Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

[David]

On Sat, 2 Jul 2016 19:00:24 +0200, you wrote:

>On Fri, 1 Jul 2016 12:28:44 -0400
>Bob Camp  wrote:
>
>> Real cascode circuits can be built with RF transistors. They also can be 
>> simulated.
>> Simulating them with the “standard” models is a PIA. The issue is that the 
>> inductance
>> of the package is not de-embedded from the test “socket” as carefully as it 
>> might be. 
>> There is also the somewhat non-intuitive need to stick a low value resistor 
>> in the base.
>> Done properly, they are very reproducible and reasonably insensitive to 
>> load. 
>
>Thanks! That resistor in the base did the trick!
>Am I right in the assumption that the resistor gives the transistor
>some negative feedback and thus prevents it from oscillating?
>
>Attila Kinali

If you can find it, "Preventing Emitter-follower Oscillation" by
Michael Chessman and Nathan Sokal has an analysis of negative
resistance oscillation in transistors and why adding dampening to one
lead is often necessary.  There is a copy of this paper in the
appendix of 1993 Linear Applications Handbook Volume II from Linear
Technology.

I do not remember where I read it but apparently Jim Williams made a
habit of preemptively adding a dampening resistor wherever he found a
transistor with low impedance on at least 2 of its 3 leads just to be
safe.

W2AEW made a video with an extreme example of this problem:
https://www.youtube.com/watch?v=oZ1Dv2dVGkU

With RF transistors the problem just gets worse and more difficult to
diagnose since the frequency of oscillation may be outside the range
of common test equipment.  Side effects like mysterious operating
point changes may be all that is visible.
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Re: [time-nuts] Switching transistors, current sources, nonidealties and noise

[David]

>Why do people use general purpose transistors in these places, even
>though RF transistors definitly improve switching behaviour?

Commercial designs do use RF transistors but only old ones are
documented.

The Tektronix 7A11 uses 2 GHz PNPs and 1 GHz NPNs but its design is
unusual since it can integrate positive or negative time and while the
transistors use emitter switching, they are not configured as
differential pairs.

The Tektronix 2440 uses a 1.2 GHz NPN differential pair for the fast
ramp switching and a 2N3906 differential pair for the slow ramp
switching.

>Having put the circuit through Spice, I see that the current through
>the tail fluctates violently during the time when the current switches
>from one transistor of the pair to the other. The reason for this seems
>to be that the f_t of the current source transistor is too low to compensate.
>Trying to replace the current source with an RF transitor like BFU520
>that has an f_t of 10GHz helps to dampen these fluctuations by a factor of 2,
>but they are still there.

Of interest in these designs is that they do not use separate
transistor current sources where fast switching is involved; the
differential pairs do double duty and the tail current is set by a
resistor to a separately decoupled bias supply.
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Re: [time-nuts] Sub-ps delay line

[David]

I did something similar a couple years ago to make an adjustable 75
nanosecond pretrigger for my sampling oscilloscope so I will just pass
along some things I learned.

Power supply noise will create jitter in single ended logic because of
lack of power supply rejection.  Temperature will be a problem with
single ended logic also although I did not care about that.  The delay
section certainly needs to be differential which the LTC6957-1 neatly
covers; I was planning to use a comparator or line receiver next time
but the LTC6957-1 looks ideal.

With the above in mind, I would use a separate reference quality
regulator for the supply voltages and any reference levels.  I only
needed 10s of picosecond stability and picosecond level jitter but I
suspect at the level of precision you desire, ground loops need to be
avoided even through a solid ground plane.

How were you planning on testing the performance?

I need to give this further thought but if you only need 1ns worth of
control and feed one input of the LTC6957-1 with a 100 MHz sine wave,
wouldn't adjusting the level of the other input work to adjust the
delay at the output?
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Re: [time-nuts] Distribution amplifier (again!) - now mostly ok but has gain peaking

[David]

On Sat, 28 Jan 2017 13:58:27 +0200, you wrote:

>...
>
>The picture gallery also shows a pulse distribution amp for 1PPS. It has an
>LT1711 comparator feeding an 74AC14 buffer with length-matched traces to
>74AC04's at the outputs. So far my length-matching didn't give zero
>output-skew between the outputs - I see around 150-200ps skew which I tried
>to tune a bit with wires and 0R resistors - without very much success.. any
>ideas for improving this - or just leave it at 200ps skew?
>
>cheers,
>Anders

200ps of skew is consistent with long traces on board material like
standard FR4 because of uneven dielectric constant produced by uneven
fiberglass weave.  One way to ameliorate this is to route traces at a
diagonal compared to the fiberglass weave.
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Re: [time-nuts] Line Frequency standard change - Possible ?

[David]

On Thu, 9 Feb 2017 19:06:51 -0500, you wrote:

>One simplistic way to look at all this is that a switcher presents a “negative
>resistance” load. If you drop voltage, current goes up. OCXO’s happen 
>to share this issue. Negative resistances are *not* what most power source
>guys want in their control loop.
>
>Bob

People working with emitter/source followers do not like it either and
I cannot see the folks using inverters wanting to pay to put big
resistive heaters across the grid to compensate.

Adding power factor correction to switching power supplies was cheap
compared adding "negative resistance" correction.
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Re: [time-nuts] Line Frequency standard change - Possible ?

[David]

On Thu, 09 Feb 2017 23:39:24 +, you wrote:

>It is harder than it sounds.
>
>Small solar inverters are the best, they an regulate down at milliseconds
>notice, and many jurisdictions impose asymetric frequency bands on
>them to exploit this.
>
>Big inverters, no matter what you put behind them, get quite a bit
>more expensive if they are designed to provide "non-VA" power,
>because you suddenly have to run the current both ways in the same
>half-cycle.
>
>Nobody wants to pay for that voluntarily, and nobody are particular
>keen to cause the first explosion/fire while they get the control-law
>debugged.

Imagine how they will scream if they have to pay for fields of big
synchronous motors to be connected.

https://en.wikipedia.org/wiki/Synchronous_condenser
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Re: [time-nuts] Line Frequency standard change - Possible ?

[David]

On Thu, 9 Feb 2017 17:19:49 -0500, you wrote:

>Isn't this "hard" lock to UTC creating a single point of failure? A 
>solar burst, an EMP, or
>a software error could leave us all in the dark.   After all, smart 
>inverters could be
>programmed to act like big lumps of rotating iron and be compatible with 
>the current
>system.
>
>Pete.

I have the same concern.  I am dubious of tying power grid reliability
to GPS reliability and doubly so in a threat environment which
includes hostile actors.  And if an alternative more reliable timing
standard was used then why use GPS at all?

Inverters lack the overload capability and resistance of rotating iron
unless they are overbuilt in which case they would be uneconomical.
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Re: [time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

[David]

On Tue, 14 Feb 2017 10:31:30 -0500, you wrote:

>On 14/02/2017 7:26 AM, Bob Camp wrote:
>
>> A direct port might be a +/- 100 ns sort of thing most of the time and a 
>> +/-10 us
>> thing every so often under some OS’s. Most desktop operating systems are not
>> designed to prioritize random pin interrupts. A dirt cheap MCU coded with a 
>> few
>> (hundred) lines of assembly code may be a better option than a typical 
>> desktop.
>> Complicating this further is the degree to which some OS’s can be directly or
>> indirectly optimized. Install *this* package and it all goes nuts. Install 
>> that package
>>   and not much happens ….
>>
>> Bob
>
>Hence, wouldn't Best Practice be boxes loaded with only the bare OS and 
>software for the time-related tasks?
>As in:
>- a dedicated machine/box for unencumbered acceptance of PPS, and
>- for systems with a business need, a dedicated NTP server/box 
>disciplined by the PPS source (with dedicated communication), while 
>maintaining internet NTP sources as backup for when the PPS source fails?
>Is there a better way?
>Other considerations?
>
>Michael

When I was doing this many years ago with PC hardware the big problem
was not the OS or load on the OS but the x86 processor's SMM (system
management mode).  Some motherboards and BIOS revisions were
completely unusable.  It was always fun to use a low level I/O port to
monitor interrupt latency with an oscilloscope; with some practice it
was possible to identify the various peaks in the histogram at a
glance.

Eventually I gave up running real time tasks on PC hardware and moved
everything to dedicated hardware in one form or another.
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Re: [time-nuts] 10MHz to 25MHz

[David]

This document covers various methods but I agree with Rick about phase
locking a separate crystal oscillator; harmonic frequency
multiplication is more useful at higher frequencies where other
methods are unavailable:

http://www.qsl.net/va3iul/Frequency_Multipliers/Frequency_Multipliers.pdf

An alternative very simple design I might try is a variation of the
active frequency multiplier where the 5th harmonic is filtered
directly from the output of the digital divide by two stage.

On Wed, 18 Jan 2017 18:28:32 +, you wrote:

>Hello,
>
>I am looking for a good X5 multiplier to use to generate a 25MHz signal from 
>my 10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass filter 
>in the output and then a 3.3 volt 25MHz signal out.
>Maybe someone has better ways?
>
>Loren Moline  WA7SKT
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Re: [time-nuts] wifi with time sync

[David]

Modern systems are very aggressive about DVFS (dynamic voltage and
frequency scaling) so it would not surprise me at all.  I have run
across this problem on the timescale of one second even on 10 year old
desktop hardware.

On Sun, 15 Jan 2017 09:32:56 -0500, you wrote:

>Hi
>
>I’d be surprised if a laptop running on wall power and doing a variety of low 
>level
>traffic every second is throttling the chip set. It *is* doing something weird 
>and 
>that certainly is one candidate. I’m not quite as concerned with the *why* the 
>bumps 
>occur (though I am curious). I’m more interested in the fact that they are 
>really
>enormous (compared to other delays). How they do microsecond timing with them
>in the mix is the big question. 
>
>Bob
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Re: [time-nuts] wifi with time sync

[David]

Sonos and I guess their competitors do this by dropping WiFi
compatibility.  They exist on their own network in the same ISM band
so I wonder how well they coexist with WiFi.  Online reports say
poorly under crowded band conditions.

On Sun, 15 Jan 2017 09:50:05 -0500, you wrote:

>Hi
>
>The push behind this is whole house audio. These guys want to be able to set 
>up WiFi
>speakers / mic's all through a home and get proper audio imaging in each room. 
>They likely
>also want to use it to figure out which mic you are talking to using time of 
>arrival. They very 
>much want to do this in real environments (300 WiFi nets in the building). 
>Since they want to
>roll it out that way, it’s got to be cheap and fairly robust. They need their 
>gizmo to work with 
>the infrastructure you already have.
>
>Bob
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Re: [time-nuts] 10MHz to 25MHz

[David]

On Thu, 19 Jan 2017 10:48:57 -0800, you wrote:

>On 1/19/2017 5:40 AM, David wrote:
>
>> oscillator.  In some applications I would also be concerned about the
>> phase of a narrow bandpass filter changing with temperature.
>
>The 5061 has tuned bandpass filter multipliers which have exactly this 
>problem.  A temperature ramp causes a phase ramp which is the same as a
>frequency offset.
>
>Rick N6RK

That is what I remembered from a discussion here about 10 MHz
distribution amplifiers
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Re: [time-nuts] 10MHz to 25MHz

[David]

On Wed, 18 Jan 2017 21:06:04 -0800, you wrote:

>On 1/18/2017 6:34 PM, David wrote:
>
>> An alternative very simple design I might try is a variation of the
>> active frequency multiplier where the 5th harmonic is filtered
>> directly from the output of the digital divide by two stage.
>
>That's a useful trick to reduce the filtering burden.  Having said
>that, if you need good spectral purity, the filtering is still
>going to be very non-trivial.  The original poster is obviously
>not an expert in filters and will not be successful trying that
>approach, except for very low performance design.  Even if
>you are a filter expert, components are hard to get.
>
>Rick N6RK

I only suggested it because Loren seemed dead set on a harmonic
frequency multiplier.  The output from a digital logic gate will
already have a strong 5th harmonic so no extra passive or active
harmonic generating stage is needed.  The document I linked discusses
the filtering requirements like notching out the strong 3rd harmonic.

If spectral purity is important, then this is the wrong way to go
about it; it would be better to phase lock a separate crystal
oscillator.  In some applications I would also be concerned about the
phase of a narrow bandpass filter changing with temperature.
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Re: [time-nuts] ADC sample voting algorithm?

[David]

I always try to calculate things like the standard deviation and
peak-to-peak to get some idea if the measurement is valid.

A DSO with infinite persistence or envelope mode is great for tracking
this sort of thing down during development.  Only toy DSOs will lack
both.

On Wed, 05 Oct 2016 22:24:09 -0700, you wrote:

>time-nuts@febo.com said:
>> That’s kind of why I’m going down the road of multiple samples - to see 
>> if
>> there’s anything to it. 
>
>I would hack up some way to grab a clump (say 10) of samples and print them 
>out where you can capture them on a PC and analyze them.
>
>I'd start by looking with the old Mark 1 eyeballs, then write hack code to 
>filter out the good stuff so I can see the bad/interesting cases.
>
>If you have a scope, it might be interesting to trigger on PPS and look at 
>the ADC trigger and input voltage.  If you have a digital scope with the 
>remember forever option, that would catch the delayed interrupt bug that Jim 
>Harman reported.
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Re: [time-nuts] Why are PPS pulses so narrow? (was: 53132A triggering)

[David]

I would not use such a narrow pulse for any of those reasons except
for power if that was an issue.  I would and have however used narrow
pulses simply because it allows for a lower volt*time product on a
transformer.

On Fri, 16 Sep 2016 21:03:12 -0400, you wrote:

>Hi
>
>It is sort of an " everybody does it " sort of thing. Various justifications:
>
>Less power is used / less heat in the drivers and terminations.
>Transformer coupling works better ( lower delay ) with narrow pulses
> Anything over 1 us has been "really long" in terms of logic speeds 
> since the 1960's
> A definite duty cycle "bias" let's you detect an inverted pulse.
>
>The only real reason is "that's the way it's done". Big Customers ask for it 
>that way. Suppliers deliver what is asked for. Nobody complains, nothing 
>changes.
>
>Bob
>
>> On Sep 16, 2016, at 7:44 PM, Peter Vince  wrote:
>> 
>> Can I ask why PPS pulses are so narrow?  It makes them difficult to see on
>> a 'scope, and difficult to detect on a PC.  And, as Bob said, far less
>> obvious if you trigger off the wrong edge.
>> 
>> Peter
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Re: [time-nuts] 53132A triggering

[David]

The new ones don't?  That would be annoying.

My old Racal-Dana 1992 remembers when in standby mode but not if it
loses power.

On Fri, 16 Sep 2016 15:21:50 -0400, you wrote:

>Thanks, Bob.  I just tried that and got solid results.  One nice thing about 
>the 5370 vs this newer stuff is that the knobs and switches stay in the same 
>place through power cycles!
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Re: [time-nuts] HP-105B Battery Replacement?

[David]

I have a pair of Liebert GTX2-700RT online UPSes and they work well; I
just replaced the batteries, lubricated the fans, and cleaned the dust
out of them a couple weeks ago.  They have that sort of standard 4
prong socket on the back for external batteries.

But unlike my two Powerware Prestige EXT UPSes, they only operate with
batteries installed.  The Prestige EXT will operate as a super power
conditioner without batteries which is just as well since it uses 5 x
12V 4AH batteries for 60 volts instead of the more standard and less
expensive 4 x 12V 7AH-9AH batteries.  These have a 4 pin Molex type of
socket on the back for battery expansion.  I have considered
converting these to use a bank of supercapacitors but I suspect the
charge circuit would have a fit charging them from zero volts.

I picked these up inexpensively from http://www.refurbups.com/ but I
have not seen any deals on refurbished online UPSes there for quite a
while now.

If your equipment can run on 12 volts DC, then there are less
expensive solutions like one of those Belkin 12 volt battery backed up
power supplies that some ISPs issue to their customers or something
home grown.

On Fri, 16 Sep 2016 04:56:35 -0400, you wrote:

>Actually the larger SmartUPS series can run for hours providing a large enough 
>battery string is available I have a SmartUPS RM3000 running data rack 
>this has 2 external battery boxes and will run everything for 6 hours.
>
>For TimeNuts applications though I'd recommend a Liebert UPS as this is a 
>'online' UPS as in input is converted to DC and used to float batteries and 
>drive a power oscillator for a true sine output and in a power interruption 
>there is no transfer time or transients on the output
>
>Content by Scott
>Typos by Siri
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Re: [time-nuts] HP-105B Battery Replacement?

[David]

High end standby UPSes support external batteries but most or all
online UPSes do.  I have 3 different online UPS models and they all
support external batteries of either 48 or 60 volts.

On Thu, 15 Sep 2016 15:13:59 -0700, you wrote:

>Since I have a 12V 100 A-H gelled electrolyte battery as a
>short-term backup (for those outages not worth firing up the generator),
>I'd like to find a UPS that uses an external battery. So far I don't see
>such a thing--do they exist?
>
>Jeremy
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David]

Worn out aluminum electrolytic capacitors usually improve in
performance lowering ripple and noise as they warm up.

On Sun, 18 Sep 2016 12:27:38 +0100, you wrote:

>Now that's interesting I just re-ran the measurement, and got a quite 
>different result which is attached.  The spurs have GONE.
>
>My only guess right now is that the E4406A power supply is getting quieter as 
>it has been on for longer (I've only had it powered for short periods before 
>now).
>
>Dave
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Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

[David]

I could not find it in the links but Magnus mentions 50 Hz instead of
100 Hz.

I would expect a 100 Hz noise signal if it was vibration coupled from
magnetostriction in a transformer; magnetostrictive strain depends on
the magnitude of the magnetic field strength and not the sign which is
why 50/60 Hz transformers hum at 100/120 Hz.  50 Hz however fits with
piezomagnetism if the optical fiber was in an oscillating magnetic
field and antiferromagnetic; for piezomagnetism, the strain does
follow the sign.

https://en.wikipedia.org/wiki/Magnetostriction
https://en.wikipedia.org/wiki/Piezomagnetism

I do not know if optical fibers are even slightly antiferromagnetic
but maybe doping can make them susceptible?

On Wed, 24 Aug 2016 09:31:57 +1200, you wrote:

>What is the coupling mechanism giving rise to the 50Hz disturbance?
>DaveB, NZ
>
>- Original Message - 
>From: "Magnus Danielson" 
>To: 
>Cc: 
>Sent: Wednesday, August 24, 2016 8:54 AM
>Subject: Re: [time-nuts] Optical link connects atomic clocks over 1400 km of 
>fibre
>
>> ...
>>
>> These links is in principle not very complex, but they are regardless 
>> somewhat sensitive. One link experienced excessive 50 Hz disturbance, 
>> which they could trace to the fact that for a short distance the fibre was 
>> laying alongside the house 400V three-phase feed-cable with quite a bit of 
>> current in it.
>>
>> ...
>>
>> Cheers,
>> Magnus
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Re: [time-nuts] DIY VNA design [VNA-Nuts?]

[David]

On Mon, 22 Aug 2016 23:44:17 +0200, you wrote:

>On Mon, 22 Aug 2016 14:20:59 -0400
>Bob Bownes  wrote:
>
>> Just finished creating it at groups.io
>>
>> *https://groups.io/g/svna *
>> and sign up. :)
>
>Is there any advantage of using groups.io compared to a traditional
>mailinglist? If not, I would prefer a traditional mailinglist.
>But maybe I am just oldfashioned :-)
>
>   Attila Kinali

It has features not typically associated with mailing lists like web
access (yuck!) and file storage and if abandoning a Yahoo group, they
can transfer the old contents over.  Traditional email clients can
still be used for access and I think threading works although I have
not really tested it.
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Re: [time-nuts] A new take on the all-hardware GPSDO concept

[David]

Is there a schematic showing what you attempted?

I went back through the discussion thread and it was not real clear to
me which design you implemented.

On Mon, 26 Sep 2016 21:18:25 -0700, you wrote:

>...
>
>The results aren’t very good.
>
>With a short TC loop filter, the PLL does lock up, but obviously the jitter of 
>the Venus’ 10 MHz output comes through.
>
>With a longer TC, the PLL never locks - or at least if it does lock, it’s 
>locking significantly off frequency.
>
>That’s with a 10 µF cap and varied resistors between 10k and 1M. The best I 
>got was at 200k - a TC of 2s. That resulted in this video. Unlike other videos 
>I’ve made comparing two GPSDOs, this one is not a time-lapse. The reference is 
>an OH300 based GPSDO.
>
>https://www.youtube.com/watch?v=hiHRp0dCJ64 
>
>
>A time constant of 10s (1M resistor) just doesn’t work at all.
>
>But the real nail in the coffin here is that the price of the PLL chip is 
>still more expensive than the microcontroller and all of the components it 
>replaces.
>
>...
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Re: [time-nuts] Caroliine .. I need to move on

[David]

I was thinking message from Cave Johnson.

On Sat, 1 Oct 2016 23:24:09 -0700, you wrote:

>Hurricane I believe
>
>-=Bryan=-
>
>> From: jim77...@gmail.com
>> 
>> Well I'm intrigued!
>> 
>> On 2 October 2016 at 15:53, Ian Stirling  wrote:
>> 
>> > going to the emergency place
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Re: [time-nuts] Temp/Humidity control systems?

[David]

Years ago I had to deal with this and the instruments and sensors we
used matched well against dry and wet bulb measurements.  I suspect
consumer level stuff varies considerably in reliability and accuracy.

The capacitive sensors are tricky to use because they require AC
excitation to prevent damage from electromigration.  I see a lot of
integrated sensors are available now and I wonder how well they really
work

On Fri, 28 Oct 2016 09:39:04 +1100, you wrote:

>You are correct to question commercial humidity sensors.
>It seems to have come about because no-one can make a dollar by selling 
>humidity.
>Manufacturers do not tell the truth, they think ours is as good as theirs so 
>we 
>should claim the same accuracy. People buy these sensors, believe them, and 
>buy more.
>
>It is not hard to measure humidity/temperature. (they should be measured 
>together).
>Cover the bulb of an ASTM32C thermometer with cotton gauze. Insert it through 
>the wall
> of a short length (18”) of 4” metal tube, insert another ASTM32C thermometer 
> through the side 
>of the tube 4” upstream. Put a computer fan on the outlet of the tube sucking 
>air over 
>the thermometer bulbs at about 4m/s. Wet the thermometer bulb, but NEVER touch 
>it with your fingers.
>In about 3 minutes you can take two temperature readings. There are a number 
>of tables and calculation methods,
>some much worse that others that will convert these values to air temperature, 
>Relative humidity,
>Dew Point temperature etc. You get accuracy of 1% from temperatures measured 
>to 0.1C.
>If anyone is interested I have basic routines for XCEL spreadsheet use to do 
>the hard work.
>This is based on the WMO Reference Psychrometer developed by Russel Wylie of 
>NML Australia.
>
>> On 28 Oct 2016, at 12:43 AM, Ron Bean  wrote:
>> 
>> And since this is time-nuts: Measuring humidity accurately is tricky. 
>> According to people who have tested them, commercial electronic humidity 
>> sensors, when tested in a lab, have never come anywhere close to the 
>> accuracy claimed in the data sheet. The best you can hope for is 
>> consistent readings, not absolute accuracy.
>> 
>> ...
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Re: [time-nuts] I love the smell of tantalum in the morning

[David]

I usually find that the pad itself has enough tin plating to melt and
adhere the part's termination so I tack it down like that, solder the
second termination, and then go back and solder the first termination.

On Mon, 7 Nov 2016 02:34:51 +, you wrote:

>The best way to hand solder small SMT parts is to put a blob of solder on one 
>pad,  position the part,  old it down with something (fingernail works well, 
>maybe tweezers),  then touch that pad/solder blob with the iron.  The blob 
>should melt and the part should push down into the blob.  Make sure the part 
>is aligned, then go to town soldering the remaining pads. Go back and touch up 
>the blob pad.
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Re: [time-nuts] Man with too many clocks.

[David]

My simple solution to this was to divide the 1 PPS signal down so the
jitter from the uncorrected GPS was a smaller part.  Of course then
each measurement takes proportionally longer.

On Fri, 4 Nov 2016 11:35:59 -0400, you wrote:

>I gave up on trying to use the GPS 1 PPS signal to calibrate the 10 MHz 
>OCXO's that
>I have.   The reason that others have pointed out is that the 
>uncorrected 1 PPS
>signal from the GPS is has just a little too much a jitter to use it for 
>calibration
>with your eye using a scope.   If it were sawtooth corrected then it 
>would be better
>but you really need a GPS disciplined oscillator.
>
>...
>
>Pete.
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Re: [time-nuts] Satellite TV messed up, how is GPS time

[David]

On Fri, 4 Nov 2016 18:23:16 -0400, you wrote:

>I no longer have DISH but I did have it a year ago and the outage 
>happened every year like clockwork , they even sent me a notice that I 
>could expect a sun outage and I did.. I also experienced outages every 
>time a thunderhead at 30,+ feet got between me and the satellite as well

We have Dish outages a couple times a year here in Missouri do to
thunderheads.  I might have thought that was do a particular dish and
receiver but when they were both upgraded, the outages do to
thunderheads remained.
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Re: [time-nuts] Thinking outside the box a super reference

[David]

On Fri, 04 Nov 2016 14:39:54 -0700, you wrote:

>On Fri, Nov 4, 2016, at 02:27 PM, Poul-Henning Kamp wrote:
>> 
>> In message <2af27ebe-9200-c348-c89b-b98f9c973...@karlquist.com>, "Richard
>> (Rick) Karlquist" w
>> rites:
>> >Also, one of the Rb isotopes is slightly radioactive.
>> >35 years ago, the guy in the next cubicle got away with
>> >storing it under his desk.  He also happily smoked
>> >cigarettes all day at his desk.  Another ERA.
>
>> Rb87 has a halflife north of the age of the planet as far
>> as I recall, and the result is a beta which goes nowhere
>> far and Sr87 which is stable.
>
>87-Rb has a half life of something like 4.9e10 years — you'll be waiting
>a while for that strontium. /gp

Various online sources say that natural rubidium is radioactive enough
to fog photographic film in 1 to 2 months but that is also the case
with unprocessed uranium ore so I would not worry about it at all.
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Re: [time-nuts] Satellite TV messed up, how is GPS time

[David]

On Fri, 4 Nov 2016 18:43:03 -0400, you wrote:

>...
>
>   There HAVE been attempts to deliberately jam cable distribution
>satellites... mostly the EIRPs used for distribution signal uplinks
>make this a bit difficult, but it has been done.   There are also some
>countermeasures in place to help quickly locate and ID rogue uplinks.
>
>...

Captain Midnight was the first satellite incident that came to mind
but I wonder how many others there have been.


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Re: [time-nuts] I love the smell of tantalum in the morning

[David]

On Sat, 5 Nov 2016 20:57:11 +0100, you wrote:

>> Having not done SMT before, how should I do it with minimal risk to the very 
>> precious PCB. Or, what equipment should I use this as a good excuse to buy?
>
>Now, for these caps, you can use a normal soldering-iron without too 
>much trouble, but I strongly recommend pre-heating the board with a 
>hot-air gun.
>
>The trick is to pre-heat the board widely so it becomes hot, but not 
>enough to melt any solder. As you now apply your soldering iron, the 
>heat-transfer won't be as large as if you had a room-temperature board, 
>simply because the lower temperature gradient.
>The effect is that your heating up goes quicker and that part of the 
>board won't experience excess heat for too long.

I have never had a problem removing surface mount parts like that with
just a single soldering iron.  If access is good so that a large heat
capacity tip can be applied, then each solder joint can be heated up
very quickly preventing damage to the board.

Through hole parts on multilayer boards which have a high heat
capacity are a different manner.

>Another trick I use is to solder new solder onto the joints. This breaks 
>through the oxide layer, which is a poor heat conductor. I solder onto 
>the joints and let them cool. Then I come back again and now the 
>soldering iron melts it all up nicely.

On newer boards this is also a great way to dilute the lead free
solder lowering the melting point making removal easier without
damaging the board.

Add some leaded solder and flux to each joint, then remove most of the
solder from each joint with braid, and then a little heat will allow
each side of the part to pop off.

>I still do SMD with my Weller WECP-20, but it's not optimal.
>At work we moved the otherwise so high valued (over-valued) Metcal to 
>the side as the new JBC stations is much better. Metcal's doesn't keep 
>the temperature good enough and the new JBCs is beeter. Metcal's also 
>have a failure-mode in their tips which makes them break way to early. 
>There exist replacement tips which is in fact better than the original.
>
>So, if you need an excuse to buy a new toy, look at the JBC-stuff:
>http://www.jbctools.com/
>
>However, I would probably be able to replace that cap before your get 
>your new and shiny toy on the table.
>
>Cheers,
>Magnus

I still use my ancient Weller Magnestat irons but have quite a
collection of tips including my overpowered vacuum desoldering head.
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Re: [time-nuts] 1PPS to 32.768 khz

[David]

On Tue, 18 Oct 2016 22:59:42 -0700, you wrote:

>> 1. Does anyone know of a device that will take a 1PPS GPS timing signal and
>> generate a 32.768 kHz sine wave output ? I have big digital clock that uses
>> an 8 bit micro processor and an external 32.768 crystal. Obviously the
>> external crystal is awful for accuracy. 
>
>I don't know of any off-the-shelf device that does that.

I do not either which I found surprising.  I did a search back through
the archives and found lots of posts about synthesizing 32.768kHz from
10 MHz but nothing about 1 PPS.

>Have you looked at the micro?  Is there a spare input pin for the PPS?  Could 
>you rewrite the software to use the PPS rather than counting to 32K?
>
>If you get a GPSDO with a 10 MHz output, then you could do it in software.  
>I'm a bit surprised that tvb doesn't already have one as an option for his 
>picDEVs.
>  http://www.leapsecond.com/pic/picdiv.htm

Lots of discussion about this in the archives.

>If you think (analog) hardware is more fun than software, you could build a 
>PLL.  I'm not a PLL wizard.  My guess is that 32K:1 is too big a step.  I'd 
>probably try 2 steps of 256:1 and 128:1.

It is not nearly that complicated.  I would almost call it trivial.
Phase performance is not critical in this application as long as
cycles are not added or lost.

Phase lock a 32.768kHz crystal oscillator to the PPS output either
directly or after dividing it down by a couple powers of 2 to remove
any ambiguity.  Several of the 10 MHz analog GPSDOs work this way. The
time constant just has to be long enough for the required holdover.

How much tuning range does a varactor tuned 32.768kHz crystal
oscillator have?  I knew at one time.

>If you like software, you can do the PLL in software.  (Less hardware than 
>the analog version.)  The idea is to run a tiny CPU at some handy frequency, 
>measure that clock using the PPS, and figure out how many cycles you need for 
>each half cycle at 32K Hz.  You don't need each (half) cycle to be super 
>accurate, but the long term has to be right.  If you knew the clock frequency 
>and it was stable, the cycles-per-tick would turn into the same sort of math 
>at Bresenham's algorithm gets for drawing diagonal lines:  some steps are N 
>cycles, some are N+1.  I'll bet the code is nice and clean after you figure 
>out how to do it.  Maybe it's just a PLL in software.

I think a PIC might be fast enough to DDS it.  The output bandpass
filter will cure a lot of sin.  Using a dedicated switched capacitor
filter would be fun but more expensive.
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Re: [time-nuts] measuring noise of power supplies (was: For those that insist on using switching power supplies)

[David]

On Tue, 18 Oct 2016 11:27:05 +0200, you wrote:

>On Fri, 14 Oct 2016 22:25:55 -0500
>David <davidwh...@gmail.com> wrote:
>
>> I have done this and it works great; the breakpoint between the
>> chopper amplifier and the low noise amplifier can be adjusted to
>> combine the wideband noise from the low noise amplifier and the 1/f
>> noise and drift of the chopper amplifier.
>> 
>> Jim Williams wrote a couple of different application notes where this
>> was used with both integrated and discrete amplifiers.
>
>Yes, there are several appnotes and papers that list this method.
>But I am not aware of any noise measurement below 0.1Hz for such
>an amplifier setup.
>
>
>   Attila Kinali

Below 0.1 Hz it is not all that interesting; the noise is just the
noise of the chopper amp and flat below the chopping frequency.  I
think Jim Williams mentioned in one of his articles that at low
frequencies, noise and drift are effectively the same thing so thermal
EMF becomes a large if not the largest contributor.

When I did it, I extended the single ended design to a fully
differential gain of 1000 amplifier using a pair of LT1028s with a
pair of LTC1150s for correction.  I used the noise curves to estimate
what the integrator gain should be and after adjusting it for minimum
noise from about 0.1 to 10 Hz, it was very close to the actual
crossover point in the datasheet specifications.  RMS noise was
measured by taking the standard deviation of the DC values from a
Fluke 8505A over 10 seconds.
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Re: [time-nuts] 1PPS to 32.768 khz

[David]

I was thinking 32.768kHz VCXO and phase detector to make a simple
analog PLL.  I found a datasheet for a suitable VCXO and assuming a
total error of 20ppm, it would only need to be divided by 2 to prevent
locking to the wrong frequency making an analog PLL pretty simple.
Safer to divide by 4 or 16 of course.

But I wonder if a microcontroller using a 32.768kHz external clock
could be the phase detector itself.  Strobe the microcontroller ADCS
from the 1 PPS to sample the sine 32.768kHz clock, simmer, and serve.
Or just count cycles to make a FLL.

The most annoying thing about using a varactor for tuning is that they
are not amendable to low drive voltages.

On Wed, 19 Oct 2016 18:14:32 -0400, you wrote:

>Hi
>
>As has been already mentioned, a lot depends on what you have. The drop dead 
>cheapest way to do it:
>
>Start with an MCU with an internal oscillator. There are *lots* to pick 
>between. Which sort really does not matter. 
>For example, I’ll use one that starts at 4 MHz. 
>
>Divide the 4 MHz down to 32,768, or as close as you can get. The common clocks 
>aren’t going to divide
>straight to 32768 so you will need to do two divides. One will be a bit fast, 
>the other a bit slow. You flip between the 
>two in a fixed pattern to get the result to average out correctly. 
>
>Next take the same 4 MHz and run a counter /timer off of it. Capture the pps 
>edge with the timer. It will drift
>a bit since the clock in the MCU is not perfect. Based on the drift, modify 
>your dividers to correct the outcome. 
>If you are “good” to 1 part in 32,768 in each second, that’s close enough for 
>a wall clock. You will have no net
>error long term if you do it right. 
>
>That’s all a sub $1 solution….
>
>Bob
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Re: [time-nuts] measuring noise of power supplies (was: For those that insist on using switching power supplies)

[David]

I have done this and it works great; the breakpoint between the
chopper amplifier and the low noise amplifier can be adjusted to
combine the wideband noise from the low noise amplifier and the 1/f
noise and drift of the chopper amplifier.

Jim Williams wrote a couple of different application notes where this
was used with both integrated and discrete amplifiers.

On Sat, 15 Oct 2016 00:53:25 +0200, you wrote:

>...
>
>The low frequency range is what we usually call the 1/f region,
>although the long term stability also belongs to it. But unlike
>the long term region you don't have to sacrifice a virgin to
>get decent measurment data. Jim William's appnote[1] has lots of
>details how to measure noise in this region. There are slightly
>more modern circuits by Todd Owen/Amit Patel[2] and Gerhard Hoffmann[3].
>I recently stumbled over a similar amplifier by Enrico Rubiola
>and Franck Lardet-Vieudrin[4]. Both [4] and [5] explain why for
>low impedance sources (like power supplies) a BJT input stage
>would be a better choice than jFETs and also cover the influence
>of temperature on the measurement. [6] gives some additional info
>on how to design the differential input stage.
>
>I wonder how an active offset voltage cancelation scheme for
>the differential pair input stage using one of the chopper stabilized
>opamps (eg LTC2057) would change the temperature dependence and long
>term stability  (aka 1/f^a noise) of the circuit, but I have not seen
>any measurements of a system like this yet.
>
>...
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Re: [time-nuts] measuring noise of power supplies

[David]

On Tue, 18 Oct 2016 14:52:15 +0200, you wrote:

>Hoi David,
>
>On Tue, 18 Oct 2016 05:25:35 -0500
>David <davidwh...@gmail.com> wrote:
>
>...
>
>> thermal EMF becomes a large if not the largest contributor.
>
>Ah.. good to know. Thanks!
>Any guess what the other big factors are?

Over time scales of 100s of milliseconds to seconds, the self heating
and temperature coefficient of the feedback network resistors causes
errors which extend settling time and look like low frequency noise.
At this level, self heating also contributes to non-linearity.

Intermodulation between frequency components of the signal close to
the chopping frequency can result in low frequency noise.  Modern
integrated chopper amplifiers do various things to prevent this so I
do not think it is a problem now.

External thermal effects are the big problem though.  Jim Williams
discusses this in Linear Technology application note 9 and includes
measurements showing noise down below 0.01 Hz.  He also discusses
other sources of noise:

http://www.linear.com/docs/4105

>> When I did it, I extended the single ended design to a fully
>> differential gain of 1000 amplifier using a pair of LT1028s with a
>> pair of LTC1150s for correction.  I used the noise curves to estimate
>> what the integrator gain should be and after adjusting it for minimum
>> noise from about 0.1 to 10 Hz, it was very close to the actual
>> crossover point in the datasheet specifications.  RMS noise was
>> measured by taking the standard deviation of the DC values from a
>> Fluke 8505A over 10 seconds.
>
>You wouldn't have the schematics and the measurments available somewhere?
>It would be interesting to have a look at them.

I may have them and my notes from more than 10 years ago but I could
redraw the schematic from memory and describe it well enough to
duplicate; the design is not complicated.  I got the basic idea from
figure 14 on page 10 Linear Technology application note 21:

http://www.linear.com/docs/4116

Mirror the standard high input impedance non-inverting amplifier
configuration top to bottom to produce a 2 operational amplifier (4 in
this case) differential amplifier.  The symmetry in the circuit helps
balance noise sources like thermocouples.  I do not remember if
synchronizing the clocks of the chopper stabilized amplifiers improved
performance but if it did, the difference was not large at least with
LTC1050s and LT1028s.

The part I found amazing when I worked with this circuit is everything
worked just as theory predicted; the calculated integrated noise level
was just about right and the crossover frequency between the
amplifiers matched the datasheet specifications.  The low frequency
noise was so low that I could measure resistance just from its low
frequency Johnson noise which scared me.

>BTW: Should this discussion be moved over to volt-nuts?
>I kind of feel we are getting too off-topic for time-nuts.
>(though my interest comes from long term time measurment)
>
>   Attila Kinali

The original non-inverting circuit would be suitable for use in the
signal chain driving the voltage control input of a crystal oscillator
preserving low noise and low drift from the DAC.  Replace the low
noise precision bipolar operational amplifier with a low noise low
input bias current operational amplifier and it might be useful for
implementing long time constant filters in an analog GPSDO design
although I suspect sacrificing input bias current (the chopper input
bias current is relatively high) for this level of precision and low
frequency noise may not be a worthwhile trade off.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

[David]

On Fri, 21 Oct 2016 10:59:59 +0200, you wrote:

>On Fri, 21 Oct 2016 00:20:43 -0400
>Scott Stobbe  wrote:
>
>> The bad side of a 7912 is in long-term stability and tempCo, the sample I
>> tested had at least a 150 ppm/degC tempCo, which is going to put a serious
>> lump/bump in the 10s tau to gps crossover point on an allan deviation plot.
>
>If the Thunderbolt ist most sensitive to the -12V input, why not use
>something like the LT3090? Its temperature coefficient is quite low
>in the order of a few ppm/°C around room temperature. Using a metal
>film resistor that should keep the output variations low as well.
>As added bonus, you get a very low output noise.
>
>And while you are at it, use three LT3090 for the positive supplies :-)
>
>   Attila Kinali

Or if space is not an issue, use a discrete reference or zener,
operational amplifier, and pass transistor for better performance yet
at less cost.  If all of the supplies are to be regulated, then use a
common reference to further save cost.

Separating the reference, error amplifier, and feedback network from
the power pass transistor lowers the effects from thermal feedback.
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Re: [time-nuts] How can I measure GPS Antenna quality?

[David]

When I was doing VHF and UHF direction finding antenna design, I would
drive out to the highest readily accessible hilltop for testing.  Once
I came up with a low sidelobe design, I started picking up things like
lamp posts, trees, and bushes in the parking lot, aircraft over LAX
and John Wayne airports 50+ miles away, etc. which limited testing
performance.

While a perfect test environment is handy for design, a GPS antenna is
going to be subject to all kinds of environmental limitations so I
would accept field testing which includes considerations like
multipath, temperature variation, and a generally hostile RF
environment.

On Mon, 21 Nov 2016 08:22:50 -0800, you wrote:

>I'm not sure about whether an anechoic (which is really "hypoechoic") 
>chamber is going to get you the data you need.  Calibrating the chamber 
>to the needed level of accuracy might be harder than doing field 
>measurements.
>
>It might just be because there's a ton of analysis software out there, 
>but the folks who really, really care about 0.1 mm shifts in phase 
>center seem to use field data in a well characterized site, and 
>accumulate it for a number of days.
>
>The GPS antenna folks at JPL, when they're testing a spacecraft antenna 
>for things like precision orbit determination (a basic choke ring sort 
>of thing) go out with the antenna and a test receiver on a cart in a 
>parking lot.
>
>Looking at it in terms of numbers:
>1mm is 1/150 wavelength, or about 2-3 degrees of phase.
>
>  sin(2 degrees) is 0.034, or -30dB.  So a spurious reflection that is 3 
>cm different path length (modulo wavelength) and 30 dB down will give 
>you a 1mm phase center error.  0.1 mm is -50dB.
>
>Now, it's true that if you had a good spherical near field range, with 
>time gating, you can probably get rid of the reflections from the 
>chamber (and, in fact, you can do the measurements in a regular lab, or 
>your garage). But even there, it's tricky, because the probe calibration 
>has to be very good, and the structure supporting the scanning probe 
>also has to be accounted for.  You might be able to do it by doing 
>transmit/receive measurements on something like a spherical target of 
>appropriate size.
>
>I've done measurements on what was essentially an interferometer with a 
>2 meter baseline, in a conventional chamber on a conventional pedestal 
>(JPL Mesa 60 ft chamber  http://mesa.jpl.nasa.gov/60_Foot_Chamber/). 
>You could easily see -40dB specular reflections as the array rotated. 
>(and you could also see things like the ladder on the positioner behind 
>the antenna we accidentally left in there, even though it was behind the 
>horn antennas in the array)
>
>I think a good test using satellites and a very well characterized 
>comparison antenna in a open air test site is probably the easiest, and 
>most accurate, way to do it.
>Arranging your test on a post well above the terrain, and making sure 
>that the surface is flat is easy.
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Re: [time-nuts] New Timestamping / Time Interval Counter: the TICC

[David]

John, 

  In what language is the GUI written?  I might be able to help on that,
or other parts of the software, if someone else hasn't yet volunteered. 

Dave, WA8YWQ 

On 2016-11-24 06:43, John Ackermann N8UR wrote:

> Hi Anders --
> 
> Thanks, and thanks for the info on the 53230A.  I have not used one of those 
> myself but the data sheet lists 20ps single-shot.
> 
> Also I should note that the TICC does not compete with counters like the 
> 53230A for high speed measurement, or frequency counting.  It does far fewer 
> measurements per second than the high-end counters -- my design criteria was 
> for use in PPS measuring system.
> 
> With the current software, the actual measurement processing time is about 1 
> millisecond; we may be able to optimize a hundred or two microseconds from 
> that as the code currently has more 64 bit operations than are necessary, and 
> there are other things that can surely be tweaked.
> 
> The killer is the serial output via USB.  It can take up to 10 ms to output 
> 20 characters, and that's what really limits the measurement rate.  I'm 
> pretty sure this can be improved (one idea is to buffer results to reduce USB 
> packetization delays), but there's other functionality that I need to finish 
> first.
> 
> BTW -- the software is open source and on github at 
> https://github.com/TAPR/TICC , so I welcome anyone who wants to work on it.  
> Bug fixes are gladly accepted, and if you're looking for work to do, I could 
> use a volunteer to work on a couple of areas, most critically finishing a UI 
> that will allow the user to set operating parameters.
> 
> John
> 
> On 11/24/2016 02:40 AM, Anders Wallin wrote: Nice work!
> On the website in the introduction you mention 22ps single-shot
> time-stamping on the 5370A/B.
> I think it's well established that the 53230A does about 11-12 ps for
> time-intervals, which corresponds to about 9 ps single-channel. see for
> example:
> http://www.anderswallin.net/wp-content/uploads/2015/04/53230A_PPS_skew.png
> 
> Anders
> 
> On Wed, Nov 23, 2016 at 11:13 PM, Peter Vince 
> wrote:
> 
> Fantastic John - well done!  Yes, I'll definitely put an order in as soon
> as possible.
> 
> Regards,
> 
> Peter  (G8ZZR, London)
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Re: [time-nuts] precision timing pulse

[David]

On Wed, 16 Nov 2016 11:14:59 -0800, you wrote:

>albertson.ch...@gmail.com said:
>> I'm wondering why everyone seems to be assuming a PIC is the right processor
>
>If you want cycle-accurate timing, one approach is to count cycles.  If you 
>have an assembly level background, the PIC is as good as any small chip.  
>Yes, it's a pain to get started if you don't have a working setup or a friend 
>with one you can copy.

Even when not counting cycles, there are other considerations.

1. PIC (and AVR and some others) are available in small DIP packages
making prototyping or one shot projects easy.

2. PIC is the least expensive followed by RS08 from NXP/Freescale, eZ8
from Zilog, and finally AVR from Atmel.

3. PIC and AVR have the most support.  I would probably prefer the AVR
ISA but PIC is 1/3rd the cost and seems to have better peripherals and
documentation.  Since Microchip bought Atmel, I worry that AVR will be
effectively discontinued.
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Re: [time-nuts] Thermal impact on OCXO

[David]

I have only heard of and never observed the problem of manufacturers
cutting the middle out of a gaussian distribution for tighter
tolerance parts.

Robert Pease of National Semiconductor had an even better story:

I recollect the story of one of the pioneering transistor companies,
back in the '60s.  They had agreed to ship to their customers
transistors with an AQL (Acceptable Quality Level) of 2%, which was
pretty good for those days.  So the tester would test 98 good parts
and put them in the box.  Then, following her instructions, she would
add 2 bad transistors to finish off the box, thus bringing the quality
to the exact level desired.  This went on for some time, until one of
the customers got suspicious, because the two bad transistors were
always in the same corner of the box! Then things were changed ...

On Thu, 17 Nov 2016 10:34:06 -0500, you wrote:

>...
>
>I once herd a story from once upon a time that, if you bought a 10%
>resistor, what you ended up with is something like this in the figure
>attached.
>
>Of course 1% percent resistors (EIA96) are manufactured in high yield
>today, but I would guess some of this still applies to OCXOs, you
>aren't likely to find a gem in the D grade parts. After pre-aging for
>a couple of weeks they are either binned, labeled D, or the ones that
>show promise are left to age some more before being tested to C grade,
>etc, etc.
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Re: [time-nuts] our favorite topics

[David]

That is always the danger when using parts for characteristics not
guaranteed in the specifications.

Sometimes a process just becomes obsolete necessitation new parts to
be fabricated on a new process.  Or a process may have enough
variation that some lots or parts meet unguaranteed specifications and
others do not.  Occasionally a minor update is made to correct a
problem or improve yield that significantly changes unguaranteed
specifications.

And of course the company could be bought resulting in the process or
parts you are relying on being discontinued.  I am currently worrying
about this with Linear Technology being bought by Analog Devices and
NXP being bought by Qualcomm.  In the case of Qualcomm, I cannot see
them being in the discrete parts business.

As far as testing, nobody likes to test for noise or low leakage for
that matter.  Test time costs money and low frequency noise testing
especially takes a lot of time.  The example I like to use for this is
the LMC6081 ($0.83) and LMC6001 ($5.76) operational amplifiers; the
later is identical to the former except it spends a lot more time on
the tester to guarantee its lower input bias current.  Common small
signal transistors are usually specified with 50 or 100 nanoamps of
leakage even though it is often 1000s of times lower because that is
as good as the automatic testers can do quickly.

On Sun, 30 Oct 2016 17:06:52 -0400, you wrote:

>It has to do with the manufacturing process and a reduction in cost. I can  
>not speak for other companies, Infinion "killed" the good phase noise   
>performance but the large signal noise is not specified in the data sheet so  
>they are legally  "clean"
> 
>>In a message dated 10/30/2016 4:56:38 P.M. Eastern Daylight Time,  
>>davidwh...@gmail.com writes:
>>
>>You  mentioned suitable transistor availablity being an increasing
>>problem and I  have run across that myself.  Do you expect Qualcomm's
>>aquisition of  NXP to have an impact?
>>
>>NXP is currently the best source I have for fast  complementary pairs
>>or even just fast PNPs.
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Re: [time-nuts] our favorite topics

[David]

You mentioned suitable transistor availablity being an increasing
problem and I have run across that myself.  Do you expect Qualcomm's
aquisition of NXP to have an impact?

NXP is currently the best source I have for fast complementary pairs
or even just fast PNPs.

On Sun, 30 Oct 2016 16:06:19 -0400, you wrote:

>Absolutely ! But not with 2N3904 but rather with a 
> 
>http://cache.nxp.com/documents/data_sheet/BFG135.pdf?pspll=1
> 
>>In a message dated 10/30/2016 3:27:36 P.M. Eastern Daylight Time,  
>>scott.j.sto...@gmail.com writes:
>>
>>Does your text provide a good discussion of the implications of operating  
>>with large signals?
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Re: [time-nuts] Opening an Isotemp OCXO

[David]

I do not think the designer was considering noise at all because tying
the inputs together would not do anything useful.  Emitter resistance
is inversely proportional to emitter current (26/mA) but putting them
in parallel lowers the current through each emitter so the total
emitter resistance stays the same.

Supply current is separate for each TTL gate so by using a single
8-input part, total power it is about half that of a dual 4-input part
and a quarter of a quad 2-input part depending on the exact operating
conditions.  Unused *outputs* should be high for lowest power.

74S30 Single 8-Input 5mA 10mA
74S20 Dual 4-Input 8mA 18mA
74S00 Quad 2-Input 16mA 36mA

One clever design I ran across used the 7420 dual 4-input NAND pinout
but wired the inputs which are pin compatible so the 7400 quad 2-input
pinout would also work.  This allows using a 74x00, 74x20, or 74S120
dual 4-input NAND buffer but it draws even more power. 

74S120 Dual 4-Input 18mA 44mA

On Fri, 28 Oct 2016 13:31:38 -0400, you wrote:

>I wounder if originally the designer was hoping to use all 8 wire or'd
>inputs to lower the input referred noise during midscale transition. Then
>backed out later for some reason.
>
>On Fri, Oct 28, 2016 at 1:03 PM, Scott Stobbe 
>wrote:
>
>> Could also be a quirk about the 74S30 that gives it better phase noise
>> over a basic buffer.
>>
>>
>> On Friday, 28 October 2016, jimlux  wrote:
>>
>>> On 10/28/16 9:13 AM, Scott Stobbe wrote:
>>>
 The OCXO82-59 datasheet lists 12V supply, 5V clock out, could also be a
 blown regulator in your ocxo, if it is indeed a 12v model.

 There you go..the design could use a 74S30 as a driver - it's fast,
>>> fairly good drive, but runs off 5V.  If the regulator is shorted, and you
>>> put 12V on it, it will cook.
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Re: [time-nuts] What would be the proper equipment and procedure?

[David]

But I got my question answered anyway. :)

On Sat, 29 Oct 2016 05:29:26 +, you wrote:

>Yep, should have gone to volt-nuts.   Recent changes Microsoft has been doing 
>to Outlook, etc have been causing all sorts of fun gltches.  One being not 
>actually taking copy-pastes of addresses and/or subject lines.  Another being 
>sorting emails into dark and crusty corners of ancient folders...   We were 
>talking about the hazards of making cadmium-tin low thermal EMF solder...
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Re: [time-nuts] For those that insist on using switching power supplies

[David]

Even if they meet the CE or FCC requirements for unintentional
radiators, they can still screw up the short wave bands and more; many
are bad enough that I can see the noise they emit on an oscilloscope
with a shorted probe.  At least in the US, there are a *lot* of cheap
products with switching regulators which cause problems including CFL
and LED lamps and FCC enforcement is poor.

That confusion between the European Economic Area CE and the China
Export CE is just shrewd.

On Thu, 13 Oct 2016 17:57:02 -0500, you wrote:

>Actually, if they have the "CE" stamp on the product, then they have very
>specific radio interference limits that they must test and meet.
>It must have been tested, certified, and the certification package
>available for inspection.
>
>Whether they actually met it, then pulled the interference supression parts
>off the board as a "cost reduction" as is common in no-name computer power
>supplies, or whether it never met it to begin with, is for you to
>speculate.  Some suppliers will explain to you that "CE" means China
>Export, not that it meets the consolidated European safety and electrical
>rules.
>
>--- Graham
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Re: [time-nuts] Totally unrelated, but..

[David]

On Thu, 8 Dec 2016 02:25:14 +0100, you wrote:

>Am 08.12.2016 um 01:20 schrieb Scott Stobbe:
>> Yes, the short hand I like to use is 4 nV*sqrt(R/1000).
>>
>> 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta
>> vbe gained up ~10x.
>
>Methinks the advantage comes from converting their reference (whatever 
>that may be)
>to a really high impedance current source where a few uF help 
>tremendously in cleaning things up.
>
>regards, Gerhard

The output stage of the LT3042 also operates with unity gain so the
reference noise is not multiplied by the gain set by the divider and
bandwidth of the error amplifier is maximized.  Some regulators
include an extra pin or the voltage divider is external so that point
can be bypassed but their reference is still in series with the error
amplifier so this does not suppress noise from the bandgap reference
itself.
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Re: [time-nuts] Totally unrelated, but..

[David]

I am pretty sure that I ran across this once as well with the
7800/LM340 series in the early 1980s with parts from a major
manufacturer like Motorola, National, or Texas Instruments; the
regulators ran hot and the output voltages were slightly low no matter
what decoupling arrangements were made at the input and output.  The
stability was poor as if the parts were oscillating but no oscillation
was apparent.

There is some discussion here about different designs for these
regulators although the photographs are broken:

http://www.righto.com/2014/09/reverse-engineering-counterfeit-7805.html

On Wed, 7 Dec 2016 15:56:55 -0500, you wrote:

>I don't think so.  I first ran into a batch of LM340-5's
>that were excellent oscillators back in the 1970's... long
>before counterfeiting was even remotely possible.
>
>The symptom is the regulator puts out only 4.5 out of 5V.
>
>LM309's were, however, totally immune.
>
>Usually, I had to be really bad to make it happen, things
>like using clip leads between the power supply and load
>with the LM340-5 dangling in between.
>
>The answer is as simple as a couple of 0.1uf ceramic caps
>soldered right at the input and ground, and the output
>and ground pins.
>
>LDO (low dropout) regulators are very susceptible to
>oscillation.  They need to have a couple of hundred uf
>of good quality capacitance right on the input and output
>leads.  Where people usually get in trouble, is in not
>knowing that electrolytic capacitors lose most of their
>capacitance as the temperature starts hovering around 0C.
>
>The circuit works great on the bench, but fails when out
>hanging on a light pole...
>
>-Chuck Harris
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Re: [time-nuts] Measuring sidereal/solar time? Re: A Leap Second is coming

[David]

To improve the accuracy, I would integrate several measurements. There
is no reason a sampled measurement at only one time needs to be made.

On Fri, 30 Dec 2016 09:18:17 -0800, you wrote:

>Hi Anders:
>
>That's something I've thought about for decades using an optical system.  A 
>few  years ago I looked at it again and 
>found that astronomical "seeing" limits the accuracy.  So the accuracy 
>achieved by a spaceborne "Stellar compass" will 
>be much better than a ground based observation.  A radio based observation 
>might work since the atmosphere would not be 
>a factor.
>http://www.prc68.com/I/StellarTime.shtml
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Re: [time-nuts] WWVB Simulator

[David]

Not all PC audio hardware includes such a low high frequency cutoff.

http://www.clarisonus.com/Research%20Reports/RR001-SoundCardEval/RR001-PCsoundCards.html

Based on the above review, the following cards which are still
available have a response that extends significantly above 60kHz:

http://www.m-audio.com/products/view/audiophile-192
http://www.lynxstudio.com/product_detail.asp?i=11
http://www.lynxstudio.com/product_detail.asp?i=12

On Wed, 4 Jan 2017 21:21:22 + (UTC), you wrote:

>A PC can certainly generate a lot of frequencies. But if you want to use the 
>audio channels at 60KHz there is a little problem. There is a brick wall 
>filter in the audio channel set at about 25 KHz. 
>
>Now I could set up the audio to output 15 KHz I and Q and mix it (quadrature 
>mixer) with 45 KHz X 4 (precision source)  to get 60 KHz. And then filter it 
>to get the 60 KHz. Which requires some op amps. And filters. A precision 45 
>KHz source. A gray code counter (divide by 4).  And stuff. 
>
>Easier to work at DC (my "audio" signal) and mix that up to 60 KHz directly. 
>Besides. I do like designing and building hardware.  Engineering is the art of 
>making what you want from what you can get at a profit. 
>I like Polywell Fusion.
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Re: [time-nuts] WWVB Simulator

[David]

I see generally how it should work but did not draw out a truth table.

Why use the 74CB3T3253 instead of a low voltage 4052 variant?

It think you could buffer just the two references and save two
operational amplifiers and 2 or 4 capacitors.

On Mon, 2 Jan 2017 21:18:12 + (UTC), you wrote:

>I have come up with a ridiculously simple WWVB simulator that simulates both 
>the AM modulation and the BPSK modulation. 
>
>A simple explanation and a link to the core schematic can be found here: 
>http://spacetimepro.blogspot.com/2017/01/wwvb-simulator.html
>I'm working on fleshing out the design and producing a PCB. Any comments or 
>suggestions before I complete the design are welcome. I will try to 
>incorporate useful suggestions in the final design. 
>
>Note: I have looked all over the 'net for a similar design or any thing 
>hinting at it. I found nothing. Once you see the design it becomes obvious. 
>
>What clarified it for me is that I looked at the last diagram in this file 
>http://www.wparc.us/presentations/SDR-2-19-2013/Tayloe_mixer_x3a.pdf  and then 
>plotted out the digital version of what the one cycle of the carrier would 
>look like given that the signal is just made up of ones and zeros. 
>The final design (as far as I have gone) incorporates a synchronizing latch so 
>the signals only change at the "zero" of the modulator. 
>
>Simon
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[David]

On Wed, 21 Dec 2016 19:29:00 +, you wrote:

> Can anyone comment on the following data, and whether they think the
> oscillator in "my" M8N is a XO or a TCXO ?
>
>Can you monitor the current draw from cold (ambient)?
>
>You may be able to identify the initial steady current drawn by the TCXO
>heater, then the cycling once it's hit the right temp?
>
>If there's no change at all in average current as it warms then it may
>not have a TCXO.
>
>Mike

What heater?  The big advantage of a TCXO (temperature compensated)
over an OCXO (oven controlled) is the lack of a heater allows low
power operation.
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[David]

On Thu, 22 Dec 2016 12:39:27 +, you wrote:

>But I find it a bit odd that HP would have a 1 Hz software option on this
>instrument, if the instrument jumped up/down 100 Hz.
>
>Now I don't yet have the 1 Hz option programmed in, and it might well
>change the behavior completely, but I'd still like to find a way, if one
>exists, of checking this with the equipment I have.
>
>The signal generator is no longer supported, but I could try my luck seeing
>if there are any known problems with this unit, or firmware upgrades
>available - currently revision 29, May 1991.
>
>...
>
>Dave

I agree with Bill, maybe something is going on at the other end.

While I do not expect this sort of thing from HP, could they have
deliberately designed the sweep generator to include those 100 Hz
bumps unless the 1 HZ software option was purchased?

Like Paul, I would not expect the kind of stability you need from a
sweep generator but that 100 Hz jump is just weird.  It does kind of
remind me of popcorn noise but without a time scale and a longer
record, it is difficult to tell.
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Re: [time-nuts] Single ended or differential input to TDC chip

[David]

On Mon, 27 Mar 2017 18:05:13 +0200, you wrote:

>...
>
>* Single-ended input in a chip might lead to shifting ground potential
>  on the chip and thus to measurment jitter.
>
>...

This is a major problem I have run across before.  Various single
ended logic families have great noise immunity as far as proper
functioning but their limited PSRR (power supply rejection ratio)
becomes vary apparent when power supply noise shifts their logic
thresholds resulting in additional jitter.  Depending on the logic
family, single ended inputs may be referenced to one or the other
supply or to both.

For this reason alone I would use differential inputs which can always
be driven single ended in less demanding applications.  Some ECL parts
include a "reference" input/output for their logic inputs and might
also be suitable.

Powering critical logic with a reference grade supply voltage and
avoiding ground loops helps mitigate the effects of poor PSRR.
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Re: [time-nuts] Antique precision timing device without electronics

[David]

I think Bob Pease of National Semiconductor fame mentioned looking for
the earliest use of phase locked loops and finding a reference to a
European clock maker who had a master pendulum clock with a mechanical
coupling that phase locked newly built clocks when left connected
overnight.

On Thu, 16 Mar 2017 20:22:42 +1100, you wrote:

>Hi all,
>
>I was recently asked to resurrect this interesting device by a colleague who 
>collects antique scientific instruments. It’s a "Chronoscope" made by the H. 
>Tinsley company in London in the early 20th century and used to measure time 
>intervals with the precision of those days. It's large and heavy in a polished 
>wooden case with a top deck that hinges up to reveal the innards. 
>
>The timing reference is a large tuning fork about 30 cm (1 foot) long and 
>running at 25 cps. It's normally in a glass fronted housing (removed for the 
>video) that includes a pair of hinged mechanical arms for starting it. It's 
>maintained in oscillation by an electromagnet and contact arrangement powered 
>from a 12V DC supply. The fork amplitude is controlled by a rheostat - too 
>much and the tines impact on the magnet. The video frame rate makes the fork 
>look slower than it actually is. I was able to extract a signal and measure 
>the frequency with a modern GPS disciplined counter - it's 0.007% off its 
>specified 25 Hz! The frequency is too low for my HP 5372A so I was not able to 
>easily get an idea of stability or do an ADEV measurement. The fork has quite 
>a high Q and takes over a minute to stop oscillating after the power is turned 
>off. There's a built in higher voltage AC power supply, probably a mains 
>transformer, potted in beeswax in a polished wooden box inside that is 
>intended t
 o
>  energise a large neon strobe lamp used to adjust the fork. Unfortunately the 
> lamp was not with the unit and is no doubt irreplaceable. 
>
>The 25 Hz signal is filtered by an LC network  and used to run a synchronous 
>motor in the Chronoscope unit. Synchronous motors not being self-starting, you 
>need to tweak a knob to get it going - there's a joke in there but I can't for 
>the life of me think what it could be ? The "Contact" switch and associated 
>socket on the back controls an electromagnetic clutch that connects the 
>clockwork counter mechanism to the motor and the contact "on" time is 
>indicated on the dials with 10 mS resolution. 
>
>There's not a single active device in there and after a clean and lube it runs 
>very nicely from a modern 12V DC plugpack. My friend is very pleased with it 
>and it will take pride of place in his collection. 
>
>I'd be interested to know if any time nuts have knowledge or experience of 
>this lovely instrument.
>
>A video of it is at  https://youtu.be/i5S8WS9iN_E
>
>Enjoy!
>
>Morris
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

Low current measurements take a lot of time on the automatic test
equipment and time in this case is measured in seconds.  The same
applies to low frequency noise.

For an example, take a look at the National (now TI) LMC6001 and
LMC6081:

https://goo.gl/LCY2vR

Unlike National, TI does not care about input bias current in their
selection guides so you will have to look that up in the datasheets:

http://www.ti.com/product/lmc6001
http://www.ti.com/product/lmc6081

The difference in the parts is that the LMC6001 is tested for an Ib of
25fA and below and this is reflected in the price which is $5.76
instead of the $0.83 of the LMC6081.

Right about the time that the LMC6001 was released, Robert Pease wrote
some articles talking about the bias current testing and the
economics.

The same thing applies to all of those small signal transistors with
25, 50, and 100nA leakage specifications.  Those numbers are simply
good enough for typical applications and what the tester can handle in
the time allotted and have nothing to do with the actual transistor
performance.

So collector-base junctions make good low leakage high voltage diodes
although they are slow which does not normally matter for an input
protection circuit and may even be preferable.  Emitter-base junctions
make good low leakage fast diodes but with low breakdown voltages.

The cheapest guaranteed low leakage diode is probably some variety of
4117/4118/4119 n-channel JFET.
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

On Wed, 5 Apr 2017 09:13:34 +1200 (NZST), you wrote:

>A protection diode needs to also have a fast turn on with little or no 
>overshoot of the forward voltage.

That would be ideal but forward turn on time is rarely specified and
usually assumed to be fast and some fast diodes have appallingly slow
turn on.  This is one of those things that needs to be qualified or
selected for if it is important.

I suspect there is some obscure processing issue with diodes that
causes slow turn-on that does not show up in transistors.

>Reverse recovery time can be an issue if one is relying on the clamp for 
>protection against a periodic overload such as when an input is overdriven by 
>a sinewave input and one wishes to make useful measurements whilst this occurs.

Definitely.

>The internal protection diodes of HCMOS devices can severely degrade the 
>device propagation delay jitter when they conduct.
>
>Bruce

They sure can but isn't this because of minority carrier injection?  I
wonder if this is only a problem with junction isolated integrated
circuit processes.  I probably knew at one point but forgot.

Dual and quad analog ICs can suffer from a different problem where
exceeding the common mode input voltage range screws up common bias
circuits causing other elements to malfunction.
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

I have run across the conductive carbon filled plastic problem before.

We did not actually use just paint.  We took black mastic electrically
insulating tape, dissolved it in thinner, and painted the parts with
it.  It dried to form a pliable black coating.

On Sat, 8 Apr 2017 17:49:01 + (UTC), you wrote:

>You need to be careful how you paint the package black.  My first electronics 
>job was in a place that made, among other things, mass spectrometers.  We made 
>very high input impedance electrometers for the mass specs using TO-5 can 
>mosfet transistors.  One batch was found to be very photo sensitive through 
>the glass/ceramic lead interface.  Someone had the idea to spray paint the 
>bottom of the package with black paint.  Not a good idea. The black paint, 
>likely loaded with carbon, decreased the electrometer input impedance by many 
>orders of magnitude.  Considering that our electrometers had an input 
>impedance of 1E-12 to 10E-15, even a fingerprint made a huge difference.  The 
>carbon filled black paint was practically a short.
>Maybe an overcoat with silicone or some other type of low leakage sealant, 
>then the black paint?
>
>Tom
>
>> From: David <davidwh...@gmail.com>
>> To: Discussion of precise time and frequency measurement 
>> <time-nuts@febo.com> 
>> Sent: Saturday, April 8, 2017 10:00 AM
>> Subject: Re: [time-nuts] TAPR TICC boxed (input protection)
>>   
>>On Fri, 7 Apr 2017 01:06:17 -0400, you wrote:
>>
>>controlling the offset voltage.
>>
>>We ended up painting the diodes black after soldering.
>>
>>I have also heard of it happening with metal TO-18 packages through
>>the lead interface under the package.
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

On Sat, 8 Apr 2017 16:30:38 -0400, you wrote:

>David wrote:
>
>> I mentioned this in connection with some manufacturers using gold
>> doping in transistors which would not normally be expected to have
>> gold doping.  So you end up with a bunch of lessor named 2N3904s which
>> meet the 2N3904 specifications but are useless if you were looking for
>> low leakage diodes.
>
>I believe all 2N3904s and 2N3906s are gold doped.  National's certainly 
>were (Processes 23 and 66), and TI's and Fairchild's are. Not heavily 
>doped, like 2N2369s (with storage times of ~20nS), but just enough to 
>bring the storage time down to ~100nS.   2N2219s, 2Ns, and 2N4401s 
>are also lightly gold doped.

I ended up qualifying 2N3904s based on manufacturer and lot and I
think we ended up using ones from Motorola.  I wish detailed process
information like National had was available from every manufacturer.

What was funny was when we did this, the lower frequency transistors
that I tested like the 2N5088/9 were much worse.

>> If [4117 leakage is] not being tested, then where is the maximum specified
>> leakage number coming from?  For a small signal bipolar transistor it
>> will typically be 25nA, 50nA, or 100nA, but the InterFET datasheet (1)
>> shows 10pA maximum and 1pA maximum for the A versions.
>>*   *   *
>> When this discussion of low leakage input protection started, I did a
>> quick search for inexpensive alternatives to the 4117/4118/4119 JFETs
>> and came up with nothing; all of the inexpensive JFETs are much worse
>
>Same as any "guaranteed by design" spec -- by the device design. The 
>4117 series is unlike any other JFET -- the geometry is TINY, and the 
>4117 Idss is only 30-90uA (hundreds of times lower than other low-Idss 
>JFETs). [BTW, lowest Idss is why I recommend the 4117 over the 4118 and 
>4119 for use as a low-leakage diode.  The 4118 and 4119 have higher Idss 
>-- up to 240uA for the 4118 and 600uA for the 4119 -- and tend to have 
>higher gate leakage, as well.]
>
>Best regards,
>
>Charles

If the 10pA specification is guaranteed by design, then wouldn't they
have to be testing the 1pA "A" parts?
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

On Sat, 8 Apr 2017 21:43:31 +0200, you wrote:

>Am 08.04.2017 um 17:52 schrieb David:
>>
>> If they are not being tested, then where is the maximum specified
>> leakage number coming from?  For a small signal bipolar transistor it
>> will typically be 25nA, 50nA, or 100nA, but the InterFET datasheet (1)
>> shows 10pA maximum and 1pA maximum for the A versions.
>
>The large print giveth and the small print taketh away.
>
>Usually there are footnotes and weasel words like "sample tested",
>"by characterisation" or "not production tested".
>The time such a small device sits on the wafer tester costs much more
>than the silicon. For 100 msec.
>At 1 pA it takes an eternity until the capacitances in the setup
>are charged. Just the waiting time makes such a diode or FET
>a premium part.

Low leakage is the defining characteristic of these JFETs so they
better be testing them.

The Calogic datasheet was the only one I checked which said anything
like "For design reference only, not 100% tested" and it did not apply
to the leakage current.

The non-A parts are only tested down to 10pA.

>Back to input protection:
>
>Someone in the sci.electronics.design group mentioned these
>< https://www.digikey.de/products/de?keywords=cmpd6001s >
>but, as usual, typical values, and watch the plot with the temperature
>as parameter. At least they are cheap.

I think these were pointed out to me before.  Since I would have to
test them to guaranty leakage below 500pA, I might as well test a
cheap small signal transistor.

If you want a laugh, take a look at NXP's various "low leakage
diodes"; they only specify and test them down to nanoamps.  But I
assume for most new EEs that *is* low leakage.

>Also interesting, while not exactly low leakage diodes, are these
>USB3 lightning arrestors:
>< https://www.digikey.de/products/de?keywords=296-25509-1-nd >
>Looks like they don't spoil the timing.
>
>regards, Gerhard

USB is not leakage sensitive.  It looks like these were only tested to
the same 100nA standard as many transistors which makes sense; they
just need to weed out bad parts.
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

They are relevant when a high input impedance buffer is used making it
easier to add series/shunt overload protection.  Protecting against
400 volts and higher is feasible this way.

Adding overload protection to a 50 ohm input is an interesting
challenge but it can be done.  Precede the 50 ohm termination if used
with a current driven diode bridge.  The current then determines the
maximum input voltage which can be passed to the 50 ohm termination
and following circuits.  Check out the design of the Tektronix 7A29
vertical amplifier and 485 oscilloscope for examples were this was
done.



On Tue, 11 Apr 2017 08:22:14 -0400, you wrote:

>I have a really naive question: how can picoamp leakage parts be relevant in 
>low impedance input pulse conditioning to an interval counter?
>
>Tim N3QE
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Re: [time-nuts] Line Frequeny Stablity

[David]

I have seen some proposals to require VAR capability in photoelectric
installations but how feasible is that?  I cannot imagine utility
customers being pleased with having to pay extra for such a nebulous
to them capability.

I could see the utility companies pushing it as a requirement in lieu
of installing banks of synchronous condensers.  Maybe this could be
integrated with net metering so that users get paid for providing VAR
correction and pay for VARs but I bet it would be politically
infeasible.

Thinking about the stability problems associated with distributed
generation gives me a headache.  I am inclined to believe that any
solution which relies on central management or timing is an invitation
to major failure.

On Wed, 5 Apr 2017 09:52:32 +0200, you wrote:

>...
>
>Until recently, photoelectric would not provide any of the rotating iron 
>properties, but the increase popularity of it now requires it to start 
>to have such properties for the stability of the system.
>
>Cheers,
>Magnus
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

On Wed, 5 Apr 2017 02:40:13 -0400, you wrote:

>David wrote:
>
>> So collector-base junctions make good low leakage high voltage diodes
>> although they are slow
>
>I guess it depends on what one means by "slow" and "fast."

I was referring to within the same transistor; emitter-base junctions
are much faster than collector-base junctions.

>The B-C junction of an MPSH10/MMBTH10 or 2N/PN/MMBT5179 switches on in 
><1nS and off in <2nS, which is comparable with Schottky microwave mixer 
>diodes such as the Agilent HSMS282x series and better than "ultra-fast" 
>silicon switching diodes such as the FD700 and 1S1585.  (I did my 
>switching tests at 20mA.)  (Note that the silicon and Schottky switching 
>diodes have reverse leakage currents from several hundred to tens of 
>thousands of times higher than the B-C junction of an MPSH10/MMBTH10.)

I have never actually tried this with RF transistors.  I know one
thing to watch out for if you are looking for low leakage is gold
doping and some less that reputable manufacturers "cheat" in this
respect so transistors used as low leakage diodes should be at least
qualified by manufacturer which is a problem with counterfeits and
unscrupulous purchasing managers.

Out of curiosity, and I tried to look this up years ago, what doping
is used for PNP RF transistors and saturated switches if it is not
gold?  Does it also increase leakage?

And I have another question if you know.  How is rb'Cc measured?
Tektronix at some point was grading 2N3906s for rb'Cc < 50ps.

>The gate junction of a 2N/PN/MMBF4117A JFET switches on in <2nS and off 
>in <4nS.
>
>> The cheapest guaranteed low leakage diode is probably some variety of
>> 4117/4118/4119 n-channel JFET.
>
>If the 5pA reverse leakage current of the MPSH10/MMBTH10 is too much and 
>one must, must, must get leakage down to 1pA, the 2N/PN/MMBF4117A is the 
>best inexpensive choice that I'm aware of.

The advantage of the 4117/4118/4119 is that the leakage is already
tested to a given specification so no qualification or testing is
necessary.
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Re: [time-nuts] Re. DIY atomic "resonator"

[David]

Some incandescent lamps can emit RF.

http://www.rexophone.com/?p=1081
http://www.radiomuseum.org/forum/rustika_lightbulb_fm_measurements.html

On Tue, 11 Apr 2017 18:09:52 +, you wrote:

>Apparently fluorescent tubes continuously emit a lot of other microwave 
>signals.  I once built a  homodyne doppler "speed" radar kit (used a coffee 
>can for the antenna).  The way you calibrated it was to point it at a 
>florescent tube and and adjust the reading to a specific value.
>
>
>
>> Seems that some fluorescent tube starters do emit a very brief burst at 
>> around 1.4 GHz
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Re: [time-nuts] RFDO - Experience and questions

[David]

If the modulation is phased locked to the carrier which is common,
then that suggests two other ways to extract the timing from the
carrier without interference from the modulation.

1. Integrate the phase comparison over a whole number of modulation
cycles; the modulation will then cancel out.  This could be seen as
using a sin(x)/x frequency response with the nulls aligned to remove
just the modulation components of the signal.

2. Gate the phase comparison for periods where the modulation is not
occurring.

On Sun, 5 Mar 2017 11:54:56 +0100, you wrote:

>I have been working for a "while"… on a reference oscillator disciplined by an 
>RF signal (162khz), Cs stabilized, but phase modulated with time coding 
>information. The phase modulation is quite significant : +/-1rad 10Hz 
>triangular shape, leading to a frequency shift of +/- 20PI (+/-6,3Hz). 
>Extracting the base signal was quite an interesting challenge… I tried many 
>options (and even a bit more…) but it was - and is still - fun...
>
>...
>
>My questions to the respected audience:
>- Can I get any better? 
>- Have I reached the limit of what the RF signal can provide? 
>(with all the perturbations encountered on the path from the transmitter to my 
>antenna...)  
>- Am I limited by the local oscillator? 
>- Or the measurement gear?
>- Or anything else…?  
>
>Thanks very much for your feedback,
>
>Gilles. 
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

On Thu, 6 Apr 2017 22:23:43 -0400, you wrote:

>David wrote:
>
>> I know one  thing to watch out for if you are looking for low
>> leakage is gold doping
>
>Anything that increases carrier mobility increases leakage current (all 
>else equal -- i.e., for each particular device geometry).  This accounts 
>for the much higher leakage of Schottky and germanium junctions.

I mentioned this in connection with some manufacturers using gold
doping in transistors which would not normally be expected to have
gold doping.  So you end up with a bunch of lessor named 2N3904s which
meet the 2N3904 specifications but are useless if you were looking for
low leakage diodes.

>> And I have another question if you know.  How is rb'Cc measured?
>
>One way is to drive the transistor with a medium-high frequency (well 
>down the 1/f portion of its current gain curve -- typically 10-50MHz for 
>small-signal BJTs) and measure the base-collector phase shift.  It can 
>also be calculated from fT and Cc-b.  There is a JEDEC standard for 
>measuring rb'Cc, but I'm not finding my copy at the moment.  It may be 
>posted on the JEDEC web site.

I thought there was a more sophisticated way but that sure sounds like
something Tektronix would have done for grading parts.

The JEDEC standard is probably what I need to find or at least start
with.  Thank you for the tip.

>> The advantage of the 4117/4118/4119 is that the leakage is already
>> tested to a given specification so no qualification or testing is
>> necessary.
>
>That may be true, but there is nothing in the data published by Vishay, 
>Fairchild, Calogic, or InterFET to indicate this.  Spot-checking, along 
>with the part design, should be sufficient to guarantee meeting the 
>spec.  I'll try to remember to ask the Vishay process engineer next time 
>I talk to her.
>
>Best regards,
>
>Charles

If they are not being tested, then where is the maximum specified
leakage number coming from?  For a small signal bipolar transistor it
will typically be 25nA, 50nA, or 100nA, but the InterFET datasheet (1)
shows 10pA maximum and 1pA maximum for the A versions.

When this discussion of low leakage input protection started, I did a
quick search for inexpensive alternatives to the 4117/4118/4119 JFETs
and came up with nothing; all of the inexpensive JFETs are much worse
until you get to premium devices.

(1) I only picked the InterFET datasheet because it was the most
readily available of the ones you mentioned.  The current Fairchild
and Linear Systems datasheets show the same thing.
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

On Fri, 7 Apr 2017 01:06:17 -0400, you wrote:

>Another thing to watch out for if you need very low leakage, is if the
>package is transparent.  All junctions are photodiodes.
>
>Maybe it's less of a problem now with SMTs, than it was with glass body
>diodes or translucent transistor packages.
>
>Andy

I got caught by this once.  We had a design which had to use hermetic
parts and this happened with the diodes used for input protection
during development and testing.  Luckily I noticed within a few
minutes that the apparent drift coincided with the angle that I was
observing the circuit leading to the discovery that my desk lamp was
controlling the offset voltage.

We ended up painting the diodes black after soldering.

I have also heard of it happening with metal TO-18 packages through
the lead interface under the package.
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Re: [time-nuts] TAPR TICC boxed (input protection)

[David]

On Fri, 7 Apr 2017 04:09:38 -0400, you wrote:

>David wrote:
>
>>> what doping is used for PNP RF transistors and saturated switches
>>> if it is not gold?  Does it also increase leakage?
>
>I replied:
>
>> Gold doping doesn't affect the speed of BJTs in the active region very
>> much -- its purpose is to reduce minority carrier lifetime and, thereby,
>> to reduce storage time when a transistor recovers from saturation.  I'm
>> not sure how manufacturers deal with this in the case of PNPs.
>
>After I posted, I recalled learning in a long-ago device physics course 
>that both Gold and Platinum doping were used to reduce minority carrier 
>lifetime in PNP saturated switches.  According to Motorola, the 
>MPS3639/3640, 2N4209, and 2N5771 were gold-doped PNP saturated switches 
>(all are now obsolete, although SMD versions of the 3640 and 5771 appear 
>to still be available).
>
>And yes, doping PNPs with either Gold or Platinum does increase reverse 
>leakage current (Platinum less so than Gold).
>
>Best regards,
>
>Charles

So gold doping does work with PNP devices.  Previously when I brought
it up, I was told gold doping only applied to NPN devices leading to
my confusion.
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Re: [time-nuts] OCXO Soft-Start

[David]

On Wed, 12 Apr 2017 20:18:38 -0700, you wrote:

>On 4/12/17 7:14 PM, Richard (Rick) Karlquist wrote:
>> 10.9 MHz is likely the B-mode of the SC cut.
>> (It's a different mode, not a different overtone).
>> This mode has a tempco of 20 ppm and is used
>> to do thermometry.
>>
>> IMHO, there is NO excuse for the oscillator
>> designer to design an oscillator that doesn't
>> oscillate unconditionally in the right mode.
>> NONE!  What was the actual manufacturer of
>> the OCXO? (AFAIK, Trimble doesn't make their
>> own).
>>
>> My old boss at Zeta Labs (a really great boss)
>> used to walk up to people who were testing
>> their latest circuit and momentarily turn
>> down the current limit on each of the power
>> supplies to see if the circuit recovered
>> correctly.  It often didn't, and then it
>> was back to the drawing board...
>>
>
>These days, a common trap is when you've got a DC/DC converter on the 
>input - with a soft start, the current goes huge, causing all kinds of 
>problems.
>
>(I'm in the middle of closing a failure report on just such a 
>sensitivity - an unexpected interaction between the source DC/DC 
>converter and the load DC/DC converter..)

Linear regulators with foldback current limiting and sometimes safe
operating area protection can do the same thing with unfriendly loads.
Safe operating area protection becomes a problem when the input to
output voltage difference is large lowering the current limit at low
output voltages.

A more insidious problem and design mistake has sometimes occurs with
thermal protection.  If the thermal protection does not have enough
hysteresis, then the regulator cannot "hard start" into a heavy load
at high temperature and turns itself into a temperature controlled
oven.
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Re: [time-nuts] Frequency counter questions

[David]

High end frequency counters usually go to some effort to prevent
synchronization between the input signal and the gate.  Some DSOs do
as well.  Synchronization can exasperate certain errors and
asynchronous operation provides better results when many measurements
are averaged.

On Tue, 25 Apr 2017 21:29:11 -0700, you wrote:

>Do typical  frequency counters start their gate in phase with the incoming 
>signal?  I guess the 
>answer would be, "It depends."  I was just thinking about how I would program 
>the STM32F7 
>counter I am designing.
>
>btw, Gilbert, a local time-nut, sold me a 5335 today so I will be able to 
>buiild one great one 
>out of the two I will have.
>
>Jerry
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Re: [time-nuts] Poor man's oven

[David]

I have never been able to find a reference to them on the internet but
there was a similar product intended for TO-99 packages that could be
used with operational amplifiers.

On Mon, 5 Jun 2017 08:35:35 + (UTC), you wrote:

>  The Crystal heater clip wasa Murata "Posistor" soldered onto a clipand they 
>were marketed by Murata.
>I once purchased a small amount of theseand used them as "poor man's ovens".
>Although not perfect by far, they did theirjob and kept my UHF gear stable.
>Murata dropped that product many yearsago and I have not been able to findany 
>similar product. The Posistors arelisted by eg. Digi-key but they do not stock 
>them.
>Ulf - SM6GXV
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Re: [time-nuts] Using 5335 frequency counter for timing

[David]

My Racal-Dana 1992 is the same way; its time interval mode is limited
to the 1 nanosecond interpolated resolution of the counter.

Some counters support time interval averaging which will produce much
much higher resolution but often they have a minimum time interval.

If the transmission line to be measured is configured as a shorted
line, then the pulse width can be measured instead to determine the
line length and pulse width averaging is much more commonly supported.

On Sun, 7 May 2017 22:05:58 -0400, you wrote:

>Hi
>
>The 53131 and 53132 will get you more resolution. The TICC, the 5370, and the 
>SR620 will do even better. None
>of them will do as well as a really fast scope.
>
>Bob
>
>> On May 7, 2017, at 8:52 PM, Jerry Hancock  wrote:
>> 
>> I was showing my son how we could measure the difference in cable lengths by 
>> using the velocity of light and cable velocity factor.  I used a scope to 
>> measure the offset and was then thinking the 5335 could do it more 
>> accurately, but I was wrong, as it only reports to the nanosecond.  I 
>> thought I had seen somewhere where people were getting higher resolution 
>> using software along with the 5335, no?
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[time-nuts] Time stamp degradation being added in javascript

[David]

Possibly not of immediate concern to time-nuts but an article had some 
trigger words for them in the initial fixes to the much publicised 
problems with Intel/AMD/ARM etc :


"After these changes, the time stamp returned by |performance.now| will 
be less precise due to lower resolution. Some browsers are going a step 
further and degrade the accuracy by adding a random jitter."


https://hackaday.com/2018/01/06/lowering-javascript-timer-resolution-thwarts-meltdown-and-spectre/

meltdown/spectre background
https://www.theregister.co.uk/2018/01/04/intel_amd_arm_cpu_vulnerability/
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Re: [time-nuts] Serial port splitter s/w

[David McGaw]

Serial outputs can usually drive several serial inputs if the cables are 
short (to avoid reflections).  You can wire it yourself, serial out from 
the TB to both LH and NTP, serial in from LH only.


David


On 2/26/14 11:51 AM, David J Taylor wrote:
I'm running Meinberg NTP on the Windows 7 x64 machine to which my 
Thunderbolt is attached.


I'd like to be able to share the serial port between LH and NTP so 
that I can run the machine as an NTP Stratum 1 server locked to the 
TB, and also be able to use LH to check things.


I looked around the with Google, and saw *numerous serial port 
splitters. Which is recommended?


Also what's the best way how to configure NTP to lock the the TB on a 
serial port?  Do I need to modify the TB to deliver the PPS down one 
of the serial data lines or will NTP work well by parsing the NMEA 
time messages?


Many thanks
David Partridge
=

David,

Can't comment on the COM port splitters.

For best results with NTP you need a PPS signal on the RS-232 DCD 
line. Using NMEA alone is often worse than just Internet sync. Look 
for a white flash with my Serial Port LEDs program:


 http://www.satsignal.eu/software/net.htm#SerialPortLEDs

The pulse needs to be rather more than a few microseconds - 100-200 
milliseconds is typically used.


Cheers,
David


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Re: [time-nuts] A small piece on HP's hydrogen maser in 1968

[David McGaw]

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Re: [time-nuts] GPSDO module connections

[David McGaw]

RG-59 cable is fine but soldering wires is not a good idea for 1.6GHz.  
Use a panel-mount BNC crimp connector made for RG-59 such as the 
Amphenol 31-343-RFX.  I presume you want to use regular 50 ohm BNC types 
rather than the 75 ohm variant.


It is preferred to use coax for the 1 PPS as any reflections will 
degrade its risetime.


Good luck,

David


On 3/3/14 1:01 PM, d0ct0r wrote:


Hello,

I am looking for the advise: what will be the better method to connect 
GPSDO module by short extension cable to put its antenna input on 
front or back panel ?


Lets say, GPSDO module has female “F” connector. And I would like to 
have BNC connector on back panel of my project. Manufacturer of GPSDO 
recommend to use RG-59 cable for antenna connection.
Is it OK if I'll take some RG-59 from CCTV, cut 6 or 12 of it, 
connect one end to GPSDO (let say this cable has compression type 
connector) and solder other end to BNC on the panel ? Or its better to 
use adapters and no soldering ? Like F connector-to-BNC adapter , 
then short BNC-to-BNC cable connected to BNC panel connector ?


And other question: is it worth to use RF cable to connect 1PPS output 
from GPSDO to distribution amplifier ? Or regular AWG-22 could do that 
job ? Thanks !




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Re: [time-nuts] ELEMEK LXK WWVB Receiver

[David McGaw]

From an ad in Radio-Electronics June 1980, it mentions that it 
phase-locks to the carrier.  I expect the new format of WWVB will give 
it fits.


https://archive.org/stream/radio_electronics_1980-06/Radio_Electronics_June_1980#page/n71/mode/2up/search/wwvb

73,

David N1HAC


On 3/11/14 1:55 PM, Tom Holmes wrote:

Does anyone have any information on this box?



It has 60 kHz and 100 kHz outputs, runs on 12 VDC. Not much info found on
the web so far.



Tom Holmes, N8ZM



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Re: [time-nuts] ELEMEK LXK WWVB Receiver

[David McGaw]

From an ad in Radio-Electronics June 1980, it mentions that it 
phase-locks to the carrier.  I expect the new format of WWVB will give 
it fits.


https://archive.org/stream/radio_electronics_1980-06/Radio_Electronics_June_1980#page/n71/mode/2up/search/wwvb

73,

David N1HAC


On 3/11/14 1:55 PM, Tom Holmes wrote:

Does anyone have any information on this box?

  


It has 60 kHz and 100 kHz outputs, runs on 12 VDC. Not much info found on
the web so far.

  


Tom Holmes, N8ZM

  


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Re: [time-nuts] Equinox and sidereal time

[David McGaw]

There is a UK version of the almanac:  http://asa.hmnao.com/

David N1HAC


On 3/24/14 7:26 AM, Tim Shoppa wrote:

Try the _Astronomical Almanac_. I am not so familiar with the
navigation almanacs, but the bread and butter of the astronomical
almanac is the equation of time and transformation between time
systems. The joint publisher is HMNAO so I'm sure not banned from
Australia :-)

On 3/24/14, Neville Michie namic...@gmail.com wrote:

Thanks Paul,
I should be able to get this information online,
but nearly all my attempts to get information from
USA military sites seem to be blocked to Australia,
or may be just to me.
I click the URL and wait two minutes and it times out.
Any time day or night.
It is very frustrating as the sites appear to be available
to everyone else.
I bought the Nautical Almanac but it does not have such information.
It is very hard to find alternate sources of the data.
cheers,
Neville Michie

On 24/03/2014, at 11:06 AM, Paul wrote:


On Sun, Mar 23, 2014 at 7:02 PM, Neville Michie namic...@gmail.com
wrote:


can anyone out there point me to a source
for the exact time of the equinoxes and solstices



I think you want this: http://aa.usno.navy.mil/data/docs/geocentric.php

e.g. RA 0 is 2014 Mar 20 16:57:07.5 or RA 12 is 2014 Sep 23 02:29:08.5
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Re: [time-nuts] Equinox and sidereal time

[David McGaw]

There is a UK version of the almanac:  http://asa.hmnao.com/

David N1HAC


On 3/24/14 7:26 AM, Tim Shoppa wrote:

Try the _Astronomical Almanac_. I am not so familiar with the
navigation almanacs, but the bread and butter of the astronomical
almanac is the equation of time and transformation between time
systems. The joint publisher is HMNAO so I'm sure not banned from
Australia :-)

On 3/24/14, Neville Michie namic...@gmail.com wrote:

Thanks Paul,
I should be able to get this information online,
but nearly all my attempts to get information from
USA military sites seem to be blocked to Australia,
or may be just to me.
I click the URL and wait two minutes and it times out.
Any time day or night.
It is very frustrating as the sites appear to be available
to everyone else.
I bought the Nautical Almanac but it does not have such information.
It is very hard to find alternate sources of the data.
cheers,
Neville Michie

On 24/03/2014, at 11:06 AM, Paul wrote:


On Sun, Mar 23, 2014 at 7:02 PM, Neville Michie namic...@gmail.com
wrote:


can anyone out there point me to a source
for the exact time of the equinoxes and solstices



I think you want this: http://aa.usno.navy.mil/data/docs/geocentric.php

e.g. RA 0 is 2014 Mar 20 16:57:07.5 or RA 12 is 2014 Sep 23 02:29:08.5
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Re: [time-nuts] Airraft Ping Timing

[David McGaw]

I am surprised it took them this long.  A number of satellite telemetry 
systems can use doppler as a matter of course for locating transmitters, 
such as Iridium and Argos.


David


On 3/25/14 12:58 AM, Peter Gottlieb wrote:
This is how ELT locating satellites work (when not relaying the newer 
GPS data bursts).  Several on another list I watch suggested this 
pretty early on and I guess INMARSAT got the message.  I'd be curious 
to know if AFRCC pointed INMARSAT in that direction.


Really shows the value of precise and stable time references!




Date: Mon, 24 Mar 2014 16:06:14 -0700 (PDT)
From: J. Forsterj...@quikus.com
To:time-nuts@febo.com
Subject: [time-nuts] Airraft Ping Timing
Message-ID:
13855.12.226.214.5.1395702374.squir...@popaccts.quikus.com
Content-Type: text/plain;charset=iso-8859-1

According to a report on FOX, INMARSAT was able to determine the Malasia
Air followed the southern traectory from the Dopplar of the pings. They
verified their model by tracking other planes.

-John

=

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Re: [time-nuts] Is this ocxo salvageable?

[David McQuate]

The output looks differentiated, as would happen if the wire connecting 
the internal circuit to the output pin became open, leaving only a very 
small capacitance to couple the square wave out.


Dave

On 4/8/2014 11:46 PM, Chris Albertson wrote:

My Bliley square wave 10MHz OCXO was working just fine for close to 30
hours until a few hours ago.  Now it puts out a rather noisy waveform about
one volt peak to peak.

Two questions:
(1) Are these things repairable, the metal can is soldered.

(2) As you can see in the attached oscilloscope photo the OCXO still puts
out a strong 10MHZ component.  What is the best way to filter this and
recover a good 10MHZ square wave?

In the linked photo, both channels are set to 1 volt per division.  The
large sine wave is from a Trimble Thunderbolt and the smaller wave is from
the failed ocxo  The EFC is left open (disconnected) and a you can see the
frequency is spot on 10MHz.

https://www.dropbox.com/s/0gy3yobd4myi4vp/waveform.jpg


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Re: [time-nuts] NIST Radio Station WWV now on 25 MHz

[David McGaw]

Yea!  I remember when they shut it down at the nadir of the sunspot 
cycle, saying no one was using it.  Duh!


David N1HAC


On 4/11/14 12:07 AM, Max Robinson wrote:
WWV used to be on 25 MHz but when the sunspot cycle hit a minimum they 
shut it down.  That was years ago.  I'm glad to know they are bringing 
it back.


Regards.

Max.  K 4 O DS.

Email: m...@maxsmusicplace.com

Transistor site http://www.funwithtransistors.net
Vacuum tube site: http://www.funwithtubes.net
Woodworking site 
http://www.angelfire.com/electronic/funwithtubes/Woodworking/wwindex.html

Music site: http://www.maxsmusicplace.com

To subscribe to the fun with transistors group send an email to.
funwithtransistors-subscr...@yahoogroups.com

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funwithtubes-subscr...@yahoogroups.com

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funwithwood-subscr...@yahoogroups.com

- Original Message - From: Gordon Batey gpba...@wildblue.net
To: Gordon Batey gpba...@wildblue.net
Sent: Thursday, April 10, 2014 3:01 PM
Subject: [time-nuts] NIST Radio Station WWV now on 25 MHz




For what it is worth a friend sent me this link.
WWV is now testing on 25 MHZ.

http://www.nist.gov/pml/div688/grp40/wwv.cfm?

73 Gordon WA4FJC


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Re: [time-nuts] NIST Radio Station WWV now on 25 MHz

[David McGaw]

Easily heard on a 12 ft wire in NH this afternoon.  Chuck - You may be 
too close and it is skipping over.


David N1HAC


On 4/11/14 8:37 PM, paul swed wrote:

Chuck
The an/urr R1051 does not have a signal meter. It has level meters for
audio.
Those navy radios. I guess they figured the radio guys could not figure out
signal strength. Come to think of it as I recall they could not figure out
ships antennas either.
That said I would give WWV a solid S5-S9 little QSB right now. Very
comfortable. I am using a multi-band beam at 90' on top of a very tall hill.

Regards
Paul
WB8TSL
Near Boston


On Fri, Apr 11, 2014 at 7:16 PM, Chuck Forsberg WA7KGX c...@omen.com wrote:


Tried three times today to get WWV on 25, heard nothing under the power
line noise.
I did have a nice QSO on 12 meters with a station in Rochester, NY so the
band is open.
WWV is currently weak on 20, strong on 15 and 10 MHz.


On 04/11/2014 12:09 PM, paul swed wrote:


Fired up the R1051 on 25 Mhz and its great to hear wwv back on the air in
Boston.
Pretty good signal.
Regards
Paul
WB8TSL


On Fri, Apr 11, 2014 at 10:12 AM, David McGaw n1...@dartmouth.edu
wrote:

  Yea!  I remember when they shut it down at the nadir of the sunspot

cycle,
saying no one was using it.  Duh!

David N1HAC



On 4/11/14 12:07 AM, Max Robinson wrote:

  WWV used to be on 25 MHz but when the sunspot cycle hit a minimum they

shut it down.  That was years ago.  I'm glad to know they are bringing
it
back.

Regards.

Max.  K 4 O DS.

Email: m...@maxsmusicplace.com

Transistor site http://www.funwithtransistors.net
Vacuum tube site: http://www.funwithtubes.net
Woodworking site http://www.angelfire.com/electronic/funwithtubes/
Woodworking/wwindex.html
Music site: http://www.maxsmusicplace.com

To subscribe to the fun with transistors group send an email to.
funwithtransistors-subscr...@yahoogroups.com

To subscribe to the fun with tubes group send an email to,
funwithtubes-subscr...@yahoogroups.com

To subscribe to the fun with wood group send a blank email to
funwithwood-subscr...@yahoogroups.com

- Original Message - From: Gordon Batey gpba...@wildblue.net
To: Gordon Batey gpba...@wildblue.net
Sent: Thursday, April 10, 2014 3:01 PM
Subject: [time-nuts] NIST Radio Station WWV now on 25 MHz



  For what it is worth a friend sent me this link.

WWV is now testing on 25 MHZ.

http://www.nist.gov/pml/div688/grp40/wwv.cfm?

73 Gordon WA4FJC


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--
  Chuck Forsberg WA7KGX   c...@omen.com   www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
   Omen Technology Inc  The High Reliability Software
10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430


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[time-nuts] Looking for GPSDO for home use

[David Feldman]

I found this reflector after searching for GPSDO that would be suitable for 
individual purchase/use. Each time I found an article about GPSDO projects, 
that lead me to a surplus GPS module that is either no longer available, not 
current production, undocumented, or otherwise difficult to source. I don't 
mind doing my own building/integration, and am not adverse to starting with a 
used or suplus component, I'm not sure where to start in terms of sourcing the 
GPS module/antenna/etc. My main need is for something to serve as a primary 
frequency standard (i.e., 10 MHz output) I can use to set a voltage controlled 
OCXO I just installed in my (otherwise cheap chinese) frequency counter. It 
seems there are some modules that have/had 10 kHz output; that would work too. 
Even 1 PPS output seems like a workable starting point, but at the expense of a 
different and/or more difficult path to get to a 10 MHz reference signal I seek.

Any advance or pointer to source (reasonable cost, whatever that means!) would 
be appreciated.

Thanks!

Dave
wb0...@yahoo.com

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Re: [time-nuts] quartz clock/watch question

[David McGaw]

I have done that as well.  The G-Shocks have a trimmer cap (I have a 
DW-6900/module 3230).  I don't remember the frequency at the adjustment 
test point but it is something like 100 Hz.


David


On 4/18/14 7:40 PM, Jim Palfreyman wrote:

I've opened up my Casio G-Shock watch, found an electrical point, put an
oscilloscope on it and successfully adjusted it. From memory the frequency
was something weird, but I still tuned it successfully to within about a
second a month. I even think I posted to time-nuts on this...

Jim Palfreyman



On 19 April 2014 09:25, Bob Albert bob91...@yahoo.com wrote:


I have tried to pick up the oscillator from my wristwatch and have been
unsuccessful.


I tried both magnetic and electric probes.  Nothing.

Bob

On Friday, April 18, 2014 4:12 PM, Tom Van Baak t...@leapsecond.com
wrote:


When a quartz watch or clock is assembled, what method is used to get it

as accurate as possible?

Bob,

First generation quartz watches had a tiny F/S (fast/slow) trimmer
capacitor. These days it's done with skip cycles and one-time factory
calibration. Think leap days or leap seconds -- it's easier and more
reliable than changing the frequency of the oscillator itself. It's also
one less part, easier to calibrate, and unlike active and passive
components, math has no environmental sensitivity.

Have a quick read of 32 kHz watch IC's like:
http://www.nxp.com/documents/data_sheet/PCA2000_2001.pdf

/tvb


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Re: [time-nuts] GPSDO and holdover

[David McQuate]

Some timing GPS units (eg Oncore UT) can be set to omit 1PPS pulses if 
no satellites are being tracked, or if the RAIM alarm limit is exceeded.


Dave

On 4/25/2014 10:20 AM, Paul wrote:

On Tue, Apr 22, 2014 at 9:57 PM, Tom Van Baakt...@leapsecond.com  wrote:


I have noticed skipped 1PPS on the Adafruit GPS also.



I've always assumed this could happen but as a result of RF signal loss not
a glitch in the gps.  So I've started recording event timestamp deltas
using the Linux kernel PPS interface.  I read assert events (e.g.
1398449188.001000242#1741672) and compute  timestamp and event deltas.  If
the t delta is  .9 something horrible must have happened and if it's  1
some didn't happen assuming the event count delta is always 1.

I wonder if this is a reasonable approach or if I'm being lazily
optimistic.  I just started (and I haven't added a join with the valid fix
indicator yet) but I've had two missing pulses in the last 24 hours.
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--
Clear Stream Technologies

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[time-nuts] Need simple test command to verify connection to UT PLUS module

[David Feldman]

I have interfaced a Motorola Oncore UT PLUS module to my Linux PC via serial 
port and RS-232 adapter. When I power up the module I see 1 PPS from the pin 
(currently connected to a LED via current limiting resistor.) The port is set 
to 9600 bps 8/N/1 but no messages are being seen (I think this is normal as the 
unit is normally/initially polled?)

As I am not using windows, I cannot make use of application program there to 
test my interface. I do not wish to implement NTP on Linux as my eventual 
target is not Linux, it is just my initial test environment.

After reading chapter 6 of the Oncore user's guide, I realize I'll need to 
generate commands that include a checksum byte. Would anyone be able send me a 
short test command byte string (with checksum) so I can verify the hardware? My 
plan is to build my own application to work with the device, but before I start 
down that path I'd like to know that I've got a workable hardware connection.

Thanks,

Dave

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[time-nuts] Beginner question - unexpected possible jitter in 1 PPS output of Motorola ONCORE UT+ module

[David Feldman]

I'm trying (in lieu of setting up a GPSDO) to use the 1 PPS output of a 
Motorola ONCORE UT+ module to do a one-time reference oscillator adjustment of 
my frequency counter (setting its reference oscillator which has a small 
trimmer).

My counter has  a totalize mode where it counts pulses from zero up, until 
the pulses disappear or the counter is reset (with a front panel button). I 
built a small CMOS divider connected to the UT+ 1 PPS output, intended to 
generate 0.05 Hz at 50% duty cycle (this is triggered on leading edge of the 1 
PPS output, so it should not be affected by the imprecise duration (pulse 
width) of the 1 PPS signal). This (0.05 Hz signal) gates the reference 
oscillator output from my frequency counter, 10 seconds on (counting up), 
followed by 10 seconds off (not counting) into the counter input in totalize 
mode. I'd expect the counter in the totalize mode to count from 0 up to 
13000 during one 0.05 Hz cycle (10 seconds of 13 MHz, the ref osc frequency 
for this counter.)

Here's the problem: my counts vary significantly (+/- 1 or more) from cycle 
to cycle, which is much higher than expected based on 50 nS period uncertainty 
of the 1 PPS output noted in UT+ specification (I think the 50 nS uncertainty 
should apply to the overall 10-second count duration in my circuit.) I'm using 
the ONCORE ENGINEERING NOTE as my documentation.

I am using TAC32 to monitor operation of the UT+ and it indicates (after about 
10 minutes acquiring satellites) 7 or 8 satellites being tracked (with Eb/No 
indicated for each one.) Often (a few times per minute) one satellite signal 
seems to disappear, another is acquired in its place. My grid square is 
correctly indicated once 4 satellites are being tracked. The unit appears to be 
in the position hold mode by default. The module was bought on ebay and I do 
not know its prior history. The UT+ is powered with 5V taken from a small USB 
power supply (same result with two different power sources.)

My question is this: Under what conditions can the 1 PPS signal be relied on to 
meet its period uncertainty spec? The UT+ emits 1 PPS regardless of whether 
satellites are visible or not (it does this as soon as power is supplied, long 
before any satellites are acquired); the documentation doesn't seem to 
elaborate under what conditions the 1 PPS signal can be considered to be within 
the period spec, which is why I'm posting here. 

Thanks!

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Re: [time-nuts] Beginner question - unexpected possible jitter in 1 PPS output of Motorola ONCORE UT+ module (Hal Murray)

[David Feldman]

I'm using 74HC series for the divider/gate.

I appreciate all the troubleshooting help, however, I still don't know under 
what conditions the 1 PPS output should be relied on (with zero satellites 
acquired? one? four? all eight?, and what can be expected of the 1 PPS output 
interval if there are zero satellites, given that the signal is still being 
generated by the module?

As for the balance of the suggestions regarding circuit and counter behavior, 
these are all very good pieces of advice; I may just put together a stand-alone 
1 PPS generator (just another oscillator and divider chain) so I can isolate 
whether this problem is possibly with the GPS module or (more likely) an 
impairment in my circuit, counter, measurement setup, or interfaces.

Thanks again!

wb0...@yahoo.com said:
 I built a small CMOS divider connected to the UT+ 1 PPS output...

What do you mean by CMOS?  Old 4000 series parts or HC or ... ?

 Here's the problem: my counts vary significantly (+/- 1 or more) from
 cycle to cycle, which is much higher than expected based on 50 nS period
 uncertainty of the 1 PPS ...

Do you have a scope?

I'd check the triggering levels.  Your counter may be setup to just barely 
trigger on your CMOS signal.  Your CMOS divider may have troubles triggering 
on the output of the UT+.

One experiment would be to connect the PPS directly to the gate input on your 
counter.  That won't tell you your crystal frequency, but if things work, it 
should get a consistent count each pulse.

If you have a digital scope, you can trigger on the PPS and look at the PPS in 
delay by a second mode.  (That tells you the accuracy of the crystal in your 
scope.)  If the PPS delayed by a second isn't stable, you know the UT+ is 
confused.



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Re: [time-nuts] Beginner question - unexpected possible jitter in 1 PPS output of Motorola ONCORE UT+ module

[David Feldman]

Picked this project back up this afternoon after couple of weeks, narrowed the 
problem down but not solved.

Refresh: My ONCORE UT+ module appears to have very extreme jitter (on on order 
of 100 uSec, not nSec random variation between leading edges of successive 
pulses) in the 1 PPS output. I am using the 1 Hz signal, divided to 0.05 Hz at 
50% duty cycle (10 seconds high, 10 seconds low), to gate my frequency 
counter's reference oscillator back into the same counter running in 
pulse-count mode so I can adjust the OCXO bias on the counter for calibration. 
10 seconds count-up, followed by 10 seconds idle where I can record the 
measurement, reset the counter, and adjust the OCXO bias.

I've now built a simple 1 Hz pulse generator using a 32768 Hz crystal and 
CD4060 divider. Using that signal instead of the ONCORE UT+, my counter is 
behaving as expected (that is, each count-up session results in the same 
result, +/- a few counts as would be expected with a simple 1 PPS signal.) This 
tells me the gating circuit and interface to the counter's reference output and 
count input are probably OK.

When using the ONCORE UT+, the counts vary by 1 or more from one 10-second 
capture to the next (each count-up period would total 130,000,000 counts if the 
ONCORE UT+ was working properly and the reference OCXO was properly adjusted.)

I am not yet able to determine why the UT+ 1 PPS signal has such severe jitter. 
TAC software tells me 7-8 satellites acquired/tracked once cold start has 
completed (10-15 minutes.) Is there something I'm missing about UT+ care and 
feeding? There are no RF or switching digital signals close to the UT+ module 
(the gating circuit is a couple of inches away, both mounted on the same perf 
board, with common ground and power supply connections.

Now that I've ruled out the counter/gating circuit interface, I begin to 
suspect the UT+ but don't really know what to expect in terms of 
normal/abnormal operation.

Any advice at this point?

Thanks,

Dave

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Re: [time-nuts] Beginner question - unexpected possible jitter in 1 PPS output of Motorola ONCORE UT+ module

[David Feldman]

Thank you, Tom - I appreciate the advice.

I am using a 74HC390 in the (divide-by-20, square wave output) divider chain, 
and sure enough, after looking more closely at the data sheet, it clocks on the 
FALLING edge (I thought otherwise - wrong)! I will stick an inverter in the 
path and that will probably fix it.

Will update again once that's taken care of.

Dave


Check rising/falling edge times, check trigger levels, check signal levels and 
load. Are you DC or AC coupled. How about power supply noise and grounding? 
Which edge are you actually triggering on? Is there crosstalk with the Tx line.

It is extremely unlikely that there's a problem with the UT+ itself -- this 
series of Motorola Oncore GPS boards has served the time  frequency community 
for two decades with no problems, or jitter, or off-by-100us errors.

It will be fun to meticulously track down the bug; don't just make it go away 
and move on. We will all learn from this interesting problem.

I'll trade you a perfect UT+ if you give up. At some point we time nuts stop 
getting excited about what works and delight in what doesn't, and why.


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Re: [time-nuts] Beginner question - unexpected possible jitter in 1 PPS output of Motorola ONCORE UT+ module

[David Feldman]

Thanks to Tom, Jean-Louis and Chris for all of the helpful advice.

Problem is now fixed.

First problem was obvious - the 74HC390 I use as a divider clocks on 
negative-going transition. Added inverter, and the problem appeared to still be 
present (!)

Next problem was not so obvious - my very cheap benchtop chinese frequency 
counter (a Zhaoxin HC-2700L, bought on ebay, and retrofitted with a 
divided-by-two Pletronics 26 MHz VCOCXO as timebase, which were for sale 
cheaply on ebay a few years ago) turns out to have a bug/defect in the 
totalizer mode; when count transitions from 99 999 999 to 00 000 000, the 
counter ignores its input for a few milliseconds while it processes something, 
so my original plan to count for 10 seconds (expecting to see 30 000 000, which 
is 130 million with the hundred-million digit wrapped off) didn't pan out. 
Small change to the counter circuit and I now count a series of 1-second 
intervals, each of 13 MHz reference oscillator in the counter.

I adjusted the counter's timebase VCOCXO bias input so that counting for seven 
1-second intervals shows 91 000 000 (13 000 000 * 7). There seems to be a +/- 1 
count uncertainty, likely due to absence of synchronization between the 
counter's timebase and the 1 PPS signal, but this accomplishes what I set out 
to do, which was a cheap-and-dirty (but certainly not quick!) calibration of 
the counter's timebase.

Thanks for everyone's advice and support!

Dave

To: jl.on...@free.fr, Discussion of precise time and frequency
   measurement time-nuts@febo.com
Subject: Re: [time-nuts] Beginner question - unexpected possible
   jitter in 1 PPS output of Motorola ONCORE UT+ module
Message-ID:
   CABbxVHvpyUYZfP7=zztTKRXGr+F=k7DBYCzNLwAG04Tr=3_...@mail.gmail.com
Content-Type: text/plain; charset=UTF-8

I posted here some days ago an admission that I did exactly this by
accident once.  It is a very hard problem to debug because everything works
just fine, except for the very high jitter.   So I go looking for noise and
what not.The problem was a wrong number of inverters.


On Sat, May 31, 2014 at 7:58 PM, Jean-Louis Oneto jl.on...@free.fr wrote:

 . So if your divider is clocked on the falling edge of the 1PPS, you
 can expect a 1 ms jitter...

-- 

Chris Albertson
Redondo Beach, California

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Re: [time-nuts] FE5680 GPS Disciplined Controller

[David Hopkins]

HI Bert and others,
Sounds like a great project. Count me in for a kit.

In your email you mention the board is 2 x 2. I take it this is in inches.

You also say the boards will be cheaper if a number are ordered.
If this is a double sided board and you can produce Gerber files then 
consider getting them made in China.


I have used this supplier several times and they produce  good boards.
The cost for ten boards double sided, plated through holes, solder 
masked and silk screened is about  $10. That's $1 per board.

The max size is 50mm X 50mm.

The service is excellent. It usually takes about 4 days to 
manufacture and they are then shipped by airmail.

Have a look at :- http://imall.iteadstudio.com/open-pcb/pcb-prototyping.html

David


t 04:49 AM 19/06/2014, you wrote:

ewkeh...@aol.com


David G. Hopkins (VK4ZF)
CAPALABA QLD
AUSTRALIA
27.32.38S 153.12.03E
QG62OL
Skype :- davhop 


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Re: [time-nuts] More FE5680 GPS Disciplined Controller

[David McQuate]

Hi Bert,
  Welcome back.

  I'm willing to help on the LCD interface code, if you'll send me--
(1) a schematic of the board,
(2) a datasheet on the LCD (or link to where I can get one)
--that includes information on control and data interfacing
(3) any existing code for this PIC (so I can integrate my code with it)
(4) information on where the data to be displayed comes from, in what 
form, and what pins

on the PIC it comes to.

  I've written (assembly) code for PICs for several of my own projects, 
most of which used a multi-line character LCD with a 4 or 8 wire data,
plus 3 wire control interface.  I have working binary to BCD PIC code, 
as well as a 32bit / 32bit divide, among other routines.


Dave

On 6/19/2014 12:36 PM, ewkeh...@aol.com wrote:

Attached is a picture of the other peace of the puzzle. This  is the
universal output module. It has two impendent ground isolated outputs  each one
can be set for 5 or 10 MHz. It also has regulators and a switcher so  all you
feed in is 17 V and you get 5 and 15 V.
The empty socket is for a PIC that will control a FTDI USB  adapter for
those that want to store controller info on a memory stick. We would  like to
add a single line LCD that shows controller info real time, would like  some
help on that
We plan to have a partial Kit  since buying individual  transformers from
mini circuits is prohibitive.Same goes for  inductors.
Bert Kehren


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--
Clear Stream Technologies

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[time-nuts] Timelab Agilent 53230a

[David Tang]

Hi everyone,

This may be a rookie question...  I am trying to measure phase noise using 
Timelab and Agilent 53230a but I get a This plot contains xDEV/phase/frequency 
data only -- no phase noise or AM noise records.  I tried the following 
settings and other variations but still get the same result.  Can someone point 
me to how to measure PN with a 53230a?  Thank you very much for your time.

In Time Lab
Measurement:  Phase noise
Acquire from HP 53220A/53230a at specified IP address
Data Type:  Time Interval  (also tried Frequency)
Input Frequency:10e6
Scale Factor 1.0
Bin Density 29
Bin Threshold: 4
Trace History:1
Trace Duration: 10 min

On the Counter
Period
Auto (also tried Continuous)

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Re: [time-nuts] Time in Phone System

[David Malone]

On Mon, Jul 21, 2014 at 11:01:19PM -0700, Hal Murray wrote:
  I expect that there's date and time information being sent in the header of
  every phone call, maybe even before the  first ring along with the Caller ID
  info. 

 Wiki says CallerID is sent between the first and second ring, and includes 
 the date and time.
   http://en.wikipedia.org/wiki/Caller_ID#Operation

Some old modems will happily decode it for you. I compared it to
NTP at some point last year. The time stamp was only given to the
nearest minute, and for my exchange it was pretty terrible - it was
slow by about 90s for a few months. I was considering adding it to
my leap second measurements, but there didn't seem to be much point.

David.
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Re: [time-nuts] Low noise powersupplies

[David Hooke]

Such as?

david

On 7/08/2014 9:30 PM, bruce-cpdlzquo8hwavxtiumw...@public.gmane.org wrote:

I have a couple of these. however their noise spectral density tends
  to rise precipitously below 1Hz or so. There  are regulators with 
significantly
lower flicker noise.

Bruce



On August 7, 2014 at 6:35 AM Tom Van Baak t...@leapsecond.com wrote:


Ole,

Thanks for bringing it to our attention.
For those that like to click instead of search:

http://www.ti.com/tool/TPS7A4701EVM-094
http://www.ti.com/lit/ug/slvu741a/slvu741a.pdf
http://www.ti.com/product/tps7a4701
http://www.ti.com/lit/ds/symlink/tps7a4701.pdf

/tvb

- Original Message -
From: Ole Petter Ronningen olep...@gmail.com
To: time-nuts@febo.com
Sent: Wednesday, August 06, 2014 11:38 PM
Subject: [time-nuts] Low noise powersupplies



Hello, all

I thought it may be of interest to some of the members of this list that TI
is selling evaluation modules for some ultra low noise regulators for $20
in their estore, shipping world wide included. The specs looks pretty
decent to me, and I've ordered up a couple of boards to use as clean up
boxes for my bench-supplies, to use on noise-sensitive projects.

1.4-30v output TPS7A4701EVM-094
3.5µVRMS (10Hz, 100KHz)
25 nV/√Hz (10Hz, 1MHz)
Maximum Output Current of 1A

+-15v version TPS7A30-49EVM-567:
15v rail:
Noise:
12.7µVRMS (20Hz to 20kHz)
15.4µVRMS (10Hz to 100kHz)
Power-Supply Ripple Rejection:
72dB (120Hz)
≥ 52dB (10Hz to 400kHz)
Maximum Output Current: 150mA


-15v rail:
Noise:
14µVRMS (20Hz to 20kHz)
15.1µVRMS (10Hz to 100kHz)
Power-Supply Ripple Rejection:
72dB (120Hz)
≥ 55dB (10Hz to 700kHz)
Maximum Output Current: 200mA

Ole



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Re: [time-nuts] FYI: NPLTime® - a new service providing a precise time signal directly traceable to Coordinated Universal Time (UTC) and independent of GPS.

[David McGaw]

There is no mention how they intend to implement this  trusted and 
traceable distribution service for the financial sector that completely 
eliminates reliance on GPS.  We saw how a loose connector can create a 
faster than light neutrino.  Good luck to them on being able to 
deliver on the promise.


David McGaw


On 8/14/14 1:34 PM, Iain Young wrote:

On 14/08/14 17:24, David J Taylor wrote:


  The National Physical Laboratory (NPL) has signed a distribution
agreement with trading technology company Intergence to deliver NPLTime®
- a new service providing a precise time signal directly traceable to
Coordinated Universal Time (UTC) and independent of GPS.  More:

http://www.npl.co.uk/news/intergence-invests-in-npltime?utm_source=measurementnewsutm_medium=emailutm_campaign=august2014


Heh. I saw this, and in fact remember it being mentioned at NPL when I
was there in May for their openday.

I'd love it, but I dread to think what the cost is, and I suspect I
might get a few odd looks when they realised they were delivering to
domestic premises!


Best Regards

Iain

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Re: [time-nuts] Need help with transformer core

[David McGaw]

So we're nuts.  I thought that was a given.

David


On 8/29/14 9:58 PM, Mark Sims wrote:

Frankly,  anybody that builds up a Simple Switcher type converter from scratch 
is more than a little nuts and/or awfully lonely.  You can buy small,  
adjustable pre-built boards (buck or boost configs) off of Ebay for as little 
as a dollar each... including shipping from Old Cathay.  I usually buy them 10 
or 20 at a time. 
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Re: [time-nuts] 10811 Thermal fuse?

[David McGaw]

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