gain probably is pretty high
on this antenna. That’s a standard that goes back to the early days of
Trimble survey GPS gear. It’s great if you happen to want to drive a 
32 port resistive splitter for your collection of GPSDO’s. If you have more
modest needs for splitting, pads would be a very good idea. 

Bob

> On Feb 6, 2018, at 8:08 AM, John Green  wrote:
> 
> Thanks for the responses. It looks similar to but not exactly like the two
> antennas referenced. They say the preamp is 3 to 5.5 volts, whereas the
> eBay antenna says its preamp is good from 3.3 to 18 volts, indicating I can
> run it off 12 volts. Regarding the internals, I must have somehow missed
> the photo which clearly shows it to be a patch antenna. It looks pretty
> similar to the Trimble I asked about recently, inside, that is. That
> Trimble had been dropped from a great height. The nylon screws that hold
> the actual antenna assembly had all been broken. I ordered new ones and
> replaced them. Disassembly was easy, reassembly not so much. Mine was made
> to have the groundplane, but doesn't have it. I suspect that since I am not
> doing surveying, it won't matter all that much. I bought an adapter for the
> 5/8 by 11 thread it uses and have a pvc pipe mount ready to go up. My
> location is not ideal. It will be atop a 40 foot Rohn 25 tower, but there
> are tall trees nearby. Since my Z3801 died, I don't have much of a GPSDO to
> use the antenna with. Just a couple of T bolts and some kind of postcard
> sized unit I need to build a housing and power supply for. Still, enough to
> experiment with.
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Re: [time-nuts] Anyone have experience with this antenna?

[Bob kb8tq]

Hi

One gotcha (if the data sheets are correct) is going to be the supply voltage.
We normally stay away from 12V antennas because TBolt’s put out 5V. In the
case of a survey antenna, 12V is what most of the gear puts out. I don’t know
of any L1 / L2 gear that puts out 5 rather than 12V ….

Bob

> On Feb 6, 2018, at 6:48 AM, Attila Kinali  wrote:
> 
> Moin,
> 
> On Mon, 5 Feb 2018 21:33:59 -0600
> John Green  wrote:
> 
>> https://www.ebay.com/itm/High-Precision-L1-L2-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-antenna/162718512935?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
>> 
>> Listed on eBay as a L1/L2 antenna with decent specs. They seem to indicate
>> it is as good as a choke ring antenna. I suspect it is just a patch in a
>> fancy package. 
> 
> It actually is. The fourth picture in the ebay listing shows that it's
> a dual, stacked patch antenna with a 4 point (0°, 90°, 180°, 270°)
> excitation using fiberglass as substrate. I am not sure I would trust
> the +/-2mm phase center error, but it's probably quite decent.
> But advertising it as "high precision" or even "chocke ring antenna
> functionality without out the size or weight" is an outright lie. 
> For one, they are too cheap to use nylon screws instead of
> metal screws in the antenna, which will lead to distortions in the
> radiation pattern. For another the fiberglass/epoxy substrate is going
> to change its dielectric constant with humidity, which will inevitably
> lead to changes in its resonance and radiation pattern. Third, the
> choke ring is to minimize influence of reflections close to or below
> the antenna horizon. This antenna does not have anything that comes even
> close to provide this feature.
> 
> Judging from the meager information on the ebay lsting, it's most likely
> a Shenzen Beitan 7151[1] or a 7201[2] ("data"sheets attached).
> 
> BTW: You can get the 7151 for 75USD and free sheeping on aliexpress.
> 
>> That is what the Leica and Trimble survey grade antennas I
>> have contain anyway. I bought one but haven't had the chance to do any
>> testing. I couldn't figure out how to get to the insides to take a peek
>> without damaging it. My antenna testing abilities are pretty feeble.
>> Mostly, I will just compare it to the Leica and Trimble to see how many
>> satellites it sees and look at position wander of the uBlox. Is there any
>> simple way to judge the quality of a GPS antenna?
> 
> If you have a known-good reference antenna and two receivers that can
> record the carrier phase data of the two antennas, then it's relatively
> easy to compare them (although there is quite a bit of math involved
> and you probably eed to write the software yourself, as i am not aware
> of any publicly, for hobbyists available software package).
> 
>   Attila Kinali
> 
> [1] http://www.sz-beitian.com/ProductsDetail?product_id=53
> [2] http://www.sz-beitian.com/ProductsDetail?product_id=52
> 
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Etching of quartz crystals

[Bob kb8tq]

Hi

> On Feb 5, 2018, at 10:31 AM, jimlux  wrote:
> 
> On 2/5/18 5:54 AM, Attila Kinali wrote:
>> On Sun, 4 Feb 2018 09:21:54 -0500
>> Bob kb8tq  wrote:
>>>> The images on this page gives a good impression about the current
>>>> skill-level in that area:
>>>> 
>>>>https://www.azonano.com/article.aspx?ArticleID=2740 
>>>> <https://www.azonano.com/article.aspx?ArticleID=2740>
>>> 
>>> The gotcha is shown in the pictures. First point is that they are etching 
>>> *very*
>>> small features. A 5 MHz 3rd overtone blank is way thicker than what they are
>>> playing with. The second issue is that even at small scale the walls are 
>>> going
>>> non-parallel.
>> That's exactly the issue here. While SAW resonators benefit quite a lot
>> from the processing skills learned from semiconductor fabrication, these
>> skills do not translate into BAW manufacturing. SAW resonators are built
>> etching or depositing small features ontop of a SiO2 wafer that is supposed
>> to be as flat as possible. On the other hand BAW oscillators are 3D 
>> structures
>> by themselves. They are lens shaped (thus not flat) to keep the oscillation
>> energy trapped in the center of the slap, thus allowing the edges to be used
>> for mounting/contacting, with minimal damping of the oscillation.
>> Yes, the shapes are simple. But not only because that's the only shapes
>> we know how to build, but also because these shapes allow us to calculate
>> how the crystal will oscialate and because the simpler the structure the
>> easier it is to build it with high precision and accuracy.
>> It would be possible to use edging of surface structures into the
>> crystal to form a Bragg reflector (instead of the lense shape).
>> But I have no idea how well it works. Considering that it is easier
>> to build a slap that is flat and then etching structures on it, than
>> to form a 3D structure, I wonder why I have not read about anyone
>> doing exactly that (beside for SAW structures).
> 
> 
> Follow the money - or lack thereof - Folks are happy with the existing 
> technology - If I'm flying a science mission that needs a space qualified 
> Ultra Stable Oscillator - I've already budgeted my several million dollars, 
> claiming that I'll just use what we already know how to build, and I spend no 
> more proposal pages talking about it.  I certainly am not going to say 
> "instead of spending $1M/oscillator for my 2 oscillators, I'm going to spend 
> $5M on an experimental process to change how the resonator is made, and by 
> the way, it might not work"
> 
> Would using ion milling and other modern fabrication techniques lead to an 
> oscillator with *significantly* better performance or *significantly* lower 
> cost?

Consider that a reasonable budget for just the gear to finish a precision 
resonator (not the fab side) is 
in the $3 to $5 million range these days. If you include the fab process, the 
question becomes “how 
far back” you go in that process. Do you start with growing the synthetic 
quartz? If so, the budget just
goot a *lot* bigger. 

People have indeed experimented a lot with alternative fab processes. There are 
alternatives out there.
So far, the precision end of things still *looks* a lot like it used to. If you 
scratch under the surface it’s
vastly different than it was 10 or 20 years ago. It’s nothing at all like it 
was in the 70’s, let alone back 
in the 50’. 

Bob


> 
> For those users for whom this is important, research focuses on looking for 
> another qualitatively different way to get there - That's sort of what the 
> CSAC and the Deep Space Atomic Clock (DSAC) are about - the ion trap clock 
> for DSAC gives you long term performance BETTER than a USO. Although probably 
> not at a lower cost, yet, there is potential for it to be so.
> The CSAC gives you "good accuracy at low power", compared to an OCXO - less 
> than 1/10th the power.
> 
> 
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Re: [time-nuts] Etching of quartz crystals (was: Rakon HSO-14)

[Bob kb8tq]

Hi


> On Feb 5, 2018, at 8:54 AM, Attila Kinali  wrote:
> 
> On Sun, 4 Feb 2018 09:21:54 -0500
> Bob kb8tq  wrote:
> 
>>> The images on this page gives a good impression about the current
>>> skill-level in that area:
>>> 
>>> https://www.azonano.com/article.aspx?ArticleID=2740 
>>> <https://www.azonano.com/article.aspx?ArticleID=2740>
>> 
>> The gotcha is shown in the pictures. First point is that they are etching 
>> *very*
>> small features. A 5 MHz 3rd overtone blank is way thicker than what they are 
>> playing with. The second issue is that even at small scale the walls are 
>> going 
>> non-parallel.
> 
> That's exactly the issue here. While SAW resonators benefit quite a lot
> from the processing skills learned from semiconductor fabrication, these
> skills do not translate into BAW manufacturing. SAW resonators are built
> etching or depositing small features ontop of a SiO2 wafer that is supposed
> to be as flat as possible. On the other hand BAW oscillators are 3D structures
> by themselves. They are lens shaped (thus not flat) to keep the oscillation
> energy trapped in the center of the slap, thus allowing the edges to be used
> for mounting/contacting, with minimal damping of the oscillation.
> 
> Yes, the shapes are simple. But not only because that's the only shapes
> we know how to build, but also because these shapes allow us to calculate
> how the crystal will oscialate and because the simpler the structure the
> easier it is to build it with high precision and accuracy.
> 
> It would be possible to use edging of surface structures into the
> crystal to form a Bragg reflector (instead of the lense shape).
> But I have no idea how well it works.

The typical quartz resonator is operating in a mode that involves 
more than a surface wave. Much of the effort involves not just that
mode but getting rid of the vast number of similar modes that can 
pop up. As you add structure complexity, you don’t just want to “improve”
the main mode. You also want to be sure you don’t encourage any 
others …..

That all said, there are indeed people out there who *do* understand how
this all works. There aren’t a lot of them, but they are out there. From what
I’ve seen, the supply of “those who know” actually exceeds the industrial 
demand for what they know. Like it or not, precision quartz resonators is
*not* a growth field. 

Bob


> Considering that it is easier
> to build a slap that is flat and then etching structures on it, than
> to form a 3D structure, I wonder why I have not read about anyone
> doing exactly that (beside for SAW structures). 
> 
> 
> 
>   Attila Kinali
> -- 
> It is upon moral qualities that a society is ultimately founded. All 
> the prosperity and technological sophistication in the world is of no 
> use without that foundation.
> -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Rakon HSO-14

[Bob kb8tq]

Hi

Obviously you need two more 8607’s ….. :)

I suspect you are correct and the OCXO is doing better than the close in data 
suggests. 

Bob

> On Feb 4, 2018, at 8:33 AM, Tom Van Baak  wrote:
> 
> FYI: here's an old plot where I evaluated an Oscilloquartz 8607 BVA against a 
> H-maser. It gets down to 8e-14 but is likely a bit better. On this plot, I 
> suspect the short-term numbers were not the BVA oscillator or the TSC 5110A 
> analyzer, but the H-maser.
> 
> /tvb
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Re: [time-nuts] Rakon HSO-14

[Bob kb8tq]

Hi

> On Feb 4, 2018, at 7:13 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message <480971424.644410.1517715556...@webmail.xtra.co.nz>, Bruce 
> Griffiths
> writes:
> 
>> It has been used to machine/polish crystal quartz waveplates and
>> to machine/polish the surface of silicon wafers before uses for
>> MEMS fabrication. Its even been used to carve channels in silicon
>> wafers in such applications.
> 
> The images on this page gives a good impression about the current
> skill-level in that area:
> 
>   https://www.azonano.com/article.aspx?ArticleID=2740 
> 

The gotcha is shown in the pictures. First point is that they are etching *very*
small features. A 5 MHz 3rd overtone blank is way thicker than what they are 
playing with. The second issue is that even at small scale the walls are going 
non-parallel. I seem to remember that you need straight walls on the cuts to
keep everything happy in terms of reflecting sound. 

There *is* a lot of work done on odd shaped crystals. Your wrist watch has a
good example of that in it. It all comes down to what sort of process is 
required 
to achieve the result. With the BVA the real answer is that you can do a mount
that achieves the same thing for a lot less money. 

Either way, you are simply taking care of one plane (just like the SC). Forces 
in the real world rarely are nice enough to only show up in one plane ….

Bob


> 
> I'm pretty sure that it is not the machine control but rather the
> metrology that would be the challenge.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Rakon HSO-14

[Bob kb8tq]

Hi

Anything like a laser that generates heat to do the “work” will twin the 
quartz. 
Once you do that, it’s pretty much useless as a resonator. The same issue 
gets you in trouble trying to wire bond to a resonator. 

Bob

> On Feb 3, 2018, at 9:46 PM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>> Unfortunately ( at the rates you must use) the “blast it with a fire hose”
>> approach is not very fast….. 
> 
> How fast to laser blasters work and/or how much do they damage the crystal?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Rakon HSO-14

[Bob kb8tq]

Hi

Unfortunately ( at the rates you must use) the “blast it with a fire hose” 
approach
is not very fast…..

Bob

> On Feb 3, 2018, at 8:15 PM, Bruce Griffiths  
> wrote:
> 
> Fluid jet polishing perhaps?
> 
> At least on fused quartz and optical glass there is no associated subsurface 
> damage.
> 
> Bruce
> 
> On 04 February 2018 at 14:05 Bob kb8tq  wrote:
> 
> Hi
> 
> If you try “normal” machining techniques on a resonator, you are very
> likely to create micro cracks in the material. Those are *really* bad for
> aging and a few other issues ….. Much of the normal production flow of the
> quartz is designed to keep the processes like sawing far enough away
> from the “end product” that more gentle techniques can be used to remove
> the (possibly) damaged material.
> 
> Since the slots are pretty darn small, there isn’t a lot of room for this and 
> that
> to be done when making them. There may well be better ways to do the
> work today than back 20 or 30 years ago. It would still take a *lot* of effort
> to validate a process.
> 
> Bob
> 
> On Feb 3, 2018, at 7:24 PM, Poul-Henning Kamp  wrote:
> 
> 
> In message <0f9a9acc-4cdf-780f-e633-616262264...@earthlink.net>, jimlux 
> writes:
> 
> [1] Surprising to me is that modern dentists are highly kitted for
> CNC-ing very hard ceramic materials at high precision.
> 
> But, small "tooth sized" pieces - how big is your crystal.
> 
> Well, they appearantly make a mouth-full at a time, so that is
> covered...
> 
> I don't think the dentist machines are precise enough though,
> as I understood it, the state-of-the-art stuff has built in
> laser-interferrometers etc.
> 
> --
> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
> 
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Re: [time-nuts] Rakon HSO-14

[Bob kb8tq]

Hi

If you try “normal” machining techniques on a resonator, you are very 
likely to create micro cracks in the material. Those are *really* bad for
aging and a few other issues ….. Much of the normal production flow of the
quartz is designed to keep the processes like sawing far enough away 
from the “end product” that more gentle techniques can be used to remove
the (possibly) damaged material. 

Since the slots are pretty darn small, there isn’t a lot of room for this and 
that
to be done when making them. There may well be better ways to do the 
work today than back 20 or 30 years ago. It would still take a *lot* of effort
to validate a process. 

Bob

> On Feb 3, 2018, at 7:24 PM, Poul-Henning Kamp  wrote:
> 
> 
> In message <0f9a9acc-4cdf-780f-e633-616262264...@earthlink.net>, jimlux 
> writes:
> 
>>> [1] Surprising to me is that modern dentists are highly kitted for
>>> CNC-ing very hard ceramic materials at high precision.
>> 
>> But, small "tooth sized" pieces - how big is your crystal.
> 
> Well, they appearantly make a mouth-full at a time, so that is
> covered...
> 
> I don't think the dentist machines are precise enough though,
> as I understood it, the state-of-the-art stuff has built in
> laser-interferrometers etc.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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