[time-nuts] Re: poor mans environmental control for time servers (with pictures)

[Eric Scace]

   My brother, who worked on gas impurity metrology at NIST, tipped me off to 
another useful temperature control guideline: 2-3 cm of styrofoam adds about an 
order of magnitude to the time needed for external environmental temperature 
change to penetrate into a chamber.

   E.g., If one sees an environmental 1º rise resulting in ½º rise internally 
after 10 minutes, adding that layer of styrofoam will roughly stretch that time 
out to 100 minutes… or 1000 minutes with double the thickness.

> On 2022 Feb 07, at 07:23 , Attila Kinali  wrote:
> 
> On Mon, 7 Feb 2022 13:55:23 +0100
> folkert  wrote:
> 
>> https://vanheusden.com/texts/usb-asic-miner-heater/
>> 
>> What it is about: I've put my time-servers in a box and now them up
>> using usb bitcoin miners (- they have no use anymore because they are no
>> longer profitable) to 35 degrees celsius. As expected/visible in graphs,
>> this stabilizes the clocks of the time-servers a bit.
> 
> Nice use of recycled electronics :-)
> 
> 
> Some small additional notes for those who want to do the same and
> use it to stabilize oscillators (OCXO, rubidium and the like)
> 
> 1) If you are building a control loop, have a temperature sensor
> with more than 0.1°C resolution. 0.1°C is quite a large dead-band
> for a control loop in a case like this and might lead to oscillations
> in the control loop. I can recommend using a BME280 break-out board
> as a temperature sensor. It's relatively cheap (at least it was
> before 2020), delivers temperature to 0.001°C with very little noise
> (noise floor is below 0.005°C) and gives you humidity as a bonus.
> Its long term stability is better than I can verify with the equipment
> I have, so good enough :-)
> 
> 2) Use a heating element that you can control with at least 10 bits.
> It doesn't really matter whether it's some PWM with 5minutes loop time
> or some heater element controlled with a DAC. Going below 10 bit will
> give too little control to hold the temperature stable and thus can
> lead to oscillations as well.
> 
> 3) If you pass cables through the lid, tape the lid shut. Most of the
> heat will be lost through convection through the holes in the lid
> 
> 4) It's not explicitly written in the article, but the small fan you
> see  in there is cruical. There is convection even in these small boxes
> and it is very slow. You want to mix the air inside the box well
> so that you don't get temperature gradients and hot/cold air bubbles
> that move around.
> 
> 
>   Attila Kinali
> 
> -- 
> The driving force behind research is the question: "Why?"
> There are things we don't understand and things we always 
> wonder about. And that's why we do research.
>   -- Kobayashi Makoto
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[time-nuts] crystal types

[Eric Scace]

   Folks working at KPH, RCA’s coastal marine radio station at Pt Reyes, 
California, asked the following question recently:
It has been noticed that on (RCA) Radiomarine Corporation of America radio 
crystals that they have a type on the case. Some of the types noted are R1, R2, 
R5, RC-2A and crystal types for Aviation service start with AV. If anyone has 
reference material or hard evidence of what these types signify, please pass 
this forward so we can all know!

   Recalling that some discussions have occurred in the past on crystals, I 
wonder if anyone in our Time Nuts community can shed light on this “type” 
identification.

   Thanks.

— Eric


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[time-nuts] Re: List Opinion/Suggestion(s)

[Eric Scace]

Hello all —

   I am working on several broadcast radio projects that require a local PTP 
server at multiple locations. The purpose of PTP in this context is to 
timestamp audio and related control data. The timestamps ensure proper 
reassembly at distant locations after transfer over public/private internets.

   The precision and stability requirements are just beyond the reach of NTP.

   Of course, once installed, such a server becomes the on-premises reference 
for other uses, including frequency reference for transmitters and transmitter 
monitoring.

   I’m considering the Time Machines TM2500C 
.
 At $750 it seems an economical solution — economical enough to install pairs 
as primary and secondary in critical locations.

   If you’ve any experience with the performance of these units, I’d appreciate 
hearing about it.

   Thanks.

— Eric

> On 22 Nov 2021, at 19:13, Shawn  wrote:
> 
> Hey Guys,
> 
> I'd like to ask for opinions from the list if I could.
> 
> I have a need to put a couple GPSDOs on some remote locations, 10MHz
> output plus NTP.  Found some Spectracom 9183s as well as some
> Symmetricom XLi units on EBay that look like they'd fill the bill.
> 
> The 10MHz will be mostly used by some Service Aggregation Routers to
> re-clock some DS1s that are being transported over packet microwave and
> the NTP is for the computers and cameras, the network is closed off
> from external access.
> 
> I'd really appreciate any insights/gotchas/other suggestions that you
> guys may have in this arena.
> 
> Thanks in advance!
> 
> Shawn
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[time-nuts] Re: time-nuts Digest, Vol 210, Issue 19

[Eric Scace]

   If one is interested in visiting the station, contact the MRHS directly. The 
station is back on the air and Covid restrictions have been gradually relaxed.

> On 2021 Oct 29, at 01:49 , Dave B via time-nuts  
> wrote:
> 
> On 29/10/2021 08:30, time-nuts-requ...@lists.febo.com wrote:
>> Hi all —
>> 
>>The Marine Radio Historical Society  out on 
>> Pt Reyes CA maintains (with the US Park Service) the KPH coastal station 
>> (originally Marconi, then RCA) as a working museum. (I highly recommend a 
>> visit if you’re anywhere nearby during your travels.)
> 
> 
> I was out there on the national sea shore back in 91/92.
> 
> I don't think the radio site was open to the public at that time, as it was 
> still a working site up to '97.  But the whole area is just superb.
> 
> 
> Sadly according to :- 
> https://www.nps.gov/pore/planyourvisit/kph_treetunnel.htm
> 
> As of October the 16th this year, it's closed until further notice. :-(
> 
> (I imagine a Covid prevention measure.)
> 
> 
>   Tour the Historic KPH Receiving Station
> 
> *Cancelled until further notice.*
> 
> Most Saturdays throughout the year, Maritime Radio Historical Society 
>  (MRHS) members welcome visitors and provide 
> guided tours of the Historic KPH Receiving Station from noon to 5 pm.
> 
> 
> 73  Dave G8KBV
> 
> 
> -- 
> Created on and sent from a Unix like PC running and using free and open 
> source software:
> 
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[time-nuts] crystal type codes

[Eric Scace]

Hi all —

   The Marine Radio Historical Society  out on Pt 
Reyes CA maintains (with the US Park Service) the KPH coastal station 
(originally Marconi, then RCA) as a working museum. (I highly recommend a visit 
if you’re anywhere nearby during your travels.)

   Today one of the volunteers put out this request for information on crystal 
types:
It has been noticed that on (RCA) Radiomarine Corporation of America radio 
crystals that they have a type on the case. Some of the types noted are R1, R2, 
R5, RC-2A and crystal types for Aviation service start with AV. If anyone has 
reference material or hard evidence of what these types signify, please pass 
this forward so we can all know!

   If you can help, please let me know.

— Eric


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[time-nuts] FEI Nanosync 2

[Eric Scace]

Hi —

   In a parallel life I work as a broadcast radio engineer. An AM transmitter's 
hybrid digital control system contains an embedded FEI Nanosync 2 GPS receiver. 
The GPS time data appears to suffer from a week 1024 rollover problem, causing 
the control system to believe (and broadcast) a date around 2000 November (if I 
remember correctly).

   I can get access to the serial port to the FEI Nanosync 2 card. Does anyone 
have experience or suggestions as to how to force this receiver to the proper 
date?

   Thanks for any help.

— Eric

p.s.: I apologize if the information requested below is in the archives 
somewhere. Is there an alternative search other than month-by-month?
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[time-nuts] potential low-RFI power supply

[Eric Scace]

Pro Audio Engineering announced a sale (through Friday) on its nominal 14 Vdc 
4A switching supply 
. The test 
results  
webpage compares noise on the DC output and noise frequency spectrum under a 
variety of conditions with a lead-acid battery, an Astron linear supply, and a 
variety of switching supplies from other manufacturers.

I have not used this and can’t vouch for its performance. Given recent 
discussions here on supplies, the analysis might be interesting. At least the 
supplier has attempted to quantify the performance of its power supply and make 
that information available to the prospective purchaser.

It would be interesting to see comparable (or more suitable) measurements made 
by others posted here.
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[time-nuts] Alfred Loomis - an early time nut

[Eric Scace]

> On 2020 May 14, at 14:21 , Skip Withrow  > wrote:
> […snip…]
> 
> A question for TVB (or anyone else that might know), what happened to
> the three Shortt clocks that he [Loomis] had?

   About 100 Shortt-Synchronome systems were manufactured. There is not a 
central database of locations for the surviving instruments, as far as I know. 
I know the location of maybe a dozen or so — but there are plenty more than 
that in existence. Some are still in the hands of their original owners; some 
are in museums; others are in private collections.

>  Also of interest would be how
> many still exist today, and how many in running condition

   Very few of the survivors of which I am aware are presently operating. The 
one at NIST’s library in Gaithersburg, for example, was maintained by a retired 
staff member. A few years ago he moved from the DC metro area. A vacuum leak 
developed in the master and the system stopped.

   The ClockWorks museum in London has had difficulty keeping their system 
operating. There are some tricks to its setup, the knowledge of which has not 
been well-maintained.

> (and
> Fedchenko

   Fedchenko engineered 4 pendulum-based systems:
a clone of the Shortt-Synchronome, of which the highest known serial number is 
#27. These were manufactured by Etalon in Leningrad. At present three complete 
(master + slave) systems are known exist, and two slave-only units. I’m not 
sure that any of the three complete systems are operational; two may be capable 
of starting up but their ability to run for long periods of time is unknown.
AChF #1 was a first generation prototype of the system for which Fedchenko is 
famous. It was placed in the first floor of a working building at KhGIMIP 
(Kharkov State Institute for Weights and Measures) and tested for 3 years 
(1955-1958) against the KKh-3 quartz clock. This model was not placed in 
production. Unless Etalon has it in archives, it may not have survived.
AChF #2 was a second generation prototype built in 1956 — maybe lost or perhaps 
in Etalon archives.
AChF #3: The highest known serial numbers, #36 and #37 (incomplete), came to 
light in the last six years. Thirteen survivors are known. Of these, four are 
in museums: one in Switzerland, one at the Greenwich Observatory, and two at 
the ClockWorks Museum (London). The remainder are in private hands. There is 
also an orphaned slave clock in private hands whose current location is unknown.
The Greenwich one was installed by Etalon as a gift and ran for a number of 
years but has stopped for unknown reasons — possibly a vacuum leak.  
Unfortunately it’s built into a display cabinet that would have to be 
disassembled in order to service the clock.
When I last visited, one of the two systems at Clockworks was operational but 
not kept in continuous service.
The operational condition of the system in Switzerland is unknown.
At least one system in private hands is kept operating, but not instrumented 
for measurements.

> and Riefler)?

   Riefler made a vast number of models. I don’t know of an inventory of the 
partial-vacuum tank clocks.

> There is something very satisfying about the tick-tock of a pendulum
> clock, though I realize the Shortt's were not direct drive.

   The seconds-driving contacts of the Shortt-Synchronome make plenty of “tick 
tock”! Synchronome used a weight-assisted contact mechanism to ensure a 
reliable “make” and the weight gets reset by a solenoid each second. With care, 
one can do a lot to quiet down the noise to acceptable residential levels. But 
that’s another lengthier discussion.

> 
> Regards,
> Skip Withrow


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Re: [time-nuts] - LightSquared is back now called Ligado

[Eric Scace]

   Caveat: I have not personally read LightSquared’s final filings with the FCC 
nor the staff recommendations to the commissioners. I’m relying on the 
assertions written in this thread for now.

   If one feels strongly that, based on the facts on record, the approval by 
the FCC will have all the harmful effects described in previous messages on 
this thread, a few courses of action would nominally have a chance of changing 
the situation:

   a) Get your congressional Representative and Senators' staffs involved. 
Having been a Federal civil service employee at NIST for a few years, I know 
that few things get one’s attention more quickly than an inquiry from a member 
of Congress’ staff. Defending the viability of constituents’ investments in 
their car and phone navigation systems sounds like an easy voter-oriented 
issue, just for start…

   b) If you work for/with companies whose products will be impaired by 
LightSquared’s service, or their industry associations, it’s time to bring 
their legal staff and (if they have one) legislative relations group up to 
speed. 

   c) If your employer is a customer of those companies — and the 
products/services your company has purchased will likely no longer work 
properly once LightSquared goes on-air — it’s time to start informing your 
supplier(s) about this situation and asking them to take action.

   I’m sure some readers will be rolling their eyes at this 7th grade 
civics-level message. But any of (a), (b), or (c) above will have a far better 
chance of generating a successful petition for reconsideration at the FCC, an 
injunction in Federal court, and/or legislative intervention than continued 
emails here.

   Personally, I don’t work for a company that falls into (b) or (c). But I’ll 
be reading those FCC documents because this sounds more important than 
fidgeting in my time lab this weekend, and then talking to my people in 
Congress.

   What about you?

— Eric
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Re: [time-nuts] OCXO and fluctuations after EFC adjustment

[Eric Scace]

Au contraire. My backgrounds lay scattered around in other fields, each of 
which have their own parallel tales where art, personalities, business, and 
legacy technologies/processes combine to produce unanticipated results.

I learn something from every one of the “uninteresting” stories about the 
details of electronic engineering and metrology — and hopefully retain enough 
to know when to ask for help in order to avoid a major pitfall when it comes to 
time lab stuff.

> On 2020 Apr 11, at 20:09 , Hal Murray  wrote:
> 
> 
> rich...@karlquist.com  said:
>> By now, few people besides Bob are still reading this. :-) 
> 

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[time-nuts] HP3588A battery

[Eric Scace]

   I had to do this myself on an HP-4195A a few months ago. It was impossible 
to locate an equivalent NiCd of the same form factor. There was enough room to 
squeeze in this somewhat larger battery 

 from Newark Electronics to replace the 1420-0306 2.4V battery on the A6 board.

— Eric

> On 2020 Mar 28, at 14:15 , Matthew Martin  > wrote:
> 
> It looks like I need to replace the battery in my HP3588A spectrum analyzer. 
> The service manual says the HP part number is 1420-0336.
> 
> Before I pull this monster off the shelf and open it up, I would like to 
> obtain a replacement battery & be ready to swap out the old battery for a new 
> one. 
> 
> Anyone out there know what might be a decent replacement battery?  I suspect 
> it is a lithium battery in the 3.5 volt range, but I don’t know. 
> 
> Any help is much appreciated!
> 
> Matt
> N6LQB
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Re: [time-nuts] tracking position & orientation

[Eric Scace]

   Thank you, everyone, for your enthusiastic guidance and observations to my 
quirky question.

   Quite a few mentioned the difficulties in measuring rotation over a short 
baseline. In response to the question of “is there another measurement point 10 
miles away”, the quick answer is yes: NIST is on the opposite side of Boulder 
City from me.

   The question of a sturdy — i.e., dimensionally stable — antenna mount 
brought to mind something I learned during my home inspection. My house is 
built at the foothills of the Front Range in North Boulder. Soils there include 
a kind of clay that swells significantly when exposed to water. As a result, 
house foundations are build on a system of screw pilings that go down to 
bedroom. The house’s cellar floor is a concrete slab poured on corrugated steel 
plates supported by cross-web girders that sit on these pilings. The cellar 
walls (to which the higher-precision pendulum clocks are mounted) are poured 
concrete that also rests on these pilings. It seems the house foundation is 
probably a better reference point for antennas than something sitting on the 
ground at the corner of my (tiny) lot.

   Of course, my house and the neighbors’ houses are obstructions to signals 
for an antenna attached directly to the foundation walls.

   The plan was to install two antennas (for two GPSDOs) mounted on short 
roof-penetrating metal tubes secured to the roof framing, just high enough to 
clear the neighborhood’s rooflines. This will give full sky access (except for 
the portion obscured by the foothills of the Front Range, a problem that 
plagues NIST as well). For time purposes, my understanding is that this should 
be fine.

   For millimeter-scale position determination, this sounds like a more 
difficult situation. The house is generally wood framing with some structural 
steel elements (not in useful locations). Position measurements would contain 
noise from the diurnal/seasonal changes of the house framing. Maybe that could 
be averaged out?

— Eric

> On 2019 Nov 22, at 00:36 , Hal Murray  wrote:
> 
> Measuring rotation will be tough if your 2 stations are only 100 ft apart.  
> Do 
> you have a friend 1, 10, or 100 miles away?
> 
> PS: Make sure that your antenna mounts are sturdy.  You don't want them 
> drifting as the house ages or you bump into them.

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[time-nuts] tracking position & orientation

[Eric Scace]

   I need another project like a hole in the head — but curiosity continues to 
nag me.

   I moved to Boulder CO a few months ago. The “curiosity” is to determine the 
position of two antennas at either end of my house and monitor it over time, 
with the idea that one could see plate movement in 3 dimensions plus rotation 
around the axes.

   What hardware/software would be suitable for a TimeNuts (PositionNuts?) 
project like this?

— Eric K3NA


> On 11/21/19 8:00 AM, Bob kb8tq wrote:
> Hi
> 
> Way back in time, the first gear out there to use what we now look at as 
> “normal” antennas 
> was survey gear. For various reasons they decided on a 12V power supply and 
> 40 to 50 db
> of gain in the preamp mounted in the antenna. They also got into L1 / L2 
> pretty quickly. 
> 
> A bit later the cell phone (and later broadcast) guys got into this. In a 
> location with a lot of 
> RF (like a cell site) having a lot of gain at the antenna didn’t work all 
> that well. IMD issues 
> got into the act pretty quickly. In addition, front end filtering was 
> required to reduce overload
> issues. The focus was on L1 only so filtering was relatively easy.
> 
> There is a whole separate set of antennas that put a big chunk of the RF 
> portion of the radio
> in the antenna. Those still survive here and there. I have one of them and 
> probably a couple
> of dozen of the more “normal” antennas. 
> 
> As time marched on, supplying 12V to antennas became a bit less popular. Most 
> of the cell 
> guys went over to a 5V antenna supply. The net result was 12V 50 db survey 
> antennas that did 
> L1/L2 and much smaller 5V 25 db antennas for “timing”. The timing antennas 
> didn’t do L1/L2 so
> not going to work for survey. The survey antennas had way to much gain and no 
> filtering so 
> not going to work for a cell site. 
> 
> Indeed things did and do get crossed up in various pro and basement systems. 
> With care and
> the right set of circumstances things may work. In other cases the result can 
> be an ongoing set
> of systems issues over an entire network of stations. 
> 
> Prices for a good new survey antenna are up in the many thousands of dollars 
> range. They have
> very stable phase centers and (usually) test results to allow correction of 
> any residual phase 
> issues. This is part of what lets you get into the “couple of mm” range on a 
> survey. 
> 
> For timing, you have to dig a bit and answer a few questions. Is your concern 
> how close you
> are to BIH? If so you will need to know all the delays in your system. This 
> includes the delays
> in the antenna filters and the preamp. Is your concern (or measure) the ADEV 
> at 1 second?
> If so the delays are not a concern. Your antenna choice may be a bit 
> different depending on
> this focus.
> 
> Bob

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[time-nuts] Mac OS and iOS leap second handling

[Eric Scace]

   Maybe someone on the list has a recent and authoritative answer to the 
following questions.

   I’ve been digging around in “civilian mode” (not an OS X or iOS developer) 
trying to determine if current Mac OS X and iOS releases handle leap seconds:
no smearing
proper display of 23:59:60, etc on the system clock & return of same to 
appropriate function calls.

   I have not been able to discover a well-documented answer to this question; 
e.g., video of an OS X/iOS system clock displaying a leap second, or 
Apple-sourced documentation stating leap second support.

   There are assertions that OS X was built around POSIX and suffers from the 
limitations of Unix epoch time decisions of long ago. Is that still the case?

   (In contrast, Microsoft docs claim Win 2018 Oct and Win Server 2019 now have 
leap second support.)

Thanks,
   — Eric
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[time-nuts] CATV assymetries

[Eric Scace]

   CATV plant in inherently asymmetric in delays. Referring to the DOCSIS (data 
over cable service interface specification) specs for North America:

Downstream to the customer:
   6 MHz channels with 64- or 256-level QAM modulation. If 256-QAM is used, the 
raw usable bandwidth is about 38 Mbit/s per channel.

Upstream from the customer:
   6.4 MHz channels (with fallback to channel widths between 0.2 and 3.2 MHz 
when talking with DOCSIS v1 equipment)
   QPSK, 8-, 16-, 32- or 64-level QAM
   DOCSIS v3.1 allows up to 1024-level, optionally also 2048 or 4096. Max rate 
with 4096-QAM and 25 kHz sub channel carrier spacing is 1.89 Gbit/s per 192 MHz 
OFDM channel.

DOCSIS 3.0 support channel bonding, allowing multiple channels to be used 
simultaneously to/from the same customers.

Downstream channels are shared and therefore traffic queuing may occur because 
of activity of other customers. Similarly, upstream channels may be shared by 
customers via TDMA or S-CDMA. Some contention can occur if customers transmit 
simultaneously.

Signal-to-noise ratios may force specific customers to use lower speeds.

These represent a large set of combinations that yield different downstream and 
upstream throughputs.

More generally, asymmetric behavior is almost guaranteed on CATV plant between 
the customer site and the cable head end. Upstream packets take longer to send 
then downstream, and may have to contend for their channel(s). Downstream 
packets are sent faster but may queue.

Between the cable head end and the public NTP server, symmetrical delays may be 
more prevalent.

   — Eric

> On 2019 Oct 20, at 19:31 , Hal Murray  wrote:
> 
> 
> f...@cattaneo.us said:
>> Maybe I should double check the routing from both ends again and make sure
>> they are really symmetric.. I can also ask my coworkers in the networking
>> group and hear what they think about it. 
> 
> We need a cable TV geek.
> 
> It wouldn't surprise me if the upstream traffic went through a couple of 
> extra 
> hoops/hops that aren't visible at the IP level using tools like ping and 
> traceroute.


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Re: [time-nuts] can of worms: time-of-day in a community radio station

[Eric Scace]

Sadly the formatting of the original message was stripped by the email server. 
Here is a slightly more comprehensible version.

On 2019 Oct 18, at 15:20 , Eric Scace  wrote:

  I fear that I am developing a reputation for bringing to the list rather 
oddball questions. In my rôle as agent provocateur, therefore, here is another 
such problem.

  Questions for you are at the end. Thanks for your thoughts,.

— Eric

ISSUE:

  A community broadcast radio station with multiple studio locations wishes to 
improve the display of time-of-day throughout the station’s operating 
environments. Its current legacy approaches (described below) cause problems 
such as:

   * on-air presenters fail to smoothly segue into scheduled program feeds 
(e.g., BBC news) because the studio clock is “a little off”… and because the 
studio clock is digital. [Quick: how many more seconds can you speak before the 
top of the hour when a digital clock shows 4:59:42? Watching an analog stepping 
second hand is much easier in this situation.]
   
   * computers that automatically capture audio programs to files in storage 
sometimes truncate the start or end of the program because the computer’s idea 
of time-of-day disagrees with that of the program source.

   * desktop computers throughout the station, including in production studios, 
all render slightly different versions of time-of-day to their users.
servers (e.g, for streaming, for archiving shows) are similarly in cheerful 
disagreement as to time of day.

   * wall clocks studios in one city show a different time to their engineers 
than the studios in another city, rendering handoffs more complicated. Ditto 
for remote broadcast sites, and even between studios in the same site.

   * requires manual intervention to bring the most egregious systems back to 
some semblance of reality



BACKGROUND & EXISTING SITUATION:

  Commercial broadcast stations have more money and technology to solve these 
problems. In contrast, “community radio” stations have limited funds and are 
largely staffed by volunteers (like me!).

  In this case, the existing systems are a hodgepodge:

   * mostly Windows OS PCs, with a couple of Macs

   * Linux servers

   * mash-mash of wall clocks, the best of which is a LaCrosse WWVB digital in 
the primary on-air studio. The WWVB signal is more than adequate but the 
LaCross display format is sub-optimal for studio use.

   * some systems are on in-house Ethernet; others on in-house wi-fi



GOALS: (first pass)

   * minimum accuracy requirement: time-of-day displayed within ±0.1 second of 
UTC timescale. (Two clocks both falling outside this range will cause program 
handoffs to be uncomfortably tight or loose.)

   * no manual intervention required for summer/winter time transitions

   * no manual intervention required for leap seconds

   * leap second treatment:

  − no smearing (minimum requirement)

  − accurate leap second display (desirable but unlikely to be achievable)

   * desirable consistency goal: time-of-day displayed within ±0.025 second 
throughout each site. At this level, two adjacent clock displays will not be 
perceived as out of step by a person.

   * presentation goals: studio/remote broadcast control point time-of-day 
displayed in both analog (with stepped seconds hands) and digital form 
(preferred H:MM).

  -- If digital form includes seconds, the seconds digits should be 
visually separated; e.g..smaller. A presenter can then, at a glance and without 
confusion, announce the time (“four twenty-three”) from the digital display.

  − Date in form “Oct 17 Thu” available.

   * medium-term desirable: displays continue within specs for 
accuracy/consistency across power cutovers (to/from generator) and public 
Internet outages.

   * maintenance goals:

  − "eschew emergencies”: no one should have to rush to the station in the 
middle of the night, nor drop what their doing during the day, because 
time-of-day display has failed or gone out-of-spec.

   − standardize on the same hardware/software everywhere:

  ... identical hardware allows more cost-effective 1:N sparing

 … identical hardware/software means less confusion and less training 
for volunteers. (There are a large number of volunteers who use these systems, 
and most contribute time less than once per week. Consistency and 
straightforwardness in the toolkit improves the quality of on-air results.)

   * not too costly

   * try to avoid stringing a lot of new cabling around… but such cabling needs 
are recognized as a one-time investment, so this preference does not eliminate 
a cable-based solution that has other operational/maintenance advantages



POTENTIAL APPROACHES:

   * potential short-term:

  − desktops and servers: better NTP configuration

  − NTP checks:

 … at least hourly?

 … verify NTP utility employs reasonable averaging of multiple NTP 
servers

 … use time.nist.

[time-nuts] can of worms: time-of-day in a community radio station

[Eric Scace]

   I fear that I am developing a reputation for bringing to the list rather 
oddball questions. In my rôle as agent provocateur, therefore, here is another 
such problem.

   Questions for you are at the end. Thanks for your thoughts,.

— Eric

Issue:
   A community broadcast radio station with multiple studio locations wishes to 
improve the display of time-of-day throughout the station’s operating 
environments. Its current legacy approaches (described below) cause problems 
such as:
on-air presenters fail to smoothly segue into scheduled program feeds (e.g., 
BBC news) because the studio clock is “a little off”… and because the studio 
clock is digital. [Quick: how many more seconds can you speak before the top of 
the hour when a digital clock shows 4:59:42? Watching an analog stepping second 
hand is much easier in this situation.]
computers that automatically capture audio programs to files in storage 
sometimes truncate the start or end of the program because the computer’s idea 
of time-of-day disagrees with that of the program source.
desktop computers throughout the station, including in production studios, all 
render slightly different versions of time-of-day to their users.
servers (e.g, for streaming, for archiving shows) are similarly in cheerful 
disagreement as to time of day.
wall clocks studios in one city show a different time to their engineers than 
the studios in another city, rendering handoffs more complicated. Ditto for 
remote broadcast sites, and even between studios in the same site.
requires manual intervention to bring the most egregious systems back to some 
semblance of reality

Background & existing situation:
   Commercial broadcast stations have more money and technology to solve these 
problems. In contrast, “community radio” stations have limited funds and are 
largely staffed by volunteers (like me!).

   In this case, the existing systems are a hodgepodge:
mostly Windows OS PCs, with a couple of Macs
Linux servers
mash-mash of wall clocks, the best of which is a LaCrosse WWVB digital in the 
primary on-air studio. The WWVB signal is more than adequate but the LaCross 
display format is sub-optimal for studio use.

Goals: (first pass)
minimum accuracy requirement: time-of-day displayed within ±0.1 second of UTC 
timescale. (Two clocks both falling outside this range will cause program 
handoffs to be uncomfortably tight or loose.)
no manual intervention required for summer/winter time transitions
no manual intervention required for leap seconds
leap second:
no smearing (minimum requirement)
accurate leap second display (desirable but unlikely to be achievable)
desirable consistency goal: time-of-day displayed within ±0.025 second 
throughout each site. At this level, two adjacent clock displays will not be 
perceived as out of step by a person.
presentation goals: studio/remote broadcast control point time-of-day displayed 
in both analog (with stepped seconds hands) and digital form (preferred H:MM).
If digital form includes seconds, the seconds digits should be visually 
separated; e.g..smaller. A presenter can then, at a glance and without 
confusion, announce the time (“four twenty-three”) from the digital display.
Date in form “Oct 17 Thu” available.
medium-term desirable: displays continue within specs for accuracy/consistency 
across power cutovers (to/from generator) and public Internet outages.
maintenance goals:
"eschew emergencies”: no one should have to rush to the station in the middle 
of the night, nor drop what their doing during the day, because time-of-day 
display has failed or gone out-of-spec.
standardize on the same hardware/software everywhere
identical hardware allows more cost-effective 1:N sparing
identical hardware/software means less confusion and less training for 
volunteers. (There are a large number of volunteers who use these systems, and 
most contribute time less than once per week. Consistency and 
straightforwardness in the toolkit improves the quality of on-air results.)
not too costly
try to avoid stringing a lot of new cabling around… but such cabling needs are 
recognized as a one-time investment, so this preference does not eliminate a 
cable-based solution that has other operational/maintenance advantages

Potential approaches:
potential short-term:
desktops and servers: better NTP configuration
NTP checks:
at least hourly?
verify NTP utility employs reasonable averaging of multiple NTP servers
use time.nist.gov  and similar higher-quality NTP servers
some systems are on in-house Ethernet; others on in-house wi-fi
clocks:
replace with refurb iPads running a dedicated time-of-day display app providing 
both analog and digital form. A refurb wall- or desk-mounted 13” iPad in 
locking frame runs about $100. Smaller sizes can be mounted immediately 
adjacent to or atop a studio mixing board.
remote field broadcast site: iPad over local wi-fi or cellular data?
IRIG displays could be awesome, but seem far mor

Re: [time-nuts] GPDSO Distribution amp that does not radiate ?

[Eric Scace]

   As others have mentioned, leaks can occur from the distribution amp via any 
connected cable (including data power cables) or from the case itself. Ditto 
for the TBolt. These lines should be “cold” at RF by making them high-Z paths.

   Proper ferrite treatment raises RF impedance in its design range and can can 
help kill RF signals leaking out via a cable. RF bypass capacitors inside the 
box (penetration point through the Faraday cage that a good chassis enclosure 
should represent) can also help.

   Similarly, the SDR itself may be picking up RF via paths other than the 
RF-input connector; e.g., power supply lines, control/data lines, audio lines, 
headphone jack.

— Eric

> On 2019 Jul 13, at 20:13 , Bob kb8tq  wrote:
> 
> Hi
> 
> Running and shielding a 10 MHz standard signal is never easy. Ground loops
> here or there are highly likely to exist and create all sorts of issues. In 
> some 
> setups, -10 to -20 dbm is not an uncommon result ( = fix the termination on 
> your Spectracom system …). Getting below -90 is actually doing pretty well.
> 
> Bob
> 
>> On Jul 13, 2019, at 12:53 PM, Jerry O. Stern  wrote:
>> 
>> I have been using a Tbolt and TAPR TADD-1 for a few years, mainly as an
>> external reference source for my workbench equipment.  Just got a SDR radio
>> kit (Ubitx) and trying to calibrate the local oscillators found this
>> annoying substantial 10MHz signal heterodyning with the LO's (45MHz and
>> 12MHz).   Taking a look on my SA with just a broad band telescopic antenna
>> in the SA input, I see a 10MHZ at about -55 dBm and no other signals > -120
>> dBm.  The Tbolt is about 4-5' away from the workbench BUT I disconnected
>> everything and it is only connected to the TADD-1 distribution amplifier
>> The TADD has no distribution coaxes attached, it is in the TAPR metal
>> cabinet which I always thought was well shielded and every port has been
>> terminated with 50 Ohm  dummy load plugs.  When I take the TADD-1 out of the
>> equation and just run the Tbolt into a 50 ohm termination plug, the 10MHz
>> signal on my SA drops down to  > -90 dBM. I duplicated this with a
>> Lucent RFTGm-Xo/Rb pair and the TADD-1 with similar results.Has anyone
>> else seen this with their distribution amp?
>> 
>> 
>> 
>> Jerry 
>> 
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[time-nuts] imprecise but adequate time

[Eric Scace]

Hi fellow time nuts —

   I’m looking for a sanity check or alternative suggestions for the problem 
and tentative solution described below.

   Thanks for your thoughts.

— Eric

Problem:

   In one of my day jobs, I am designing a global network of systems (using 
open-source software) that provide well-researched information about rights and 
licenses for musical works (e.g., songs, compositions).

   Claiming rights, registering licenses (some of which are temporary), and 
time-stamping changes to data each exemplify cases where date/time must be 
included. In many cases the time order of events can be important — potentially 
changing who gets paid how much when music is performed or distributed.

   The machines are scattered around the planet and the usual problems of time 
distribution exist. Furthermore, systems are operated independently. We assume  
occasional use of NTP to correct system clocks, but not a local GPS-provided 
time. The software development team is generally oblivious to the issues of 
time in distributed computer networks.

   A grim picture — but, fortunately, this application does not require high 
precision time.

My tentative proposal:

   1. To avoid burdening systems with multiple local time conversions, all 
date/time information throughout the system shall be UTC. Implications:
user apps will be responsible for converting from a human user’s local time to 
UTC
thus, user app developers will have to do this conversion correctly

   2. Date/time stamps in the data shall be rounded to the nearest EVEN second 
by the system instances; e.g., to 2019 May 28 14:24:28 UTC. Implications:
user apps that submit claims or updates will have their claims/updates 
date/time-stamped by the receiving system node with this rounding method. 
Example: “John Smith claims that he and Jane Doe wrote these lyrics, making an 
equal contribution between them, on 2019 May 27 15:00:00 UTC. His claim was 
received by the system at 2019 May 28 14:26:50 UTC.” One or more blockchain 
ledgers record a hash of the musical work [the lyrics, in this example], the 
claim [who wrote the lyrics when], and which app/system registered the claim 
and when.
events occurring roughly within ±1 second of each other will be deemed to have 
occurred simultaneously. This is entirely adequate for this application.
competing leap second smearing methods employed by different operating systems 
and data center operators will be washed out of the time stamp by this rounding 
requirement.

— end —
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[time-nuts] HP 330B distortion analyzer: free + shipping

[Eric Scace]

Hi all —

   I know some folks have amazing knowledge and collections of previous 
generations of HP test gear.

   In cleaning out my father's lab, I uncovered an HP-330B distortion analyzer 
. It’s 
available for free to an interested Time Nut.  Please either pick-up in Boston 
by Jun 03, or reimburse me for shipping.

   I am moving to Boulder CO. If this doesn’t find a taker by Jun 3, sadly it 
will go to the city recycler.

   Thanks.

— Eric K3NA
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time-nuts@lists.febo.com

[Eric Scace]

Warning: websites cited here can be seriously time-consuming rabbit holes!

   An anonymous engineer using the pseudonym NwAvGuy 
 got fed up with the subjective nature of 
discussions about DACs and amplifiers in the world of high fidelity audio. To 
clear away the smoke, in 2011 he started publishing independent measurements, 
along with some blog posts about what measurements and goals were detectable. 
As one might imagine, this was very controversial.

  Later that year he (or she) concluded it was possible to build a replicable 
DAC and a headphone amplifier 
 that could exceed the 
performance of so-called high-end units being sold for 10e3 - 10e5 dollars, yet 
cost the consumer an order of magnitude less. His blog posts describe the 
design process from requirements to finished result.

   Relevant to this thread was NwAvGuy’s long list of PC board routing and 
enclosure topics that significantly affect performance of otherwise identical 
parts and circuit:
ground routing, ground planes, floods & fills
EMI loops
inductive coupling
parasitics
failure to follow the PC layout developed by the component manufacturer
component placement, aka “rows and columns may not be your friend”
track placement: moving a single track can change increase distortion [by 26 
dB] was one example given
all this at audio frequencies.

   So, yes, I cringe at the thought of developing such systems at frequencies 
and performance levels we talk about here on Time-Nuts. There are not enough 
lifetimes to learn how to do this well, I feel. :-(

   Hats off to all those people who’ve mastered and advanced this craft.

— Eric K3NA

p.s.: NwAvGuy’s resulting DAC/amp has been available in kit or assembled form 
since 2012 from companies such as JDS Labs 
 ($280), built 
exactly according to the design spelled out by NwAvGuy.
   NwAvGuy’s identity has been closely guarded by the few individuals who know 
it. (I am not one of those.) She stopped posting in 2012 and disappeared from 
the scene.
   More recently, Audio Science Review 
 has started publishing 
objective measurements of commercial audio equipment, including DACs 

 and headphone amps 

 that somewhat exceed the performance of the NwAvGuy’s solution but remain in 
similar price ranges. The site’s admin and principle author employs a pseudonym 
amirm , 
claims to be in the Seattle area — and some wonder if this is the same person 
as NwAvGuy.

> On 2018 Dec 20, at 01:41 , ed breya  wrote:
> 
> Yup, I've seen plenty of "top cover effects," and other strange things. That 
> sort of thing is evident even when you don't have to reach E-12 resolution 
> levels - like a million times less. The instrument cabinet and hardware are 
> indeed a part of the electronic system and circuits. So are what it's hooked 
> up to, and its various characteristics, and so on.

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Re: [time-nuts] Boulder / UC-Boulder JILA

[Eric Scace]

We love McGuckin’s!

> On 2018 Oct 23, at 14:57 , David Van Horn 
>  wrote:
> 
> Can't help you there, but be sure to swing by McGuckin Hardware. 😊

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[time-nuts] Boulder / UC-Boulder JILA

[Eric Scace]

Hi all —

   Although I live in Boston at present, I find myself with a free Monday in 
Boulder CO next week.

   Intriguing time & frequency R&D occurs in the JILA Precision Measurement 
labs — but I don’t know anyone personally. I would feel a bit uneasy just 
wandering about the building interrupting people’s work.

   Does anyone know whether an interested engineer/physicist/software dev would 
be welcomed by someone for an hour or two — and who that someone might be?

   In the long term, there is an excellent chance that I will be relocating to 
Boulder in the next few years. I’d like to meet some people who work in the 
time & frequency R&D area there, with hopes that I could study/volunteer at the 
labs when that day comes.

   Thanks in advance for any suggestions — and please respond directly to my 
email address (rather than bother everyone else on the list).

Regards,
   — Eric K3NA
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Re: [time-nuts] XKCD on time :)

[Eric Scace]

Which, if I recall correctly, was the system used in Japan immediately before 
the adoption of Western time methods. Each day’s interval between 
sunrise-sunset was divided into a six units… so, in comparison with an absolute 
scale, the absolute duration of each unit of time varied from day to day and 
location to location.

More details here .

> On 2018 Sep 28, at 04:58 , Hal Murray  wrote:
> 
>  https://xkcd.com/2050/
> 
> A new meaning for rubber seconds.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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[time-nuts] time-nuts humor

[Eric Scace]

For a good time, call 303-499-7111

(Sorry! My girlfriend made me do this.)


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