[time-nuts] Re: Tuning a GPSDO loop for optimal disturbance handling

[Dana Whitlow]

Eric,

Do the observed DAC steps correspond in polarity to the observed frequency
changes, or just the reverse?  That's a key determination to make in placing
blame, for it tells you whether the DAC steps are causative to the frequency
changes, or rather the PLL's reaction to problems in, say, the VCO itself.

Dana


On Tue, Mar 22, 2022 at 2:10 PM Erik Kaashoek  wrote:

> Hi Bob,
> By your advice I went for a 6.5 digit DVM and after logging and plotting
> the DAC output its clear there are some stability issues in the DAC
> output. The voltage is wandering around at about the level of frequency
> wandering observed.
> A different supply topology for the DAC and VCXO will have to be
> created.. The DAC resolution is 50 uV (2.048 V / 40 steps) but the
> random variations are about 4 times p-p larger.
> Once this is done I hope longer term logging of frequency and voltage
> will make sense.
> Or is it better to have a low pass filter between the DAC and the VCXO
> Vtune input so the loop is fast enough to remove the remaining drift?
> If so, what should the time constant of the filter be compared to the
> intersect of the ADEV of the GPS and the VCXO (100 s)?
> Having a big time constant (10s?) will be a pain in the initial tuning
> and will require active components.
> Does owning a 6.5 digit DVM qualify one as a volt-nut? Or should first
> some voltage references be added?
> Erik.
>
> On 5-3-2022 20:50, Bob kb8tq wrote:
> > Hi
> >
> > One suggestion on the frequency plot:
> >
> > TimeLab as you have it set does a “per pixel” process on its charts. You
> have
> > a limited screen resolution and a ton of data. You have to do something.
> There
> > is no way to display it all.
> >
> > It’s a good idea to zoom in to some of the “problem regions” and see
> > what is really going on. This reduces the number of data points that
> > map to one pixel and potentially changes what you see a bit. The closer
> you
> > get to one data point per pixel, the closer you are to “reality” without
> any
> > processing potentially getting in the way.
> >
> > On the DVM, eBay (with some time spent shopping) will sell you a working
> > 6 1/2 digit device for < $100 if you are patient. If you need it now,
> it’s still
> > likely to be below $200. Yes it will be a big clunky box that takes up
> bench
> > space. It will be HPIB and not serial i/o. The display might be a bit
> fun in
> > bright lighting.
> >
> > While you are shopping, I would get set up for phase noise as well. Often
> > it can spot issues that are tough to find with a second to second data
> stream.
> > The setup does not have to be very fancy or terribly expensive.
> >
> > Bob
> >
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[time-nuts] Re: HP 5065A, no 2nd harmonic.

[Dana Whitlow]

TVB, I'm interested in the nitty-gritty of this problem and would appreciate
it if you OK this thread's being kept on the group.

Dana


On Thu, Nov 18, 2021 at 6:58 PM Jared Cabot via time-nuts <
time-nuts@lists.febo.com> wrote:

> Hi,
> Your help is appreciated. We can keep this on-list for now I guess, on the
> chance it helps someone in the future.
>
> Jared.
>
> ‐‐‐ Original Message ‐‐‐
> On Friday, November 19th, 2021 at 08:25, paul swed 
> wrote:
>
> > Jared I would be happy to see if I can help remotely. We may want to
> take this offline or not. Others may find it interesting.
> > Regards
> > Paul
> > WB8TSL
> >
>
> > On Thu, Nov 18, 2021 at 12:56 PM Jared Cabot via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
>
> > > Hi all,
> > >
>
> > > I have a 5065A Rubidium Standard that was working ok, but has lost the
> 2nd harmonic.
> > > My voltages are all ok, the physics package hasn't overheated and I
> have replaced the usual resistors on the lamp assembly (and it was running
> fine afterward for a while), the lamp illuminates, and I've done the
> procedure to remove cell flooding.
> > > All readings on the 'circuit check' switch are nominal, apart from the
> 2nd harmonic position. No matter what I do, I can no longer get it to raise
> above 0.
> > > However, when I first turn the unit on, the needle drops to 0 and
> flicks a little before settling on 0 and staying there.
> > >
>
> > > Can someone help me get this unit up and running again?
> > >
>
> > > Thanks!
> > > Jared___
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[time-nuts] Re: FS740 Thoughts?

[Dana Whitlow]

Bob, I seem to remember reading in the manual on the PRS-10 where they
expounded
at length about how they took great pains to make the unit work well with
typical noisy
GPS PPS input.

I'm using a CNS Clock II as my primary GPSDO, checking phase slippage with
respect
to my PRS-10 to make decisions about when (or when not) to manually tweak
the PRS-10.
The CNS seems awfully noisy to me, even though the mfr says that it has
strong hanging
bridge correction.  I run the two 10 MHz signals through a quadrature
demodulator whose
I & Q outputs go into a 2-channel DSO running in extremely low "roll
mode".  I take a glance
at it several times per day, with each glance showing me the most recent
~4-hour history.
When I do tweak, I strive to set the PRS-10 about 1E-11 low in frequency,
which yields a
couple of months of hands-off operation before it drifts to 1E-11 on the
high side.  For
now, that has to suffice.  But I'd rather not have to pay so much attention
to it, which is
why I dream about buying a new PRS-10 with PPS locking capability.

Dana


On Thu, Nov 18, 2021 at 8:47 AM Poul-Henning Kamp 
wrote:

> 
> Bob kb8tq writes:
>
> > The 'filter' in the PRS-10 is not really set up for a GPS sort of signal.
>
> It is particularly bad at handling GPS's because of the "hanging bridge"
> phenomena, and the better the GPS, the worse the result...
>
> I tried injecting the "negative sawtooth" via the serial port to my
> PRS10 but firmware features/bugs prevented that.
>
> The offset could only be changed permanently in the saved configuration,
> you could not change the running value on a second to second basis.
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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[time-nuts] Re: FS740 Thoughts?

[Dana Whitlow]

Poul,

You did not really answer the basic question: "Does the 2.5 Hz
(or 5 Hz if applicable) C-field reversal cause the 2-sec bump in
the ADEV plot for  the PRS-10?".

BTW, some radio hams are involved with microwave and even
MMW communications between mobile stations, and I'd bet they
benefit quite a bit from any scheme that reduces magnetic field
sensitivity of their frequency references.  Therefore, the C-field
reversal thing cannot be *all* bad.

DanaK8YUM


Dana


On Thu, Nov 18, 2021 at 2:41 AM Poul-Henning Kamp 
wrote:

> 
> Matt Huszagh writes:
> > "Poul-Henning Kamp"  writes:
> >
> > > The PRS-10 switches the polarity of the C-field solenoid at 5Hz to
> > > cancel out varying external magnetic fields.
> > >
> > > If that is not a concern for you, for instance because you use it
> > > in a stationary application, it can be disabled with the "MS0" command.
> > >
> > > It's all in the manual.
> >
> > How does the 5Hz switching relate to the 2s hump in the ADEV plot?
>
> The manual says:
>
> "[...]the current in the coil is switched at a 5 Hz rate."
>
> You can either read that as:
>
> "There are five positive and five negative periods every second"
>
> or
> "The sign changes five times per second"
>
> It is not entirely obvious which reading is the correct one.
>
> When I experimented with it ages ago, I concluded the latter fit
> my data best, but that was a pretty early firmware version, with
> quite a number of variances from the manual.
>
> If your ambient magnetic field is stable, and it should be for
> time-nuts purposes, modulating the hyperfine transition is a bad
> idea, no matter the frequency.
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
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[time-nuts] Re: FS740 Thoughts?

[Dana Whitlow]

But if you can stand the ADEV hump around 2 sec, the PRS-10 is delightful.

BTW, the ordinary factory new PRS-10 does provide for direct locking to 1
PPS,
but many of the available surplus units had that feature removed.  Tne new
PRS-10's sold for years for $1595, but I see that it has gone up to $1695
since
I had last checked.

Dana


On Wed, Nov 17, 2021 at 9:52 AM Bob kb8tq  wrote:

> Hi
>
> In this case it’s not thermal. I’ve tested a ton of parts in the same
> environment ( maybe
> not 2,000 pounds but several hundred OCXO’s ).
>
> The PRS-10 gives you that hump at 2 seconds no matter what you do. It’s
> part of the
> basic design of the unit ….
>
> Bob
>
> > On Nov 17, 2021, at 10:16 AM, Matt Huszagh 
> wrote:
> >
> > Bob kb8tq  writes:
> >
> >> I have a 740 as do others on the list. The big gotcha is the OCXO in
> the device.
> >> It has various quirks that limit the performance of the device. The
> ADEV plot they
> >> show for the OCXO is a “sometimes / maybe / might” sort of thing. One
> of the
> >> “get to it eventually” projects here is to see if it can be replaced
> with something
> >> that has better ADEV performance.
> >
> > Good to know. Have you tried disciplining the PRS-10 in one of these
> > units? Based on Dana's comments, it sounds like this may not exhibit the
> > same ADEV susceptibility to the thermal environment.
> >
> > Matt
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[time-nuts] Re: GPS Elevation Mask Values.

[Dana Whitlow]

Dan, in recent years I've read that DOD (or some such agency) has been
running
spoofing tests here and there, but always in remote thinly-populated areas
(for
what should be obvious reasons).

As to why not all your receivers exhibit the "finger", I point out that the
appearance
of a GPS satellite "in the hole" must be treated as an exception, and
different
combinations of receiver HW & FW with different analysis & display  SW could
plausibly react differently to such exceptions.  I suppose such behavior
should
be called "bugs", but I would not be too harsh on the designers unless this
"bug"
also led to erroneous PVT output.

In any event, about all I can say is "What a grand mystery!".

Dana


On Mon, Nov 15, 2021 at 8:24 PM Dan Kemppainen 
wrote:

> Hi,
>
> The adafruit board had a run with the LTE-LITE and Ublox. Adafruit board
> shows no birds above the north pole. Same as does the LTE-LITE on this
> run. Again, the Ublox shows them up there according to LH. (At least
> everything is consistent!) (The curious of you can view the attached plots)
>
> Currently running some logs of raw data from all three GPS modules.
> We'll give the logs 24 hours and run them through U-Center tomorrow.
>
> As for right now, eliminating the antenna and mounting location are the
> most important part. It's getting to be winter here, and snow makes
> getting to the antenna difficult/dangerous.
>
>
> Dana,
>
> I would be highly surprised if anyone were spoofing GPS here. We're
> pretty much in the middle of nowhere. Besides, why only Ublox modules
> giving the fits on LH?
>
>
> Keelan,
>
> Thus the confusion as to why there's birds above the north pole. This
> has happened on two PC's with Two different models of Ublox Modules. Two
> other brand modules seem OK on LH.
>
> Certainly odd.
>
> Thanks,
> Dan
>
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[time-nuts] Re: GPS Elevation Mask Values.

[Dana Whitlow]

In fact, I believe that the satellite positions shown on screen plots are
those
calculated from almanac data.  My reasoning is that most GPS receivers
seem able to put up such plots first thing after turn-on, before ephemeris
data from even a single satellite is available.

IMO, if the almanac positions differ from ephemeris positions enough to
be resolvable on such plots, either the whole GPS system is in deep trouble,
or the receiver in question has not been turned on for a very long time.

Dana

On Mon, Nov 15, 2021 at 12:03 AM Keelan Lightfoot 
wrote:

>
> Isn’t the position of the satellite in these plots calculated from
> ephemeris rather than based on observations? It seems to me that you’d need
> multiple  receivers in different locations on the ground to figure out the
> position of a satellite in the sky based on observations alone.
>
> - Keelan
>
> > On Nov 14, 2021, at 2:27 PM, Dan Kemppainen 
> wrote:
> >
> > Hi,
> >
> > Still trying to sort out the cause of that 'finger' of signal.
> >
> > Hooked up two more different GPS modules. A ZED-F9P, and a Jackson Labs
> LTE-LITE eval board.
> >
> > The F9P sees the same finger in the north as the other Ublox GPS module.
> The Venus receiver in the LTE Lite does not report signal above the north
> pole. See attached images.
> >
> > The data for these images was all recorded concurrently. All three GPS
> Modules are attached to a splitter on the same antenna, with nearly the
> same length jumper cables running from the splitter to each module.
> >
> > Currently running the same test again with the Ublox Timing module, the
> LTE Lite, and an adifruit "Ultimate GPS Breakout board V3" (MediaTek
> MT3339).
> >
> > Dan
> >
> >
> >
> >> On 11/11/2021 3:30 AM, time-nuts-requ...@lists.febo.com wrote:
> >> Message: 1
> >> Date: Wed, 10 Nov 2021 09:54:09 -0500
> >> From: Dan Kemppainen
> >> Subject: [time-nuts] Re: GPS Elevation Mask Values.
> >> To:time-nuts@lists.febo.com
> >> Message-ID:
> >> Content-Type: text/plain; charset=utf-8; format=flowed
> >> Hi,
> >> So, that finger of signal appearing above the north pole shows up even
> >> after the GPS survey is done. Any ideas on how to figure out what's
> >> causing that?
> >> My first thought is to try look at it with a different model of GPS
> unit.
> >> Is it possible it could be a signal reflection in the cable or something
> >> weird going on in the feed???
> >> Another thought would be to log the GPS data, to sort out which birds
> >> the GPS thinks is up there. Comparing to where they actually are would
> >> help sort out what the signal might be bouncing off of.
> >> Dan
> > ___
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[time-nuts] Re: GPS Elevation Mask Values.

[Dana Whitlow]

Dan, could it be that you have a spoofer in the area?

Dana


On Sun, Nov 14, 2021 at 4:27 PM Dan Kemppainen 
wrote:

> Hi,
>
> Still trying to sort out the cause of that 'finger' of signal.
>
> Hooked up two more different GPS modules. A ZED-F9P, and a Jackson Labs
> LTE-LITE eval board.
>
> The F9P sees the same finger in the north as the other Ublox GPS module.
> The Venus receiver in the LTE Lite does not report signal above the
> north pole. See attached images.
>
> The data for these images was all recorded concurrently. All three GPS
> Modules are attached to a splitter on the same antenna, with nearly the
> same length jumper cables running from the splitter to each module.
>
> Currently running the same test again with the Ublox Timing module, the
> LTE Lite, and an adifruit "Ultimate GPS Breakout board V3" (MediaTek
> MT3339).
>
> Dan
>
>
>
> On 11/11/2021 3:30 AM, time-nuts-requ...@lists.febo.com wrote:
> > Message: 1
> > Date: Wed, 10 Nov 2021 09:54:09 -0500
> > From: Dan Kemppainen
> > Subject: [time-nuts] Re: GPS Elevation Mask Values.
> > To:time-nuts@lists.febo.com
> > Message-ID:
> > Content-Type: text/plain; charset=utf-8; format=flowed
> >
> > Hi,
> >
> > So, that finger of signal appearing above the north pole shows up even
> > after the GPS survey is done. Any ideas on how to figure out what's
> > causing that?
> >
> > My first thought is to try look at it with a different model of GPS unit.
> >
> > Is it possible it could be a signal reflection in the cable or something
> > weird going on in the feed???
> >
> > Another thought would be to log the GPS data, to sort out which birds
> > the GPS thinks is up there. Comparing to where they actually are would
> > help sort out what the signal might be bouncing off of.
> >
> > Dan
> >
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[time-nuts] Re: GPS Elevation Mask Values.

[Dana Whitlow]

I own at least two Garmin handhelds that park out-of-service sat symbols
 at due north on the horizon.  But they don't do anything like that finger.

Dana


On Wed, Nov 10, 2021 at 9:30 AM Bob kb8tq  wrote:

> Hi
>
> Your GPS antenna does not have a clue where signals are coming from. The
> only
> way things get plotted is based on the almanac data. If it sees sat Id 21,
> it looks in
> the almanac for id 21. If the almanac says it’s over India, that’s where
> it goes on the
> resulting plot.
>
> Best guess: you are seeing intermod of some sort that your receiver
> interprets as a
> signal from a sat that can’t actually be in view.
>
> Bob
>
> > On Nov 10, 2021, at 9:54 AM, Dan Kemppainen 
> wrote:
> >
> > Hi,
> >
> > So, that finger of signal appearing above the north pole shows up even
> after the GPS survey is done. Any ideas on how to figure out what's causing
> that?
> >
> > My first thought is to try look at it with a different model of GPS unit.
> >
> > Is it possible it could be a signal reflection in the cable or something
> weird going on in the feed???
> >
> > Another thought would be to log the GPS data, to sort out which birds
> the GPS thinks is up there. Comparing to where they actually are would help
> sort out what the signal might be bouncing off of.
> >
> > Dan
> >
> >
> > On 11/9/2021 3:30 AM, time-nuts-requ...@lists.febo.com wrote:
> >> Message: 1
> >> Date: Mon, 08 Nov 2021 16:36:49 -0800
> >> From: Hal Murray 
> >> What's the blue finger sticking out into the North Pole hole?
> > ___
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[time-nuts] Re: GPS Elevation Mask Values.

[Dana Whitlow]

Hal, that looks suspiciously like the fickle finger of fate to me.

Dan, since you have good low-angle coverage I might
suggest setting the elevation cutoff as low as 10 deg or so
and taking a look at the results for a few weeks.  Then
start raising the elevation cutoff and repeating the
experiment, etc, and in time your answer should become
fairly apparent.

Dana


On Mon, Nov 8, 2021 at 6:37 PM Hal Murray 
wrote:

> What's the blue finger sticking out into the North Pole hole?
>
>
> --
> These are my opinions.  I hate spam.
>
>
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[time-nuts] Re: Rubidium oscillator : pack it in styrofoam or attach it to a heath-sink?

[Dana Whitlow]

I wonder what the detailed thermal model of telecom Rb's looks like.  I
cool my PRS-10's
hear sink surface to ~55C with a heatsink, but parts of some other surfaces
of the package
run several degrees hotter.  This rather puzzles me, and worries me.

Dana


On Tue, Oct 5, 2021 at 10:46 AM Bob kb8tq  wrote:

> Hi
>
> Rubidiums are somewhat unusual beasts. They typically have two heated
> zones ( = two ovens) in
> them. One is a bit hotter than the other. Because of the basic physics,
> those ovens are right next
> to each other / in contact with each other.
>
> If you go to crazy with the insulation, the “colder” oven will heat up due
> to heat leakage from the
> “hotter” oven.  You need a certain amount of heat coming off the package
> to allow this to happen.
>
> The bigger issue is that there is a pretty big batch of electronics near
> the ovens in the typical telecom
> Rb. Unless you heatsink things pretty well these parts heat up. When they
> do their MTBF drops
> quite a bit. You save a couple of watts of heat (maybe) and loose the Rb
> after a year or two. Not
> a great tradeoff.
>
> Yes, there are a lot of different designs for lab grade Rb’s. There are
> also some really tiny little
> guys running around. Neither category is all that easy to get on the
> surplus market. If you want
> to dive into either of those categories, there are issues, they just may
> not be quite the same.
>
> Bob
>
> > On Oct 4, 2021, at 1:39 PM, Wim Peeters  wrote:
> >
> > Insulation decreases the power consumption.  But it will also increase
> the temperature of the electronics.
> >
> > A heath-sink will cool the electronics but will increase the power
> consumption.
> >
> > Or maybe insulate the  part of the case that gets hot, and put a
> heat-sink on the other parts?
> >
> > Wim Peeters
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[time-nuts] Re: When did computer clocks get so bad?

[Dana Whitlow]

Alec,

I seem to perceive that PC clocks have gotten quite a bit better since
their early days.  What do others think?

Dana

On Wed, Sep 29, 2021 at 3:10 PM Alec Teal 
wrote:

> Hi there,
>
> I have a question and I cannot think of anyone better to ask, for a
> project we need to time some things which are connected to a computer,
> using NTP and later using a GPS over bluetooth serial ports, we have
> discovered that computer clocks are terrible
>
> If you remove a linear drift (for example assuming it ticks at 1.00026
> seconds per second) it gets less terrible, and Linux can do this but it
> is clear that the computer clock doesn't expose this coefficient to the
> OS to let it compensate, it must be found (eg through NTP) - any ideas why?
>
>
> But more concretely, my watch is actually pretty good, it's off by < 3
> seconds and hasn't been set probably this year (I don't tend to bother
> with DST stuff, not for any reason just never get round to it) - when I
> was growing up and even now wall-clocks are not so terrible that I have
> to fix them (or NTP does with computers) very routinely.
>
> My theory is that super cheap crappy quartz clocks are now used in
> things which can be reasonably expected to be online most of the time,
> and thus use NTP - my watch cannot (and probably has temperature
> correction too? Given the varied temps it is exposed to) any truth to this?
>
> This is a very open ended question I understand, but if clocks were as
> terrible as I've found every computer and thing I've checked recently,
> why don't I remember setting wall clocks easily once a week?
>
>
> Alec
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[time-nuts] Re: Death of a Capacitor

[Dana Whitlow]

One other thing to consider with LDOs:  some types can go  unstable and
oscillate with
the wrong (combination of) capacitors on input and output.  So any time you
design in
an LDO, it is important to closely scrutinize the datasheet and application
note(s) and
heed their warnings.  Unless you like rude surprises, that is :-)

Dana


On Mon, Sep 27, 2021 at 3:16 AM n...@lazygranch.com 
wrote:

> I've only designed one LDO as a discrete chip (as opposed to a portion
> of a chip where performance just has to be good enough), so I have no
> guru status. That said, what spikes pass through a LDO if you do it
> right is simply a capacitor divider comprised of the capacitance across
> the pass device and the filter capacitor. This is a bit more
> predictable with a PFET pass than a PNP.
>
> https://www.analog.com/en/products/lt3045.html
>
> You can see the PSRR after a point (200kHz) rolls off and appears to
> flatten. I assume the error amp is out of loop gain. It goes flat for a
> while. The idea here is the drive on the pass device is constant
> and just maintains the DC voltage. The AC rejection is mostly due to
> capacitance ratios. This being a bipolar pass device there is some
> secondary effect here where after 2MHz the rejection improves then goes
> flat again.
>
> The bipolar pass control is harder than MOS since you are trying to
> keep the device out of saturation. That is besides the error amp there
> is some sort of anti-saturation circuit controlling the drive on the
> pass device.
>
> My thinking here is small signal. If you have huge spikes the
> performace even in the region where you do have loop gain can be
> nonlinear. For example the error amp can be slew rate limited.
>
> This looks like fine performance given the chip only draws 2.2mA.
>
> Just trawling the interwebs I found this on the TI website:
> https://training.ti.com/ldo-architecture-review
> At about the 18 minute point he goes into the regions of PSRR.  I poked
> around so I can't vouch more all of the talk,
>
> .
>
> On Sun, 26 Sep 2021 18:21:36 -0400
> John Ackermann N8UR  wrote:
>
> > I got some interesting and unintended data today. I was measuring low
> > phase noise oscillators using a set of power supplies I just finished
> > putting together.
> >
> > The configuration is ~24 VDC into a TPS-53400 switching regulator
> > that outputs 19.2 volts at up to 3 amps.  That output is fed to
> > separate regulator boards for each oscillator.  Those boards each
> > have an LT-1086 linear pre-regulator that drops the input to about 17
> > volts, which then goes into an ultra-low-noise LT3045A outputting 15
> > volt to drive the oscillator.  So there are two linear regulators and
> > lots of caps, inductors, and ferrite beads to isolate the oscillators
> > from the switching supply.
> >
> > Due to an error by an assembly tech who will remain nameless, the
> > wrong electrolytic was installed on the output side of the switching
> > regulator.  It should have been 33uF at 50 volts, but what got
> > installed was 330 uF at 16 volts, so it was rated below the operating
> > voltage. (I was building two boards at the same time, one for 5V and
> > one for 19.2V. Apart from the voltage setting resistor, the only
> > difference between the two was the output cap.  I managed to swap
> > them.)
> >
> > I tested the system on the bench for 24 hours and everything worked
> > fine, so I buttoned up the enclosure and started a 4 hour data
> > capture. About 70 minutes in, the electrolytic became very unhappy
> > and whatever it turned into caused the switcher to start spewing all
> > sorts of crud. The regulator kept working (sort of) through the end
> > of the run, but when I came into the lab the next morning it had shut
> > down completely and troubleshooting showed that the cap had shorted
> > at some point after the run completed, and the regulator chip went
> > into shutdown.
> >
> > Attached are a plot of frequency showing the whole run with the very
> > obvious change when the cap failed, and another zoomed view of the
> > critical moment.  The failure was very abrupt with no visible lead-in.
> >
> > What I find interesting is that all that crud got through not one,
> > but two linear regulators, one of which is touted for its extremely
> > high PSRR (and I did my best to follow the recommended PCB layout for
> > that chip).  That must have been one ugly 19V line when the cap
> > went...
> >
> > John
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[time-nuts] Re: ammonia, cesium, masers, etc.

[Dana Whitlow]

My dad worked in the absorption air conditioning field using ammonia and
water,
and he once told me that ammonia-water was hell on aluminum copper points,
or
even aluminum tubing that had impurities in the form of tiny copper flakes
in it.

As to dry ammonia, intuition suggests to me that things would not be so bad,
but if I were building one of these clocks I think I'd try to avoid
aluminum-copper
joints on general principles.

Once in a while Dad would take me with him when he went to work in the lab
on a Saturday morning.  The ammonia odor was mighty potent, but he didn't
seem bothered by it at all.  And despite his exposure to this supposedly
toxic
substance (by current thinking, anyway), he lived to be 94 years old.  I
guess
it can't be all bad.

Dana


On Mon, Sep 20, 2021 at 5:34 PM ed breya  wrote:

> That's a fascinating article.
>
> Regarding ammonia
>
> Anhydrous liquid ammonia is a common commodity material, but probably
> comes in many grades, depending on use. I'd break it into three basic
> ranges. For something like this, you would want to look at reagent/lab
> grade, to get it as clean and dry as possible to start with, with
> minimal grief. Refrigeration grade may be good enough too, if you put
> impurity traps and dryers in your system. The crappiest versions are
> probably agricultural - as crude and cheap as possible. Don't forget,
> you'd also need a bought or leased tank, and proper manifold/regulator
> set to actually use it.
>
> I don't recall how compatible ammonia is with copper or aluminum, but I
> know it's good with steel, and most likely all stainless steels. Keeping
> it absolutely dry would help to avoid any materials grief, but even so,
> it's a good idea to check out the chemistry before committing to a design.
>
> Regarding microwave gear
>
> Like Jim mentioned, the 22-24 GHz microwave stuff is in the right
> ballpark. I scrounged up some 1980s 22 and 38 GHz point to point
> transceiver head-ends over the years, and saved the goodies for possible
> re-use. In front of me right now are a couple of 22 GHz plumbing
> sections. At first glance, it appears they use Gunn oscillator modules
> as LOs, although they could be DROs, or a combination - hard to tell
> from outside. Then there's a bunch of waveguide BPF sections, with lots
> of tuning screws, and some directional couplers, altogether doing
> filtering and diplexing. I think these sorts of parts from this era
> would be great for this application. With all the fancy filters, it
> could be that besides TX/RX separation, the LOs may operate at lower
> frequencies, and the filters just let the right harmonics through. Can't
> tell yet, without more investigation.
>
> I have some newer - probably 1990s - pieces in 22 and 38 GHz, where the
> guts are much more highly integrated into big modules that do
> everything, and just have the waveguide directional couplers sticking
> out, to connect an external diplexer. I've looked inside some of these
> over the years, and recall that none use a fundamental LO - they were
> all synthesized LOs in the maybe 6-8 GHz range, then amplified and
> multiplied up.
>
> Regarding waveguide
>
> It seems that they had the right kind of waveguide stock in the 1950s,
> so why not now? I know you can get flexible guide section, which is
> corrugated, but I don't know if there's such a thing as a smooth,
> semi-rigid form that can be bent or rolled up - kind of equivalent to
> semi-rigid coax. Maybe there is, or maybe not. Another option, for
> anyone with NC machines, could be to machine the internal structure into
> a block, say in a spiral or serpentine form, then cap it off from the
> side. It would have to be sealed though, somehow, to be good RF-wise and
> ammonia-wise.
>
> Ed
>
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[time-nuts] Re: in-ground clock room

[Dana Whitlow]

It may be that the time constant of eddy current damping would be too
limited by the
inavailability of sufficiently good conductors (ar room temp, anyway).  To
get really
long time constants one basically needs superconductivity somewhere in the
system.

Dana


On Sat, Sep 11, 2021 at 11:54 PM Tom Holmes  wrote:

> Which suggests a possible damping mechanism.
>
> From Tom Holmes, N8ZM
>
> > On Sep 11, 2021, at 10:08 AM, Adrian Godwin  wrote:
> >
> > Doesn't that depend on the configuration of the fields ?
> > For instance, a pair of facing like poles will repel and, as you say,
> make
> > a good spring.
> > But a magnet falling down an aluminium tube will go slowly, because of
> the
> > generated eddy currents and their subsequent fading due to the lossy
> > aluminium.
> >
> >
> >> On Sat, Sep 11, 2021 at 2:02 PM Poul-Henning Kamp 
> >> wrote:
> >>
> >> 
> >> Gilles Clement writes:
> >>
> >>> Magnetic levitation, dampening external vibrations ?
> >>
> >> By theselves magnetic fields are just really good springs.
> >>
> >> To get any kind of dampening you either need to add a
> >> dash-pot (=shock-absorber) as a dissipative device or
> >> you need to modulate the magnitic field to emulate
> >> the same result.
> >>
> >> I'm told the latter is much harder than it sounds.
> >>
> >> --
> >> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> >> p...@freebsd.org | TCP/IP since RFC 956
> >> FreeBSD committer   | BSD since 4.3-tahoe
> >> Never attribute to malice what can adequately be explained by
> incompetence.
> >> ___
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> >>
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[time-nuts] Re: in-ground clock room

[Dana Whitlow]

One might also consider mounting smaller items inside the cylinders of the
engine block,
to get the most out of its thermal mass.

Dana


On Thu, Sep 9, 2021 at 11:03 AM Joseph Gwinn  wrote:

> On Thu, 09 Sep 2021 03:30:35 -0400, time-nuts-requ...@lists.febo.com
> wrote:
> Re: time-nuts Digest, Vol 209, Issue 6
>
>
> > --
> > > Date: Wed, 8 Sep 2021 18:54:03 -0700
> > From: Tom Van Baak 
> > Subject: [time-nuts] in-ground clock room
> > To: Discussion of precise time and frequency measurement
> >   
> > Message-ID: <4037f6cb-ade3-8c01-8c36-7edf19327...@leapsecond.com>
> > Content-Type: text/plain; charset=utf-8; format=flowed
> >
> > I am considering a below ground "clock room" away from the house. This
> > will be for some low-drift quartz oscillators and also a couple of
> > precision pendulum clocks. The goal is long-term, unattended, and very
> > undisturbed operation.
> >
> > For scale, assume the room is 1 meter × 1 meter × 2 meters deep. So
> > that's vastly smaller than digging a basement, but much larger than
> > drilling a 8 inch round pipe. Digging down gives some natural isolation
> > and temperature regulation. A couple tons of concrete gives high
> > stability vertical walls for the pendulum clocks.
> >
> > If any of you have personal or professional experience with the design
> > or construction of this sort of thing, especially experience with
> > precast (utility) vaults or poured concrete, please let me know.
> >
> > In case this gets too off-topic for time-nuts, off-list email to me is
> > fine (t...@leapsecond.com).
>
> As others have said, it may not be economically practical to build an
> underground clock room.
>
> Assuming that you have a basement of other suitable room in your
> house, I'd suggest an insulated box or room containing a big lump of
> iron riding on an inner-tube suspension of some kind.   The big lump
> of iron can be a 500-pound truck engine head or block from a
> junkyard, steam cleaned (to remove oil) and painted (to keep the rust
> under control).  Drill and tap holes as needed for mounting.
>
> This box/room plus block can be set up as a temperature-controlled
> oven with a few extra components, including a PID controller.
>
> Bolt a thick plywood floor to the top of the iron hunk, and attach
> the clocks to this floor.
>
> Joe Gwinn
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[time-nuts] Re: in-ground clock room

[Dana Whitlow]

Tom,

Andy brings up good points, especially about water leaks.
Are you familiar with "Whitlow's 5th law" (which can be summarized
as "everything leaks")?

Dana Whitlow


On Thu, Sep 9, 2021 at 7:29 AM Andy Gardner, ZL3AG via time-nuts <
time-nuts@lists.febo.com> wrote:

>
>
> So the 2 things you're after are thermal insulation and vibration
> insulation?
>
> Digging can be expensive, and you have to worry about water table in many
> locations.
>
> How about the thickest concrete water tank you can find, plonk it in a
> nice location, spray layers of polyurethane foam over the top and sides for
> thermal insulation, then build a wind shield ("shed") around it. The shed
> could be an old coolstore, adding more insulation.
>
> Concrete water tanks are out of fashion these days due to plastics, so if
> you shop around you can find a cheap used one, and then it's just the
> trucking/crane charges.
>
>
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[time-nuts] Re: in-ground clock room

[Dana Whitlow]

It seems to me that in order to derive much thermal stabilization, the *top*
of the space would need to be several feet underground (depending on
geographic location).  And I think that the means for human access would
likely "spoil the broth" unless fairly extreme measures were taken.

Wouldn't it be sufficient to use a space whose thermal coupling were weak
enough to make the time constant a few days (instead of months)?  Then,
ordinary inexpensive means like GPS-locked Rb standards with suitable
(longish) time constants should clean up "GPS noise", yet enable the loop
to take care of low rate temperature variations in the protected space due
to outside temperature changes.

Remember, perfection in clocks is expensive- according to recent things I've
read about entropy of timekeeping, a perfect clock would require infinite
power,
and that alone would blow away all one's efforts at temperature control.

Dana


On Thu, Sep 9, 2021 at 6:19 AM B Riches via time-nuts <
time-nuts@lists.febo.com> wrote:

>  How about using a round septic tank.  Mine is about 5 feet wide and 6
> feet deep  Large hole in the top - put ladder for entry.
> 73,
> Bill, WA2DVUCape May, NJ
> On Thursday, September 9, 2021, 02:29:40 AM EDT, Bill Beam <
> wb...@gci.net> wrote:
>
>  On Wed, 08 Sep 2021 18:36:11 -0800, Bill Beam wrote:
>
> >On Wed, 8 Sep 2021 18:54:03 -0700, Tom Van Baak wrote:
>
> >>I am considering a below ground "clock room" away from the house. This
> >>will be for some low-drift quartz oscillators and also a couple of
> >>precision pendulum clocks. The goal is long-term, unattended, and very
> >>undisturbed operation.
>
> >>For scale, assume the room is 1 meter +— 1 meter +— 2 meters deep. So
> >>that's vastly smaller than digging a basement, but much larger than
> >>drilling a 8 inch round pipe. Digging down gives some natural isolation
> >>and temperature regulation. A couple tons of concrete gives high
> >>stability vertical walls for the pendulum clocks.
>
> >>If any of you have personal or professional experience with the design
> >>or construction of this sort of thing, especially experience with
> >>precast (utility) vaults or poured concrete, please let me know.
>
> >>In case this gets too off-topic for time-nuts, off-list email to me is
> >>fine (t...@leapsecond.com).
>
> >>Thanks,
> >>/tvb
>
> >Tom,
>
> >How long do you expect your proposed voult to go undisturbed?
> >I have several pendulum clocks.  They are disturbed every couple of months
> >by earth quakes.  By disturbed, I mean pendulum banging against the case
> walls
> >Any ground motion that can be felt will upset the clocks.  Often the
> clocks will
> >signal an earth quake that is not felt.
>
> >Good luck.
>
> I spent a few years as a geotechnic/soils engineer and learned as others
> have pointed out
> that a thermal wave of period one year and wave length of several meters
> propagates
> downward thru the soil.  Peak amplitude of a few degrees can be expected
> near the surface.
>
> Consider building an "oven" with the clock vault freely floating in a
> water-ice mixture.  This will
> provide constant temperature (0C) and limited mechanical isolation from
> earth quakes.
>
> But of course this will be expensive to operate.
>
> As you know 'good' clocks require a lot of energy and generate a lot of
> entropy.
>
> Protecting the quartz oscillators is much easier than protecting the
> pendulum clocks.
>
>
>
>
> Bill Beam
> NL7F
>
>
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[time-nuts] Re: thermodynamics of time keeping

[Dana Whitlow]

Perhaps the author is trying to include Schmitt triggers to sort of emulate
mechanical escapements.
I've occasionally used the things (Schmitt triggers) to help square up
sinewaves, but never in a case
where I was concerned about stability or jitter.

BTW, how do three inverters constitute a Schmitt trigger?  Note: Wikipedia
spells it 'Schmitt',
'not 'Schmidt'.

Dana


Dana



On Tue, Sep 7, 2021 at 3:11 PM Poul-Henning Kamp  wrote:

> 
> Richard Karlquist writes:
>
> > He lost me when he started talking about quartz clocks utilizing
> >
> > Schmidtt triggers.  Never heard of that before and I'm going on
> >
> > 50 years of designing oscillators.
>
> I bet you just forgot about it:  The classical 3-TTL-inverter
> clock-generator was used almost everywhere, including in quite
> a number of HP products.
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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[time-nuts] Re: Affordable 160 GHz Sampler

[Dana Whitlow]

I'm curious- is this a realtime sampler, or is it one of these things
like early sampling 'scopes used?

Dana


On Wed, Sep 1, 2021 at 1:10 PM Mike Monett  wrote:

> Conventional samplers for home brewers usually go to 1 GHz. The SD-32
> sampler for the Tektronix 11801C mainframe goes to 50 GHz. The HP 110GHz
> oscilloscope costs around $1.3 Million USD, with a 10-bit resolution. Very
> impressive.
>
> https://www.youtube.com/watch?v=DXYje2B04xE
>
> I have invented a new sampling technology that promises 160 GHz bandwidth,
> yet is affordable to home experimenters. If you can afford an IPhone or
> IPad, you can afford this sampler.
>
> This technology is not pie-in-the-sky. I made a basic 5 GHz version for the
> University of Ludwigshafen, Germany, and they were very pleased with the
> results. I am attaching images of the response compared to a
> Tektronix 1502 TDR and the pcb as proof.
>
> This was the first prototype, and I have made significant improvements
> since then.
>
> I have two questions for the time-nuts group:
>
> 1. where would a sampler with this bandwidth be useful?
>
> 2. where can I find signal sources at these frequencies to check the
> response?
>
> Thanks,
>
> Mike
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[time-nuts] Re: BNC connectors for the distribution of frequency or time...

[Dana Whitlow]

Another point should be mentioned:

Many inexpensive RF products use floating BNC connectors (those with shells
that are insulated
from the bulkhead in which they are mounted).  These are virtually
guaranteed to be common-mode
leaks, and should be avoided like the plague.  Nobody will admit to this in
the specifications, but
where photos are shown in the ads, one can often tell by inspection.

Remember, folks, that electricity does not go through wires- it travels in
dielectric space.  Only the
*current* actually goes through wires.  Current alone does not carry
energy- it is only a "side effect"
manifestation of the magnetic field component of the EM fields in the
vicinity.

Dana


On Tue, Aug 31, 2021 at 6:08 AM Ulf Kylenfall via time-nuts <
time-nuts@lists.febo.com> wrote:

>
> Greetings.
> At my work, all connectors used for the distributionof frequency or time
> are types N, TNC or SMA.
> Bayonett types are prohibited for useexcept where they cannot be
> substitutedi.e. "EXT REF INPUT" on rear side ofsignal generators or
> similar...
>
> Cheers
> Ulf Kylenfall
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Dana Whitlow]

Andy,

Balanced twisted pair may be helpful, but only if adequate precautions are
taken to
avoid creation of common mode *currents *on the line*.*

Dana


On Sun, Aug 29, 2021 at 9:34 AM Andy Talbot  wrote:

> Hence my observation that balanced twisted pair might be a better solution
> than coax for 10MHz distribution
> Removes all possibility of ground loops
>
> Andy
> www.g4jnt.com
>
>
>
> On Sun, 29 Aug 2021 at 15:22, Dana Whitlow  wrote:
>
> > I believe that a significant problem in my case was not leakage through
> the shield,
> > but
> > rather common-mode currents on the cable.  My experiences were with RG-6
> style
> > cable,
> > namely a cable that mostly went around the outside of the house for TV
> > distribution.
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[time-nuts] Re: About 10 MHz Optical Distro

[Dana Whitlow]

Paul is right, and it can be difficult to figure out which cable works well
at a given
wavelength and which connector type is which.  A phone conversation with an
applications person at the cable supplier ought to help avoid any of the
traps

At the Arecibo Observatory we had some bad experiences with fiber to
ethernet
converters.
As a class, these things seemed to have problems with UHF/microwave leakage
and often had to be put in properly-shielding enclosures of our own
design.  Of
course, being a radio observatory, we might have been a wee bit more
sensitive
to such EMI than would many garden-variety users :-)

Dana


On Sun, Aug 29, 2021 at 9:04 AM paul swed  wrote:

> I did see the tp link. Pretty amazing. For the group these devices are
> pretty useful.
> But watch out for the wavelength of the light you typically need matching
> fiber. Also note the connectors and get the matching units.
> I have no idea how well 1350 light would pass on multimode for 850 nm.
> Regards
> Paul
> WB8TSL
>
> On Sat, Aug 28, 2021 at 11:57 PM Lux, Jim  wrote:
>
> > On 8/28/21 7:13 PM, AC0XU (Jim) wrote:
> > > Thanks to all the posters. Especially to Dana -  That is exactly what I
> > was looking for - suggestions for parts and/or circuits to do the job. I
> > was originally thinking that I would go with a digital circuit (sine to
> > square to sine), but maybe analog/sinewave would be simpler and perform
> > about as well.
> > >
> > > Anyway, I have ordered some of the recommended optical transceivers.
> > We'll see how that works out.
> > >
> > > One or two posters mentioned that phase noise and/or thermal stability
> > may be issues. The referenced research papers don't seem to indicate that
> > phase noise is a problem. I don't think that thermal effects will be a
> big
> > problem for me - I just need to check the phase calibration from time to
> > time. Certainly there are expensive commerical optical clock distribution
> > systems with excellent properties. Maybe the devil is in the details...
> > >
> > > My specifical application at the moment is putting several SDRs at
> > diverse antenna locs and feeding the IF via ethernet-converted-to-optical
> > to my computer. I may want to transmit at some point but receiving is
> all I
> > want to do for now. Still need a way to get a stable ref clock to each
> > radio to provide phase coherence I only need 50-60 meters but an
> > optical solution with single mode fibers can go many km if I ever wanted
> to
> > scale up. Anyway, my plan is to have only power carried by copper.
> > >
> > > I don't want to go with coax, twisted pair, or any other copper
> solution
> > because of high ambient noise levels in my area and a desire to avoid
> > adding to it. Stringing several 100 meters of copper about my yard,
> > carrying 10 MHz clock signals, no matter if the cables are well shielded,
> > doesn't seem like a great idea.
> >
> > This is totally the thing that OVRO LWA dealt with.. Not only is fiber a
> > LOT cheaper than coax, it solves a lot of problems.
> >
> > Ethernet to fiber is really cheap ($20 for an endpoint from TP-link )
> > $20 from newegg
> >
> >
> >
> https://www.newegg.com/tp-link-mc100cm/p/N82E16833704015?item=N82E16833704015
> >
> >
> >
> >
> > ___
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> send
> > an email to time-nuts-le...@lists.febo.com
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Dana Whitlow]

I believe that a significant problem in my case was not leakage through the
shield, but
rather common-mode currents on the cable.  My experiences were with RG-6
style cable,
namely a cable that mostly went around the outside of the house for TV
distribution.
I get all the TV I want with an indoor dipole, and I had had plans of using
that TV
cable for ham purposes.  One thing I have noted is that adding ferrite
common mode
chokes near the ends of the cable did help quite a  bit, just not enough.

Those who are conversant with RF shielding concepts will recognize that
this puts most
of the blame squarely on my own shoulders, for not putting my kluges in
proper enclosures.
But I'm retired, old, shaky, tired, etc, and am not too ambitious any
more.  But I take
some solace in the observation that I'm not the only one; much of the
commercially-built
equipment I own has similar (and quite obvious) flaws.

I worked in the Tektronix spectrum analyzer group some years back, and one
of my side
tasks was taking instruments over to the EMI lab for compliance tests.  On
more than
one occasion those people told me that they were always delighted to test
stuff designed
by our group, because it was designed and built well enough that it almost
always passed
FCC specs on the first round.

Dana


On Sun, Aug 29, 2021 at 8:52 AM Bob kb8tq  wrote:

> Hi
>
> Skin depth is what gets you with most coax at 10 MHz, even with the
> “double
> shield” stuff. Hardline with a nice heavy outer would do better. It’s not
> terribly
> practical around the typical lab. Might not be a bad choice for a “burry
> in the yard”
> setup though. With normal cable, the losses from the soil at normal burial
> depths make a good shield, that makes dealing with it questionable even
> there ….
>
> Bob
>
> > On Aug 29, 2021, at 9:36 AM, Robert DiRosario 
> wrote:
> >
> > What about double shielded RG-223, or Thinnet ethernet cable?
> > Most Thinnet has both a braided shield and a foil wrap.
> >
> > Robert
> >
> > On 08/28/2021 08:26 PM, Bob kb8tq wrote:
> >> Hi
> >>
> >> Anything you do that has a bunch of 10 MHz cables running out from here
> or there
> >> will impact your ability to listen to WWV at 10 MHz :)  Other than
> killing all the sources,
> >> there is no silver bullet.
> >>
> >> Bob
> >>
> >>> On Aug 28, 2021, at 7:57 PM, Dana Whitlow 
> wrote:
> >>>
> >>> Bob, my own motivation  for going to fiber was entirely different.  I
> >>> simply wanted to
> >>> run 10 MHz all over the place from reference sources in disparate
> >>> locations in the
> >>> house, and I quickly discovered that cable leakage was embarrassingly
> >>> severe.  So
> >>> I shut down and began contemplating a fiber link.  But then reality
> set in
> >>> and I realized
> >>> that running fiber across the house had its own big problems, so I set
> the
> >>> project aside.
> >>>
> >>> Dana
> >>>
> >>>
> >>> On Sat, Aug 28, 2021 at 3:32 PM Bob kb8tq  wrote:
> >>>
> >>>> Hi
> >>>>
> >>>> With a whole variety of pretty good OCXO’s going for cheap money
> >>>> on eBay, it’s likely less expensive to do cleanup oscillators on the
> link
> >>>> compared to going crazy with low noise optical this or that. Yes, you
> >>>> will be getting something in the high 150’s for noise, but still
> pretty
> >>>> good
> >>>> for $10.
> >>>>
> >>>> If you need better, spend $50 or so on a 10811. Still less money than
> >>>> some of the crazy fiber stuff.
> >>>>
> >>>> With either one, send over a high enough frequency that the loop isn’t
> >>>> dealing with reference spurs in any significant way. Given the clock
> rates
> >>>> Ethernet runs at these days, that part should be fairly
> straightforward.
> >>>>
> >>>> This *assumes* that there is a crossover somewhere practical between
> >>>> the fiber noise and the noise on the optical gear. You should be able
> to
> >>>> work out what it is with some fairly normal phase noise or ADEV
> testing.
> >>>>
> >>>> Bob
> >>>>
> >>>>> On Aug 28, 2021, at 3:03 PM, Dana Whitlow 
> wrote:
> >>>>>
> >>>>> I was looking for something similar about 18 months or so ago.
> Although
> >>>> I
> >>>>> haven't taken any
> >>>>>

[time-nuts] Re: Query about List and about 10 MHz Distro

[Dana Whitlow]

Bob,

In my case simply disconnecting the long interconnecting cables at both
ends almost
completely eliminated the problem.  Hence my expectation that use of fiber
optics
would be effective.

Dana


On Sat, Aug 28, 2021 at 7:27 PM Bob kb8tq  wrote:

> Hi
>
> Anything you do that has a bunch of 10 MHz cables running out from here or
> there
> will impact your ability to listen to WWV at 10 MHz :)  Other than killing
> all the sources,
> there is no silver bullet.
>
> Bob
>
> > On Aug 28, 2021, at 7:57 PM, Dana Whitlow  wrote:
> >
> > Bob, my own motivation  for going to fiber was entirely different.  I
> > simply wanted to
> > run 10 MHz all over the place from reference sources in disparate
> > locations in the
> > house, and I quickly discovered that cable leakage was embarrassingly
> > severe.  So
> > I shut down and began contemplating a fiber link.  But then reality set
> in
> > and I realized
> > that running fiber across the house had its own big problems, so I set
> the
> > project aside.
> >
> > Dana
> >
> >
> > On Sat, Aug 28, 2021 at 3:32 PM Bob kb8tq  wrote:
> >
> >> Hi
> >>
> >> With a whole variety of pretty good OCXO’s going for cheap money
> >> on eBay, it’s likely less expensive to do cleanup oscillators on the
> link
> >> compared to going crazy with low noise optical this or that. Yes, you
> >> will be getting something in the high 150’s for noise, but still pretty
> >> good
> >> for $10.
> >>
> >> If you need better, spend $50 or so on a 10811. Still less money than
> >> some of the crazy fiber stuff.
> >>
> >> With either one, send over a high enough frequency that the loop isn’t
> >> dealing with reference spurs in any significant way. Given the clock
> rates
> >> Ethernet runs at these days, that part should be fairly straightforward.
> >>
> >> This *assumes* that there is a crossover somewhere practical between
> >> the fiber noise and the noise on the optical gear. You should be able to
> >> work out what it is with some fairly normal phase noise or ADEV testing.
> >>
> >> Bob
> >>
> >>> On Aug 28, 2021, at 3:03 PM, Dana Whitlow 
> wrote:
> >>>
> >>> I was looking for something similar about 18 months or so ago.
> Although
> >> I
> >>> haven't taken any
> >>> action yet, I concluded that one could do a nice job for under $200 per
> >>> segment, including the
> >>> transmitter and receiver modules and lots of connectorized multimode
> >>> fiber.  What I *don't* know
> >>> is what the phase noise performance would be, except that I do know
> that
> >>> the fiber's VF *is*
> >>> materially influenced by temperature.
> >>>
> >>> I was looking primarily at the HFBR-2416 for the fiber receiver, and
> the
> >>> HFBR-1412 (standard
> >>> power) or the HFBR-1414 (high power option) for the transmitter
>  Unlike
> >>> most of the available
> >>> models, these are fundamentally analog devices, meaning that you can
> >>> transmit sinewave
> >>> 10 MHz through them.  At the time I was looking, Mouser was selling
> these
> >>> for about $20 each.
> >>>
> >>> See the datasheet at
> >>>
> >>
> https://www.mouser.com/datasheet/2/678/AV02-0176EN_2019-02-15-1827546.pdf
> >>> with particular attention to page 21 regarding the HFBR-2416 receiver.
> >>>
> >>> I was also looking at Fiber Instrument Sales for patch cords.  We
> bought
> >> a
> >>> lot of fiber stuff from
> >>> them at Arecibo, and I was always happy with them.  See:
> >>>
> >>
> https://www.fiberinstrumentsales.com/catalog-cable-assemblies?gclid=Cj0KCQjwvaeJBhCvARIsABgTDM7eNTkP2nQbyFzhcwDE38VnSEP879MBKV1ZyDq2YrnEtOn7_VfzjbkaAtpfEALw_wcB
> >>>
> >>> Somebody had pointed out yet another source of connectorized fibers
> >> ("patch
> >>> cords") to me, but I cannot find the name
> >>> at the moment.
> >>>
> >>> Dana   K8YUM
> >>>
> >>>
> >>> On Sat, Aug 28, 2021 at 11:52 AM AC0XU (Jim) <
> james.schatz...@ac0xu.com>
> >>> wrote:
> >>>
> >>>> I am hoping that you can help me about a couple of things:
> >>>>
> >>>> 1) My time-nuts summaries sometimes appear unformatted and u

[time-nuts] Re: Query about List and about 10 MHz Distro

[Dana Whitlow]

Bob, my own motivation  for going to fiber was entirely different.  I
simply wanted to
run 10 MHz all over the place from reference sources in disparate
locations in the
house, and I quickly discovered that cable leakage was embarrassingly
severe.  So
I shut down and began contemplating a fiber link.  But then reality set in
and I realized
that running fiber across the house had its own big problems, so I set the
project aside.

Dana


On Sat, Aug 28, 2021 at 3:32 PM Bob kb8tq  wrote:

> Hi
>
> With a whole variety of pretty good OCXO’s going for cheap money
> on eBay, it’s likely less expensive to do cleanup oscillators on the link
> compared to going crazy with low noise optical this or that. Yes, you
> will be getting something in the high 150’s for noise, but still pretty
> good
> for $10.
>
> If you need better, spend $50 or so on a 10811. Still less money than
> some of the crazy fiber stuff.
>
> With either one, send over a high enough frequency that the loop isn’t
> dealing with reference spurs in any significant way. Given the clock rates
> Ethernet runs at these days, that part should be fairly straightforward.
>
> This *assumes* that there is a crossover somewhere practical between
> the fiber noise and the noise on the optical gear. You should be able to
> work out what it is with some fairly normal phase noise or ADEV testing.
>
> Bob
>
> > On Aug 28, 2021, at 3:03 PM, Dana Whitlow  wrote:
> >
> > I was looking for something similar about 18 months or so ago.  Although
> I
> > haven't taken any
> > action yet, I concluded that one could do a nice job for under $200 per
> > segment, including the
> > transmitter and receiver modules and lots of connectorized multimode
> > fiber.  What I *don't* know
> > is what the phase noise performance would be, except that I do know that
> > the fiber's VF *is*
> > materially influenced by temperature.
> >
> > I was looking primarily at the HFBR-2416 for the fiber receiver, and the
> > HFBR-1412 (standard
> > power) or the HFBR-1414 (high power option) for the transmitter   Unlike
> > most of the available
> > models, these are fundamentally analog devices, meaning that you can
> > transmit sinewave
> > 10 MHz through them.  At the time I was looking, Mouser was selling these
> > for about $20 each.
> >
> > See the datasheet at
> >
> https://www.mouser.com/datasheet/2/678/AV02-0176EN_2019-02-15-1827546.pdf
> > with particular attention to page 21 regarding the HFBR-2416 receiver.
> >
> > I was also looking at Fiber Instrument Sales for patch cords.  We bought
> a
> > lot of fiber stuff from
> > them at Arecibo, and I was always happy with them.  See:
> >
> https://www.fiberinstrumentsales.com/catalog-cable-assemblies?gclid=Cj0KCQjwvaeJBhCvARIsABgTDM7eNTkP2nQbyFzhcwDE38VnSEP879MBKV1ZyDq2YrnEtOn7_VfzjbkaAtpfEALw_wcB
> >
> > Somebody had pointed out yet another source of connectorized fibers
> ("patch
> > cords") to me, but I cannot find the name
> > at the moment.
> >
> > Dana   K8YUM
> >
> >
> > On Sat, Aug 28, 2021 at 11:52 AM AC0XU (Jim) 
> > wrote:
> >
> >> I am hoping that you can help me about a couple of things:
> >>
> >> 1) My time-nuts summaries sometimes appear unformatted and unreadable.
> All
> >> the text from all the postings is crammed together without spacing. How
> can
> >> I fix it?
> >>
> >> 2) I want to distribute 10 MHz references by fiber. There are
> >> RF-over-Fiber products available, but too expensive for me (thousands of
> >> $$$ per xmit/rcv set).  I am thinking that it should be possible to use
> >> fiber Ethernet components to do this. I don't mean IEEE 1588 but a much
> >> simpler, no-computer-required, solution. Possibly just converting sine
> wave
> >> (coax) to square wave (fiber) to sine wave (coax). I am looking for a
> low
> >> cost solution. Any thoughts or recommendations??
> >>
> >> Thanks!
> >>
> >> Jim
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
> send
> >> an email to time-nuts-le...@lists.febo.com
> >> To unsubscribe, go to and follow the instructions there.
> >>
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[time-nuts] Re: Query about List and about 10 MHz Distro

[Dana Whitlow]

I was looking for something similar about 18 months or so ago.  Although I
haven't taken any
action yet, I concluded that one could do a nice job for under $200 per
segment, including the
transmitter and receiver modules and lots of connectorized multimode
fiber.  What I *don't* know
is what the phase noise performance would be, except that I do know that
the fiber's VF *is*
materially influenced by temperature.

I was looking primarily at the HFBR-2416 for the fiber receiver, and the
HFBR-1412 (standard
power) or the HFBR-1414 (high power option) for the transmitter   Unlike
most of the available
models, these are fundamentally analog devices, meaning that you can
transmit sinewave
10 MHz through them.  At the time I was looking, Mouser was selling these
for about $20 each.

See the datasheet at
https://www.mouser.com/datasheet/2/678/AV02-0176EN_2019-02-15-1827546.pdf
with particular attention to page 21 regarding the HFBR-2416 receiver.

I was also looking at Fiber Instrument Sales for patch cords.  We bought a
lot of fiber stuff from
them at Arecibo, and I was always happy with them.  See:
https://www.fiberinstrumentsales.com/catalog-cable-assemblies?gclid=Cj0KCQjwvaeJBhCvARIsABgTDM7eNTkP2nQbyFzhcwDE38VnSEP879MBKV1ZyDq2YrnEtOn7_VfzjbkaAtpfEALw_wcB

Somebody had pointed out yet another source of connectorized fibers ("patch
cords") to me, but I cannot find the name
at the moment.

Dana   K8YUM


On Sat, Aug 28, 2021 at 11:52 AM AC0XU (Jim) 
wrote:

> I am hoping that you can help me about a couple of things:
>
> 1) My time-nuts summaries sometimes appear unformatted and unreadable. All
> the text from all the postings is crammed together without spacing. How can
> I fix it?
>
> 2) I want to distribute 10 MHz references by fiber. There are
> RF-over-Fiber products available, but too expensive for me (thousands of
> $$$ per xmit/rcv set).  I am thinking that it should be possible to use
> fiber Ethernet components to do this. I don't mean IEEE 1588 but a much
> simpler, no-computer-required, solution. Possibly just converting sine wave
> (coax) to square wave (fiber) to sine wave (coax). I am looking for a low
> cost solution. Any thoughts or recommendations??
>
> Thanks!
>
> Jim
> ___
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> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
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[time-nuts] Re: Leviton VTP24 Is this Time Accurate enough?

[Dana Whitlow]

If my watch were that bad, I'd toss it out and go shopping for a new one.
I wonder if Leviton offers a version with an external ref input.

Dana


On Fri, Aug 27, 2021 at 12:12 AM D. Resor  wrote:

> I inquired with Leviton as to the accuracy of the VTP24 24 Hour
> Programmable
> Timer with DST.
>
> https://www.leviton.com/en/products/vpt24-1pz
>
> Don Resor
>
> Here is the reply I received:
>
> Hello,
>
> Thank you for contacting Leviton technical support. According to the code
> it
> meets, it is required to have time keeping accuracy within 5 minutes every
> year.
>
> It also uses a crystal to keep time, as it must maintain the time even
> during power outages.
>
> Regards,
>
> Virgilio Dominguez
> Technical Services Representative II
> Leviton Manufacturing Co., Inc.
> 201 North Service Road., Melville, NY 11747
>
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[time-nuts] Re: uncertainty/SNR of IQ measurements

[Dana Whitlow]

Just to be clear, the shift has to be in phase, not time per se.  A 90 deg
phase
shifter based on a constant delay will not work well at other frequencies.
That's
why phasing-type SSB exciters got so messy in the audio phase
splitter department
(in the old days).
Nowadays with digital processing, the mathematical transformation required
can
be done accurately over rather wide bandwidths.

Dana


On Thu, Aug 26, 2021 at 7:05 PM Graham / KE9H  wrote:

> I think Dana's explanation is a much clearer way to think of what is going
> on in an I-Q receiver.
>
> Until you are really far down the signal chain, at the demodulator, where
> you might process the I and Q signals differently,
> there is no 'splitting' or division of the signal into I and Q.
> The signal in the I and Q channels is the same, just shifted in time /
> phase in one of the channels, relative to the other.
>
> --- Graham
>
> ==
>
> On Thu, Aug 26, 2021 at 4:43 PM Dana Whitlow 
> wrote:
>
> > Hi Jim,
> >
> > I think the best way is to view the signal as a phasor, with any
> > noise present adding a
> > random trajectory (a fuzzball) to the tip of the signal vector.
> > Conceptually speaking,
> > this eliminates needing to worry about the distribution of power between
> I
> > & Q, etc.
> > It lets you view the whole thing without regard for choice of axes,
> > coordinate system,
> > and all that.
> >
> > If the S/N is good, the fuzzball is small in size compared to the length
> of
> > the phasor,
> > and you can immediately see that neither the length nor the angle of the
> > sum vector
> > is much affected.
> >
> > But as the SNR is reduced, you eventually reach the point where some of
> the
> > noise
> > peaks almost reach down to the origin, and as the vector tip swings near
> > the origin
> > the phase angle changes very rapidly by nearly 180 deg, but the effect
> is a
> > temporary
> > glitch of zero area.
> >
> > But if the noise peak is a little bit bigger, the vector tip swings all
> the
> > way around the
> > origin, yielding an eventual effect of an added 360 deg (a whole extra
> > cycle) in phase
> > shift.  This tends to have a far more deleterious effect on a signal.  I
> > had a text given
> > to me by a friend in which the author used this kind of explanation to
> > explain, for
> > example, the "threshold effect" of noise in FM demodulation.  I just
> > looked, but could
> > not find the book, else I'd have given you the title and author
> > information.
> >
> > This mode of thought also leads towards an understanding of the "FM
> capture
> > effect",
> > which spec was always highlighted in datasheets of HiFi FM tuners.  But
> one
> > hears
> > little of it nowadays, I suspect because the advent of fast ICs has made
> it
> > so easy
> > to very- closely approach the "theoretical limit" that everybody is about
> > the same.
> > BTW, said "theoretical limit" is not fixed until one specifies other
> > parameters, and
> > at one time there was a standard test definition so that such a limit
> could
> > be defined
> > and measured against.
> >
> > In IQ demodulation I find the ATAN2 function a good deal more useful than
> > the old
> > arctan function, which needs a lot of help in order to work usefully.
> The
> > ATAN2
> > function takes two arguments (I & Q values) and automatically places the
> > angular
> > result in the correct quadrant and is not bothered by either of the
> > arguments being
> > zero.  The only place it gets in trouble is if *both* arguments are zero,
> > which is an
> > infinitely-tough nut to crack in any case.
> >
> > As with all the inverse trig functions, ATAN2 has a limited angular
> range,
> > from
> > -180 deg through zero to +180 deg, then snaps back to -180 deg again.
> > But it's not too difficult to "unwrap" the results so that a continuous
> > rotation of a
> > phasor leads to a nice smooth phase ramp with no discontinuities at all.
> > In many
> > cases this presentation makes the picture much clearer, although overly
> > high
> > noise peaks can create what some will call a false transition.  If you're
> > really
> > interested in the signal alone, yes you have a problem then.  But if you
> > consider
> > the "signal" to be the composite vector sum of some signal and added
> noise,
> > the unwrap process works correctly.
> >
> > Whew!
> >
> &g

[time-nuts] Re: uncertainty/SNR of IQ measurements

[Dana Whitlow]

Hi Jim,

I think the best way is to view the signal as a phasor, with any
noise present adding a
random trajectory (a fuzzball) to the tip of the signal vector.
Conceptually speaking,
this eliminates needing to worry about the distribution of power between I
& Q, etc.
It lets you view the whole thing without regard for choice of axes,
coordinate system,
and all that.

If the S/N is good, the fuzzball is small in size compared to the length of
the phasor,
and you can immediately see that neither the length nor the angle of the
sum vector
is much affected.

But as the SNR is reduced, you eventually reach the point where some of the
noise
peaks almost reach down to the origin, and as the vector tip swings near
the origin
the phase angle changes very rapidly by nearly 180 deg, but the effect is a
temporary
glitch of zero area.

But if the noise peak is a little bit bigger, the vector tip swings all the
way around the
origin, yielding an eventual effect of an added 360 deg (a whole extra
cycle) in phase
shift.  This tends to have a far more deleterious effect on a signal.  I
had a text given
to me by a friend in which the author used this kind of explanation to
explain, for
example, the "threshold effect" of noise in FM demodulation.  I just
looked, but could
not find the book, else I'd have given you the title and author information.

This mode of thought also leads towards an understanding of the "FM capture
effect",
which spec was always highlighted in datasheets of HiFi FM tuners.  But one
hears
little of it nowadays, I suspect because the advent of fast ICs has made it
so easy
to very- closely approach the "theoretical limit" that everybody is about
the same.
BTW, said "theoretical limit" is not fixed until one specifies other
parameters, and
at one time there was a standard test definition so that such a limit could
be defined
and measured against.

In IQ demodulation I find the ATAN2 function a good deal more useful than
the old
arctan function, which needs a lot of help in order to work usefully.  The
ATAN2
function takes two arguments (I & Q values) and automatically places the
angular
result in the correct quadrant and is not bothered by either of the
arguments being
zero.  The only place it gets in trouble is if *both* arguments are zero,
which is an
infinitely-tough nut to crack in any case.

As with all the inverse trig functions, ATAN2 has a limited angular range,
from
-180 deg through zero to +180 deg, then snaps back to -180 deg again.
But it's not too difficult to "unwrap" the results so that a continuous
rotation of a
phasor leads to a nice smooth phase ramp with no discontinuities at all.
In many
cases this presentation makes the picture much clearer, although overly high
noise peaks can create what some will call a false transition.  If you're
really
interested in the signal alone, yes you have a problem then.  But if you
consider
the "signal" to be the composite vector sum of some signal and added noise,
the unwrap process works correctly.

Whew!

Dana   K8YUM



On Thu, Aug 26, 2021 at 3:52 PM Poul-Henning Kamp 
wrote:

> 
> Lux, Jim writes:
>
> >I'm looking for a simplified treatment of the uncertainty of I/Q
> >measurements.  Say you've got some input signal with a given SNR and you
> >run it into a I/Q demodulator - you get a series of I and Q measurements
> >(which might, later, be turned into mag and phase).
> >
> >[...]
> >
> >I'm looking for a sort of not super quantitative and analytical
> >treatment that I can point folks to.
>
> Good luck with that :-)
>
> Some of the noise processes will be along the "vector" and distributed
> between I & Q components depending on the phase, while other noise
> processes affect the components individually.
>
> To make matters worse, both kinds of noise processes may depend on the
> phase, usually because of cross-talk and/or insufficient isolation.
>
> Low-resolution ADC's are a particular nasty problem, because they add
> +/-1 count jitter independent of the phase, and that causes very
> large arctangent errors.
>
> Counterintuitive as it may sound, it is easier to process the bits from
> ADC's where the low two bits are pure noise, than ADC's where all bits
> are good...
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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[time-nuts] Re: Comparison/evaluation of u-blox timing receivers

[Dana Whitlow]

Thanks very much, John.

Dana


On Mon, Aug 23, 2021 at 8:52 PM John Ackermann N8UR  wrote:

> In 2020 I did an extensive evaluation of the timing ability of the
> u-blox LEA-M8F, NEO-M8N, NEO-M8T, NEO-M9N, ZED-F9P, and ZED-F9T.  The
> work was made possible by support from the HamSci consortium
> (https://hamsci.org) under NSF grants supporting HamSci activities.
>
> I was sure I'd posted about the paper on time-nuts, but I can't find any
> record that I did, so this is a belated announcement.  It's available
> for download from
>
>
> https://hamsci.org/sites/default/files/publications/2020_TAPR_DCC/N8UR_GPS_Evaluation_August2020.pdf
>
> As BobC says, "Lots of fun!"
>
> John
>
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[time-nuts] Re: Efratom LPRO-101 Rubidium question....

[Dana Whitlow]

I connect one signal to the LO input of the demodulator, and the other
signal to the
RF input.  I should draw up a schematic of this, and will do so.

Dana


On Mon, Aug 23, 2021 at 4:59 PM Robert DiRosario  wrote:

> Dana,
>
> >I make phase comparisons between the 10 MHz outputs of a GPSDO and the Rb
> >under test using a simple quadrature demodulator, with the I & Q outputs
> >displayed on a 2-chan DSO.
>
> Can you explain what you do?  Do you just connect the two 10 MHz signals
> to the input of the demodulator?
>
> Robert
>
>
> On 08/22/2021 11:16 AM, Dana Whitlow wrote:
> > C'mon guys- when you speak of a frequency error in Hz, you should also
> > specify "at
> > what frequency" *in the same breath*.  Or better yet, always specify
> > frequency errors in
> > relative terms.
> >
> > Hundreds of Hz at 10 Mhz is unthinkable for a Rb.   Even at 8.2 GHz, 100
> Hz
> > error is about
> > 12E-9, which is likely to be outside the EFC tuning range of some (if not
> > most) Rb standards.
> > Both of my Rbs have a tuning range of only roughly 2E-9 via the EFC
> input.
> > Outside that
> > range, much sterner measures must be taken, which I frankly dread.
> >
> > The two Rbs that I own (an L-Pro and a PRS-10) both tend to drift upwards
> > in frequency
> > to the tune of about 1E-11 or 2E-11 per month.  Superimposed on that are
> > random
> > variations of around 1E-11 on a time scale of a few hours.
> >
> > I make phase comparisons between the 10 MHz outputs of a GPSDO and the Rb
> > under
> > test using a simple quadrature demodulator, with the I & Q outputs
> > displayed on a 2-chan
> > DSO.  I use the "roll mode" display feature on the DSO at its slowest
> speed
> > (1000 sec/div)
> > and just leave things running continuously for up to several days.  On my
> > DSO a full screen
> > width is 14000 sec (slightly under 4 hours), and I just take a glance
> from
> > time to time as I
> > happen to pass by.
> >
> > Someone suggested a 100 sec measurement with a counter, but that is right
> > in the realm
> > where GPSDOs are typically the most noisy, so a single measurement is
> > likely to have
> > rather large errors.  One would have to record a fairly large number of
> > such measurements
> > (several hundreds of them) and plot them out to get a good assessment of
> > what the Rb is
> > actually doing.  WIth the IQ phase difference display, one can get a
> pretty
> > decent estimate of
> > the needed tuning correction, without doing any real work at all, in a
> day
> > or so.
> >
> > When I'm doing something requiring the best frequency accuracy, I keep
> the
> > 'scope display
> > running while I'm doing the serious work, and note the frequency error of
> > the Rb at the time
> > for use in correcting the final result.  BTW, I don't see much "settling"
> > effect after making
> > tuning changes- the correction made seems to take effect essentially
> > immediately (as best
> > as one can tell in the presence of GPS noise).  By comparing two Rbs, I
> can
> > investigate
> > settling effects quite well without the noise having anything to do with
> it.
> >
> > Dana
> >
> >
> > On Sun, Aug 22, 2021 at 8:41 AM Matthias Welwarsky <
> time-n...@welwarsky.de>
> > wrote:
> >
> >> Hi,
> >>
> >> a Rb will not be long-term accurate. I'd trust a GPSDO to be long-term
> >> accurate. A hundreds-of-Hz offset between the LPRO and the GPSDO
> certainly
> >> points into the direction of the LPRO being off the mark.
> >>
> >> When you adjust the LPRO, be sure to give it ample time to stabilize.
> >>
> >> BR,
> >> Matthias
> >>
> >> On Samstag, 21. August 2021 14:50:24 CEST mp...@clanbaker.org wrote:
> >>> Hello Time-Nutters--
> >>>
> >>> I am working on building a downlinking AZ/EL tracking dish set up to
> >>> receive the 8.2 GHz telemetry from the Suomi JPSS polar orbit
> >>> meteorological/environmental satellite.  The receiver seems to be
> >>> working OK but it periodically appears to slowly drift frequency by
> >>> 300 Hz to 400 Hz.  I need some way to accurately determine what
> >>> the actual RX receive frequency is.
> >>>
> >>> I have a vintage Efratom LPRO-101 Rubidium 10 MHz oscillator.
> >>> I originally got it thinking that it would provide a decent
> >>> phase-lock referen

[time-nuts] Re: Efratom LPRO-101 Rubidium question....

[Dana Whitlow]

Dan,  close but no ceegar!  On this one I just needed fair accuracy, at 10
MHz only, and
didn't want to be handling little teeny things and/or laying out an ECB.
Instead I bought
packaged components from Mini Circuits. and cable them up with 0.086"
"hand-flex"
cable I bought from Amazon.  I did all this on Cu-clad board, and soldered
down some
BNC connectors from the junk box.

The MCL components are:

>  1 ea  MSC-2-1W+   0 deg power splitter, used as the LO splitter.
>  1 ea  PSCQ-2-51W+   2-way 90 deg splitter, used as the RF splitter
>  2 ea  SBL-1   Mixer

This was all wired up in the most naive possible configuration, with no
precautions taken to avoid  cross-coupling of harmonic components
between mixers, etc.  The only thing a bit unusual is that I did not
terminate
the IF ports in 50 ohms.  Instead each is terminated to GND with a 510 ohm
resistor, then a series resistor of 10 k, then a shunt capacitor of 0.1 uF,
to
make an RC lowpass filter of about 160 Hz BW.  Then there is a 51 ohm
resistor to the center pin of the I or Q BNC connector (as the case may be),
which is expected to connect to a Hi-Z load such as an o'scope input.  This
arrangement yields significantly higher signal voltage output below the
compression point.

I usually drive the RF input at about -18 dBm ((IRC) and get I & Q outputs
of
about 60 mV p-p.  I should be driving the LO input at about +10 to +11 dBm,
but it seems to work OK at levels of +8 to +9 dBm, which is all I can
usually
manage to give it.

If I plot I & Q on an X-Y 'scope display through at least one full cycle of
phase
difference, the expected circle is visibly slightly distorted into an
ellipse slanted
at approx 45 deg, but it's not real bad.  I would not use this as-is for
precision
phase measurement, but for my present purposes of tuning an Rb onto GPS it's
more than good enough.

For my precision work at "all" frequencies, I use a Signal Hound SA44B  (USB
Spectrum Analyzer).  It does a nice job in terms of IQ accuracy, but
finding out
*exactly* where it's tuned can be a bitch.

Hope this helps...

Dana


On Mon, Aug 23, 2021 at 10:33 AM Dan Kemppainen 
wrote:

> Dana,
>
> Just curious, can you share some details on what you are using for the
> IQ demodulator? Is this a 'roll your own' solution Gilbert cell mixer, etc?
>
> Thanks,
> Dan
>
>
> On 8/23/2021 3:30 AM, time-nuts-requ...@lists.febo.com wrote:
> > Message: 4
> > Date: Sun, 22 Aug 2021 10:16:56 -0500
> > From: Dana Whitlow
> > Subject: [time-nuts] Re: Efratom LPRO-101 Rubidium question
> > To: Discussion of precise time and frequency measurement
> >   
> > Message-ID:
> >   <
> cadhrwpeyiqa1pwrvtb_htmzc8oxe-wr+fzyz4oz4vucnc4h...@mail.gmail.com>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > C'mon guys- when you speak of a frequency error in Hz, you should also
> > specify "at
> > what frequency"*in the same breath*.  Or better yet, always specify
> > frequency errors in
> > relative terms.
> >
> > Hundreds of Hz at 10 Mhz is unthinkable for a Rb.   Even at 8.2 GHz, 100
> Hz
> > error is about
> > 12E-9, which is likely to be outside the EFC tuning range of some (if not
> > most) Rb standards.
> > Both of my Rbs have a tuning range of only roughly 2E-9 via the EFC
> input.
> > Outside that
> > range, much sterner measures must be taken, which I frankly dread.
> >
> > The two Rbs that I own (an L-Pro and a PRS-10) both tend to drift upwards
> > in frequency
> > to the tune of about 1E-11 or 2E-11 per month.  Superimposed on that are
> > random
> > variations of around 1E-11 on a time scale of a few hours.
> >
> > I make phase comparisons between the 10 MHz outputs of a GPSDO and the Rb
> > under
> > test using a simple quadrature demodulator, with the I & Q outputs
> > displayed on a 2-chan
> > DSO.  I use the "roll mode" display feature on the DSO at its slowest
> speed
> > (1000 sec/div)
> > and just leave things running continuously for up to several days.  On my
> > DSO a full screen
> > width is 14000 sec (slightly under 4 hours), and I just take a glance
> from
> > time to time as I
> > happen to pass by.
> >
> > Someone suggested a 100 sec measurement with a counter, but that is right
> > in the realm
> > where GPSDOs are typically the most noisy, so a single measurement is
> > likely to have
> > rather large errors.  One would have to record a fairly large number of
> > such measurements
> > (several hundreds of them) and plot them out to get a good assessment of
> > what the Rb is
> > actually doing.  WIth the IQ phase difference display, one can get

[time-nuts] Re: Efratom LPRO-101 Rubidium question....

[Dana Whitlow]

C'mon guys- when you speak of a frequency error in Hz, you should also
specify "at
what frequency" *in the same breath*.  Or better yet, always specify
frequency errors in
relative terms.

Hundreds of Hz at 10 Mhz is unthinkable for a Rb.   Even at 8.2 GHz, 100 Hz
error is about
12E-9, which is likely to be outside the EFC tuning range of some (if not
most) Rb standards.
Both of my Rbs have a tuning range of only roughly 2E-9 via the EFC input.
Outside that
range, much sterner measures must be taken, which I frankly dread.

The two Rbs that I own (an L-Pro and a PRS-10) both tend to drift upwards
in frequency
to the tune of about 1E-11 or 2E-11 per month.  Superimposed on that are
random
variations of around 1E-11 on a time scale of a few hours.

I make phase comparisons between the 10 MHz outputs of a GPSDO and the Rb
under
test using a simple quadrature demodulator, with the I & Q outputs
displayed on a 2-chan
DSO.  I use the "roll mode" display feature on the DSO at its slowest speed
(1000 sec/div)
and just leave things running continuously for up to several days.  On my
DSO a full screen
width is 14000 sec (slightly under 4 hours), and I just take a glance from
time to time as I
happen to pass by.

Someone suggested a 100 sec measurement with a counter, but that is right
in the realm
where GPSDOs are typically the most noisy, so a single measurement is
likely to have
rather large errors.  One would have to record a fairly large number of
such measurements
(several hundreds of them) and plot them out to get a good assessment of
what the Rb is
actually doing.  WIth the IQ phase difference display, one can get a pretty
decent estimate of
the needed tuning correction, without doing any real work at all, in a day
or so.

When I'm doing something requiring the best frequency accuracy, I keep the
'scope display
running while I'm doing the serious work, and note the frequency error of
the Rb at the time
for use in correcting the final result.  BTW, I don't see much "settling"
effect after making
tuning changes- the correction made seems to take effect essentially
immediately (as best
as one can tell in the presence of GPS noise).  By comparing two Rbs, I can
investigate
settling effects quite well without the noise having anything to do with it.

Dana


On Sun, Aug 22, 2021 at 8:41 AM Matthias Welwarsky 
wrote:

> Hi,
>
> a Rb will not be long-term accurate. I'd trust a GPSDO to be long-term
> accurate. A hundreds-of-Hz offset between the LPRO and the GPSDO certainly
> points into the direction of the LPRO being off the mark.
>
> When you adjust the LPRO, be sure to give it ample time to stabilize.
>
> BR,
> Matthias
>
> On Samstag, 21. August 2021 14:50:24 CEST mp...@clanbaker.org wrote:
> > Hello Time-Nutters--
> >
> > I am working on building a downlinking AZ/EL tracking dish set up to
> > receive the 8.2 GHz telemetry from the Suomi JPSS polar orbit
> > meteorological/environmental satellite.  The receiver seems to be
> > working OK but it periodically appears to slowly drift frequency by
> > 300 Hz to 400 Hz.  I need some way to accurately determine what
> > the actual RX receive frequency is.
> >
> > I have a vintage Efratom LPRO-101 Rubidium 10 MHz oscillator.
> > I originally got it thinking that it would provide a decent
> > phase-lock reference for my freq-counters, o-scopes, spectrum
> > analyzers and Agilent/HP vector network analyzer.
> >
> > The only other item I have that has (or should have) a reasonably
> > accurate 10 MHz reference output is a Trimble Thunderbolt.
> > However, there is a several hundred Hz freq difference between the
> > Efratom and the Trimble T-bolt.
> >
> > My question is how do I go confirming the frequency of the T-Bolt
> > or the Efratom Rubidium?  The Efratom has an adjustment pot
> > to fine-tune its output frequency.  How do Time-Nutters go about
> > confirming the accuracy of frequency references such as my
> > T-Bolt or Efratom rubidium oscillator?
> >
> > Thanks for any feedback / suggestions on this !!
> >
> > Off-list communications on this via my email is OK!!
> >
> > Mike Baker   mp...@clanbaker.org
> > Micanopy/Gainesville  North Central Florida
> > **
> >
> > ___
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> send an
> > email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow
> > the instructions there.
>
>
>
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[time-nuts] Re: Testing a GPS mag mount antenna

[Dana Whitlow]

I love Dan's idea, with one caveat.  The transmission through a
powered-down LNA
is an unknown, probably even to the manufacturer.  Thus comparing output
signal
levels with power on or off is pretty meaningless.

But his test with power on should be a great way to get some clue that the
antenna
is working, and is clearly simpler to perform than what I was suggesting
yesterday.

Dana

On Sat, Aug 21, 2021 at 9:49 AM Daniel Schultz  wrote:

> > Should I be able to "see something" on or around the GPS frequency other
> > than what I suspect will be something visual looking like a noise/pulse
> > source/signal?
>
> You could try sweeping a harmonic from a signal generator across the
> antenna
> passband, this would be visible on the spectrum analyzer and might give
> you an
> idea if the preamp is amplifying or attenuating the signal. Try it with the
> preamp power on and off. If your signal generator does not generate
> sufficient
> harmonics at L band you can feed the signal into an overdriven MMIC
> amplifier.
>
> Dan Schultz N8FGV
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[time-nuts] Re: Testing a GPS mag mount antenna

[Dana Whitlow]

Skipp,

Several responders have correctly referred to the "noise floor", but I
believe that
none have said what level that is.  And it's not trivial to say so, either,
because it
is dependent on the extent to which the antenna under test sees the sky and
ignores blackbody radiation from the ground.  An ideal GPS antenna would see
only the sky, but not the ground at all.  But none are ideal in this regard
unless
placed on a large level metallic "ground plane".

It may happen that in this era of higher-powered L1 transmitters aboard some
of the satellites, their total noise power spectral density might exceed
cold sky
noise by enough to be obvious on a spectrum analyzer looking at the output
of
an active GPS antenna.

But I've saved the good news for last.  The noise PSD of the ground as
sensed
by a passive antenna is about -114 dBm in 1 MHz BW, or -174 dBm in 1 Hz BW.

So here is what I suggest for your antenna functional tests:
Mount the antenna under test on the end of an insulating horizontal rod,
which
can be rotated to make the antenna face either the ground or the sky.

Examine the spectrum on a span setting of several MHz, and see if the noise
level over a BW of a few MHz is higher with the antenna pointed down than
when pointed up.  Oh, I forgot to mention: for tests like this the antenna
should
be supported a few feet above the ground level, so that input noise of the
LNA
does not get reflected off the ground and back into the antenna to an
appreciable
extent.  It also helps if the ground is very rough, like maybe tall grass.

What you may see with the antenna looking at the ground is blackbody
radiation
from the ground being filtered by the input filter of the LNA- and that
filter hump
is indicative (but not yet proof) of the antenna's working.  When the
antenna faces
the sky, the ground noise hump should disappear and be replaced by the
spectrum
of the combined signals from all the GPS satellites above you.

This is all provided the cascaded combination of the GPS antenna's LNA  and
the
SA's noise floor is is very quiet.  With practical antennas and SA's, this
is unlikely
to ever yield a rise of more than a very few dB if that much.  So, to see
this, you
should setup the SA so that you get an average power spectrum, meaning using
lots of video filtering on an old-fashioned swept analyzer, or trace
averaging of many
traces on an FFT-type SA.  The required averaging time to get good
smoothing of
the noise levels will be minimized by using as wide a resolution bandwidth
as you
can, but always less than the BW of the spread-spectrum GPS signals or the
antenna's
inpuy filter.  But you don't want to go too wide, either, for you will lose
the frequency
resolution that may  let you distinguish between the antenna's filter hump
shape and
that spectrum comprising the GPS signals in view at the time.  I'd suggest
starting with
a BW of around 100 kHz as a fair compromise.  For more on this aspect of
things,
look up "radiometer equation" on the web- we'll make a radio astronomer of
you yet :-)

BTW, it will likely be needed to add some additional gain between the
antenna and the
SA's input.  Many of the older SA's have really rotten NF, like 30 dB or
worse.

DanaK8YUM


On Fri, Aug 20, 2021 at 4:33 PM Gerhard Hoffmann <
g...@hoffmann-hochfrequenz.de> wrote:

>
> Am 20.08.21 um 22:14 schrieb skipp isaham via time-nuts:
> >
> > Hello to the Group,
> >
> > I picked a box of used (removed from commercial radio APRS type
> > service) mobile/vehicle GPS Antennas. They are mostly the classic
> > square molded, black plastic magnetic mount type, about the size of a
> > bar of soap when cut to square (2/3 the size of a large bar of soap).
> > The coax length terminates to an SMA connector.
> >
> > I'd like to use some of these unmarked (obviously also unbranded)
> > antennas for a few projects. The initial goal is to first set up a
> > system to test (good/bad) the antennas, then determine their operation
> > voltage, I suspect them to be 3.x to 5.x Volts. They are probably not
> > "new enough" to be the type to operate of 3 or 5 Volts DC.
> >
> > For testing... I purchased a nice NOS Mini-Circuits bias-Tee.
> >
> > The intent is to now operate the antenna through the bias-tee, in to
> > an analyzer. I would initially start the bias supply off at 3 Vdc,
> > while also monitoring current.  If I don't receive an adequate/valid
> > GPS signal off air, I could increase the bias up to 5 Vdc (rinse/repeat).
> >
> > Should I be able to "see something" on or around the GPS frequency
> > other than what I suspect will be something visual looking like a
> > noise/pulse source/signal?
>
> You won't see anything interesting on the spectrum analyzer. The
> signal(s) look like noise, and they are buried in the real noise.
>
> Deeply!  In a real receiver, there are probably just 1 bit ADCs, aka
> comparators, and the receiver  needs to know the pseudo random
>
> polynomial that was used to blow up the bandwidth of the 50 baud 

[time-nuts] Re: Antenna return loss

[Dana Whitlow]

Andy,

Good point, up to a point.  But even if the antenna's amplifier itself has
a good return
loss, cheap cables like RG-174 are pure garbage and could be doing just
about
anything along their length.  And if the bottom end connector is put on by
a person
without training and the correct tooling, very bad things can happen there,
too.

Complicating the situation is the mismatch likely to occur when one tries
to power
said antenna through a bias tee or whatever.  Fortunately, if the right
kind of splitter
is used, such mismatches will occur in a "safe" location (downstream of the
splitter).

Nothing's ever simple ...

Dana


On Thu, Jul 29, 2021 at 3:42 AM Andy Talbot  wrote:

> Much talk about source return loss and splitters.
> All active GPS antennas I've met have masses of gain at the top end, 40dB
> or more.   Most of the small puck ones come with several metres of RG174
> thin coax.
>
> This is so lossy at 1.6GHz that that several metres may have perhaps 10 -
> 15dB loss.   So there's your good source impedance for the splitter 20 -
> 30dB RLoss without even considering the head amp itself.
>
> Even several metres of UR43 should have enough loss to constitute a decent
> match.
>
> Andy
> www.g4jnt.com
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[time-nuts] Re: Trimble GSPDO - ISSUE

[Dana Whitlow]

I'm not worried about the F connector itself- rather, it's
irresistible temptation to use
wrong-impedance cables, often rather long ones.

Agreed that LNA inputs don't tend to make good matches, but that's what the
splitter
largely addresses.  It's the wrong impedance of the source that foils the
benefit of the
splitter, and which most people ignore altogether.  I think we'd get along
better if the
antenna output impedance were 75 ohms, F connectors were used, and 75 ohm
splitters were used.  Then good isolation would be preserved at low cost no
matter
what load impedances were present on the splitter's outputs.  The simple
mismatch
loss between 50 ohms and 75 ohms is pretty negligible in this context.

When I see an attenuator with only about 15 dB return loss at L-band, it
goes straight
into the trash.  To me, the anticipated main benefit of having a nanoVNA is
that I'll
be able to identify such defective items at flea markets before spending
money on it.
That is, if there are ever any more flea markets (because of Covid).  I'm
not optimistic.

Dana



On Wed, Jul 28, 2021 at 7:58 AM Bob kb8tq  wrote:

> Hi
>
> If you measure the input impedance of most low noise receivers, it’s not
> going to be 50 ohms pure resistive. There are multiple reasons for this.
> Since the “load” is not a match to either 50 or 75 ohm cable, it’s not that
> big a deal.
>
> The amp in the antenna with it’s post filtering may or may not present a
> 50 ohm source. They rarely hit a 14 db return loss spec in any case. Indeed
> there are a lot of attenuators out there that don’t get to 14 db at 1.5
> GHz.
>
> Trimble did a *lot* of testing before they put the F connector on the
> TBolt.
> They could find no impact at all.
>
> Bob
>
> > On Jul 28, 2021, at 8:23 AM, Dana Whitlow  wrote:
> >
> > Most general purpose passive splitters for the L-band regime are
> > essentially variations
> > on the Watkinson splitter, which provides good isolation between the
> output
> > ports, if
> > (and only if) the input port is driven from a matched source.
> >
> > So if your GPS antenna, whether active or passive, has a good output
> match
> > then
> > the Samsung's input impedance will not affect operation of the Trimble.
> > But, again,
> > this is true only if the antenna's output impedance is matched to the
> > splitter's
> > characteristic impedance (including consideration of any impedance
> > transformation
> > in the transmission line between the antenna and the splitter).
> >
> > I cringe at the cavalier treatment given to line impedances used in GPS
> > systems.
> > AFAIK, all GPS equipment is designed for 50 ohms, yet a great deal of
> such
> > equipment is provided with 'F' connectors, which invite the use of
> > inexpensive RG-6
> > line, which is 75 ohm cable.  In addition to problems with impedances and
> > loading,
> > It's a built-in source of multipath, all at no extra charge!
> >
> > Dana   K8YUM
> >
> >
> > On Tue, Jul 27, 2021 at 3:01 PM Don Cross  wrote:
> >
> >> On Tue, Jul 27, 2021 at 2:54 PM ordnit via time-nuts <
> >> time-nuts@lists.febo.com> wrote:
> >>
> >>>
> >>> Any guess? Do I have to throw the unit from the window? For your
> >>> reference, I have a samsung unit connected to same antenna via a
> >>> splitter. The GPSDO is performing very well.
> >>>
> >>>
> >> Hi Ordnit,
> >>
> >> I'm hardly an expert, but I wonder about the splitter. Is this a
> passive or
> >> active splitter? If passive, it could be the input impedance of your
> >> Samsung is much lower than for your new Trimble and it is making the
> signal
> >> seen by the Trimble too weak. If you are willing to disconnect the
> Samsung
> >> temporarily, perhaps you could try connecting your antenna to the
> Trimble
> >> only and see what happens.
> >>
> >> Don
> >> ___
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> >>
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[time-nuts] Re: Trimble GSPDO - ISSUE

[Dana Whitlow]

Most general purpose passive splitters for the L-band regime are
essentially variations
on the Watkinson splitter, which provides good isolation between the output
ports, if
(and only if) the input port is driven from a matched source.

So if your GPS antenna, whether active or passive, has a good output match
then
the Samsung's input impedance will not affect operation of the Trimble.
But, again,
this is true only if the antenna's output impedance is matched to the
splitter's
characteristic impedance (including consideration of any impedance
transformation
in the transmission line between the antenna and the splitter).

I cringe at the cavalier treatment given to line impedances used in GPS
systems.
AFAIK, all GPS equipment is designed for 50 ohms, yet a great deal of such
equipment is provided with 'F' connectors, which invite the use of
inexpensive RG-6
line, which is 75 ohm cable.  In addition to problems with impedances and
loading,
It's a built-in source of multipath, all at no extra charge!

Dana   K8YUM


On Tue, Jul 27, 2021 at 3:01 PM Don Cross  wrote:

> On Tue, Jul 27, 2021 at 2:54 PM ordnit via time-nuts <
> time-nuts@lists.febo.com> wrote:
>
> >
> > Any guess? Do I have to throw the unit from the window? For your
> > reference, I have a samsung unit connected to same antenna via a
> > splitter. The GPSDO is performing very well.
> >
> >
> Hi Ordnit,
>
> I'm hardly an expert, but I wonder about the splitter. Is this a passive or
> active splitter? If passive, it could be the input impedance of your
> Samsung is much lower than for your new Trimble and it is making the signal
> seen by the Trimble too weak. If you are willing to disconnect the Samsung
> temporarily, perhaps you could try connecting your antenna to the Trimble
> only and see what happens.
>
> Don
> ___
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[time-nuts] Re: GPS antenna question

[Dana Whitlow]

I think there might be a down side to using more sensitive GNSS receivers,
which is
that such a receiver will be willing to include more impaired signals in
its time and/or
position solutions, leading to poorer overall accuracy.

Does anybody know?

I certainly concur that good antenna siting is very important, much more so
than
worrying about a few inches of sway in the mount.

Dana

On Fri, Jul 23, 2021 at 1:59 AM Hal Murray 
wrote:

>
> > especially for covering the 0-satellite case.
>
> It's more complicated than just figuring out the error in the satellite's
> clock.  You also have to consider the error in the satellite orbit, the
> difference between where you think it is and where it actually is.
>
>
> > I wish stuff like this could be on a web page or FAQ or something, where
> it
> > was easily discoverable.
>
> It's complicated.
>
>
>
> This probably comes under tha category of more than you want to know...
>
> Stanford published a series of lectures on GPS.
>   https://www.youtube.com/playlist?list=PLGvhNIiu1ubyEOJga50LJMzVXtbUq6CPo
>
> I think there is a good book or two with enough info to design hardware
> and write software.
>
> --
> These are my opinions.  I hate spam.
>
>
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[time-nuts] Re: Thunderbolts

[Dana Whitlow]

Bob, I'm aware of the hump, but it's so much smaller than what I see from
GPSDO that
I don't mind it too much.

My current usage scenario is that I use one or more GPSDOs as a reference
for
tweaking one of my Rb stds to reasonable conformance with GPS.  Frequency
noise on either gets in the way of doing this most accurately, and greatly
extends
the observation time required to do a good tweak job.  I "observe" with the
aid of
a home-built quadrature demodulator and a duan-channel DSO running in very
slow "roll mode", with its two channels driven by I & Q outputs of the
demod.
Thus I can learn a lot just by an occasional glance at the display as I
happen
to pass near the 'scope in the course of other activities.

I currently own a new CNS *Clock II* and three older T'Bolts.  The CNS unit
has a very fast
tracking loop, with an estimated time constant of only a very few seconds
(not user-
adjustable).  It's 10 MHz output is incredibly noisy, with
frequent frequency excursions
of several PPB either way.  But at least it does not have much trouble with
ambient
temperature sensitivity.  The T'Bolts have user-adjustable time constant,
and I've
spent a lot of time playing with those.  For very short TC settings the GPS
noise dominates
the picture, and for very long settings ambient temperature fluctuations on
the GPSDO's
VCXO dominate.  I keep going back to the CNS clock because although its
frequency
fluctuations are more severe, I find it's easier to visually estimate tweak
amounts.

My desire is to maintain an Rb within 10 PPT most or all of the time with
little or no
manual attention.

In response to your latest, I'm sure I saw mention of a double-oven in
connection with the
T'Bolt E, on the Trimble site.  But perhaps this is an extra cost option.
Thanks for mentioning
this.

As an amusing side note I occasionally rely on a local taxi service, and
one of the regular
drivers' last names is Trimble.  Perhaps I should inquire if there is any
connection :-)

Dana


On Wed, Jul 21, 2021 at 8:20 AM Bob kb8tq  wrote:

> Hi
>
> With the PRS-10 you get that hump in the ADEV. I’m not saying that it’s
> the
> end of the world, but it really does bug me that it’s there ….
>
> Bob
>
> > On Jul 20, 2021, at 10:03 PM, Dana Whitlow 
> wrote:
> >
> > Bert, remember that I need a very long locking loop time constant
> setting in
> > order to smooth out GPS noise, so in a sense the GPSDo is *almost* in a
> > holdover state anyway, all the time.
> >
> > Probably the smartest thing for me to do is to buy a spanking new PRS-10,
> > with the PPS locking feature present.  Then I could just leave it locked
> to
> > GPS most all the time, but disconnect the PPS and let it go into holdover
> > on the rare occasions when I need a few hours of even better stability.
> >
> > Dana
> >
> >
> > On Tue, Jul 20, 2021 at 6:56 PM ew via time-nuts <
> time-nuts@lists.febo.com>
> > wrote:
> >
> >> There is a lot of misinformation out there. It is not the OCXO that
> >> changes, Bruce did extensive testing and I did some too. The Vectron is
> >> super, would like to know what is in it but do not want to open one.
> Once
> >> warmed up the stable OCXO temperature is a main contributor to the board
> >> temperature. Using a Dual Oven may give you a warm feeling but only
> adds 1
> >> more Watt of stable heat to the board making the temperature change
> >> smaller. The OCXO is important during Hold Over and that is why it is
> >> there. The changes are the DAC which is updated once a second. Very
> >> temperature sensitive. Cheap. We have done the tests   10811, OSA 8600,
> FRK
> >> and M100. For fun did use a cheap small OCXO, no performance change. Was
> >> done in Juerg's temperature stable basement.  See attached picture.
> >>
> >>Bert Kehren
> >> My experiences with the T'Bolt have not been entirely satisfactory.  If
> I
> >> set the loop
> >> lime constant long enough to get a satisfying smoothing of the GPS
> noise (a
> >> few hundred
> >> seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears
> its
> >> ugly head and
> >> I see a lot of my HVAC system cycling instead.  The T'Bolt E supposedly
> has
> >> a double-
> >> oven XO, so I'd like to give that a try.  But my wallet says "whoa"!
> >>
> >> According to Bodnar, his units do have some choices in the time constant
> >> setting.
> >> I've been considering ordering a Bodnar just for frequency agility, but
> >> have been
> >> holding off out of concern for the complications of deal

[time-nuts] Re: Thunderbolts

[Dana Whitlow]

Bert, remember that I need a very long locking loop time constant setting in
order to smooth out GPS noise, so in a sense the GPSDo is *almost* in a
holdover state anyway, all the time.

Probably the smartest thing for me to do is to buy a spanking new PRS-10,
with the PPS locking feature present.  Then I could just leave it locked to
GPS most all the time, but disconnect the PPS and let it go into holdover
on the rare occasions when I need a few hours of even better stability.

Dana


On Tue, Jul 20, 2021 at 6:56 PM ew via time-nuts 
wrote:

> There is a lot of misinformation out there. It is not the OCXO that
> changes, Bruce did extensive testing and I did some too. The Vectron is
> super, would like to know what is in it but do not want to open one. Once
> warmed up the stable OCXO temperature is a main contributor to the board
> temperature. Using a Dual Oven may give you a warm feeling but only adds 1
> more Watt of stable heat to the board making the temperature change
> smaller. The OCXO is important during Hold Over and that is why it is
> there. The changes are the DAC which is updated once a second. Very
> temperature sensitive. Cheap. We have done the tests   10811, OSA 8600, FRK
> and M100. For fun did use a cheap small OCXO, no performance change. Was
> done in Juerg's temperature stable basement.  See attached picture.
>
> Bert Kehren
> My experiences with the T'Bolt have not been entirely satisfactory.  If I
> set the loop
> lime constant long enough to get a satisfying smoothing of the GPS noise (a
> few hundred
> seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears its
> ugly head and
> I see a lot of my HVAC system cycling instead.  The T'Bolt E supposedly has
> a double-
> oven XO, so I'd like to give that a try.  But my wallet says "whoa"!
>
> According to Bodnar, his units do have some choices in the time constant
> setting.
> I've been considering ordering a Bodnar just for frequency agility, but
> have been
> holding off out of concern for the complications of dealing with a foreign
> supplier.
>
> Dana
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[time-nuts] Re: Thunderbolts ...

[Dana Whitlow]

My experiences with the T'Bolt have not been entirely satisfactory.  If I
set the loop
lime constant long enough to get a satisfying smoothing of the GPS noise (a
few hundred
seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears its
ugly head and
I see a lot of my HVAC system cycling instead.  The T'Bolt E supposedly has
a double-
oven XO, so I'd like to give that a try.  But my wallet says "whoa"!

According to Bodnar, his units do have some choices in the time constant
setting.
I've been considering ordering a Bodnar just for frequency agility, but
have been
holding off out of concern for the complications of dealing with a foreign
supplier.

Dana




On Tue, Jul 20, 2021 at 12:42 PM John Ackermann  wrote:

> The Bodnar GPSDO is great for what it is, and has the great advantages of
> small size, low power consumption, low cost, and frequency agility.  But it
> doesn't have an OCXO so its short term and holdover performance isn't in
> the same league as the T'bolt or Z38whatever boxes.
>
> John
>
> On Jul 20, 2021, 1:11 PM, at 1:11 PM, Bob Darlington <
> rdarling...@gmail.com> wrote:
> >Same.  He probably got 250+ requests in short order.  I'm curious how
> >the
> >Leo Bodnar GPSDOs compare.   I'm considering one of these over a
> >thunderbolt for field use for ham radio EME work.
> >
> >-Bob N3XKB
> >
> >On Tue, Jul 20, 2021 at 10:59 AM Wes  wrote:
> >
> >> I wrote Tom, at the address he gave, on Saturday with a query.  So
> >far, no
> >> reply.
> >>
> >> Wes  N7WS
> >>
> >>   On 7/19/2021 4:59 PM, John Miles wrote:
> >> > If you're looking for a low cost surplus GPSDO, the ones Tom
> >mentioned in
> >> > his post on Saturday are the ones you want.  Not a Thunderbolt-E,
> >and not
> >> > something from the China surplus/e-waste market.
> >> >
> >> > -- john, KE5FX
> >> >
> >> ___
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[time-nuts] Re: Thunderbolts ...

[Dana Whitlow]

Agreed, Ziggy.

I'm actually thinking (a little bit) about getting a Thunderbolt E.  But
the price does
kind of hurt.

Dana


On Mon, Jul 19, 2021 at 1:08 PM Ziggy 
wrote:

> $650 for the _starter_ kit - $124 for the carrier board with module. So
> I'd say that's affordable. But the ±7us over a 5-minute period and
> 100ppb over 24 hours holdover spec seems a bit inferior.
>
> On 7/18/2021 9:40 PM, djl wrote:
> > Newer module:  $650.00   meh
> >
> > On 2021-07-17 19:45, Gary E. Miller wrote:
> >> Yo Dave!
> >>
> >> On Sat, 17 Jul 2021 00:06:42 +0100
> >> Dave  wrote:
> >>
> >>> I'm a bit of a newbie at this, but is it possible to buy thunderbolts
> >>
> >> WHy?  They newer Trimble GNSS timing modules work beter.  Like the
> >> ICM SMT 360:
> >>
> >>
> https://timing.trimble.com/products/gnss-receivers/icm-smt-360-multi-gnss-timing-module/
> >>
> >>
> >>> If so, where ?
> >>
> >> Hobbyist GNSS receivers are in short supply.  You gotta look harder than
> >> before COVID.
> >>
> >> An ICM SMT 360 on a carrier board is $125:
> >>
> >> https://novotech.com/icm-smt-360-337.html
> >>
> >> RGDS
> >> GARY
> >>
> ---
> >>
> >> Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
> >> g...@rellim.com  Tel:+1 541 382 8588
> >>
> >> Veritas liberabit vos. -- Quid est veritas?
> >> "If you can't measure it, you can't improve it." - Lord Kelvin
> >>
> >> ___
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[time-nuts] Re: Z3801A Temperature

[Dana Whitlow]

Hal, in cases where it is physically applicable, the temperature rating is
generally
that of the flange which is intended to be bolted to a heat sink.

Dana


On Mon, Jul 19, 2021 at 7:30 AM Hal Murray 
wrote:

>
> I have one sitting on a shelf.  No air-conditioning.  The top plate is
> warm,
> far from hot.
>
> Will they be happy if I stack another one on top of it?
>
> The users guide says 50C.  What does that mean if they don't specify the
> air
> flow?  Is there an assumption that it is floating with lots of empty space
> around it or something similar?
>
>
> --
> These are my opinions.  I hate spam.
>
>
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[time-nuts] Re: Thunderbolts ...

[Dana Whitlow]

Thanks, Bob, for the clue about Novotech- it looks somewhat promising.

Dana


On Sat, Jul 17, 2021 at 2:52 PM Bob kb8tq  wrote:

> Hi
>
> Current version of the Thunderbolt is a Thunderbolt E. The device we call a
> Thunderbolt has been out of production for a *long* time.
>
> These guys:
>
> https://novotech.com/products/timing-modules.html <
> https://novotech.com/products/timing-modules.html>
>
> At least have a listing suggesting you can buy a Thunderbolt E.
>
> Bob
>
>
> > On Jul 17, 2021, at 3:28 PM, Dana Whitlow  wrote:
> >
> > Dave,
> >
> > The usual source for old used Thunderbolts is either on eBay, or private
> > sales by
> > individuals.
> >
> > I've twice now requested a quote for a new model from Trimble, and they
> did
> > not
> > even bother to respond.  Perhaps there are distributors, but if so I
> > haven't been
> > able to identify any.
> >
> > Dana
> >
> >
> > On Sat, Jul 17, 2021 at 2:18 PM Dave  wrote:
> >
> >> I'm a bit of a newbie at this, but is it possible to buy thunderbolts ??
> >>
> >> If so, where ?
> >>
> >> Regards,
> >> Dave
> >>
> >> ___
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[time-nuts] Re: Thunderbolts ...

[Dana Whitlow]

Dave,

The usual source for old used Thunderbolts is either on eBay, or private
sales by
individuals.

I've twice now requested a quote for a new model from Trimble, and they did
not
even bother to respond.  Perhaps there are distributors, but if so I
haven't been
able to identify any.

Dana


On Sat, Jul 17, 2021 at 2:18 PM Dave  wrote:

> I'm a bit of a newbie at this, but is it possible to buy thunderbolts ??
>
> If so, where ?
>
> Regards,
> Dave
>
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[time-nuts] Re: LH "No usable sats"

[Dana Whitlow]

I believe that your problem still remains somewhat unsolved, as you should
be
getting good coverage over most of the compass except for the northern
"doughnut
hole".  Instead, you're apparently getting coverage only to the W through
NW.

BTW, when using a T'Bolt I have my AMU thresholds set at 3.0.  This works
well
most of the time, although in some cases the unit takes an hour or more to
get
going after turn-on.  I have the local coordinates stored in memory via
"Tboltmon.exe",
and the unit set to start up in "overdetermined clock" mode.  I'm using an
indoor
antenna on the SE side of the house.  My latitude is just over 30 deg N.

I'm definitely not particularly pleased about that startup delay issue.  I
have two
fairly inexpensive Garmin receivers, one a handheld, the other an
automotive unit,
and both reliably start within a minute or two after a full cold start
turn-on, while
indoors.  Too bad neither has an  overdetermined clock/precison timing/0D
mode.

Dana


On Thu, Jul 8, 2021 at 4:31 AM Admin  wrote:

> Thanks to all takers.
>
> Now, I recognize my mistake. I shouldn't invoke LH by the Sims's
> executable. It is not enough to change the TZ and location, as I did. It
> seems to me that the signal strenght algoritm continues referencing to
> Seattle. Thus, most of the birds flying outside  (270 to 315 deg.) are
> received below 1 AMU (27 dBc) at my location, and thereupon filtered.
>
> I sincerely apologize for my silly mistake.
>
> Regards,
>
> Antonio/CT1TE
>
> --
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[time-nuts] Re: GPS antenna distribution???

[Dana Whitlow]

A resistive splitter has essentially no useful port-to-port isolation, in
addition to the
excess splitting loss problem.  For this reason, resistive splitters are
usually used
only when very broad frequency ("DC to daylight") coverage is needed.

Many RF splitters are of the Wilkinson variety, or some variant thereof.
In principal
these have good isolation between the output ports over some useful
frequency
range, *but if and only if the source impedance well matched to Zo*.  This
last point
is often overlooked, which is unfortunate because many sources are in fact
rather
poorly matched.

So if the system need includes good isolation between output ports of a
splitter, it
is best to sprinkle the system with amplifiers and attenuators, which if
properly
chosen and configured will provide excellent isolation between output ports
regardless.

Dana




On Tue, Jun 29, 2021 at 7:45 AM Bob kb8tq  wrote:

> Hi
>
> Pretty much *any* splitter will have issues with outputs being
> un-terminated.
> Resistive splitters are really no worse that others. The problem that they
> have
> is 6db of loss per split rather than 3db.
>
> The Symmetricom units are not immune to this. They have a single amplifier
> that
> drives a splitter.
>
> A “DC output” module or receiver normally will be quite happy running into
> a
> blocking capacitor. The dirt cheap ebay parts seem to do fine. It is rare
> to find
> a device that refuses to work this way. The “why” is that basement crazies
> aren’t
> the only ones to run splitters …..
>
> Bob
>
> > On Jun 29, 2021, at 2:16 AM, Julien Goodwin 
> wrote:
> >
> > I keep forgetting to do a thread about this.
> >
> > I recently (er, perhaps a year ago) picked up a Microlab unit, and was
> > very disappointed, notably the output simply isn't built to handle being
> > plugged into units that provide antenna power, with each port ending up
> > having a DC path to ground (at 200 ohm, so not too terrible, but it's
> > still not great). Plus being a simple resistive splitter it's not ideal
> > if all outputs aren't terminated.
> >
> > Luckily the Sysmocom unit mentioned elsewhere is fine with this (up to
> > 12v because I specifically talked to them about this exact issue when
> > they were working on it).
> >
> > On 27/6/21 1:49 pm, lstosk...@cox.net wrote:
> >> I seem to have an gathering of GPS antenna on my window ledge.  I seem
> to have missed info on building a splitter/amp to take one signal and
> distribute it.  Quick reference?  N0UU
> >> ___
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[time-nuts] Re: GPS antenna distribution?

[Dana Whitlow]

Or, it could be that the UV coating is really a multi-layer dielectric
coating, not metal at all,
in which case it would have negligible impact on L-band signals.

Dana


On Mon, Jun 28, 2021 at 6:17 PM Dana Whitlow  wrote:

> Could be that north-facing window/reflector is actually helping you a bit
> with signals
> from the south coming through the house.  Stranger things have happened ...
>
> Dana
>
>
> On Mon, Jun 28, 2021 at 4:03 PM  wrote:
>
>> Thanks guys.  Opened a lot of things to think of.  Makes me wonder how I
>> get any results from a north facing window with the UV coating!  Will work
>> out something.  N0UU
>> ___
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[time-nuts] Re: GPS antenna distribution?

[Dana Whitlow]

Could be that north-facing window/reflector is actually helping you a bit
with signals
from the south coming through the house.  Stranger things have happened ...

Dana


On Mon, Jun 28, 2021 at 4:03 PM  wrote:

> Thanks guys.  Opened a lot of things to think of.  Makes me wonder how I
> get any results from a north facing window with the UV coating!  Will work
> out something.  N0UU
> ___
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[time-nuts] Re: PRS-10 heatsink design

[Dana Whitlow]

I mount my PRS-10 vertically (so that the channels between the fins are
vertical),
with the connector on top.  This orientation was chosen simply for best
access to
the connector, but yields heat sink temperatures down around 45C to 50C.
 The
unit is open and fully exposed to the air.  I run it at 24Vdc.

The open mounting is obviously best for natural convective cooling, but does
leave the stability somewhat vulnerable to ambient temperature variations,
drafts, etc, although I've not had obvious problems with this.

If you want to combine good cooling with low dependence on rapid variations
in ambient temperature, I suspect the best way is to interpose a very thick
aluminum (or copper) block between the heatsink flange of the PRS-10 and
the heatsink.  The block will add minimal thermal resistance, but will
serve as
a thermal lowpass filter.  The downside to this is that full warmup of the
PRS-10
will take longer.

Dana


On Wed, Jun 23, 2021 at 2:05 AM James Wilson  wrote:

> My limited experience with the factory heatsink for the PRS-10 has left me
> pretty unsatisfied. It seems ok for brief bench evaluation but not for
> permanent enclosure installation. Reported unit temps are in the 70 - 75 °C
> range with it sitting on a bench in a 25 °C room. It needs to be turned on
> its side or upside down for any convection to take heat away, or for fans
> to be directed at the fins. There are no side or top screw holes on the
> PRS-10 so you can’t mount it in that orientation. Has anyone found or built
> a better heatsink that can use active cooling?
> ___
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[time-nuts] Re: Help ID'ing Frequency Standard

[Dana Whitlow]

John,

At least you seem to have enough info to power it up safely.   From its
evident
complexity, I think it might well be a Rb standard.

Dana


On Sun, Jun 6, 2021 at 9:23 AM John Ackermann N8UR  wrote:

> Looking through the junk box I came upon a metal box labeled:
>
> Frequency Standard
> 05110-6014
> Series 330
>
> It's about 4 1/2 x 5 1/2 x 3 inches and has odd voltage inputs -- -16V,
> +10V, -12.6V along with a terminal for "meter switch" and 2 BNC jacks.
> There are several adjustment points accessible through the box.
>
> Google doesn't turn up anything.  Anyone know what this beast is?
>
> Thanks!
> John
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[time-nuts] Re: time-nuts Digest, Vol 201, Issue 24

[Dana Whitlow]

Dave, you just did it yourself.  So there!

Dana


On Thu, Apr 15, 2021 at 7:39 AM Dave B via time-nuts <
time-nuts@lists.febo.com> wrote:

> Someone used 'php' and 'secure' in the same sentence?  :-)
>
>  Dave G8KBV
>
>
> On 15/04/2021 08:30, time-nuts-requ...@lists.febo.com wrote:
> > php = a sort of more secure, advanced html (web page format)
>
> --
> Created on and sent from a Unix like PC running and using free and open
> source software:
> ___
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[time-nuts] Re: Sparkfun lists SA.35m

[Dana Whitlow]

I knew about the use of the VCSEL, but I'd bet a good dinner that it's not a
Rubidium laser!  Last I heard, none of the elements in that corner of the
periodic table were semiconductors, and it's hard to imagine a vapor-based
VCSEL.

Dana


On Sat, Apr 3, 2021 at 7:31 AM Lux, Jim  wrote:

> On 4/3/21 4:22 AM, Dana Whitlow wrote:
> > "rubidium laser" ???
> >
> > Dana
>
> I don't know about the MAC, but the CSAC uses a VCSEL to shine through
> the gas cell.
>
> The MAC is a pretty big thing compared to the CSAC - it's in the usual
> 2x2" package and draws 5-8W (after warmup)
>
> >
> > On Sat, Apr 3, 2021 at 2:15 AM Poul-Henning Kamp 
> wrote:
> >
> >> I know it's not a particular outstanding atomic clock, but I was still
> >> surprised to see that Sparkfun lists the SA.35m for $1995...
> >>
> >>  https://www.sparkfun.com/products/14830
> >>
> >> Not in stock though...
> >>
> >> --
> >> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> >> p...@freebsd.org | TCP/IP since RFC 956
> >> FreeBSD committer   | BSD since 4.3-tahoe
> >> Never attribute to malice what can adequately be explained by
> incompetence.
> >> ___
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> send
> >> an email to time-nuts-le...@lists.febo.com
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> >>
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[time-nuts] Re: Sparkfun lists SA.35m

[Dana Whitlow]

"rubidium laser" ???

Dana


On Sat, Apr 3, 2021 at 2:15 AM Poul-Henning Kamp  wrote:

> I know it's not a particular outstanding atomic clock, but I was still
> surprised to see that Sparkfun lists the SA.35m for $1995...
>
> https://www.sparkfun.com/products/14830
>
> Not in stock though...
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
> ___
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[time-nuts] Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New Yorker]

[Dana Whitlow]

I have not yet heard what GB wants to do, but if it's long range work
(return time of
10's of sec or longer), the problems related to T/R switching, Tn
degradation of the
receiver, etc, get a lot more tractable than one might suppose.

At Arecibo, the S-band radar was intended solely for long range work.  A
big part ot
T/R switching was to use separate (optimized) feeds for transmitting and
receiving,
and swap feeds during turnaround.  The receive feed was covered by a
carefully-
fitted sliding cover during transmit times, which provided excellent
isolation.  There
was a microswitch to sense cover position and which would block
transmission if
it was not satisfied.

Feed horn turnaround time was about 7 seconds as I recall.

The transmitter was basically operated CW, and the "imaging" technique was
"range-
Doppler".  So, the transmitter was run for slightly under the round-trip
travel time, then
feed turnaround was initiated, timed to finish shortly before the leading
edge of the
return was expected.  The receiver would do its thing for the duration of
the return.
Note that it was also necessary to completely shut down the beam current of
the
transmit Klystrons during receive so that shot noise on the beam did not
spoil the
receiver's noise temperature.  After the receive interval was finished, the
feeds were
again swapped and a new cycle was started.  During each transmit period the
crew of scientists would have time for a preliminary look at the
just-recorded data
to see if anything was going wrong.

OTOH, Arecibo's 430 MHz ISR for ionospheric studies clearly had to have
almost
instantaneous turnaround time, and arrangements were rather more complicated
(more so than I can take time to describe at the moment).  But they worked
well,
and loss in the receive state of some big PIN switches in the path was
tolerably low.
The first 35-40 dB of TX-RX isolation came from use of a "turnstile
junction", with
the remainder coming from the PIN switches.

For both radars, the non-participating receivers would also be covered, but
with
a simpler flap arrangement, some powered by small DC motors and some by
small pneumatic cylinders.

Dana
(retired from Arecibo Dec 2016)


On Wed, Mar 31, 2021 at 2:30 PM ew via time-nuts 
wrote:

> During my days at UTC I was among other things responsible for our
> Industrial Laser Group. We sold some 50 KW CW CO2 lasers! We had the only
> aero dynamic window that allowed  a vacuum on one side. When not in use you
> put a pencil through it. Patented.
>  Bert Kehren In a message dated 3/31/2021 3:17:21 PM
> Eastern Standard Time, rich...@karlquist.com writes:
>
>
> On 3/31/2021 11:57 AM, Lux, Jim wrote:
>
> >
> > In some ways it's like high power laser labs. It's not the direct beam
> > you worry about - nobody is going to put their hand in the beam path.
> > It's the stray reflection when something gets bumped and falls across
> > the optical bench and reflects a stray beam at 0.01% power into your
> eyes.
>
> I did consulting at Coherent Laser Group working on CO2 lasers.
> In that lab, actually, many people had the misfortune of accidentally
> putting their hand or arm in the invisible beam.  You could see the
> scars on their arms.  There were also accidents where the laser
> burned the ceiling, etc.  Very scary place to work; fortunately,
> I never got injured.  They made lasers up to 1kW optical power out.
>
> Rick N6RK
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[time-nuts] Re: Ublox NEO-M8T-0-10​as a LO question

[Dana Whitlow]

Andy, I agree with you if that's the intended use.  But unless I've missed
something, the
original inquirer has yet to state what he is trying to do, so the sky's
the limit.

Dana


On Wed, Mar 31, 2021 at 7:40 AM Andy Talbot  wrote:

> More to do with amateurs using narrow band modulations, and the LB GPSDO
> being moderately good close in.   Phase noise out beyond a few kHz goes
> more or less unnoticed on SSB
>
> Andy
> www.g4jnt.com
>
>
>
> On Wed, 31 Mar 2021 at 13:35, Dana Whitlow  wrote:
>
> > Chris,
> >
> > It may be that the modulation and subsequent demodulation scheme used for
> > satellite TV and the
> > like is rather more robust than many people give it credit for.
> >
> > Dana
> >
> >
> > On Wed, Mar 31, 2021 at 7:09 AM Chris Wilson 
> wrote:
> >
> > > Hello everyone
> > >
> > >  Monday, March 29, 2021
> > >
> > >  Thanks for the replies, some went a little over my head, which is not
> > > hard :) I am wondering how people successfully use a Leo Bodnar
> > > programmable GPS source to provide an external LO for an LNB as opposed
> > to
> > > its internal xtal. What is different, in simple terms please, between
> my
> > > Ublox output and the Leo Bodnar one?
> > >
> > >
> > > Best regards,
> > >  Chrismailto:ch...@chriswilson.tv
> > >
> > >
> > > LJ> On 3/29/21 10:14 AM, John Ackermann N8UR wrote:
> > > >> That's probably a really bad idea.  The phase noise from the
> TIMEPULSE
> > > >> output is pretty bad compared to a "real" RF source, and by the time
> > > >> it's multiplied up to 10 GHz you'll have more noise than signal.
> > > >> Attached are some phase noise plots and a couple of spectrum
> analyzer
> > > >> captures to give you some idea what to expect.
> > >
> > > >> BTW, even the Bodnar unit may not look too good at 10 GHz --
> remember
> > > >> that you increase phase noise by 20 dB for 10 times multiplication.
> > >
> > > >> John
> > >
> > > LJ> What's the signal bandwidth from Es'Hail?
> > >
> > > LJ> The optimum strategy is a *very quiet* crystal oscillator that you
> > > LJ> discipline with the 1pps, and choose that oscillator so its
> frequency
> > > is
> > > LJ> what you need.
> > >
> > > LJ> What we've done in the past is use the reference to clock a NCO in
> > > FPGA,
> > > LJ> and use one of the well known spur reduction techniques that pushes
> > the
> > > LJ> spurs away from the center before running it to the DAC. This
> > degrades
> > > LJ> the performance at, say, 100kHz away, but improves the performance
> > > LJ> within 1 kHz. This relies on knowing what the loop bandwidth is in
> > your
> > > LJ> 10GHz LO PLL, since inside that bandwidth it's the reference, but
> > > LJ> outside it's the DRO or GaAs oscillator.
> > >
> > >
> > > LJ> There might be some DDS chips that implement this kind of thing -
> the
> > > LJ> latest chips from ADI are pretty sophisticated.
> > >
> > >
> > >
> > >
> > >
> > > >> On 3/29/21 12:25 PM, Chris Wilson wrote:
> > >
> > >
> > > >>>29/03/2021 17:20
> > >
> > > >>> Can I use my Ublox NEO-M8T-0-10​  as a LO for  a  modified
> satellite
> > > >>> LNB on 10 GHz? It needs 25 MHz and the Ublox is my only GPS locked
> > > >>> source for such a frequency. I want to receive the Es Hail downlink
> > > >>> with excellent stability. I can lock the receiver to 10 MHz which
> is
> > > >>> available from my Trimble Thunderbolt. If the Ublox would do I
> would
> > > >>> not have to buy something like the Leo Bodnar GPS. Thanks.
> > >
> > >
> > > >> ___
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> unsubscribe
> > > send an email to time-nuts-le...@lists.febo.com
> > > >> To unsubscribe, go to and follow the instructions there.
> > >
> > > LJ> ___
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> > > LJ> unsubscribe send an email to time-nuts-le...@lists.febo.com
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[time-nuts] Re: Ublox NEO-M8T-0-10​as a LO question

[Dana Whitlow]

Chris,

It may be that the modulation and subsequent demodulation scheme used for
satellite TV and the
like is rather more robust than many people give it credit for.

Dana


On Wed, Mar 31, 2021 at 7:09 AM Chris Wilson  wrote:

> Hello everyone
>
>  Monday, March 29, 2021
>
>  Thanks for the replies, some went a little over my head, which is not
> hard :) I am wondering how people successfully use a Leo Bodnar
> programmable GPS source to provide an external LO for an LNB as opposed to
> its internal xtal. What is different, in simple terms please, between my
> Ublox output and the Leo Bodnar one?
>
>
> Best regards,
>  Chrismailto:ch...@chriswilson.tv
>
>
> LJ> On 3/29/21 10:14 AM, John Ackermann N8UR wrote:
> >> That's probably a really bad idea.  The phase noise from the TIMEPULSE
> >> output is pretty bad compared to a "real" RF source, and by the time
> >> it's multiplied up to 10 GHz you'll have more noise than signal.
> >> Attached are some phase noise plots and a couple of spectrum analyzer
> >> captures to give you some idea what to expect.
>
> >> BTW, even the Bodnar unit may not look too good at 10 GHz -- remember
> >> that you increase phase noise by 20 dB for 10 times multiplication.
>
> >> John
>
> LJ> What's the signal bandwidth from Es'Hail?
>
> LJ> The optimum strategy is a *very quiet* crystal oscillator that you
> LJ> discipline with the 1pps, and choose that oscillator so its frequency
> is
> LJ> what you need.
>
> LJ> What we've done in the past is use the reference to clock a NCO in
> FPGA,
> LJ> and use one of the well known spur reduction techniques that pushes the
> LJ> spurs away from the center before running it to the DAC. This degrades
> LJ> the performance at, say, 100kHz away, but improves the performance
> LJ> within 1 kHz. This relies on knowing what the loop bandwidth is in your
> LJ> 10GHz LO PLL, since inside that bandwidth it's the reference, but
> LJ> outside it's the DRO or GaAs oscillator.
>
>
> LJ> There might be some DDS chips that implement this kind of thing - the
> LJ> latest chips from ADI are pretty sophisticated.
>
>
>
>
>
> >> On 3/29/21 12:25 PM, Chris Wilson wrote:
>
>
> >>>29/03/2021 17:20
>
> >>> Can I use my Ublox NEO-M8T-0-10​  as a LO for  a  modified satellite
> >>> LNB on 10 GHz? It needs 25 MHz and the Ublox is my only GPS locked
> >>> source for such a frequency. I want to receive the Es Hail downlink
> >>> with excellent stability. I can lock the receiver to 10 MHz which is
> >>> available from my Trimble Thunderbolt. If the Ublox would do I would
> >>> not have to buy something like the Leo Bodnar GPS. Thanks.
>
>
> >> ___
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>
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[time-nuts] Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New Yorker]

[Dana Whitlow]

Jim, how large is the Goldstone antenna to which you referred?

Dana


On Tue, Mar 30, 2021 at 4:01 PM Lux, Jim  wrote:

> On 3/30/21 6:40 AM, Wes wrote:
> > Was a pity.  China's FAST is receive only.  I believe that leaves
> > Green Bank as the biggest transmitting telescope.
>
> More likely the Goldstone Solar System Radar function of DSN on the 70m
> (DSS-14) - 500kW in X band at 8560 MHz
>
> There *is* a new transmitter for GB - but it's a demo - 700 W and
> temporarily installed up at the feed for a test.  I don't know what
> frequency.  People are pitching a 500kW system, but we shall see.
>
>
>
> >
> > I remember 417s.  I had them in a copy of a design by W2AZL.  I also
> > had a two-meter preamp I designed using 416Bs.  Of course uW cooled
> > preamps are not unusual now, but back then a blower on a receive
> > amplifier was unusual :-)
> >
> > Wes Stewart N7WS
> >
> > On 3/30/2021 4:06 AM, ew via time-nuts wrote:
> >> GOOD Morning Tom  Thank you for the super information Read it over
> >> and over. To me no joy, sadness for Astronomy, Science, Puerto Rico
> >> and the US. China is now the leader with a 500 meter unit! Did follow
> >> it since the seventies because of the low noise receivers. Remember
> >> the 417 Triodes? I had some for Ham use.
> >>Any body knows what happened to its Maser?
> >>  Bert Kehren
> >> ___
> > ___
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> >
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[time-nuts] Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New Yorker]

[Dana Whitlow]

Arecibo's long-standing maser (Symmetricom MHM-2010) died right at the end
of 2018.
In communications with the mfr it came to pass that "repair" was deemed to
be economically
infeasible. so the observatory fell back on a FS725 locked to PPS from a
CNS Clock II,
both of which I had purchased a few years prior to my retirement "just in
case".
(The FS725 is a PRS-10 at heart, but built into a nice looking enclosure
along with the
power supplies and several isolating 10 MHz distribution amplifiers.)

Sometime last year (I don't recall just when) the GPSDRb system was
replaced by
another H-maser, a loaner as I understand it.  I never heard what brand or
model it is.  As
of a few minutes ago when I checked, it is still ticking along just fine.
The Clock Room at
Arecibo is located in the operations bldg, at  18.346559, -66.753496
(these coordinates
are even roughly at the right location in the bldg).  That building complex
was very lucky
in coming through the collapse essentially undamaged, and continues in
operation to
this day.

Remember, the Arecibo Observatory is more than just the big telescope.
There are two
optical labs on campus, one dedicated to LIDAR studies of the upper
atmosphere and
the other to airglow studies.  Also there is a separate 12m fully-steerable
radio telescope
on a hilltop at roughly  18.348394, -66.751469  (I say "roughly" because
that seems to
be on s stitching boundary in the Google Earth image of the hilltop, and my
attempted
coordinate determination for the dish itself failed).  That telescope is
partly operational,
but may have suffered some damage from H. Maria back in 2017.

Anyway, each of these other research activities requires either (or both
of) accurate time
and frequency.

Bob is correct in saying that groups are looking at what could be done to
"rebuild" the
large telescope, in altogether new form, to surpass (not just replace) the
old one in
performance.   Persuading the NSF *not* to scuttle the affair, and finding
several hundred
megabucks in funding, are the big issues right now.

Dana
(former Keeper of The Clock at Arecibo, retired ~4 years ago)




On Tue, Mar 30, 2021 at 6:07 AM ew via time-nuts 
wrote:

> GOOD Morning Tom
>
>  Thank you for the super information Read it over and over.
> To me no joy, sadness for Astronomy, Science, Puerto Rico and the US. China
> is now the leader with a 500 meter unit! Did follow it since the seventies
> because of the low noise receivers.  Remember the 417 Triodes? I had some
> for Ham use.
>Any body knows what happened to its Maser?
>
>Bert Kehren
> ___
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> an email to time-nuts-le...@lists.febo.com
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[time-nuts] Re: Water in connectors

[Dana Whitlow]

Ah, yes.  The wonderful thing about our modern science (and the toys that
arise from it)
is that there is a bottomless treasure trove of interesting things to
investigate.

It occurred to me that one could expand a bit on Bob's point to include the
probable
variation of water's dielectric constant when it goes between liquid and
solid states.

I once had a big problem with a 2m repeater's transmission line wherein a
connector
near the bottom end "filled" with water.  I think the amount was little
more than a ml,
but its effect was to bring the repeater to its knees.  I unscrewed the
connector,
drained a few drops from it, dried it with a hanky, and all was back to
normal upon
reassembly.  This should not be too surprising considering water's
dielectric constant
of around 80.

Good luck with your own investigations.

Dana


On Sat, Mar 27, 2021 at 11:53 AM Ole Petter Rønningen 
wrote:

> Oh, no qustion that it would be interesting, but I’d hate to «tie up» the
> gear for a month on a low cost patch antenna, when I have a much better one
> temorarily taken down - basically I just wanted a quick check of how much
> worse things are on «low end gear» - somewhat predictably that only served
> to uncover more questions than it answered..
>
> > 27. mar. 2021 kl. 17:39 skrev Dana Whitlow :
> >
> > My own belief is that almost everything can be blamed on GPS, but then
> much
> > if not
> > most is my own fault for using an indoor antenna only about 6 or 7 feet
> > above ground
> > level.
> >
> > Except when excessive lightning activity is around, I run a
> > continuous setup comparing
> > 10 MHz phase between a T'Bolt GPSDO and a Rb, showing I & Q waveforms on
> a
> > very
> > slow roll-mode 'scope display which shows the most recent 4 hours.  It
> just
> > sits there
> > and runs, and I glance at it many times per day in passing.  It gets very
> > messy much
> > of the time.
> >
> > A month-long recording could net you quite a bit of couch time  :-)
> >
> > Dana
> >
> >
> >> On Sat, Mar 27, 2021 at 11:21 AM Ole Petter Rønningen <
> opronnin...@gmail.com>
> >> wrote:
> >>
> >> Active HM, yes - nothing in the logs that corresponds, except a .5 degC
> >> diurnal temperature change - which roughly coincides with the outdoor
> temp,
> >> so no help there..
> >>
> >> This was meant as a quick-and-dirty check, so a months is not in the
> cards
> >> - but that second antenna/receiver is climbing on my list of
> priorities, in
> >> imminent danger of surpassing «doing nothing on the couch»! :)
> >>
> >>>> 27. mar. 2021 kl. 16:52 skrev Dana Whitlow :
> >>>
> >>> Ole,
> >>>
> >>> If you can stand the suspense, a time error recording of a month or
> more
> >>> duration
> >>> would probably be pretty informative (and interesting for us to see).
> >>>
> >>> And when you speak of the maser, is that an active hydrogen maser?  If
> >> so,
> >>> you're
> >>> a lucky man (unless it's in the process of dying).  But there should be
> >>> scads of
> >>> diagnostics being logged, which should be enough to enable making a
> >> fairly
> >>> good
> >>> confidence check on it.
> >>>
> >>> Dana
> >>>
> >>>
> >>>> On Sat, Mar 27, 2021 at 8:33 AM Ole Petter Rønningen <
> >> opronnin...@gmail.com>
> >>>> wrote:
> >>>>
> >>>> Hi, Dana
> >>>>
> >>>> Thats the peculiar thing - these last 48 hors theres been a pretty
> clear
> >>>> 24 hour cycle, pointing to temperature as the culprit; but the
> >> preceeding
> >>>> 48 hours the phase shift did not follow a 24 hour period at all; the
> >>>> wheather has been all over the place, so it is hard to say.. More data
> >>>> needed! As always..
> >>>>
> >>>> (of course, there is always a possibility that I’ve somehow bungled
> the
> >>>> data, and the period has been 24 hours all along)
> >>>>
> >>>> This is why I am looking for ballpark figures for the two main
> suspects;
> >>>> water and temperature.
> >>>>
> >>>> I guess I should bite the bullet and rig up a second receiver/antenna
> >> so I
> >>>> can take the maser out of the equation.. (and reseal the connectors
> >>>> properly)
> >>>>
> >>>&

[time-nuts] Re: Water in connectors

[Dana Whitlow]

My own belief is that almost everything can be blamed on GPS, but then much
if not
most is my own fault for using an indoor antenna only about 6 or 7 feet
above ground
level.

Except when excessive lightning activity is around, I run a
continuous setup comparing
10 MHz phase between a T'Bolt GPSDO and a Rb, showing I & Q waveforms on a
very
slow roll-mode 'scope display which shows the most recent 4 hours.  It just
sits there
and runs, and I glance at it many times per day in passing.  It gets very
messy much
of the time.

A month-long recording could net you quite a bit of couch time  :-)

Dana


On Sat, Mar 27, 2021 at 11:21 AM Ole Petter Rønningen 
wrote:

> Active HM, yes - nothing in the logs that corresponds, except a .5 degC
> diurnal temperature change - which roughly coincides with the outdoor temp,
> so no help there..
>
> This was meant as a quick-and-dirty check, so a months is not in the cards
> - but that second antenna/receiver is climbing on my list of priorities, in
> imminent danger of surpassing «doing nothing on the couch»! :)
>
> > 27. mar. 2021 kl. 16:52 skrev Dana Whitlow :
> >
> > Ole,
> >
> > If you can stand the suspense, a time error recording of a month or more
> > duration
> > would probably be pretty informative (and interesting for us to see).
> >
> > And when you speak of the maser, is that an active hydrogen maser?  If
> so,
> > you're
> > a lucky man (unless it's in the process of dying).  But there should be
> > scads of
> > diagnostics being logged, which should be enough to enable making a
> fairly
> > good
> > confidence check on it.
> >
> > Dana
> >
> >
> >> On Sat, Mar 27, 2021 at 8:33 AM Ole Petter Rønningen <
> opronnin...@gmail.com>
> >> wrote:
> >>
> >> Hi, Dana
> >>
> >> Thats the peculiar thing - these last 48 hors theres been a pretty clear
> >> 24 hour cycle, pointing to temperature as the culprit; but the
> preceeding
> >> 48 hours the phase shift did not follow a 24 hour period at all; the
> >> wheather has been all over the place, so it is hard to say.. More data
> >> needed! As always..
> >>
> >> (of course, there is always a possibility that I’ve somehow bungled the
> >> data, and the period has been 24 hours all along)
> >>
> >> This is why I am looking for ballpark figures for the two main suspects;
> >> water and temperature.
> >>
> >> I guess I should bite the bullet and rig up a second receiver/antenna
> so I
> >> can take the maser out of the equation.. (and reseal the connectors
> >> properly)
> >>
> >>
> >>>> 27. mar. 2021 kl. 14:04 skrev Dana Whitlow :
> >>>
> >>> Ole,
> >>>
> >>> You did not mention whether this timing anomaly is periodic or steadily
> >>> growing.
> >>> That information could be of considerable diagnostic significance.
> >>>
> >>> Dana
> >>>
> >>>
> >>>> On Sat, Mar 27, 2021 at 6:08 AM Ole Petter Ronningen <
> >> opronnin...@gmail.com>
> >>>> wrote:
> >>>>
> >>>> Hi, All
> >>>>
> >>>> I am trying to chase down a 2-3-4 ns/day "anomaly" in a gpsdo I am
> >> working
> >>>> on - it could be temperature sensitivity in the antenna (cheap patch
> >>>> jobbie), or I suspect my sealing of the outside connectors may not be
> >>>> watertight. I just wanted to ask the list of anyone know of/has an
> >> estimate
> >>>> of how much the propagation delay on an N and/or SMA can reasonably be
> >>>> expected to change in the presence of water? is 3 ns in the right
> >> ballpark,
> >>>> or would that effect be way bigger/smaller?
> >>>>
> >>>> Likewise, does anyone have reasonably accurate figures for how much
> >>>> temperature could be expected to affect the delay of signals? 20 ps?
> 20
> >> ns?
> >>>> Looking for some rough figures so I can look in the right direction..
> >>>>
> >>>> I've used the same gpsdo, cable and location with a high quality
> antenna
> >>>> without seeing these effects, so I am fairly certain it is the antenna
> >> (or
> >>>> my reference maser giving up the ghost..)
> >>>>
> >>>> Thanks!
> >>>> Ole
> >>>> 

[time-nuts] Re: Water in connectors

[Dana Whitlow]

Ole,

If you can stand the suspense, a time error recording of a month or more
duration
would probably be pretty informative (and interesting for us to see).

And when you speak of the maser, is that an active hydrogen maser?  If so,
you're
a lucky man (unless it's in the process of dying).  But there should be
scads of
diagnostics being logged, which should be enough to enable making a fairly
good
confidence check on it.

Dana


On Sat, Mar 27, 2021 at 8:33 AM Ole Petter Rønningen 
wrote:

> Hi, Dana
>
> Thats the peculiar thing - these last 48 hors theres been a pretty clear
> 24 hour cycle, pointing to temperature as the culprit; but the preceeding
> 48 hours the phase shift did not follow a 24 hour period at all; the
> wheather has been all over the place, so it is hard to say.. More data
> needed! As always..
>
> (of course, there is always a possibility that I’ve somehow bungled the
> data, and the period has been 24 hours all along)
>
> This is why I am looking for ballpark figures for the two main suspects;
> water and temperature.
>
> I guess I should bite the bullet and rig up a second receiver/antenna so I
> can take the maser out of the equation.. (and reseal the connectors
> properly)
>
>
> > 27. mar. 2021 kl. 14:04 skrev Dana Whitlow :
> >
> > Ole,
> >
> > You did not mention whether this timing anomaly is periodic or steadily
> > growing.
> > That information could be of considerable diagnostic significance.
> >
> > Dana
> >
> >
> >> On Sat, Mar 27, 2021 at 6:08 AM Ole Petter Ronningen <
> opronnin...@gmail.com>
> >> wrote:
> >>
> >> Hi, All
> >>
> >> I am trying to chase down a 2-3-4 ns/day "anomaly" in a gpsdo I am
> working
> >> on - it could be temperature sensitivity in the antenna (cheap patch
> >> jobbie), or I suspect my sealing of the outside connectors may not be
> >> watertight. I just wanted to ask the list of anyone know of/has an
> estimate
> >> of how much the propagation delay on an N and/or SMA can reasonably be
> >> expected to change in the presence of water? is 3 ns in the right
> ballpark,
> >> or would that effect be way bigger/smaller?
> >>
> >> Likewise, does anyone have reasonably accurate figures for how much
> >> temperature could be expected to affect the delay of signals? 20 ps? 20
> ns?
> >> Looking for some rough figures so I can look in the right direction..
> >>
> >> I've used the same gpsdo, cable and location with a high quality antenna
> >> without seeing these effects, so I am fairly certain it is the antenna
> (or
> >> my reference maser giving up the ghost..)
> >>
> >> Thanks!
> >> Ole
> >> ___
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> send
> >> an email to time-nuts-le...@lists.febo.com
> >> To unsubscribe, go to and follow the instructions there.
> >>
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[time-nuts] Re: Water in connectors

[Dana Whitlow]

Ole,

You did not mention whether this timing anomaly is periodic or steadily
growing.
That information could be of considerable diagnostic significance.

Dana


On Sat, Mar 27, 2021 at 6:08 AM Ole Petter Ronningen 
wrote:

> Hi, All
>
> I am trying to chase down a 2-3-4 ns/day "anomaly" in a gpsdo I am working
> on - it could be temperature sensitivity in the antenna (cheap patch
> jobbie), or I suspect my sealing of the outside connectors may not be
> watertight. I just wanted to ask the list of anyone know of/has an estimate
> of how much the propagation delay on an N and/or SMA can reasonably be
> expected to change in the presence of water? is 3 ns in the right ballpark,
> or would that effect be way bigger/smaller?
>
> Likewise, does anyone have reasonably accurate figures for how much
> temperature could be expected to affect the delay of signals? 20 ps? 20 ns?
> Looking for some rough figures so I can look in the right direction..
>
> I've used the same gpsdo, cable and location with a high quality antenna
> without seeing these effects, so I am fairly certain it is the antenna (or
> my reference maser giving up the ghost..)
>
> Thanks!
> Ole
> ___
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> an email to time-nuts-le...@lists.febo.com
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Re: [time-nuts] Grandfather clock sync'd to 1PPS (from time-nuts Digest, Vol 200, Issue 4)

[Dana Whitlow]

Philip,

You and I are definitely "in sync" regarding cheating to alter the pendulum
motions!

I had a very similar thought for effectively making the pendulum based
system into sort
of a VCO, except that instead of a metal plate, use a small Nd magnet
polarized
vertically, stealthily-attached to the back of the pendulum bob near the
bottom.  Then a
current applied through the control coil could either increase of decrease
the effective pull
of gravity at will, and in a well-tuned system would average near zero
current.  Thus if the
power to the system failed, the clock would continue to run very close to
the correct
rate for good holdover.

My big problem is that I'd never remember to "rewind" the clock's primary
energy storage
mechanism.

Dana


On Wed, Mar 10, 2021 at 10:10 AM Philip Gladstone <
pjsg-timen...@nospam.gladstonefamily.net> wrote:

> I've been wanting to do this as well, but I feel that it is "cheating" to
> actively drive the pendulum. I want to have a passive approach to
> disciplining the clock so that the clock itself is keeping time.
>
> One approach that I have seen was to put a magnet at the bottom of the
> pendulum and then have a metal plate beneath it -- and the correction is
> performed by adjusting the vertical position of the plate. This effectively
> changes the local gravity and hence the tick period. However, I don't think
> that this will look "nice". I'm hoping that I can do the same magnet trick,
> but put it much higher on the pendulum so that it is hidden when you open
> the clock case door. I envisage having the metal plate position being
> controlled by a small stepper motor. I'd like to have a range of maybe
> +/-50ppm with a resolution of around 1ppm. This seems doable
>
> Thoughts?
>
> Philip
>
> On Sat, Mar 6, 2021 at 2:12 PM Gerald Swann  wrote:
>
> > Eamonn and all,
> >
> >You mentioned you hope to get your grandfather clock time synchronized
> > to a 1PPS signal.  That would be a very satisfying project, I can assure
> > you.  I did that with my own grandfather clock.  My father built the
> clock
> > quite a number of years ago from a kit, and used walnut wood from a tree
> > that was harvested from somewhere in Indiana to build the actual clock
> > body.
> >
> >On github at https://github.com/gds32571/gdsPendulum you can see the
> > operating code for the Arduino-based controller that performs this feat.
> >  There are lots of comments within the code, but I don't want to leave
> that
> > as the only info to help you understand, so some explanation follows.
> > Within the README.md file are links to pictures and to a graph showing
> data
> > regarding the pendulum swing.
> >
> >There were several interesting descriptions of how one might use a
> > magnet to influence the swing of the pendulum. I took an approach not
> > mentioned in the digest email.  For a simple pendulum, only two factors
> > affect the period: the length of the pendulum and the gravity field the
> > pendulum is swinging in.
> >
> >I fastened a steel screw held in an alligator clip to the bottom of
> the
> > pendulum, and then adjusted the pendulum weight so that the pendulum
> would
> > swing a little slower than necessary to keep time.  I took the coil from
> a
> > 24v relay and mounted it on a cardboard rack sitting in the bottom of the
> > clock cabinet such that the steel screw swings just above the core of the
> > relay coil.  This relay coil, when energized, has the effect of slightly
> > increasing the attraction of the pendulum towards the center of earth -
> > more gravity you might say.
> >
> >The same cardboard rack holds a blue LED and a phototransistor
> > (TEPT5600) such that the light from the LED shines on the
> phototransistor.
> > The weight attached to the end of the pendulum, blocks the light every
> > swing.  This generates a signal I use to measure the phase of the
> pendulum
> > relative to the 1PPS signal.
> >
> >When I started thinking about this, I thought I could use some fancy
> > timing to generate pulses that could speed up or slow down the pendulum,
> as
> > I desired.  That was not to be, at least within my ability, the pendulum
> > can only be sped up.  So I just measure the phase of the pendulum
> relative
> > to the 1PPS and energize the coil if the pendulum is lagging behind.  The
> > arduino controller energizes the coil for a number of seconds each
> minute.
> > In the graph, you can see that the magnetism time is 19 beats for this
> > minute.
> >
> >I didn't notice before I started this project, the pendulum period is
> > not 2 seconds as I would have expected.  It actually swings 33 times in
> one
> > minute, giving a period of 1.81818 seconds.  This means that the phase
> > measurement of the swing will line up with only one pulse from the GPS
> > every ten seconds.
> >
> >The arduino outputs a text message once a minute with some control
> info
> > including the phase, the time spent energizing the magnet, etc.  

Re: [time-nuts] World's most precise.... wall clock

[Dana Whitlow]

Hal,

The older (and probably the newer models, too) Trimble Thunderbolt GPSDOs
have
a user-adjustable time constant accessible via the serial port using a
program like
"Tboltmon.exe" (from Trimble).  I suspect that  "Lady Heather"  may also do
this.  I
am fortunate in owning a still functioning PC with an actual hardware RS232
port
and a usable O/S (Win XP), so running Tboltmon is a trivial exercise for me.

In addition to time constant, tboltmon also lets one examine (and set,
where appropriate)
a large number of other items, and it's reasonably intuitive to use.  I've
never had to resort
to a manual. (if there even is one) to do what I needed.

My own experience is that a time constant around 50 sec works best in my
environment,
providing the best compromise between filtering PPS jitter from out of the
unit's GPS
receiver and tamping down OCXO wanderings due to my home HVAC system's
cycling.
Setting a far longer time constant value (say, much longer than 500 sec)
tends to lead
to "funny business" so I just don't go there.

I have convinced myself that the PPS output from my Tbolt is derived from
the produced
10 MHz output, because if I trigger an o'scope from the PPS output, the 10
MHz sinewave
shows very little time jitter, perhaps 1 or 2 nsec.  So, I'm pretty happy
with the T'bolt, with
two (minor) exceptions:

>  Its RF sensitivity seems rather poor compared to that of "modern"
receivers (my unit
was apparently made in the early 2000s).

>  In tboltmon, the signal "strength" indications are displayed in units
called 'AMU',
for which I've been unable to find a definition.

Dana


On Wed, Mar 10, 2021 at 6:53 AM Hal Murray  wrote:

>
> kb...@n1k.org said:
> > The gotcha here is that if you want accurate *time*, you are better off
> using
> > the sawtooth corrected output from a (good) GPS module rather than a
> GPSDO.
>
> Why is that?
>
> I would have guessed that a GPSDO would average over many GPS pulses thus
> reducing the noise.
>
> Is it something like GPSDOs are normally designed for good frequency
> rather
> than good time, so when they find the time is off, they use a small
> frequency
> offset for a long time to correct rather than a big frequency offset for a
> short time?
>
> Are there any GPSDOs designed for good time?  Or any with parameters that
> can
> be tweaked to provide good time?
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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Re: [time-nuts] Old Crystal.

[Dana Whitlow]

Re: light producing crystals-

If you view  https://en.wikipedia.org/wiki/Sonoluminescence
you'll learn that this is not the explanation for the blue glow
seen in the crystals.  Sonoluminescence involves collapsing
tiny bubbles in liquids driven by high power acoustic fields.

I think it's safe to assume that these crystals are *not* liquid filled.
I agree with what Ed just sent, with the added comment that the
"gas" may just be residual from an imperfect vacuum (as all
vacuums are).

Dana


On Sat, Mar 6, 2021 at 3:26 PM Dan Kemppainen  wrote:

> Hi All,
>
> Just to be clear, I am not the person who made the crystals glow blue. I
> just noticed some pictures of that happening on the auction site:
>
>
> https://www.ebay.com/itm/8x-Quartz-Resonator-1000-kHz-Crystal-oscillator-gold-Sonoluminescence-effect-NOS/113862454353
>
>
> https://www.ebay.com/itm/1x-Quartz-Resonator-1000-kHz-Crystal-oscillator-gold-Sonoluminescence-effect/113874435589
>
> I certainly will not abuse these crystals this way!
>
>
>
> As for measurements, I'm trying to take some measurements with the
> equipment on hand. Currently, that is an Agilent 33220A signal
> generator, and TDS3000B oscilloscope + Active FET Probe.
>
> Years ago I put together a little Excel Macro program that sweeps the
> signal generator through a range of frequencies, and measures the
> voltage and phase of the signals on the oscilloscope. Basically, the
> sampled signals are run through a sine fit routine, which gives very
> good estimation of sine amplitude and phase shift (With frequency being
> set by the signal generator).
>
> Using this setup, the first try involved making a voltage divider with a
> fixed resistor and the crystal. The signal generator was used to drive
> signal into the resistor, through the crystal to ground. A standard 10x
> probe monitored the signal generator voltage, and the FET probe in
> series with a 1K resistor (for more isolation) was used to monitor the
> crystal voltage. (The probes were compared before the test, and channel
> skew adjusted to zero).
>
> Basically, this is a voltage divider made with a resistor and a crystal.
>  From this, a frequency response curve was generated. See attached image.
> The -3dB and +/-45 deg phase shift points match well. They are also
> quite close to the Fs frequency (999,999.800 Hz). Those -3dB points come
> out to be 999,990.640 Hz and 999,990.910Hz.
>
> However, I'm a bit concerned that the Q calculated with these numbers is
> a bit higher than expected based on what I've read. Running the test
> with a smaller series resistor (100 Ohm) results in a lower Q (As would
> be expected as the 'load' on the crystal is higher), although even these
> numbers are quite high.
>
> In order to try to measure Rs, the voltages of the divider were measured
> at Fs, and RS was calculated accordingly (Easy calculation, as phase
> shift = 0 deg). This was repeated with several series resistor values
> (10, 100, and 1000 Ohm). These tests resulted in Rs = between 4 to 7
> ohms (depending on the series resistor).
>
> My concern is, are there any potential pitfalls in this measurement
> setup? Is there something that will give more accurate results, given
> the equipment on hand? Certainly the Q value seems unreasonably high,
> and Rs seems quite low. However, these are large low frequency
> resonators (being 25mm in dia.).
>
>
> Thanks,
> Dan
>
>
> On 3/6/2021 12:00 PM, time-nuts-requ...@lists.febo.com wrote:
> > Message: 4
> > Date: Fri, 5 Mar 2021 16:03:51 -0600
> > From: Dana Whitlow
> > To: Discussion of precise time and frequency measurement
> >   
> > Subject: Re: [time-nuts] Old Crystal.
> > Message-ID:
> >dt0gv5...@mail.gmail.com>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > Blue LEDs under Nixie tubes might have a deeper purpose than appearance-
> > they can also
> > help the Nixie tubes get started upon turn-on (especially if they're
> > getting old).  I once stayed
> > in a hotel room whose light switches had neon indicators to help one find
> > them in the dark,
> > and the one near the entrance door was getting awfully marginal.  I
> > happened to have a blue
> > LED penlight with me, and I found that shining that on the switch face
> made
> > a radical
> > improvement in making the neon indicator keep going, even at a range of >
> > 20 feet.  And
> > this flashlight was no powerhouse either- it was a single LED with no
> > auxiliary focussing
> > optics.
> >
> > Dana
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Re: [time-nuts] Old Crystal.

[Dana Whitlow]

Blue LEDs under Nixie tubes might have a deeper purpose than appearance-
they can also
help the Nixie tubes get started upon turn-on (especially if they're
getting old).  I once stayed
in a hotel room whose light switches had neon indicators to help one find
them in the dark,
and the one near the entrance door was getting awfully marginal.  I
happened to have a blue
LED penlight with me, and I found that shining that on the switch face made
a radical
improvement in making the neon indicator keep going, even at a range of >
20 feet.  And
this flashlight was no powerhouse either- it was a single LED with no
auxiliary focussing
optics.

Dana


On Fri, Mar 5, 2021 at 1:05 PM John Moran, Scawby Design <
j...@scawbydesign.co.uk> wrote:

> Ref. the original comment about a blue glow seen in a crystal, I would
> suggest that it was simply a blue LED used in exactly the same way that
> constructers of Nixie Clocks add LEDs under the Nixie tubes to make them
> look more dramatic.
>
> John
>
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Re: [time-nuts] U-blox teaser

[Dana Whitlow]

Thanks for the link, Bob.  I got to know both Victor Zhang and Mike
Lombardi during my
stay at Arecibo, but to my regret have never met either in person.

Dana


On Sat, Feb 27, 2021 at 6:01 PM Bob kb8tq  wrote:

> Hi
>
>
>
> > On Feb 27, 2021, at 11:18 AM, Dana Whitlow 
> wrote:
> >
> > Thanks, Bob.
> >
> > It seems to me that, depending on the positions of sats visible to one's
> GPS
> > antenna and the spatial distribution of free electron density in the
> > ionosphere,
> > the ionospheric contribution to position errors could sometimes largely
> > cancel.
> > But that observation may (or may not) reflect strongly on one's ability
> to
> > get
> > accurate absolute time from GPS on "average" days.
> >
> > During my Arecibo Observatory days we used NIST's TMAS service to keep
> > our H-maser-based station clock synced with UTC.  Our user community
> > (mainly VLBI and pulsar timing people) seemed pretty satisfied with +/-
> > 100ns
> > accuracy, so I tried to do better by keeping things well within +/- 50 ns
> > during
> > my reign.  IIRC, NIST was claiming that TMAS could produce results mostly
> > within about +/- 20 ns.
> >
> > To be honest I'm baffled by how time transfer much better than that could
> > be achieved in practice.
>
> One way (mentioned about a month back on the list) is a two way transfer
> via satellite. The “delay is equal in both directions” assumption is
> pretty good
> in this case. Once you have that as a baseline, you can measure the
> performance
> of other approaches.
>
> One of *many* starting points to rumble down this rabbit hole:
>
>
> https://www.nist.gov/pml/time-and-frequency-division/time-services/common-view-gps-time-transfer
> <
> https://www.nist.gov/pml/time-and-frequency-division/time-services/common-view-gps-time-transfer
> >
>
> I would suggest starting with David Allan’s paper (referenced in the link
> above) as a
> pretty good starting point.
>
> Bob
>
> >
> > Regarding Q3, yes I'm aware that *some* GPS receivers do the estimation
> of
> > ionospheric delay.  What I was asking was:  Do any of the relatively
> > inexpensive
> > receivers to which we time-nuts have access do this?  Here I'm speaking
> of
> > those being sold for no more than a few hundred USD.
> >
> > Dana
> >
> >
> >
> > On Sat, Feb 27, 2021 at 9:08 AM Bob kb8tq  wrote:
> >
> >> Hi
> >>
> >>
> >>
> >>> On Feb 27, 2021, at 9:41 AM, Dana Whitlow 
> wrote:
> >>>
> >>> I've long understood that ionospheric delays and variations thereof
> lead
> >> to
> >>> *position*
> >>> uncertainties in GPS navigation receivers, to the tune of perhaps 10m
> >>> (2DRMS IIRC).,
> >>> and that these are said to constitute the single largest GPS error
> >> source.
> >>>
> >>> Q1: Would this not imply timing errors of comparable magnitude (10's of
> >>> nsec)
> >>>  for a single band GPS?
> >>
> >> Once all the signals “hit” the antenna, the delays are mostly common
> mode.
> >> Instead of showing up as a position error, they show up as an error in
> the
> >> time estimate. Since time is one of the things you estimate in the
> >> solution
> >> (along with X,Y, and Z) it get’s it’s own independent solution.
> >>>
> >>> Q2: Why have I not seen this issue raised in connection with the
> present
> >>> discussion
> >>> about achievable absolute timing accuracy?
> >>
> >> GPS time transfer is often done to the sub-ns level. There are a number
> of
> >> papers on this.
> >>
> >>>
> >>> Q3: Do any of the "modern" timing GPS receivers available to civilians
> do
> >>> dual-band
> >>> reception in a way that includes estimation of (and correction for)
> >>> said delays and
> >>> their variations?  I know that Garmin, for one, is now selling
> L1/L5
> >>> handheld GPS
> >>> receivers (GPSMAP66sr and GPSMAP65s), but I've seen no indication
> >>> that these
> >>> units make any attempt at doing such corrections.
> >>
> >> Yes, some receivers do an estimate of ionospheric delay based on the
> >> variation of that delay with frequency. This does not help with
> >> tropospheric
> >> delay or all of the various “common mode” issues we have been talking
> >&g

Re: [time-nuts] U-blox teaser

[Dana Whitlow]

Thanks, Bob.

It seems to me that, depending on the positions of sats visible to one's GPS
antenna and the spatial distribution of free electron density in the
ionosphere,
the ionospheric contribution to position errors could sometimes largely
cancel.
But that observation may (or may not) reflect strongly on one's ability to
get
accurate absolute time from GPS on "average" days.

During my Arecibo Observatory days we used NIST's TMAS service to keep
our H-maser-based station clock synced with UTC.  Our user community
(mainly VLBI and pulsar timing people) seemed pretty satisfied with +/-
100ns
accuracy, so I tried to do better by keeping things well within +/- 50 ns
during
my reign.  IIRC, NIST was claiming that TMAS could produce results mostly
within about +/- 20 ns.

To be honest I'm baffled by how time transfer much better than that could
be achieved in practice.

Regarding Q3, yes I'm aware that *some* GPS receivers do the estimation of
ionospheric delay.  What I was asking was:  Do any of the relatively
inexpensive
receivers to which we time-nuts have access do this?  Here I'm speaking of
those being sold for no more than a few hundred USD.

Dana



On Sat, Feb 27, 2021 at 9:08 AM Bob kb8tq  wrote:

> Hi
>
>
>
> > On Feb 27, 2021, at 9:41 AM, Dana Whitlow  wrote:
> >
> > I've long understood that ionospheric delays and variations thereof lead
> to
> > *position*
> > uncertainties in GPS navigation receivers, to the tune of perhaps 10m
> > (2DRMS IIRC).,
> > and that these are said to constitute the single largest GPS error
> source.
> >
> > Q1: Would this not imply timing errors of comparable magnitude (10's of
> > nsec)
> >   for a single band GPS?
>
> Once all the signals “hit” the antenna, the delays are mostly common mode.
> Instead of showing up as a position error, they show up as an error in the
> time estimate. Since time is one of the things you estimate in the
> solution
> (along with X,Y, and Z) it get’s it’s own independent solution.
> >
> > Q2: Why have I not seen this issue raised in connection with the present
> > discussion
> >  about achievable absolute timing accuracy?
>
> GPS time transfer is often done to the sub-ns level. There are a number of
> papers on this.
>
> >
> > Q3: Do any of the "modern" timing GPS receivers available to civilians do
> > dual-band
> >  reception in a way that includes estimation of (and correction for)
> > said delays and
> >  their variations?  I know that Garmin, for one, is now selling L1/L5
> > handheld GPS
> >  receivers (GPSMAP66sr and GPSMAP65s), but I've seen no indication
> > that these
> >  units make any attempt at doing such corrections.
>
> Yes, some receivers do an estimate of ionospheric delay based on the
> variation of that delay with frequency. This does not help with
> tropospheric
> delay or all of the various “common mode” issues we have been talking
> about.
> It is also unclear how the “unknown” timing variation between the bands
> due to the antenna impacts these solutions…..
>
> Bob
>
> >
> > Dana
> >
> >
> >
> > On Sat, Feb 27, 2021 at 7:43 AM Bob kb8tq  wrote:
> >
> >> Hi
> >>
> >> The same 20 or so ns delay in a saw would also apply to the
> >> saw (or tight filter) in some timing antennas. It also would apply
> >> to the saw(s) in some modules. Even if the tolerance is “only”
> >> a couple ns on each of them, you *could* have 3 or more in the
> >> chain.
> >>
> >> Lots of numbers to crunch to get to 5 ns “absolute”. One could go
> >> grab a GPS simulator and start poking. First step would be to find
> >> a simulator that is spec’d for a < 5 ns tolerance on the PPS into
> >> GPS out. I do believe that rules out the eBay marvels that some
> >> of us have lying around …..
> >>
> >> Simpler answer would be a quick “clock trip” with your car full
> >> of 5071’s …… hour drive over to NIST and then back home.
> >> That sounds practical for most of us :) :)
> >>
> >> Bob
> >>
> >>> On Feb 26, 2021, at 9:29 PM, John Ackermann N8UR  wrote:
> >>>
> >>> A while ago I tried doing a decidedly non-anechoic measurement with a
> >> VNA exciter going to a 1500 MHz ground plane and the receiver connected
> to
> >> the antenna (with a known delay cable) and I got a similar result, but
> >> there was enough noise that I didn't think I could nail it down to
> within
> >> 10 ns.
> >>>
> >>> I've also measured GPS antenna splitters and they tend to have 2

Re: [time-nuts] U-blox teaser

[Dana Whitlow]

I've long understood that ionospheric delays and variations thereof lead to
*position*
uncertainties in GPS navigation receivers, to the tune of perhaps 10m
(2DRMS IIRC).,
and that these are said to constitute the single largest GPS error source.

Q1: Would this not imply timing errors of comparable magnitude (10's of
nsec)
   for a single band GPS?

Q2: Why have I not seen this issue raised in connection with the present
discussion
  about achievable absolute timing accuracy?

Q3: Do any of the "modern" timing GPS receivers available to civilians do
dual-band
  reception in a way that includes estimation of (and correction for)
said delays and
  their variations?  I know that Garmin, for one, is now selling L1/L5
handheld GPS
  receivers (GPSMAP66sr and GPSMAP65s), but I've seen no indication
that these
  units make any attempt at doing such corrections.

Dana



On Sat, Feb 27, 2021 at 7:43 AM Bob kb8tq  wrote:

> Hi
>
> The same 20 or so ns delay in a saw would also apply to the
> saw (or tight filter) in some timing antennas. It also would apply
> to the saw(s) in some modules. Even if the tolerance is “only”
> a couple ns on each of them, you *could* have 3 or more in the
> chain.
>
> Lots of numbers to crunch to get to 5 ns “absolute”. One could go
> grab a GPS simulator and start poking. First step would be to find
> a simulator that is spec’d for a < 5 ns tolerance on the PPS into
> GPS out. I do believe that rules out the eBay marvels that some
> of us have lying around …..
>
> Simpler answer would be a quick “clock trip” with your car full
> of 5071’s …… hour drive over to NIST and then back home.
> That sounds practical for most of us :) :)
>
> Bob
>
> > On Feb 26, 2021, at 9:29 PM, John Ackermann N8UR  wrote:
> >
> > A while ago I tried doing a decidedly non-anechoic measurement with a
> VNA exciter going to a 1500 MHz ground plane and the receiver connected to
> the antenna (with a known delay cable) and I got a similar result, but
> there was enough noise that I didn't think I could nail it down to within
> 10 ns.
> >
> > I've also measured GPS antenna splitters and they tend to have 20-ish ns
> delays, mainly due to the SAW filters.  I did surgery on an HP splitter to
> remove the filters so it could be used for L1 and L2 and that dropped the
> delay down to only 1 or 2 ns.
> >
> > So there's definitely lots of stuff to calibrate if you want to get
> accurate time transfer.
> >
> > John
> > 
> >
> > On 2/26/21 8:02 PM, Michael Wouters wrote:
> >> Typical L1 antenna delays range from 20 to 70 ns.
> >> I know of only one antenna for which a delay is given by the vendor and
> the
> >> technique used was just to measure the electronic delay ie by injecting
> a
> >> signal into the circuit. To do it properly, you need a setup in a
> microwave
> >> anechoic chamber with transmitting antenna etc. The practical difference
> >> may be small though, 1 or 2 ns ( sample of one antenna!).
> >> Cheers
> >> Michael
> >> On Sat, 27 Feb 2021 at 11:42 am, John Ackermann N8UR 
> wrote:
> >>> They're claiming "even better than" 5 ns for relative time, which given
> >>> the 4 ns jitter seems at least sort-of reasonable.  But until someone
> >>> shows me otherwise, I'm still thinking that getting better than 25 ns
> >>> absolute accuracy is a pretty good day's work.
> >>>
> >>> John
> >>> 
> >>>
> >>> On 2/26/21 5:26 PM, Bob kb8tq wrote:
>  Hi
> 
>  I can’t think of many antennas (multi band or single band) that claim
> to
> >>> know their
>  delay to < 5 ns. Simply having a *differential* delay spec of < 5 ns
> is
> >>> quite good.
>  Same thing with delay ripple, you see specs out to around 15 ns on a
> lot
> >>> of antennas.
>  None of this is getting you to the actual total delay of the antenna.
> >>> It’s a pretty good
>  bet that number is a bit larger than either of these.
> 
>  Some of the ripple probably comes out in the standard modeling. I’m
> not
> >>> sure that
>  the differential delay is taken out that way. Total delay, not taken
> out
> >>> in any obvious
>  fashion ( at least that I can see). If the F9 has a built in antenna
> >>> database, that’s not
>  mentioned in the doc’s. Any benefit from the corrections would have to
> >>> be part of
>  post processing.
> 
>  No, that’s not the same as talking about the F9 it’s self doing X ns,
> >>> but it would be part
>  of any practical system trying to get close to 5 ns absolute accuracy.
> 
>  5 ns *relative* accuracy between two F9’s? I probably could buy that
> if
> >>> the appropriate
>  one sigma / on a clear day / with the wind in the right direction sort
> >>> of qualifiers are
>  attached.
> 
>  Bob
> 
> > On Feb 26, 2021, at 4:27 PM, John Ackermann N8UR 
> wrote:
> >
> > It's interesting that they talk about the F9 receivers offering 5 ns
> >>> absolute time accuracy.  Does anyone know of tests confirming 

Re: [time-nuts] Daft idea with the National Grid

[Dana Whitlow]

Not daft at all, Andy.  Closely related would be measurements of phase
change between
near the switched load and far away, over a stretch of a few system time
constants.
This would be more challenging, but perhaps doable.

Dana   K8YUM


On Sun, Feb 7, 2021 at 3:44 PM Andy Talbot  wrote:

> The UK has a standalone frequency locked grid supply, nominal 50Hz, which
> typically wanders +/- about 0.15Hz RMS over several minutes , with
> occasional short-lived excursions out to 0.2 or 0.3Hz.  Average number of
> cycles per period generally is normalised to 50Hz after a few days.
> The typical loading for the country ranges over ~25GW to 45GW
>
> Now, I wonder:
> I can probably measure the grid frequency to a few micro Hz   over a period
> of tens of seconds. So I make a continuous recording of this, averaged over
> say 10 second periods.
> Now take a 7kW load (the maximum reasonably possible on a domestic circuit)
> and switch it on and off at intervals of perhaps 10 minutes, precisely
> timed so it can be correlated with the frequency log.  That 7kW load will
> be about 0.2ppm of the average for that for the whole of the UK.By post
> processing, and some deep correlation covering days worth of cycles of load
> on-off with the frequency, I wonder if it would be possible to see the
> loading, the mean frequency changing by a few uHz.
> Not sure what the time constant of the grid control is, but for* small
> signals* I doubt it can be faster than a few minutes.
>
> There was a serious outage on 9 August 2019 that caused frequency to drop
> below 49.5Hz and initiate automatic load shedding;   that happened over a
> period of a couple of minutes but was a large scale problem.
>
> https://www.ofgem.gov.uk/publications-and-updates/investigation-9-august-2019-power-outage
>
> Andy
> www.g4jnt.com
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Re: [time-nuts] "Q for dummies"

[Dana Whitlow]

If anybody can even approach doing justice to the Q concept, including why
it
matters, in just two sentences, that person will have definitely earned the
"Qulitzer prize" in technical journalism.

Here's my entry:

"A circuit's Q is closely related to its internal energy losses compared to
external
energy exchanges.  A high Q can mean better efficiency, better conformance
with
expected performance (especially in filter applications), longer
ringdown times
(wineglass compared to milk glass) and (unfortunately) higher price."

Dana


On Tue, Jan 26, 2021 at 8:14 AM Lux, Jim  wrote:

> On 1/26/21 5:29 AM, Dave Daniel wrote:
> > That doesn’t really illustrate the fundamental concept of Q. I’ll try
> and think of something that is still non-mathematical but nonetheless
> illustrates the concept of Q.
> >
> > DaveD
>
> Ultimately, Q is about internal (or external) losses (leaving aside
> antennas) - how much energy is stored, vs (how much is radiated) or lost
> to heat
>
> A big heavy pendulum will swing for a lot longer than a light one,
> because more energy is stored in the system, relative to the amount lost
> to air and mechanical friction.
>
> And that, like the wine glass (which is a nice mechanical analogy - the
> fine crystal has less internal damping) is a "impulse response" system,
> not a "driven system"
>
>
>
> But how that relates to bandwidth is a bit tricky, because then you need
> to get into a discussion "driven systems" and then into resonance - and
> that is where the train will come off the rails, particularly with
> respect to antennas.
>
>
>
>
> >> On Jan 26, 2021, at 07:28, Ole Petter Ronningen 
> wrote:
> >>
> >> Hi, All
> >>
> >> I am going to give a presentation to non-nuts, and in one of the slides
> I
> >> touch on Q - not wanting to spend more than a sentence or two on the
> >> subject, I wonder if the following analogy works:
> >>
> >> "A quality long-stemmed, thin-walled wine glass will ring for a long
> time
> >> after we give it a little tap - this is high Q. A thick-walled, stubby
> milk
> >> glass will barely ring at all, just a dull "plink" - this is low Q. The
> >> energy we put in dies out very quickly."
> >>
> >> As I am sure is embarrassingly evident, I have a rather tentative grip
> on
> >> the subject myself..
> >>
> >> Ole
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Re: [time-nuts] Leakage, tinySA

[Dana Whitlow]

Hal, my 10 MHz birdie is at a level of about -95 dBm, which puts it a
little more than
10 db above the noise floor in 3 kHz BW.

I've found that the "spur removal" function sometimes works, but not
always, if I
change the IF frequency setting to 433.9 MHz.  It's mostly bimodal behavior-
sometimes the spur remover kills it entirely, but on some sweeps it only
reduces
the spur level by about 10 dB.  And on occasional sweeps the improvement is
by some other amount.

Dana


On Mon, Jan 18, 2021 at 2:47 PM Hal Murray  wrote:

>
> notfad...@gmail.com said:
> > FWIW I don't have spurs at 10MHz.
>
> Have you looked carefully?  I have to zoom in on the bandwidth in order to
> see
> it.  Somebody else called it a birdie.
>
> My unit came from R  I'm reasonably sure it's genuine.
>
> If I look at 10 MHz center and 25 or 100 k span, there is a faint
> something
> down in the noise.  Most of the time, the marker that automagically ends
> up on
> top of the highest peak is in the middle.  At a quick glance, there is
> nothing
> there.  If I look carefully, there is usually a small bump about 3 kHz
> wide.
>  It's easier to see at 25 kHz since it's wider.  It's faintly visible on a
> waterfall.
>
> That's with the antenna terminated or when I wander down the street.
> There is
> a similar thing at 50 MHz.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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Re: [time-nuts] Leakage, tinySA

[Dana Whitlow]

BTW, I did purchase my 10MHz-"leaky" TinySA through R & L.  Had I not had
the clue that R & L was a reliable source, I would never have ordered one ot
these things at all.

Tom, I don't walk around- I pedal around on a recumbent trike.

Dana


On Mon, Jan 18, 2021 at 5:20 AM Bill Notfaded  wrote:

> Knock offs is part of the reason I posted the main US distributer earlier.
> The software is basically open source so anyone could theoretically make
> one.  There's only one original manufacturer though.  R Electronics is
> the only sanctioned US distributer I'm aware of.  Also they have the best
> price in US you can find for obvious reasons.  FWIW I don't have spurs at
> 10MHz.
>
> Bill in AZ
>
> On Sun, Jan 17, 2021, 5:35 PM Dana Whitlow  wrote:
>
> > Hi Dan,
> >
> > I remember seeing the list of checks to make regarding knockoff clones,
> > and even remember a few of them: to wit:
> >
> > 1. Comes in molded packaging, not poly foam.  Check!
> > 2. Has the internal shielding.  Check!
> > 3. Passes all the self tests, including 7 & 8.  Check!
> >
> > I had high hopes of moving the birdie off 10 MHz by changing the IF
> > frequency
> > setting, but this did no good.  I'd sure like to see a detailed block
> > diagram, but
> > do not know where to look.
> >
> > I also tried turning on the "spur eliminator", which did help by several
> > dB, but
> > my birdie still sits a few dB able the displayed noise floor in the
> > narrowest
> > available resolution BW of ~ 3 kHz.
> >
> > So, for the moment, I'm out of ideas.
> >
> > Thanks,
> >
> > Dana
> >
> >
> > On Sun, Jan 17, 2021 at 5:21 PM Dan Kemppainen 
> > wrote:
> >
> > > Dana,
> > >
> > > Just an FYI. Apparently, there are knockoff clone copies of the TinySA
> > > out there. (Yes, making a knockoff clone of a $50 spectrum analyzer is
> a
> > > thing, go figure!)
> > >
> > > Apparently, these have substandard performance, and a host of
> > > issues/concerns. I ran into this on the TinySA web site. They have some
> > > hints on how to detect if you have a clone or not. Might be worth
> > > looking into to see if you have a sub-par copy.
> > >
> > > Dan
> > >
> > >
> > >
> > >
> > > On 1/16/2021 12:00 PM, time-nuts-requ...@lists.febo.com wrote:
> > > > Date: Sat, 16 Jan 2021 05:45:19 -0600
> > > > From: Dana Whitlow
> > > > To: Discussion of precise time and frequency measurement
> > > >   
> > > > Subject: Re: [time-nuts] Leakage, tinySA
> > > > Message-ID:
> > > >> > qrjlg-bw68wgdahmlhe9qulpupijuqedapz...@mail.gmail.com>
> > > > Content-Type: text/plain; charset="UTF-8"
> > > >
> > > > Another data point:  My newly-received TinySA has a big birdie at 10
> > MHz,
> > > > which is a
> > > > disappointment since I had hoped to use the unit as a sniffer to
> track
> > > down
> > > > leaks in my
> > > > 10 MHz distribution system.  This birdie in the TinySA persists even
> > when
> > > > nothing is
> > > > connected to the input and does not vary in amplitude when I move
> > around
> > > > the house,
> > > > or with time while I'm sitting still with the unit.
> > > >
> > > > I, too, received no manual.
> > > >
> > > > Dana
> > >
> > > ___
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> > > To unsubscribe, go to
> > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > and follow the instructions there.
> > >
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Re: [time-nuts] Leakage, tinySA

[Dana Whitlow]

Hi Dan,

I remember seeing the list of checks to make regarding knockoff clones,
and even remember a few of them: to wit:

1. Comes in molded packaging, not poly foam.  Check!
2. Has the internal shielding.  Check!
3. Passes all the self tests, including 7 & 8.  Check!

I had high hopes of moving the birdie off 10 MHz by changing the IF
frequency
setting, but this did no good.  I'd sure like to see a detailed block
diagram, but
do not know where to look.

I also tried turning on the "spur eliminator", which did help by several
dB, but
my birdie still sits a few dB able the displayed noise floor in the
narrowest
available resolution BW of ~ 3 kHz.

So, for the moment, I'm out of ideas.

Thanks,

Dana


On Sun, Jan 17, 2021 at 5:21 PM Dan Kemppainen 
wrote:

> Dana,
>
> Just an FYI. Apparently, there are knockoff clone copies of the TinySA
> out there. (Yes, making a knockoff clone of a $50 spectrum analyzer is a
> thing, go figure!)
>
> Apparently, these have substandard performance, and a host of
> issues/concerns. I ran into this on the TinySA web site. They have some
> hints on how to detect if you have a clone or not. Might be worth
> looking into to see if you have a sub-par copy.
>
> Dan
>
>
>
>
> On 1/16/2021 12:00 PM, time-nuts-requ...@lists.febo.com wrote:
> > Date: Sat, 16 Jan 2021 05:45:19 -0600
> > From: Dana Whitlow
> > To: Discussion of precise time and frequency measurement
> >   
> > Subject: Re: [time-nuts] Leakage, tinySA
> > Message-ID:
> >qrjlg-bw68wgdahmlhe9qulpupijuqedapz...@mail.gmail.com>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > Another data point:  My newly-received TinySA has a big birdie at 10 MHz,
> > which is a
> > disappointment since I had hoped to use the unit as a sniffer to track
> down
> > leaks in my
> > 10 MHz distribution system.  This birdie in the TinySA persists even when
> > nothing is
> > connected to the input and does not vary in amplitude when I move around
> > the house,
> > or with time while I'm sitting still with the unit.
> >
> > I, too, received no manual.
> >
> > Dana
>
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Re: [time-nuts] Leakage, tinySA

[Dana Whitlow]

Another data point:  My newly-received TinySA has a big birdie at 10 MHz,
which is a
disappointment since I had hoped to use the unit as a sniffer to track down
leaks in my
10 MHz distribution system.  This birdie in the TinySA persists even when
nothing is
connected to the input and does not vary in amplitude when I move around
the house,
or with time while I'm sitting still with the unit.

I, too, received no manual.

Dana


On Sat, Jan 16, 2021 at 5:28 AM Hal Murray  wrote:

>
> My tinySA arrived a  few days ago.  I'm happy.
>
> It comes in a nice box with an antenna that extends to a foot, a USB
> charging
> cable (mini, not micro) and a couple of cables.
>
> It doesn't come with a manual.  I haven't found a manual online.  Their
> web
> site is pretty good, but sometimes I like a document organized to be read
> by
> turning pages rather than following links.
>
> The minimum receive bandwidth is 3.1 kHz.
>
> The specs say the lower frequency limit is 100 kHz but the UI doesn't
> enforce
> that.
>
> My strongest signal is at 30 MHz.  It's -60 to -80 dBm as I wave it
> around.
> At 100 kHz bandwidth, the noise floor is -110 dBm.  The 30 MHz blip is
> clean
> enough to see the shape of the receive bandwidth filter.  (I'm assuming
> the
> raw signal is much narrower than 3 kHz.)
>
> I haven't figured out where it is coming from.  At first, I thought it was
> coming from low power do-it-yourself PCs.
>   https://www.mini-box.com/
> If I get near them, lots of spurs near 30 MHz come up out of the noise.
> But
> powering them off doesn't change the 30 MHz.
>
> The 30 MHz is clean.  I'm guessing it's the 3rd harmonic of 10 MHz.  I
> only
> have a few of them, but I don't like turning them off.  Or maybe the 2nd
> harmonic from the Lucent boxes.  ??
>
> The 10 MHz is stronger near coax carrying 10 MHz and next to a Z3801A.
> I'll
> have to try some good cables.  Anybody have a favorite source?  Is there a
> magic word?  Do I have to specify the type of coax?
>
> I have lots of Gigabit Ethernet.  I have a blob at 125 MHz, and spurs at
> 120
> MHz and 130 MHz.  120 has a little brother 18 kHz higher.
>
> The normal power up mode scans 0 to 350 MHz with enough attenuation so
> that
> most of my signals are lost in the noise.  Sometimes it comes up without
> the
> attenuation.  Then I can see all sorts of stuff.  The biggest ones are at
> 240
> and 288 MHz.
>
> I think there is a mode for overlaying displays.  I haven't investigated.
>
>
> Their web page has links to software to talk to it over the USB cable.  I
> haven't investigated.  Plugging in the USB cable adds lots of cruft.  The
> software would be unusable unless you are looking at a strong signal or at
> something in a hole that the cruft misses.  It might work if you can
> freeze
> the display, then plug in the USB cable to capture it.
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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Re: [time-nuts] PRS10 not locking to 1PPS

[Dana Whitlow]

Erik,

When I was working at my last (pre-retirement) job, I encountered an old
PRS-10
gathering dust.  It worked well free-running, but when I tried to lock it
to 1PPS,
it would do nothing for a while, then would begin deviating further and
further
from a correct lock.  Over a period of a few hours it would basically run
amok.

Dana


On Thu, Jan 7, 2021 at 10:10 AM  wrote:

> Hi All,
>
> I have done an experiment using the PSR10.
> I have set the Magnetic offset to mid-range MO2950
> Than set the Set frequency to 0 SF0. To have 0 frequency offset.
> Measured the output frequency and calculate the average deviation.
> By using the Frequency Synthesizer Table from Appendix A I have selected
> the
> smallest frequency deviation by changing via the Frequency Synthesizer
> Control command SP.
> Than measured the frequency deviation again and use the Set frequency
> command for
> the correction of the deviation (by SF). By monitoring the Magnetic read
> you
> are able to see
> the Magnetic C field effect from the SF setting. Than enter the Magnetic
> offset to the value of
> magnetic read via MO. Finally set the SF to 0.
> By this procedure the frequency deviation is < than a few parts to -12.
> And within the Magnetic offset range.
> However still the 1pps control is not working and stops the internal time
> interval.
> Maybe by corrupted eprom TO setting.
> But the unit is good for un-steered operation.
>
> Thanks for your help
>
> Erik (PE1RQF)
>
>
>
> -Original Message-
> From: time-nuts  On Behalf Of Dana
> Whitlow
> Sent: maandag 4 januari 2021 21:02
> To: Discussion of precise time and frequency measurement
> 
> Subject: Re: [time-nuts] PRS10 not locking to 1PPS
>
> Erik, the PRS-10 does have provisions for changing the internal
> synthesizer's "ratio",  which could provide a way of getting an essentially
> fresh start on aging.
> There's a
> big table of values somewhere in the documentation (but not necessarily in
> any convenient order).
>
> My old PRS-10 is getting towards one end of its magnetic tuning range and
> will probably "die" in another couple of years use, but I have high
> expectations of winning it back via this mechanism.
>
> Have you looked into this?
>
> Dana
>
>
> On Mon, Jan 4, 2021 at 1:36 PM  wrote:
>
> > Hi all,
> >
> > The PSR10 is working now for 15 years at my place (total >25 years).
> > For the 1pps a Trimble Resolution T is used and has a good 1pps signal.
> > The Magnetic Offset MO is on the limit value of 2300 when using the
> > 1pps correction.
> > Therefore I think the unit is on end of life. I tried a factory reset
> > to see what will happen.
> > However due to the change of the TO to 1814 the unit stopped measuring
> > the 1pps time pulses after 256 measurements and no 1pps measurement
> > are possible when PL=1.
> > The other values are responsive. Only after a RS1 it will measure
> > again the pps.
> > My thought was due to the strange TO of 1814 (before factory reset is
> > was
> > -1814)
> > the internal calculation is messed up.
> > When PL=0 the pps measurements continues but the MO is not controlled
> > to GPS.
> > I am not sure how to update the firmware.
> > While the unit is still stable, it has now an frequency offset of
> > -2.7E-10 Hz/Hz stability still is
> > 2.4E-12 for 20k seconds.
> > Probably I need another rubidium frequency standard.
> >
> > ST5 when PL=0
> > 3 = PPL disabled,  < 256 good 1pps inputs Provide stable 1pps inputs
> >
> > ST5 when PL=1 and when 1pps hangs
> > 4 = Excessive time interval (while 1pps is still good of the GPS)
> >
> > Regards,
> > Erik (PE1RQF)
> >
> >
> >
> >
> > -Original Message-
> > From: Miikka Raninen 
> > Sent: zondag 3 januari 2021 21:44
> > To: time-nuts@lists.febo.com
> > Cc: e.j.kr...@vathorstnet.nl
> > Subject: PRS10 not locking to 1PPS
> >
> > > Hello Time-Nuts,
> > >
> > > I am an user of a PRS10 Rubidium standard.
> > > The unit has firmware revision 3.15.
> > > After reset to factory settings the Time Offset (TO) was set to 1814.
> > > Normally it was -1814. Now de PRS10 is not locking to the 1PPS anymore.
> > > It will freeze when PL = 1. It will freeze after 256 seconds.
> > > Is there a known way to set the TO back to -1814 for the firmware
> > revision?
> > > As it is a factory setting for this firmware revision.
> > >
> > > Regards,
> > > Erik pe1RQF (former time keeper for the Netherlands at VSL)
> >
> >

Re: [time-nuts] PRS10 not locking to 1PPS

[Dana Whitlow]

Erik, the PRS-10 does have provisions for changing the internal
synthesizer's "ratio",
 which could provide a way of getting an essentially fresh start on aging.
There's a
big table of values somewhere in the documentation (but not necessarily in
any
convenient order).

My old PRS-10 is getting towards one end of its magnetic tuning range and
will probably
"die" in another couple of years use, but I have high expectations of
winning it back via
this mechanism.

Have you looked into this?

Dana


On Mon, Jan 4, 2021 at 1:36 PM  wrote:

> Hi all,
>
> The PSR10 is working now for 15 years at my place (total >25 years).
> For the 1pps a Trimble Resolution T is used and has a good 1pps signal.
> The Magnetic Offset MO is on the limit value of 2300 when using the 1pps
> correction.
> Therefore I think the unit is on end of life. I tried a factory reset to
> see what will happen.
> However due to the change of the TO to 1814 the unit stopped measuring the
> 1pps time pulses
> after 256 measurements and no 1pps measurement are possible when PL=1.
> The other values are responsive. Only after a RS1 it will measure again
> the pps.
> My thought was due to the strange TO of 1814 (before factory reset is was
> -1814)
> the internal calculation is messed up.
> When PL=0 the pps measurements continues but the MO is not controlled to
> GPS.
> I am not sure how to update the firmware.
> While the unit is still stable, it has now an frequency offset of -2.7E-10
> Hz/Hz stability still is
> 2.4E-12 for 20k seconds.
> Probably I need another rubidium frequency standard.
>
> ST5 when PL=0
> 3 = PPL disabled,  < 256 good 1pps inputs Provide stable 1pps inputs
>
> ST5 when PL=1 and when 1pps hangs
> 4 = Excessive time interval (while 1pps is still good of the GPS)
>
> Regards,
> Erik (PE1RQF)
>
>
>
>
> -Original Message-
> From: Miikka Raninen 
> Sent: zondag 3 januari 2021 21:44
> To: time-nuts@lists.febo.com
> Cc: e.j.kr...@vathorstnet.nl
> Subject: PRS10 not locking to 1PPS
>
> > Hello Time-Nuts,
> >
> > I am an user of a PRS10 Rubidium standard.
> > The unit has firmware revision 3.15.
> > After reset to factory settings the Time Offset (TO) was set to 1814.
> > Normally it was -1814. Now de PRS10 is not locking to the 1PPS anymore.
> > It will freeze when PL = 1. It will freeze after 256 seconds.
> > Is there a known way to set the TO back to -1814 for the firmware
> revision?
> > As it is a factory setting for this firmware revision.
> >
> > Regards,
> > Erik pe1RQF (former time keeper for the Netherlands at VSL)
>
> Ref manual for PRS10 :
> https://www.thinksrs.com/downloads/pdfs/manuals/PRS10m.pdf
>
> Check the quality of the input 1PPS. When the unit fails to lock on to
> 1PSS input after 256 seconds it is usually due to the 1PPS being too
> unstable in phase
>
> What do you mean by freezing? Can you check the status bytes with ST?
> command? They might indicate the reason for the fault :
>
> ST5: Frequency Lock to External 1pps
> ST5 bit Condition which sets bit Corrective Action
>
> 0 PLL disabled Send PL 1 to enable
> 1 < 256 good 1pps inputs Provide stable 1pps inputs
> 2 PLL active
> 3 > 256 bad 1pps inputs Provide stable 1pps inputs
> 4 Excessive time interval Provide accurate 1pps
> 5 PLL restarted Provide stable 1pps inputs
> 6 f control saturated Wait, check 1pps inputs
> 7 No 1pps input Provide 1pps input
>
> You might also want to consider updating the firmware as "(Note:
> Firmware revisions prior to Rev 3.23 do not allow user TO! commands.
> Check the firmware revision with the ID? command)"
>
> - Miikka Raninen OH3GPJ
>
>
> --
> This email has been checked for viruses by AVG.
> https://www.avg.com
>
>
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Re: [time-nuts] Rebroadcasting time signals [WAS: La Crosse Clocks - ]

[Dana Whitlow]

Hal, I just ordered a "TinySA", largely with leak tracking in mind.  I
won't have it until
about mid month (January), but have high hopes for it.  I'm planning to use
it with
a small single-turn electrostatically-shielded loop, which I believe will
yield adequate
sensitivity for the purpose while not picking up many legitimate signals
which would
just confuse the display (and me).

Dana   (K8YUM)


On Sat, Jan 2, 2021 at 6:08 PM Hal Murray  wrote:

> Bob kb8tq said:
> > If you can hear it on your radio with your normal antenna …. it’s
> leaking.
>
> Thanks.
>
> I don't have a radio that covers 10 MHz.
>
> Is there any particular brand/model of radio that people recommend for
> general
> time-nuts sort of hacking?  Or where do the radio-nuts hang out?
>
> Is there a sweet spot on the price/performance curve?  Or an old classic
> unit
> that everybody loves?
>
> I'm happy with used gear.  I'll spend several hundred dollars but not
> mortgage
> the house.
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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Re: [time-nuts] Rebroadcasting time signals [WAS: La Crosse Clocks - ]

[Dana Whitlow]

It just occurred to me that one of the TinySA's could be handy for tracking
down
leaks like this.

Dana


On Sun, Dec 27, 2020 at 8:02 AM Bob kb8tq  wrote:

> Hi
>
> If you can hear it on your radio with your normal antenna …. it’s leaking.
>
> If you want to track it down, normal radio frequency direction finding
> techniques
> work. At 10 MHz a loop or rod antenna is likely your best bet.
>
> Bob
>
> > On Dec 27, 2020, at 5:05 AM, Hal Murray  wrote:
> >
> >
> > csteinm...@yandex.com said:
> >> (I know whereof I speak -- I spent quite a lot of effort  a few years
> ago
> >> chasing down a leaking 10MHz reference of very dubious  quality in use
> by a
> >> local ham nearly a kilometer from me.)
> >
> > Could you say more?  What was the nature of the leak?  How did you track
> it
> > down?
> >
> > Is there a simple way that those of us who aren't radio-nuts can measure
> how
> > much our GPSDOs are leaking?
> >
> > There is also "leakage" from switching power supplies.
> >
> >
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
> >
> > ___
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Re: [time-nuts] Holiday Hydrogen Glow!

[Dana Whitlow]

It appears that the pink glow is reaching at least several inches from
the discharge region.  Am I correct in thinking that it stems from
recombination of electrons and protons into neutral atome?  And
regardless of the precise mechanism, do any significant number
of the glow-causing species make it through the state selector into
the storage bulb?  I'm wondering if one could peek into the microwave
cavity through a small aperture and see a glow from the storage bulb
itself.

Dana


On Fri, Dec 25, 2020 at 12:13 PM  wrote:

> And here is an EFOS2 Maser glow.
>
> Happy holidays, and Merry Christmas!
>
> Corby___
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Re: [time-nuts] TECs in cooling below ambient

[Dana Whitlow]

The optical sensing of despoint by dew-on-the-mirror was used in a device
designed
at the Whirlpool Research labs in St. Joseph, MI.  It apparently never made
it into
production, but a number of units were built and sold or given away (I'm
not sure).
I know about this because I interned at the lab during college summer
breaks, and
on one occasion I was asked to replace the Peltier (TEC) module in one of
these
units.  These units had a thermocouple buried under the cold mirror's
surface, and
use of the device required that the user provide the instrument to read the
thermo-
couple's temperature.

I've long wondered how this system dealt with the fact that the desired
operating
point of the loop is on a sharp corner of the light versus temperature
curve where
dew is just beginning to form, and there is no "negative dew" on the warm
side of
that point.  I hadn't thought of this complication when I was working with
this thing,
however, or I would have asked.  Oh, well, an opportunity missed.  Sigh!

Dana


On Wed, Dec 23, 2020 at 6:53 PM Bruce Griffiths 
wrote:

> You could always use a TEC as the heart of a dewpoint sensor by optically
> sensing the temperature required for dew to form on a cooled mirror.
> In practice the temperature at which the dew vanishes is typically used.
> A collimated light beam together with a photodiode is typically used to
> sense the presence of dew droplets on the mirror.
>
> Bruce
> > On 24 December 2020 at 08:57 ed breya  wrote:
> >
> >
> > This recent TEC talk reminded of some of my long term planned projects,
> > and related issues. I have at least four "someday" projects involving
> > TECs, to regulate device temperatures near or below "normal" room
> > temperature, including a high precision DC voltage standard, a sub-fA
> > electrometer circuit, a constant temperature block for nonlinear analog
> > computing elements, and a small general purpose heat/cool box for device
> > and circuit testing. Each has its own particular system, application,
> > and environment issues, but common to all is the lower limit of running
> > temperature, based on the local climate conditions and dew point. I plan
> > to estimate the lowest possible operating temperatures for expected
> > conditions, that avoids condensation, and not having to resort to
> > special packaging.
> >
> > An essential thing for this is a dew point calculator. I found lots
> > online, but this is my favorite so far. It's slider-based, so you don't
> > even have to enter numbers.
> >
> > http://www.dpcalc.org/
> >
> > The harder part is finding the normal range of local climate conditions.
> >
> > Ed
> >
> > ___
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Re: [time-nuts] SMPS or conventional?

[Dana Whitlow]

A properly-tuned PID system does not cycle!

Dana


On Mon, Dec 21, 2020 at 6:49 PM Bob kb8tq  wrote:

> Hi
>
> Finding a data sheet on a TEC that goes past *very* basic stuff is
> essentially
> impossible. The bottom line is that the people who make them very much
> want to sell them to you. Finding information in those data sheets that
> suggest
> problems … not so much.
>
> The problem is (mainly) physical. The expansion / contraction of the
> device is
> a big deal. KHz level PWM is (likely) not a problem. Aggressive cycling
> from
> something like a PID is indeed an issue.
>
> Bob
>
> > On Dec 21, 2020, at 6:43 PM, Hal Murray  wrote:
> >
> > [Old mail, context is TECs]
> >
> > bruce.griffi...@xtra.co.nz said:
> >> If the drive current ripple is too high fatigue failure from cyclic
> >> thermomechanical stress can be significant.
> >
> > Do good data sheets say anything about that?
> >
> > Is there a frequency term in there?  Can I use PWM, which is as much
> ripple as
> > you can get, as long as the frequency is high enough?  If yes, ballpark
> of how
> > high?
> >
> > Physically, where is the heat/cold generated?  Is it mostly at the
> junction?
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
> >
> > ___
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> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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Re: [time-nuts] HP105B Help

[Dana Whitlow]

If you're thinking it's the 10811, here's something to try:

Arrange to measure output frequency, and tune voltage, and put the curves up
on a dual-trace o'scope.  If the output frequency fluctuations correlate in
the
correct direction of the tune voltage fluctuations, then the problem is
probably
not in the 10811.  But if the tune voltage appears to be fighting the output
frequency variations, then it's most likely to be the 10811 (or perhaps
just its
power supply source) who's at fault.

Dana


On Sun, Dec 13, 2020 at 6:31 PM Bob kb8tq  wrote:

> Hi
>
> If the inside of the 105 went under water long enough to rust out a lot
> of parts on the boards, it’s a good bet that the 10811 in the unit got
> hit pretty hard as well.
>
> Simple answer: Spend $40 on an eBay replacement for the 10811.
> It should just plug in ….
>
> Bob
>
> > On Dec 13, 2020, at 5:15 PM, Dave Miller  wrote:
> >
> > I am in the middle of resurrecting a HP105B, It is one of the later
> models
> > with an 10811 in.
> >
> > I have fixed the obvious issues like the electrolytics that were missing
> > and other parts that had leads evaporated due to corrosion.
> >
> > The basics seem to work, A not bad looking sine wave etc.
> > But the ADEV numbers are terrible.
> > I am going back to make sure it's not a measurement setup issue. That is
> > good. Just tested another OCXO and the test setup is good.
> > Attached in a link to a .tim file
> > https://www.dropbox.com/s/zebwiqy913v7k0k/HP105B%20test.tim?dl=0
> > I am hoping one of the more knowledgeable folks might suggest where to
> > start looking.
> > I have checked all the other electrolytics and the ESR and capacitance
> > looks good. I think the power supply seemed clean.
> >
> > I have taken out the easy to get boards and cleaned card edges etc but
> this
> > persists.
> >
> > The saw tooth on the original phase is yelling something at me but I
> > don't have a clue.
> >
> > Thanks
> > Dave
> >
> > --
> > 72 de Dave
> > VE7HR
> > ___
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Re: [time-nuts] HP 5065 Rb update

[Dana Whitlow]

Rheostats are not necessarily stable because the current is 1st-order
dependent
on the contact resistance.

I had missed the part about the nearby lightning strike.  Could it be that
the mu-metal
shielding got partly magnetized by the high current pulse of the
lightning?  If so, there
ought to be some stability benefit from performing a degaussing operation.
If not
degaussed, the magnetization of the mu-metal will likely change over time
due to
physical knocks, changes in orientation of the Rb in the Earth's field,
temperature
changes, etc, all of which will make the Rb less stable than it could be.

Dana


On Mon, Dec 7, 2020 at 6:18 PM Bob kb8tq  wrote:

> Hi
>
> The existing c field winding is *inside* the magnetic shield on the
> physics package.
> Simply getting a second winding inside that package involves some (scary
> to most
> of us) tearing apart (an re-assembly) of the physics package.
>
> Next up, the mag field needs to be reasonably uniform. That means that the
> “new”
> winding needs to overlap pretty much all of the “old” winding. Again a bit
> of a chore.
>
> Finally, that “crude rheostat” circuit is pretty stable. The current needs
> to be stable into
> the << 100 ppm sort of range to keep the device happy. Ideally something
> that does
> a couple ppm ( 1 to 3ppm) would be the “best case” in terms of device
> stability.  Noise
> is (obviously) an issue as well.
>
> Since the sensitivity to mag field decreases with C Field current ( also
> with the assumption
> there is no stray field ….) there is a tradeoff between “tuning range” and
> required stability.
>
> One alternative is to brew up a fixed C field regulator board. Set the
> field to the lowest
> practical value using that board. Then tune the device by other means.
>
> Bob
>
> > On Dec 7, 2020, at 2:31 PM, Dana Whitlow  wrote:
> >
> > Paul,
> > Would it be feasible to add a smaller winding around the outside of
> > the existing C-field winding, and drive it from something other than
> > the crude rheostat circuit?  Then you could make finer adjustments
> > than the existing driver permits, and would rely only on the existing
> > driver to provide only a coarse tuning field.  Admittedly this would
> > still involve a "dangling pot", but now entirely on your own terms.
> >
> > Dana
> >
> >
> > On Mon, Dec 7, 2020 at 12:37 PM paul swed  wrote:
> >
> >> Ed
> >> Like you I don't like dangling pots either. But since I had the system
> open
> >> I took a look to see how hard that would be to accomplish. The pots on
> the
> >> digital counter and its actually quite small. The 3 leads all fit into
> an
> >> area about the size of a pencil eraser. To work on it requires removing
> the
> >> front panel. Decided to leave that alone. To risky.
> >> The systems all re-assembled stable and working about the way it always
> >> has. I did go with Bobs suggestion using a different synth count and the
> >> lower cfield current.
> >> Regards
> >> Paul.
> >> WB8TSL
> >>
> >> On Mon, Dec 7, 2020 at 1:12 PM ed breya  wrote:
> >>
> >>> OK, I see now what the circuit looks like, in the manual. The pot is
> >>> used in rheostat mode, so the specific value is needed, and it would
> >>> take some more modification of the circuit to increase the setting
> >>> resolution.
> >>>
> >>> I would recommend making a simple change to the existing pot hookup
> >>> though, which is to tie the "NC" end of the pot to the wiper - I have
> >>> this thing about not leaving dangling ends on pots used as variable
> >>> resistors. The most likely possible failure mode in a pot is an open or
> >>> intermittent wiper. In this circuit, if the wiper should open for some
> >>> reason, the circuit will go open-loop, and self-limit at around 13 mA
> >>> through the coil (or somewhat less if the coil's resistance is higher
> >>> than 700 ohms or so) - twice the normal maximum setting, or four times
> >>> the power dissipation. I don't know if this matters here, but for
> higher
> >>> reliability, tying that pot's loose end to the wiper will ensure that
> >>> this can't happen - the circuit will limit at the maximum of the normal
> >>> adjustment range.
> >>>
> >>> Ed
> >>>
> >>> ___
> >>> time-nuts mailing list -- time-nuts@lists.febo.com
> >>> To unsubscribe, go to
> >>> http://lists.febo.com/mailm

Re: [time-nuts] HP 5065 Rb update

[Dana Whitlow]

Paul,
Would it be feasible to add a smaller winding around the outside of
the existing C-field winding, and drive it from something other than
the crude rheostat circuit?  Then you could make finer adjustments
than the existing driver permits, and would rely only on the existing
driver to provide only a coarse tuning field.  Admittedly this would
still involve a "dangling pot", but now entirely on your own terms.

Dana


On Mon, Dec 7, 2020 at 12:37 PM paul swed  wrote:

> Ed
> Like you I don't like dangling pots either. But since I had the system open
> I took a look to see how hard that would be to accomplish. The pots on the
> digital counter and its actually quite small. The 3 leads all fit into an
> area about the size of a pencil eraser. To work on it requires removing the
> front panel. Decided to leave that alone. To risky.
> The systems all re-assembled stable and working about the way it always
> has. I did go with Bobs suggestion using a different synth count and the
> lower cfield current.
> Regards
> Paul.
> WB8TSL
>
> On Mon, Dec 7, 2020 at 1:12 PM ed breya  wrote:
>
> > OK, I see now what the circuit looks like, in the manual. The pot is
> > used in rheostat mode, so the specific value is needed, and it would
> > take some more modification of the circuit to increase the setting
> > resolution.
> >
> > I would recommend making a simple change to the existing pot hookup
> > though, which is to tie the "NC" end of the pot to the wiper - I have
> > this thing about not leaving dangling ends on pots used as variable
> > resistors. The most likely possible failure mode in a pot is an open or
> > intermittent wiper. In this circuit, if the wiper should open for some
> > reason, the circuit will go open-loop, and self-limit at around 13 mA
> > through the coil (or somewhat less if the coil's resistance is higher
> > than 700 ohms or so) - twice the normal maximum setting, or four times
> > the power dissipation. I don't know if this matters here, but for higher
> > reliability, tying that pot's loose end to the wiper will ensure that
> > this can't happen - the circuit will limit at the maximum of the normal
> > adjustment range.
> >
> > Ed
> >
> > ___
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> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
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Re: [time-nuts] HP5061 Cesium ion pump question

[Dana Whitlow]

I wonder if it might be good to power up the ion pump with the heaters
cold, then
after the ion current trails off to nil, begin operating the filaments at
very low voltage
(and all other voltages off except for the ion pump) and gradually ramp the
the filament
voltages up towards normal operating voltage, doing so slowly enough that
the ion
pump never trips off.  Then, once things have settled down at normal
filament voltage,
set up and fire up the whole instrument.  I think this might be easier on
both the filaments
and the ion pump.

Comments?

Dana


On Thu, Dec 3, 2020 at 8:34 PM  wrote:

> Thanks very much for this info Corby. It explains the behaviour of my spare
> 5061A perfectly.
>
> It also raises the question of what I could do with the spare tube I have.
> I
> can connect a +3500V supply to the ion pump but that won't do anything
> about
> any gas molecules adsorbed onto the filaments as you described. Is it worth
> powering up the filaments to get rid of them or can that be left for some
> indefinite time in the future when the tube could be reinstalled in a
> 5061A?
>
> Morris
>
> ---
> Date: Wed, 2 Dec 2020 11:06:22 -0800
> From: 
> To: time-nuts@lists.febo.com
> Subject: [time-nuts] HP5061 Cesium ion pump question
>
> The gettering in the tube is only for capturing any stray Cesium atoms
> that don't get caught in the main gettering patch. If the gettering fails
> or gets too loaded up then the Cesium background level will get too high
> causing poor SN.
>
> The ion pump is for any gases.
>
> When a tube is off for extended times any gas atoms lingering or leaking
> slowly into the tube than happen to impinge on either the mass
> Spectrometer filament or the Cs oven filaments get capture by the
> filaments. They function as excellent getters!  (this even if the ion
> pump is on)
>
> Now this is not by design but results in the filaments being "loaded"
> with the gas atoms.
>
> Then when you turn the tube on the filaments light up and expell a burst
> of gas.
>
> This of coarse causes the ion pump current to rise and trips off the
> filaments,
>
> Once the ion pump removes the burst the cycle repeats until the filaments
> have expelled the trapped gases.
>
> Then the ion pump can handle the load and pump the tube down completely.
>
> Cheers,
>
> Corby
>
>
> *
>
>
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Re: [time-nuts] L1/L2 survey antenna $125 new

[Dana Whitlow]

Some people would probably say that the alcoholized iced tea is more
effective.
Long Island Iced Tea IIRC.

I get along pretty well with ordinary Coca Cola, alternating between diet
and regular.
It doesn't have much odor, but it sure tastes a lot better than coffee!

BTW, I have a fair number of TNC(m) to SMA(f) adapters I "bought" on ebay
while
I lived in Oregon.  I was buying some BNC(m) to SMA(f) adapters, and the guy
mentioned that he also had the TNC version.  When I asked what he wanted for
the TNC version, he said he'd throw some in for free, and he did.  Anyway,
if you
ever need such a thing, let me know.

Cheers,

Dana


On Fri, Nov 13, 2020 at 7:22 PM Tom Holmes  wrote:

> Wow! I sure got that wrong! The picture definitely
> shows a female TNC with the normal pin
> configuration. Guess I need to drink stronger iced
> tea.
>
> Tom Holmes, N8ZM
>
> -Original Message-
> From: time-nuts 
> On Behalf Of Tom Holmes
> Sent: Friday, November 13, 2020 4:47 PM
> To: 'Discussion of precise time and frequency
> measurement' 
> Subject: Re: [time-nuts] L1/L2 survey antenna $125
> new
>
> Dana, it is a male TNC RP, which means reverse
> polarity. The center pins are reversed from the
> normal condition. Very commonly done on WiFi gear
> in the US due to some FCC paranoia about people
> hooking up amplifiers, which the aftermarket world
> immediately addressed. Ain't capitalism grand?!
>
> Tom Holmes, N8ZM
>
> -Original Message-
> From: time-nuts 
> On Behalf Of Dana Whitlow
> Sent: Friday, November 13, 2020 3:17 PM
> To: Discussion of precise time and frequency
> measurement 
> Subject: Re: [time-nuts] L1/L2 survey antenna $125
> new
>
> Thanks, Bob.  I zoomed in on the image that shows
> the connector without the
> cover,
> and it sure looks like a female connector to me
> (contradicting what the
> SparkFun
> description says).  I could not determine which
> handedness applies to the
> threads,
> however- not quite enough resolution in the photo.
>
> I'm inclined to suspect that this is in fact a
> standard TNC female
> connector.  What
> possible motive could an industry have for using a
> non-standard connector
> type
> except for meeting some silly FCC regulation
> (which clearly does not apply
> here).
>
> Dana
>
>
> On Fri, Nov 13, 2020 at 1:34 PM Robert LaJeunesse
> 
> wrote:
>
> > Just spotted this:
> https://www.sparkfun.com/products/17382
> >
> > Datasheet:
> >
> https://cdn.sparkfun.com/assets/6/e/a/9/2/BT-147_G
> NSS_Antenna_Datasheet.pdf
> >
> > Chokeplate design, 40dB LNA, TNC connector
> >
> > ___
> > time-nuts mailing list --
> time-nuts@lists.febo.com
> > To unsubscribe, go to
> >
> http://lists.febo.com/mailman/listinfo/time-nuts_l
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> > and follow the instructions there.
> >
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Re: [time-nuts] L1/L2 survey antenna $125 new

[Dana Whitlow]

I quote the description on the SparKfun page via the WIndows clipboard:

"Note: This antenna has a TNC Male RP connector found on nearly all
surveying antennas. We recommend a TNC Male RP to SMA adapter

or
cable when using with our GNSS receivers."

But the photo on the site appears to show a receptacle, not a pin, for the
center conductor, hence
a standard female configuration.  So unless the thread is left-handed,
which I really can't tell,
this is a standard (not RP)* female* connector.  That's my story and I'm
sticking to it!

Bob, are you by chance thinking of buying one of these?  If so, please let
us know which it
is right away when it arrives.

Dana


On Fri, Nov 13, 2020 at 1:34 PM Robert LaJeunesse 
wrote:

> Just spotted this: https://www.sparkfun.com/products/17382
>
> Datasheet:
> https://cdn.sparkfun.com/assets/6/e/a/9/2/BT-147_GNSS_Antenna_Datasheet.pdf
>
> Chokeplate design, 40dB LNA, TNC connector
>
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Re: [time-nuts] L1/L2 survey antenna $125 new

[Dana Whitlow]

Thanks, Bob.  I zoomed in on the image that shows the connector without the
cover,
and it sure looks like a female connector to me (contradicting what the
SparkFun
description says).  I could not determine which handedness applies to the
threads,
however- not quite enough resolution in the photo.

I'm inclined to suspect that this is in fact a standard TNC female
connector.  What
possible motive could an industry have for using a non-standard connector
type
except for meeting some silly FCC regulation (which clearly does not apply
here).

Dana


On Fri, Nov 13, 2020 at 1:34 PM Robert LaJeunesse 
wrote:

> Just spotted this: https://www.sparkfun.com/products/17382
>
> Datasheet:
> https://cdn.sparkfun.com/assets/6/e/a/9/2/BT-147_GNSS_Antenna_Datasheet.pdf
>
> Chokeplate design, 40dB LNA, TNC connector
>
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Re: [time-nuts] OCXO housings - Why copper and not iron/steel?

[Dana Whitlow]

And for the serious low-noise enthusiast, a side benefit of cooling to
cryogenic
temperatures like 15K or so is that the thermal conductivity of copper is
something
like 25X what it is at room temperature.

Dana


On Fri, Oct 30, 2020 at 9:11 PM Mark Sims  wrote:

>
> And (if I remember the numbers properly) Isotopically pure diamond has
> twice the thermal conductivity of natural diamond.  There are places that
> make diamond-like carbon thermal pads.  Also places that make actual
> diamond ones (which are not as expensive as you would think),
>
> -
>
> > Actually, diamond has five times better thermal conductivity than silver,
> so is the most conductive element, although graphene is suspected to be
> better still.
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Re: [time-nuts] ES100 Atomic Clock Receiver Back in Stock

[Dana Whitlow]

Just to be clear, is the ES-100 the receiver used in the Ultratomic clocks
made by Lacrosse?

Dana


On Thu, Oct 29, 2020 at 7:38 AM Ben Hall  wrote:

> Good morning all,
>
> Universal Solder is showing the ES-100 WWVB BPSK clock kits back in
> stock.  Just put me one on order.  :)
>
> <
> https://www.universal-solder.ca/product/canaduino-application-development-kit-with-everset-es100-mod-wwvb-bpsk-atomic-clock-receiver-module/
> >
>
> Thanks much and 73,
> ben, kd5byb
>
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Re: [time-nuts] power supply for Z3801

[Dana Whitlow]

For heaven's sake don't try to power equipment from a trickle charger.  The
thing may
be more like a current source than a voltage source.  Also it may not be
isolated from
the safety ground, which would rule out connecting several in series.

A good power supply is so crucial to happiness and long life (for your
equipment) that
the P.S. is the last thing you want to cut corners on.

Dana


On Wed, Oct 28, 2020 at 5:57 PM jimlux  wrote:

> The 48-ish volt power supply for my Z3801 gave up the ghost..
>
> What's the latest in off-the-shelf power supplies (external is fine,
> uncased is fine)?
>
> There were plenty of suggestions on the list a few years back, and I can
> pick one of those up, but hey, someone else might have walked this path
> before more recently.
>
> Or, should I go get 4 12V sealed lead acid, 4 12V wallwart trickle
> chargers and make a 48 Volt supply? (I can't imagine it would be cheaper
> than some Meanwell PS)
>
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Re: [time-nuts] SMPS or conventional?

[Dana Whitlow]

I prefer the use of non-switching power supplies, in part because I am
forced to use
indoor receiving antennas not very far from my equipment setup.  However,
one of my
Rb standards, an used L-Pro which I bought from another ham, came with a
SMPS
and I've never noted any particular problem.  So, my advice is: if you
have  SMPS
that you trust not to fail and blow up your Rb, first give it a try to see
what happens.

Regarding cooling of Rb standards:
Truly, the addition of a fixed-speed fan will reduce the thermal resistance
between
"ambient" temperature and the device being cooled.  However, said reduction
of
the thermal resistance shortens the thermal time constant, increasing the
responsivity
to ambient temperature variations.

I see two likely approaches to improving the situation:

a)  As has been mentioned several times, substantially increase the thermal
mass of
 the device being cooled, combined with fan cooling of the heatsink.  A
downside
 of this is that system warmup time may be increased enough to be
bothersome.

b)  Use a variable-speed fan controlled by a loop which strives to maintain
a constant
 temperature of the heatsink to which the device is attached once a
reasonable
 temperature (moderately above ambient yet still comfortable for the
device) is
 reached.

I believe that (b) is probably the more effective way to go.  If done well,
it could
provide superior frequency stability as well as the shortest warmup time.
However,
choice (b) adds to the system complexity hence risk of an expensive failure.

Dana




On Wed, Oct 21, 2020 at 7:46 AM Wannes Sels  wrote:

> There are conflicting requirements regarding temperature in Rb's:
>
> - For best performance, the rubidium and quartz oscillators must be kept at
> a high and stable temperature.
> - For reliability, the supporting electronics must be kept at a lower
> temperature.
>
> The heater takes care of the high temperature. The stability of the
> temperature can be improved by increasing the thermal mass, i.e. adding a
> block of aluminium or copper.
> The electronics can be kept cooler with a heatsink, and forced ventilation
> if needed.
>
> When you stick both the electronics and physics in a small package, this
> becomes more difficult. For the PRS-10 some form of heatsink is pretty much
> required to keep the electronics cool enough. Although I seem to remember
> reading somewhere that the "benchtop" heatsink they offer now is lighter
> than older units.
>
> If the room temperature is not stable enough, you might want to increase
> the size of the heatsink and add a fan. This reduces the temperature swing
> inside the unit, while still cooling the electronics, at the cost of
> increased power draw for the heater.
>
>
>
>
> On Wed, Oct 21, 2020 at 5:38 AM Hal Murray 
> wrote:
>
> >
> > > I spent a lot of years buying Rb’s and putting them on small heatsinks.
> > I
> > > always was disappointed in their reliability. That continued to be the
> > case
> > > up to the point that the baseplate temp’s got into the 40C region.  In
> my
> > > case, that took a fan ….
> >
> > How well did it work if the heat sink wasn't small?  What is your version
> > of
> > small?
> >
> > Do you have any data (or vague memories) of how much it helps to orient
> > the
> > heat sink so the fins are vertical so they encourage warm air to flow up
> > past
> > the fins?
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
> >
> > ___
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> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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> >
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Re: [time-nuts] WWVB Dephaser Question

[Dana Whitlow]

Direct IQ demodulation to zero-IF is indeed subject to problems from LO
leakage into the
mixers.  Said leakage will displace the center of the IQ plot away from the
origin, which
then requires correction later on, which is a pain to do well.

A pretty good way to deal with all this is to downconvert the 60 kHz to a
lower IF (say,
a few hundred Hz or maybe even a few kHz) in a conventional mixer, then
clean up
the garbage with an analog filter.  Next digitize the IF (now a quite slow
A/D will suffice),
then do quadrature demodulation to zero-IF in SW.  Once there, use the
ATAN2 function
to obtain phase in the time domain.  The catch is this: that 1st LO must be
right on, hence
phase locked, or else let it drift around a bit as it pleases and phase
lock the 2nd (SW)
LO to obtain the locked zero-IF.  This kind of stuff is pretty easy to do
if you are doing it
in post-processing from a recorded signal.  But I can see it getting rather
more involved
when one wants to do it in real time, something I've never tackled.  Good
luck!

Dana



On Fri, Oct 9, 2020 at 5:56 PM  wrote:

> Paul,
> I was seeing a -10 dBm on the SA when they enter high power mode at
> night. At low power they are only a couple of dB above the nearby noise
> makers. But that is at the output of the last stage of my receiver. The
> WWVB signal was about 10-15 dB above the noise makers in my work shop. I
> don't know what the actual WWVB signal level is and have no way to
> measure it. I estimate the ferrite antenna to be approx 20k ohm which
> doesn't match the 50 ohm input of the SA. Maybe feed the rod antenna
> into a single stage op amp with a gain of 1 to feed the SA would work
> give me a rough idea?? I previously said I had 1 mV of daytime signal
> according to the WWVB maps. But that was wrong. In my mind I was
> thinking 1000 uV when the maps show the 100 uV coverage area. So receive
> level during the day should be around 0.1 mV. I have PCB's on order that
> hopefully will improve the receiver performance.
>
> Bob,
> I'm still trying to figure out if a software or hardware solution is
> better. I've looked at the Costas loop and a PLL angle. But I run into
> the problem of the LO being on the same frequency as WWVB. Plus as Paul
> said the math is intimidating to me. Locking WWVB to a HF oscillator and
> dividing down to 10 kHz or so for the control voltage and I/Q
> demodulation may be an answer but involves more hardware.
>
> For a software solution I don't know exactly how to approach the task. I
> don't have any DSP software experience so that option is out. I haven't
> made a decision on the CPU yet. I will just use whatever it takes for
> the job, probably a STM32 part of some sort. I have a couple of STM32
> development boards I can use when I get to that point.
>
> Ray
>
>
>  Original Message 
> Subject: Re: [time-nuts] WWVB Dephaser Question
> From: Bob kb8tq 
> Date: Fri, October 09, 2020 12:23 pm
> To: Discussion of precise time and frequency measurement
> 
>
> Hi
>
> Since you need a MCU to decode the data, you might as well get
> things in there sooner rather than later. There are a number of MCU’s
> out there that have fast enough ADC’s to do the job. They do have
> limited
> dynamic range. You can go to one of the 24 bit converters and have
> a ton of dynamic range. It’s all up to you.
>
> Once it’s into the MCU, it’s just code :). Depending on how much cpu
>
> horsepower you have (and how much code you want to write) you can
> go more or less crazy …. PHK has some interesting tidbits on his web
> site. http://phk.freebsd.dk/AducLoran/AducLoran-0.0.pdf
> 
>
> Bob
>
>
> > On Oct 9, 2020, at 1:38 PM, rcb...@atcelectronics.com wrote:
> >
> > Paul, Bob,
> >
> > I am not using any commercial receiver. I am building everything from
> > scratch. The RF front end starts with a ferrite rod antenna feeding a
> > differential first op amp followed by 5 stages of op amp filtering and
> > amplification. When the last stage is fed to my spectrum analyzer
> > (through attenuators) the WWVB signal is clearly visible. I'm now trying
> > to figure out how to detect the phase shift so I can get the time data
> > for my CPU to process and send to a display.
> >
> > I already have a GPS based clock that I built so I thought the WWVB
> > phase clock would be an interesting project.
> >
> > Ray
> >
> >  Original Message 
> > Subject: Re: [time-nuts] WWVB Dephaser Question
> > From: Bob kb8tq 
> > Date: Fri, October 09, 2020 7:35 am
> > To: Discussion of precise time and frequency measurement
> > 
> >
> > Hi
> >
> > At least to me, anything dimensioned in the 100’s of feet is
> > “massive” compared to
> > the rod antennas normally seen in WWVB use ….
> >
> > The other point being that if the antenna is some sort of large loop,
> > it’s going to be
> > a good long ways away from the receiver. You get both a larger signal
> > voltage and better
> > isolation …..

Re: [time-nuts] Help needed with frequency standard

[Dana Whitlow]

Mark:

I don't have a PPS syncable PRS-10 yet, but will probably be getting one
within a
year or so.  My expectations are not great, however, because I already know
that
the received GPS time has diurnal wiggles to the tune of up to 10's of nsec
p-p.
And I also know that the PRS-10 (and probably all others in its price
class) make
seemingly random frequency "adjustments" on a time scale of just a few
hours.
For a GPS disciplining loop to fix both, it would have to have a loop time
constant
long compared to a day on the one hand, yet a loop time constant of well
under a
day on the other.  It's kind of tough to have one loop with both properties
at once.

Dana


On Tue, Sep 29, 2020 at 1:22 PM Mark Spencer 
wrote:

> I would be curious to hear from those who have a GPS disciplined PRS 10 in
> their home time labs.   I was never that impressed with the performance of
> one of mine in that configuration from a 10 MHz ADEV perspective (I did try
> making a few parameter changes.) I ended up essentially free running mine
> but would occasionally apply a 1pps signal to mine as means of adjusting
> its output frequency on an as needed basis.
>
> I may try this again with a different PRS10 (the 1pps output on the unit
> in question failed a few years ago but I have a spare that has been
> recently put into service.)   Perhaps the second unit will work better.
>  Both units were obtained via the usual auction site.
>
> Mark Spencer
> m...@alignedsolutions.com
> 604 762 4099
>
> > On Sep 29, 2020, at 8:02 AM, Luiz Alberto Saba 
> wrote:
> >
> > Hi guys
> >
> >
> > I want a stable & reliable frequency standard.
> >
> > I do NOT have a cesium beam.
> >
> > I DO have a lot of gpsdos and some rubidiums.
> >
> > Since I have one PRS-10 and this device has a 1 pps input, you already
> know what I'm thinking...
> >
> > What I have:
> >
> > Trimble Thunderbolt
> >
> > Trimble UCCM
> >
> > Symmetricom UCCM
> >
> > Samsung UCCM
> >
> > HP 58503A
> >
> > TruePosition
> >
> > Oscilloquartz Star 4+
> >
> > and a little board with a ublox LEA 5T and 1 pps output.
> >
> > Which device is more suitable for disciplining the PRS-10?
> >
> > My gps antenna setup is:
> >
> > Symmetricom 58532A on the top of the water tank of my building with a
> very good sky view.
> >
> > A Raven Industries LA-21-1575-100-T. About 50 m of RG6.
> >
> > A Symmetricom antenna distributor (don't remember the code but is the 4
> outputs one)
> >
> > By the way... Someone knows the delay of the inline amplifier and the
> antenna distributor? (for Lady Heather)
> >
> > Mark Sims is out there reading this list? I'm having problems with LH
> 6.14 and the UCCM units.
> >
> > Any help you can give me will be welcomed.
> >
> >
> > Thanks
> >
> >
> > Luiz Alberto Saba
> >
> > from Santos - São Paulo - Brazil
> >
> >
> >
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Re: [time-nuts] Chelsea Chronoquartz dividers

[Dana Whitlow]

It may be that he's looking for info on how to drive the stepper motor(s),
such as
pulse sequences etc.

Dana


On Fri, Sep 11, 2020 at 2:59 PM Graham / KE9H  wrote:

> 2^22 = 4,194,304
> So divide by two, 22 times in a row to get to 1 Hz.
> --- Graham
>
>
> On Fri, Sep 11, 2020 at 12:42 PM Bill S  wrote:
>
> > A friend has acquired a Chelsea Clock Company Chronoquartz which was
> > probably made in the 70's. He has measured the oscillator frequency at
> > approximately 4.194304 MHz. He wanted to know what arrangement of
> > dividers they used to run the 4 pole stepper motor to step seconds.
> > Anybody know?
> >
> > Thanks,
> >
> > Bill_S
> >
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Re: [time-nuts] LPRO 101 heat sink question

[Dana Whitlow]

That's what I did with my LPRO, and it seems to be happy- I've been using
it for a
couple of years now with no apparent difficulty.

Dana


On Thu, Sep 10, 2020 at 9:29 AM Jim Harman  wrote:

> I recently purchased an LPRO rubidium from the auction site. The mounting
> surface is covered with a thin soft, dry light blue material with a sheet
> of brownish plastic film underneath. I assume this is the remains of an
> adhesive thermal pad.
>
> Should I peel this off and expose the bare metal mounting surface before
> attaching the LPRO to an appropriate heat sink? After removing the pad, can
> I use ordinary thermal grease between the LPRO and the heat sink?
>
> Thanks for any advice.
>
> --
>
> --Jim Harman
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