Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

[Dana Whitlow]

I don't know of any particular reason why a DVD-player laser should be
faster,
since neither CD nor DVD players need to deliberately modulate the lasers
anyway.  At least, that's the first blush answer.

However, these diode lasers are generally noisy, apparently due to the
inevitable presence of optical reflections back into the diodes.  I once
read that deliberately FM'ing the laser by applying a high frequency RF
tone along with the DC bias current could be helpful in mitigating the
problem.  But this was in connection with the *analog* Laser Disk video
recording format.  I don't know if the laser noise was ever much of a
problem
with reading the digital formats of CDs and DVDs.  If not, then surely the
makers of diodes for these mass market applications would not be investing
effort in making the lasers fast.

On additional factor is that CD players and DVD players use different light
wavelengths: ~780 nm for CDs, ~650 nm for DVDs.  It might be that the
difference in semiconductor composition between the two types makes
a significant difference in the response speed.  However, I doubt that this
would would be relevant for present purposes, unless Rb also has some
*useful* transitions in the 650 nm regime.

Dana


On Thu, Jun 14, 2018 at 11:25 PM, Hal Murray 
wrote:

>
> k8yumdoo...@gmail.com said:
> > I've been told that CD player type diodes can be successfully modulated
> up to
> > about 600 MHz, but that going much further is either difficult or perhaps
> > impossible.
>
> Are DVD lasers faster?
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

[Dana Whitlow]

I've been told that CD player type diodes can be successfully modulated
up to about 600 MHz, but that going much further is either difficult or
perhaps impossible.  This came from a guy (at Tektronix) who worked with
various types
of diode lasers a lot, back in the 1980's.  But at least they are cheap.  I
suspect that the leaded
package is a significant part of the issue; this ought to be somewhat
mitigated
by a suitable RF matching network.

Dana


On Thu, Jun 14, 2018 at 10:51 AM, Attila Kinali  wrote:

> On Mon, 11 Jun 2018 22:29:42 +0800
> mimitech mimitech  wrote:
>
> > I think your information is very interesting. I didn't realize which type
> > of common LDs can do GHz level modulation (anyway I didn’t have much
> > knowledge on laser diode before).
>
> Hehe. Same here. When I looked into CPT I thought that one needs
> a fast laser diode as well. Then, a few years ago, I had the chance
> to talk to John Kitching who corrected a few of my assumptions.
>
> > It would be great If you could recommend
> > several good Laser diodes (which vendor/part number) with possible 1-2GHz
> > modulation bandwidth. Thanks!
>
> Sorry, unfortunately I do not have any reliable data on the bandwidth
> of standard laser diodes. The easiest would be probably if you select
> some diodes that you can easily acquire, then contact the manufacturer.
> Manufacturers almost always have more data on their devices than they
> put into the datasheet. They do not include it because they can either
> not sufficiently control those parameters during production, cannot
> test for it or testing would be too expensive.
>
> Attila Kinali
>
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
>  -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Spectracom 8140T Line Tap Schematic

[Dana Whitlow]

Hi Bob & Julien,

Why bother with the short on the downstream end of that DC-blocking
attenuator?  At 10 MHz I'd expect
leakage radiation to be negligible.

Dana

On Thu, Jun 14, 2018 at 10:43 AM, Bob kb8tq  wrote:

> Hi
>
> > On Jun 14, 2018, at 9:31 AM, gandalfg8--- via time-nuts <
> time-nuts@febo.com> wrote:
> >
> >
> > Hi Julien,
> >
> >
> >
> > Earlier replies that discussed removing the DC supply from the 8140
> outputs gave me the impression your requirement was to connect directly the
> outputs of the 8140 without line tap modules, which is what I was
> addressing with my recent suggestion of a series capacitor, but can see now
> that's not the case.
> >
> >
> >
> > If you were to build your own termination the same principle would still
> apply of course but perhaps another option for a reasonably compact
> solution, aside from a coaxial DC block followed by a 50 ohm termination,
> might be a DC blocking attenuator followed by a BNC shorting dust cap, as
> the latter are generally quite small.
> >
> >
> > For example, current Ebay item 332461304064 is a DC blocked 20dB
> attenuator, they are also available in pairs at a slight discount, and that
> fitted with a shorting cap would give you a return loss of 40dB, which is
> probably as good as you'd get from most 50 ohm terminations anyway and
> would save having to build your own.
>
>
> I would be very surprised if the original terminations did any better than
> 20 to 30 db return loss. They are not fancy devices.
> I’ve also seen a lot of attenuators that only make it to about 20 db of
> return loss …..
>
> Bob
>
>
> >
> >
> > The VersaTaps phase lock an internal crystal, any frequency between 4
> and 20MHz, to the 10MHz input and then provide an output at the crystal
> frequency or the crystal frequency divided by a fixed integer between 1 and
> 8,192, so in that sense yes they're a synthesiser but the few I've seen
> were still supplied preset for a specific frequency.
> >
> >
> > However, "versatile" does not necessarilly mean quick or convenient to
> reprogram.
> > Aside from perhaps needing  to change the crystal the division ratio
> needs to be set by adding or removing links across pairs of holes in the
> circuit board. Those holes are on a standard 0.1inch pitch so fitting
> headers that would take shorting links should be straightfoward enough, and
> I suspect what was originally intended, but the units I have were supplied
> preprogrammed using resistor style wire ended zero ohm links mounted above
> the circuit board and soldered from below. Reprogramming one of these would
> involve unsoldering and perhaps removing all the connectors etc in order to
> remove the circuit board, so I'd certainly make darn sure they had headers
> fitted before being returned to the box!
> >
> >
> >
> > Nigel, GM8PZR
> >
> >
> >
> >
> >
> >
> > -Original Message-
> > From: Julien Goodwin 
> > To: gandalfg8 ; Discussion of precise time and
> frequency measurement 
> > Sent: Thu, 14 Jun 2018 11:36
> > Subject: Re: [time-nuts] Spectracom 8140T Line Tap Schematic
> >
> > I'm somewhat tempted to take the schematic and see if I can fit it in
> > the comparatively tiny Pomona boxes, although I have far too many side
> > projects already, enough 10MHz taps, and I still need to do the
> terminators.
> >
> > The VersaTaps are supposed to be an actual synthesizer IIRC.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
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Re: [time-nuts] Casio Wave Ceptor wrist watch - quick accuracy test

[Dana Whitlow]

I should have mentioned that my Casio (module 3405) is a G-Shock "diving
watch" with a 20-bar
(~200m depth) rating.   In so far as possible, I never take it off my wrist
(TSA check points being the
occasional exception), and don't want any leak problems even though I never
dive.

I once bought a watch rated at 20m, and it only lasted about a month before
it leaked.  Apparently
normal living stresses are equivalent to diving to moderate to substantial
depths.

Dana


On Mon, Jun 11, 2018 at 2:44 PM, David G. McGaw  wrote:

> I think you guys won the luck of the draw.  I have had a Casio WV200DA-1AV
> Wave Ceptor for a while, module 3140.  Nice watch, but it gains about 1/2
> sec per day when not synchronized.  I recently got a Casio GW-M5610
> G-Shock, module 3153.  I have not run it unsychronized, so have not checked
> its drift, but other G-Shocks have been quite good.  It is the higher-end
> line with tighter specs and they actually have a trimmer inside.
>
> David N1HAC
>
>
>
> On 6/11/18 6:30 AM, Dana Whitlow wrote:
>
>> I bought a Casio 'atomic watch" about 3 months ago, one which uses the
>> '3405' module.
>> I've also been running checks with radio setting turned off, and mine is
>> coming in at
>> just under 1 sec per month, based on seeing how long it takes to drift one
>> second.
>>
>> But I find that visual/aural coordination is a poor way to do business- if
>> the error is near
>> zero (or an integer number of seconds), my eye/ear/brain will shift to
>> make
>> it look like
>> it's "right on" within a few seconds even if the initial look says it's a
>> little bit off.
>>
>> I hadn't thought of the video approach- sure wish I had a means to record
>> video and
>> then view it frame by frame.
>>
>> Dana
>>
>>
>> On Mon, Jun 11, 2018 at 3:20 AM, Esa Heikkinen  wrote:
>>
>> Hi!
>>>
>>> There seems to be some kind of comeback going on with 80's style digital
>>> watches. You may find replicas of some 80's models or even re-makes of
>>> the
>>> original models from original manufacturer.
>>>
>>> So I decided to get one. As a time-nut my primary goal was to have radio
>>> controlled 'atomic' model. So I ended up to Casio Wave Ceptor
>>> WV-59DE-1AVEF. There's many models available from basic digital models
>>> like
>>> this to very nice ones with with full titanium body (analog style). But
>>> because of the 80's is hot it had to be digital...
>>>
>>> Wave Ceptors suport all time signals formats (US, UK/German and Japan)
>>> and
>>> correct standard is automatically selected when home city is set.
>>>
>>> One of the first things to do was to test the accuracy with radio
>>> syncronization turned off. Correct time was fist set with DCF77. Then I
>>> switched off the synconization. After beign about three days off there
>>> was
>>> no significiant visible error on time. In the video we can see however
>>> about one frame error, which means about 40 milliseconds. Still that's
>>> pretty good result for wrist watch. Also, the syncronization will occur
>>> once per day when the reception is good.
>>>
>>> So the watch must be at least calibrated in the factory. Don't know if
>>> the
>>> watch performs any kind of self-calibration according to radio
>>> syncronization results, most likely not - but it would be technically
>>> possible.
>>>
>>> So far so good, it's accurate enough - at least as new. When
>>> syncronization is turned on, there should never be visible error on time.
>>>
>>> Here's my test video:
>>> https://na01.safelinks.protection.outlook.com/?url=https%3A%
>>> 2F%2Fwww.youtube.com%2Fwatch%3Fv%3D_A23buFeHd0=02%
>>> 7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7Ca8e76ed2d4b54ed75dce0
>>> 8d5cf866ee5%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C636
>>> 643098739784325=EH0F8vRQK0jmROrREGrD9jDMcd2JQglutxZO%
>>> 2BVff7t0%3D=0
>>>
>>> --
>>> 73s!
>>> Esa
>>> OH4KJU
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to https://na01.safelinks.protect
>>> ion.outlook.com/?url=https%3A%2F%2Fwww.febo.com%2Fcgi-bin%
>>> 2Fm=02%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7Ca8e76e
>>> d2d4b54ed75dce08d5cf866ee5%7C995b093648d640e5a31ebf689ec9446
>>> f%7C0%7C0%7C636643098739784325=1oe%2FezDZCqH7LxIeCJqwc
>>> CwW3wcduBUL8fB2hmcYGTg%3D=0
>>>

Re: [time-nuts] where can I purchase 794.7 nm VCSEL for building CPT rubidium clock?

[Dana Whitlow]

I should have written more clearly- the adhesive in question was *not* in
the optical path.

As is usual, variations are possible, one supposedly being that the crystal
that lases
at 1064 nm is also doped with something to make it nonlinear (so I've
read).  I kind of
have my doubts over this, however it seems like asking too much of a single
substance to do "double" duty without some unwanted compromises.

Dana


On Mon, Jun 11, 2018 at 6:06 AM, Bruce Griffiths  wrote:

> The better ones use optically contacted crystals to avoid browning of the
> adhesive due to the high power densities of the 1064nm laser required for
> efficient frequency doubling.
>
> Brue
> > On 11 June 2018 at 22:52 Dana Whitlow  wrote:
> >
> >
> > Mark's description about how (most) green laser pointers work The better
> is a bit in
> > error, and is perhaps
> > over-simplified- the reality is actually more fascinating yet:
> >
> > First a diode laser operating at around 808 or 809 nm is used to
> optically
> > pump a solid
> > state laser which generates light at 1064 nm.  This light is then
> frequency
> > doubled with an
> > intra-cavity nonlinear element to produce the final  output at 532 nm.
> >  For all this to work
> > the optical elements must be critically aligned, and to me the most
> amazing
> > thing about
> > the low selling price is how this alignment is effected so cheaply.  One
> of
> > these units I've
> > opened up has the doubler crystal held down by a lump of cement on one
> > side- it looks
> > for all the world like it must have pushed into alignment and "held"
> there
> > while the cement
> > was cured.  Green pointers made in this way are characterized by quite
> good
> > beam quality
> > and very little wavelength spread from unit to unit. However, they are
> > generally quite
> > delicate and ruined by mechanical shock.
> >
> > Although not commonly known, at least one outfit (Z-Bolt) is now selling
> > "direct diode"
> > green pointers, where there is just one laser which emits directly in the
> > green, at around
> > 515-530 nm.   These are much more robust, operate well over a wider
> > temperature range,
> > but have the usual poor beam quality (non-circular beam with some
> residual
> > astigmatism)
> > characteristic of diode lasers made with simple collimating optics.  And,
> > the output
> > wavelength spread from unit to unit is quite large.
> >
> > Dana
> >
> >
> > On Mon, Jun 11, 2018 at 2:43 AM, Mark Sims  wrote:
> >
> > > Well, no.  Green laser pointers convert a rather high power 800 nm
> laser
> > > to 1600 nm in one crystal then divide it to 533 nm in another one.
>  The
> > > physics and manufacturing of them is best described as black magic.
> They
> > > are cheap because China developed the process to grow the crystals in
> bulk
> > > and crank out zillions of them for consumer products.
> > >
> > > I suspect that a 1600-ish nm to 800-ish nm converter is not a stock
> > > consumer-quantity device and will cost a pretty penny or two... like a
> > > red/IR laser diode can be had for 50 cents and a telecom VCSEL diode
> can be
> > > $500.
> > >
> > > --
> > >
> > > > It cannot be too much, given the fact that these are used in
> > > green laser pointers.
> > > ___
> > > time-nuts mailing list -- time-nuts@febo.com
> > > To unsubscribe, go to https://www.febo.com/cgi-bin/
> > > mailman/listinfo/time-nuts
> > > and follow the instructions there.
> > >
> > ___
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> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
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Re: [time-nuts] where can I purchase 794.7 nm VCSEL for building CPT rubidium clock?

[Dana Whitlow]

Mark's description about how (most) green laser pointers work is a bit in
error, and is perhaps
over-simplified- the reality is actually more fascinating yet:

First a diode laser operating at around 808 or 809 nm is used to optically
pump a solid
state laser which generates light at 1064 nm.  This light is then frequency
doubled with an
intra-cavity nonlinear element to produce the final  output at 532 nm.
 For all this to work
the optical elements must be critically aligned, and to me the most amazing
thing about
the low selling price is how this alignment is effected so cheaply.  One of
these units I've
opened up has the doubler crystal held down by a lump of cement on one
side- it looks
for all the world like it must have pushed into alignment and "held" there
while the cement
was cured.  Green pointers made in this way are characterized by quite good
beam quality
and very little wavelength spread from unit to unit. However, they are
generally quite
delicate and ruined by mechanical shock.

Although not commonly known, at least one outfit (Z-Bolt) is now selling
"direct diode"
green pointers, where there is just one laser which emits directly in the
green, at around
515-530 nm.   These are much more robust, operate well over a wider
temperature range,
but have the usual poor beam quality (non-circular beam with some residual
astigmatism)
characteristic of diode lasers made with simple collimating optics.  And,
the output
wavelength spread from unit to unit is quite large.

Dana


On Mon, Jun 11, 2018 at 2:43 AM, Mark Sims  wrote:

> Well, no.  Green laser pointers convert a rather high power 800 nm laser
> to 1600 nm in one crystal then divide it to 533 nm in another one.   The
> physics and manufacturing of them is best described as black magic.  They
> are cheap because China developed the process to grow the crystals in bulk
> and crank out zillions of them for consumer products.
>
> I suspect that a 1600-ish nm to 800-ish nm converter is not a stock
> consumer-quantity device and will cost a pretty penny or two... like a
> red/IR laser diode can be had for 50 cents and a telecom VCSEL diode can be
> $500.
>
> --
>
> > It cannot be too much, given the fact that these are used in
> green laser pointers.
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
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>
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Re: [time-nuts] Casio Wave Ceptor wrist watch - quick accuracy test

[Dana Whitlow]

I bought a Casio 'atomic watch" about 3 months ago, one which uses the
'3405' module.
I've also been running checks with radio setting turned off, and mine is
coming in at
just under 1 sec per month, based on seeing how long it takes to drift one
second.

But I find that visual/aural coordination is a poor way to do business- if
the error is near
zero (or an integer number of seconds), my eye/ear/brain will shift to make
it look like
it's "right on" within a few seconds even if the initial look says it's a
little bit off.

I hadn't thought of the video approach- sure wish I had a means to record
video and
then view it frame by frame.

Dana


On Mon, Jun 11, 2018 at 3:20 AM, Esa Heikkinen  wrote:

> Hi!
>
> There seems to be some kind of comeback going on with 80's style digital
> watches. You may find replicas of some 80's models or even re-makes of the
> original models from original manufacturer.
>
> So I decided to get one. As a time-nut my primary goal was to have radio
> controlled 'atomic' model. So I ended up to Casio Wave Ceptor
> WV-59DE-1AVEF. There's many models available from basic digital models like
> this to very nice ones with with full titanium body (analog style). But
> because of the 80's is hot it had to be digital...
>
> Wave Ceptors suport all time signals formats (US, UK/German and Japan) and
> correct standard is automatically selected when home city is set.
>
> One of the first things to do was to test the accuracy with radio
> syncronization turned off. Correct time was fist set with DCF77. Then I
> switched off the synconization. After beign about three days off there was
> no significiant visible error on time. In the video we can see however
> about one frame error, which means about 40 milliseconds. Still that's
> pretty good result for wrist watch. Also, the syncronization will occur
> once per day when the reception is good.
>
> So the watch must be at least calibrated in the factory. Don't know if the
> watch performs any kind of self-calibration according to radio
> syncronization results, most likely not - but it would be technically
> possible.
>
> So far so good, it's accurate enough - at least as new. When
> syncronization is turned on, there should never be visible error on time.
>
> Here's my test video:
> https://www.youtube.com/watch?v=_A23buFeHd0
>
> --
> 73s!
> Esa
> OH4KJU
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/m
> ailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?

[Dana Whitlow]

What is an 'FRK'?

Thanks,

Dana


On Sat, Jun 9, 2018 at 7:51 AM, ew via time-nuts  wrote:

> Having followed the conversation and having looked at the p[possibility
> using a FRK with laser diode, it is low on our list because of all the
> ongoing projects but please if you want to spend time and money use any
> thing but a FE5680. I was one of the first using it and noticed and posted
> a 4 Hz constant deviation using my Tracor 527 E subsequent confirmed by the
> attached. Do not have info as to who posted it.
> Using a FRK is the easiest way to do so if interested contact me off list,
> based on our tests is a close second to the HP 5065A.
> Bert Kehren
>
> In a message dated 6/9/2018 7:23:45 AM Eastern Standard Time,
> bruce.griffi...@xtra.co.nz writes:
>
>
>  Theres also
>
> http://www.photonics.philips.com/application-areas/sensing/components
>
> and
>
> https://www.sacher-laser.com/home/industriallasers/point_
> and_line_laser_module/industrial_laser_modules/micron_laser.html
> Bruce
> > On 09 June 2018 at 20:54 mimitech mimitech  wrote:
> >
> >
> > Thanks Attila for your suggestion.
> >
> > I prefer the 780/795nm VCSEL scheme for its simplicity. After some
> > searching, looks like the 780nm VCSELs are also not easy to source,
> > although other types of 780nm LD are common.
> >
> > I have purchased small amount of Vixar P/N “795S--BC01” 795nm single
> > mode VCSEL from a local distributor, price is about $500/pcs. I'm not
> sure
> > whether this model could work in CPT rubidium clock.
> >
> > A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
> > VCSEL, with unit price $800, which was proved to work as this paper
> > "A compact atomic magnetometer for cubesats",
> > https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_
> 0017N_11402.pdf
> > ,
> >
> > this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
> > Trapping (CPT) in Rubidium"
> > http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_
> Thesis_with_papers_V7.pdf
> >
> > and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
> > series. The cheapest model is SA.31m priced about $1100 at Digikey /
> > Mouser.
> >
> > Another paper "VCSEL Laser System for Atomic Clocks"
> > http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
> > several VCSEL from different vendors and found the ULM 794.7 nm single
> mode
> > VCSEL can work.
> >
> > Thanks.
> >
> > mimitech.
> >
> >
> > On Tue, 5 Jun 2018 11:11:59 +0200, Attila Kinali 
> wrote:
> > >
> > > On Mon, 4 Jun 2018 21:31:56 +0800
> > > mimitech mimitech  wrote:
> > >
> > > > I'm planning to build a CPT (coherent-population-trapping) rubidium
> > clock
> > > > as my next hobby project. The main purpose is to learn the principles
> > > > behind CPT rubidium clock, and hopefully got similar or better
> > performance
> > > > than commercial miniature rubidium clock such as FE-5680A.
> > >
> > > Building a CPT clock is slightly more involved than you might think
> > > at first. The laser diode is only one part of it. You will most likely
> > > be able to improve on the short-term stability of the FE-5680 (which
> > > is rather poor). But I doubt you will be able to improve much on
> > > the long term stability, which is where things actually become
> > interesting,
> > > if you use a naive approach.
> > >
> > > Nevertheless, I have not seen many 794/795nm diodes around. The only
> > > one that I have the datasheet of is the one from Vixar.
> > > You might want want to consider going for the D2 line instead of the
> > > D1 line, as 780nm diodes are more commonly available than 795nm. You
> will
> > > also need to buy several of those and select the ones that come closest
> > > to the wavelength at the desired opearating conditions (usuall spread
> > > is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
> > > temperature and current (rule of thumb is that you get about 10GHz
> > > per °C and mA). If you need more tuning range, you will need to add an
> > > external cavity (can give you up to 5nm range), which then needs to be
> > > tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
> > >
> > > Alternatively, you can get two S1-0780-XXX from Sacher Laser
> > > (cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical
> PLL).
> > > If you have enough money to spend, I'd go for two Cateye diode laser
> CEL's
> > > from Moglabs (cost AFAIK 5000€ each)
> > >
> > > No matter what you choose, you will need some wavelength stabilization
> > > scheme. You can either do that with the vapor cell itself or use
> > > an additional cell and do a DVALL or a saturated absorption locking.
> > > Note that this addtional cell will need to be without buffer gas.
> > > An external cell will offer better stability and thus lower noise,
> > > which directly translates into higher stability.
> > >
> > > As polarisation scheme, I suggest using σ+/σ- as it seems to be more
> > > robust than the 

Re: [time-nuts] Terminators on empty outputs/connectors

[Dana Whitlow]

I recommend putting terminators on unused ports, on general principles.
But I don't
think it would ordinarily be necessary to use big-bucks terms, unless the
distro amp is
really cheaply made.

If you have access to a VNA, it would be interesting to measure the complex
transmission
coefficient from input to one of the output ports while experimenting with
variations of
the number and locations of terminations for the other output ports.  If
you find that none
of such manipulations have any visible effect, then you can probably skip
using terms
on unused ports.  I should mention that any such measurements should best
be performed
at roughly the intended operating RF power level.

And for extra credit, report your findings to this discussion group.

Dana


On Thu, May 24, 2018 at 3:41 AM, Clay Autery  wrote:

> Putting in a hardware order...
>
> Question:  Is it recommended to put terminators on all unused GPS Distro
> amp ports?  Output ports on GPSDO and NTP servers (10MHz and PPS).
>
> Thanks!
>
> --
> __
> Clay Autery
> MONTAC Enterprises
> (318) 518-1389
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/m
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Re: [time-nuts] Cesium Clock Avialable

[Dana Whitlow]

Don't Cesium clocks have a beam current integrator of sorts so that it's
possible
to pretty accurately assess the remaining life of the tube?  If not, I'm
terribly
surprised and disappointed.

Also, beginning with a new tube, roughly how long can one be run until it
reaches exhaustion?  Are we speaking months, years, decades, or what?

Dana


On Sat, May 19, 2018 at 10:01 AM, Bob kb8tq  wrote:

> Hi
>
> Unfortunately there really is no way to tell how much Cs is left in the
> tube. You can
> look at beam current and make a guess. All that really will tell you is
> that the fuel
> gauge is on empty or at least just off of empty.
>
> Bob
>
> > On May 19, 2018, at 2:30 AM, Paul Bicknell 
> wrote:
> >
> > Hi Doug
> >
> > Is it possible to test its operation and
> > can the time left on the cesium be calculated   Regards Paul
> >
> > -Original Message-
> > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Doug
> Millar
> > via time-nuts
> > Sent: 19 May 2018 05:04
> > To: time-nuts@febo.com
> > Subject: [time-nuts] Cesium Clock Avialable
> >
> > Hi, I am willing to part with my HP 5061A cesium standard and manual. The
> > unit was rebuilt and functioning some years ago and not used since then.
> > There is usable cesium in the tube and the unit worked. I have not
> tested it
> > recently. It has a Patek-Philippe analogue clock in the front. The unit
> is
> > in great physical condition.  Asking $600 plus shipping from Long Beach,
> CA.
> > 90806
> > I also have an ESI 242D resistance calibrator and a Julie primary
> resistance
> > standard in an oven. Let me know if you are interested. Very reasonable.
> >  Thanks, Doug K6JEY
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
> >
> > -
> > No virus found in this message.
> > Checked by AVG - www.avg.com
> > Version: 2016.0.8048 / Virus Database: 4793/15670 - Release Date:
> 05/19/18
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
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Re: [time-nuts] Bodnar "Precision Frequency Reference (GPS Clock)" AND LeoNTP Networked Time NTP Server Questions

[Dana Whitlow]

Caution, folks, about USB cable radiation.  While the intended signals
flowing through the
cable presumably contribute a bit to the overall picture, common-mode
currents on the cable
are the most likely cause of severe radiation problems.  These currents
arise not merely from
intended USB signals, but from *all* the digital activity within the
device, and will be present
whether or not USB communications are going on.

The keys to controlling this problem are:

1) Shielding on the USB cable.
2) Proper design inside the USB device, rarely done beyond the point of
(barely) meeting
 government regulations, which are far too forgiving IMHO.
3) Use of a ferrite choke on the cable to reduce those residual currents
that get by anyway.

Note that only item 3 might be under the control of the user to any useful
extent.

So please don't just assume that using a USB cable for charging only solves
anything.

Note that the above comments are also generally applicable to *all *cables,
including power
cables, that are plugged into *any* digital device.

DanaK8YUM



On Fri, May 18, 2018 at 5:15 AM, David J Taylor via time-nuts <
time-nuts@febo.com> wrote:

> Anyone who is using one (or both) of these, and/or folks who have a
> logical opinion:
> []
> There's more...  but this is a good start.  Just want to try and get
> parts on the way.  Have to build a separate outboard regulator for the
> timing GPS antenna, too.
>
> Thanks!
>
> Clay Autery
> =
>
> Clay,
>
> I have all three of these units, all powered off USB.  I don't see any
> reason why you shouldn't use a USB cable with just the DC part connected,
> so that there's no issue about radiation.  A standard USB port would only
> supply 0.5A so that's an upper limit on the power consumption.  If it's a
> very long USB cable (you mention mast-head) check the resistance.
>
> As a crude guide...
>
> - The (larger box) NTP server feels cold to the touch.
>
> - The smaller, single output frequency source feels very slightly warm to
> the touch (feeding an Icom IC-R8600)
>
> - The larger, dual-output frequency source feels slightly warm to the
> touch.
>
> There's an e-mail address where you could ask:  supp...@leobodnar.com
>
> Cheers,
> David
> --
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-tay...@blueyonder.co.uk
> Twitter: @gm8arv
> ___
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> and follow the instructions there.
>
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Re: [time-nuts] GPS Timing Antenna Failure - Long

[Dana Whitlow]

Flux can provide just the right kind of ionic leakage path that leads to
whisky growth
and eventual sudden shorts.

Dana


On Sun, May 13, 2018 at 12:23 AM, Hal Murray 
wrote:

>
> lmcda...@lmceng.com said:
> > To make this very long story into a short one, I learned that the  HP/
> > Symmetricom 58532A GPS Reference (timing) antennas use a simple patch
> > antenna instead of a quadrafilar antenna and that old solder flux
> residue
> > will attenuate the even amplified GPS signal out of this antenna.
>
> Flux seems unlikely to produce a sudden failure.
>
> If flux was the problem, I'd expect it to work poorly when first
> installed,
> or maybe decay slowly over time as something changed.
>
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
> ___
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> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] Anybody have suggestions for time related science fair projects?

[Dana Whitlow]

Indeed; however, with single mode fiber the limit is not too bad.  At
Arecibo we routinely ran bandwidths in
excess of 1 GHz through fibers of about 1500 ft length with no problems.
For the science fair project a
bandwidth of a few MHz should suffice for lengths of, say, 500 ft.  It's
just that I don't know how bad the
multimode dispersion problem would be when using shorter wavelengths, and
I'm sure not equipped to
make any measurements at home now that I'm retired and far away from the
observatory.

Dana


On Sat, May 12, 2018 at 5:44 PM, Bruce Griffiths <bruce.griffi...@xtra.co.nz
> wrote:

> Even with single mode fiber its finite group delay dispersion will likely
> restrict the usable light source bandwidth.
>
> Bruce
> > On 13 May 2018 at 03:38 Dana Whitlow <k8yumdoo...@gmail.com> wrote:
> >
> >
> > It may  be that a nicely-written request to Corning could yield the loan
> of
> > a big spool of fiber
> > for the duration of a science fair project.
> >
> > Another alternative, perhaps easier to implement, might be an
> > electrically-driven light modulator
> > at the detector end.  For the source, an LED or diode laser is easy to
> > modulate at respectable
> > rates.  This approach should allow use of such high frequencies that an
> > open optical path using
> > mirrors might even suffice.
> >
> > Or here's an intermediate scheme:
> > If one were to use two modulated sources (or one with a beamsplitter),
> with
> > one path delayed
> > by the long(ish) fiber and the other by a minimal-length local fiber,
> > something resembling a streak
> > camera (implemented with a rotating mirror) might permit use of
> > substantially higher pulse rates
> > than with a rotating disk, without incurring the need for anything very
> > fancy in the way of mechanics.
> > Only the modulated source should require a reasonably accurate drive
> > frequency- the "detector"
> > would be essentially self-calibrating.  A small mirror, say of cm size,
> > could probably be safely
> > rotated at Dremel speeds approaching 500 rev/s, and if 1 mrad angular
> > resolution is attained,
> > this would yield a resolution of ~160 ns.  So a fiber length of 500 ft
> > (approx 750 ns one-way delay)
> > should yield an angular separation of nearly five "dots" between delayed
> > and undelayed dots.
> > And if the sources are modulated at a rate such that a few pulse
> > repetitions are visible in the
> > field of view, the scheme is self-calibrating as long as the PRF and the
> > velocity factor in the fiber
> > are known.  Probably the only precision work would be the optics required
> > to focus a reasonable
> > amount of light from the source(s) onto the two fibers., and I believe
> this
> > requirement could be
> > adequately met with microscope objectives borrowed from one's school's
> > biology lab.
> >
> > A fly in the ointment is that if ordinary (read, inexpensive) IR fiber is
> > used at convenient visible
> > wavelengths, propagation will occur in more than one spatial mode, with
> > different modes propagating
> > at different speeds.   I don't know how much of a problem this would
> > raise.  But it may be that if
> > tweaking of the transmitting end illumination is done, both in angle and
> > transverse position, most
> > of the propagating light could be confined to a single mode.  I speak of
> > visible wavelengths simply
> > because using these avoids the cost of electronic detectors,
> oscilloscopes,
> > etc, potentially saving
> > a lot on the cost of the experiment as well as making for a more
> satisfying
> > presentation.
> >
> > Dana
> >
> >
> > On Sat, May 12, 2018 at 9:45 AM, Bob kb8tq <kb...@n1k.org> wrote:
> >
> > > Hi
> > >
> > >
> > >
> > > > On May 12, 2018, at 7:01 AM, jimlux <jim...@earthlink.net> wrote:
> > > >
> > > > On 5/11/18 9:08 PM, Jeff Woolsey wrote:
> > > >> David.vanhorn wrote:
> > > >>> Measuring the speed of light (Fizeau or Michelson method? Other
> ways)
> > > >>>
> > > >>>
> > > >>> I saw a great demo of this at the Exploratorium in SF.  They had a
> > > long spool of fiber optic, a disc with holes, and a light source.  When
> > > static, if the light shines through the hole in the disc into the
> fiber,
> > > then you can see the light coming out the other end of the fiber
> through a
> > > different hole.   When rotating, you

Re: [time-nuts] Anybody have suggestions for time related science fair projects?

[Dana Whitlow]

It may  be that a nicely-written request to Corning could yield the loan of
a big spool of fiber
for the duration of a science fair project.

Another alternative, perhaps easier to implement, might be an
electrically-driven light modulator
at the detector end.  For the source, an LED or diode laser is easy to
modulate at respectable
rates.  This approach should allow use of such high frequencies that an
open optical path using
mirrors might even suffice.

Or here's an intermediate scheme:
If one were to use two modulated sources (or one with a beamsplitter), with
one path delayed
by the long(ish) fiber and the other by a minimal-length local fiber,
something resembling a streak
camera (implemented with a rotating mirror) might permit use of
substantially higher pulse rates
than with a rotating disk, without incurring the need for anything very
fancy in the way of mechanics.
Only the modulated source should require a reasonably accurate drive
frequency- the "detector"
would be essentially self-calibrating.  A small mirror, say of cm size,
could probably be safely
rotated at Dremel speeds approaching 500 rev/s, and if 1 mrad angular
resolution is attained,
this would yield a resolution of ~160 ns.  So a fiber length of 500 ft
(approx 750 ns one-way delay)
should yield an angular separation of nearly five "dots" between delayed
and undelayed dots.
And if the sources are modulated at a rate such that a few pulse
repetitions are visible in the
field of view, the scheme is self-calibrating as long as the PRF and the
velocity factor in the fiber
are known.  Probably the only precision work would be the optics required
to focus a reasonable
amount of light from the source(s) onto the two fibers., and I believe this
requirement could be
adequately met with microscope objectives borrowed from one's school's
biology lab.

A fly in the ointment is that if ordinary (read, inexpensive) IR fiber is
used at convenient visible
wavelengths, propagation will occur in more than one spatial mode, with
different modes propagating
at different speeds.   I don't know how much of a problem this would
raise.  But it may be that if
tweaking of the transmitting end illumination is done, both in angle and
transverse position, most
of the propagating light could be confined to a single mode.  I speak of
visible wavelengths simply
because using these avoids the cost of electronic detectors, oscilloscopes,
etc, potentially saving
a lot on the cost of the experiment as well as making for a more satisfying
presentation.

Dana


On Sat, May 12, 2018 at 9:45 AM, Bob kb8tq  wrote:

> Hi
>
>
>
> > On May 12, 2018, at 7:01 AM, jimlux  wrote:
> >
> > On 5/11/18 9:08 PM, Jeff Woolsey wrote:
> >> David.vanhorn wrote:
> >>> Measuring the speed of light (Fizeau or Michelson method? Other ways)
> >>>
> >>>
> >>> I saw a great demo of this at the Exploratorium in SF.  They had a
> long spool of fiber optic, a disc with holes, and a light source.  When
> static, if the light shines through the hole in the disc into the fiber,
> then you can see the light coming out the other end of the fiber through a
> different hole.   When rotating, you increase speed and the fiber output
> gets dimmer and dimmer till it's gone.   At that point, the light going
> into the fiber arrives when the other end is blocked, and vice versa.  High
> tech, but simple.
> >>>
> >> My favorite exhibit that we never see anymore.   IIRC it was a quarter
> >> mile of fiber and a green laser.  And ISTR that the disc had one hole on
> >> one arm and two radially on the other, but I can't remember why.  I
> >> thought that the light would pass through the same hole twice, once on
> >> the way in and on the way out when that same hole rotated 180 degrees to
> >> the other end of the fiber.  The disk spun somewhere around 50 rps (60
> >> with an AC motor?).
> >
> >
> > 1km in free space would be 6 microseconds round trip. I'm not sure a
> disk spinning at 3600 rpm would work.  you'd need to have the "hole
> spacing" be on the order of 6 microseconds - and at 100 rps (6000 RPM), 10
> ms/rev, you'd need the sending and receiving hole 6/1 of a rev apart
> (about 0.2 degrees).
> >
> > if you had 10 km of fiber, it would be a bit easier.
>
> I think the term “long fiber” in this case should really be “very very
> long”.  Exactly how the typical student
> funds the acquisition of something in the “many miles” range, I have no
> idea.
>
> You could use an optical grating of some sort as your “spinning disk”. The
> end of the fiber is going to be
> mighty small. The spacing on the grating could be quite tight. Where you
> get a circular part like that ….
> again no idea.
>
> Bob
>
>
> > ___
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> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
> ___

Re: [time-nuts] HP 5372A

[Dana Whitlow]

When I was working at the Arecibo Observatory and we were running the
ionospheric heater
at 5.1 MHz (think Mini-HAARP), I'd sometimes go home (about 3 miles away)
and listen to the
signal there.There was frequently substantial random fading of the
signal, suggesting that I
was hearing the vector sum of an NVIS signal off the ionosphere and the
usual sidelobe leakage
from the dish.  Said fading could be said to have a characteristic period
of around 1 or 2 seconds,
and was occasionally quite deep.

So, I'm definitely a believer in short path propagation variations.

Dana   K8YUM


On Fri, May 11, 2018 at 1:09 PM, Bob kb8tq  wrote:

> Hi
>
> Well, having actually run FMT virtually “in the back yard” of the
> transmitting station …. it’s surprising
> what 70 miles will do. In this case, back yard really does mean on the
> premises. There is a lot that
> gets into even fairly sort distance propagation.
>
> Bob
>
> > On May 11, 2018, at 1:52 PM, Jerry Hancock  wrote:
> >
> > If you were in Connie’s back yard or had a very stable ground wave, then
> yes, you could automate the testing.
> >
> > There are a number of challenges with this method as looking at the data
> with a simple graph will tell.  You might have large fluctuations on the
> high frequency side only, for instance, that any averaging or algorithm
> would assume to be valid data.
> >
> > The next issue is the length of the dataset as the key-down time is only
> a few minutes so you end-up with not that many samples.
> >
> > Regards,
> >
> > Jerry
> >
> >> On May 10, 2018, at 5:59 AM, Don Murray via time-nuts <
> time-nuts@febo.com> wrote:
> >>
> >> Hi Magnus...
> >>
> >>
> >> Appreciate any help!
> >>
> >> I participate in the ARRL Frequency Measuring Test,
> >> and I would like to automate the measuring process.
> >>
> >> I have two frequencies, A and B...
> >>
> >> A is a GPS locked HP 3336B set to 455,000.000 Hz
> >>
> >> I use the 3336B instead of the 455,000Hz BFO
> >> signal from my GPS locked Racal receiver so
> >> that I can measure AM stations without the
> >> annoying beat note.  ;-)
> >>
> >> B is an IF signal which should appear between
> >> 455,000.000Hz and 455,001.000 Hz
> >>
> >> I would like the 5372A to calculate the B minus A
> >> delta, over a manually started and automatically
> >> stopped measurement period of 110 seconds.
> >>
> >> I would like a delta resolution of 0.001Hz to be
> >> developed by the box.
> >>
> >> Now, there will be doppler.  I want the box
> >> to analyze and give me a best statistical guess
> >> for the B minus A delta.
> >>
> >> BTW the B minus A delta will be added to the
> >> frequency of my Racal receiver to give me the
> >> best "guess" as to the correct frequency of the
> >> target signal.
> >>
> >> The Racal reads out to the Hz, and I am able to
> >> accurately determine if the Racal is tuned above
> >> or below the "target" frequency.
> >>
> >> I will be tuned below the "target" and within
> >> 1 Hz of the "target."
> >>
> >> I assume I will be in the one frequency mode.
> >>
> >> Can the box give me the desired resolution?
> >>
> >> What sampling period would be the best to use?
> >>
> >> What statistical result would I use as my delta?
> >>
> >> Appreciate your help.  My head is spinning whenever I
> >> get into the operating manual!
> >>
> >> TNX...
> >>
> >>
> >> 73
> >> Don
> >> W4WJ
> >>
> >> In a message dated 5/10/2018 2:19:49 AM Central Standard Time,
> mag...@rubidium.dyndns.org writes:
> >>
> >>
> >> Hi,
> >>
> >> What issues do you have?
> >>
> >> Cheers,
> >> Magnus
> >>
> >> On 05/08/2018 02:32 AM, Don Murray via time-nuts wrote:
> >>> Hello Time Nuts...
> >>>
> >>>
> >>>
> >>> Who is the resident expert on the HP5372A?
> >>>
> >>> I have some operational questions.  ;-)
> >>>
> >>> email off list please.  w4wj at aol.com
> >>>
> >>> TNX all...
> >>>
> >>> 73
> >>> Don
> >>> W4WJ
> >>>
> >>>
> >>> ___
> >>> time-nuts mailing list -- time-nuts@febo.com
> >>> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> >>> and follow the instructions there.
> >>>
> >> ___
> >> time-nuts mailing list -- time-nuts@febo.com
> >> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> >> and follow the instructions there.
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> mailman/listinfo/time-nuts
> >> and follow the instructions there.
> >
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> > and follow the instructions there.
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Re: [time-nuts] Anybody have suggestions for time related science fair projects?

[Dana Whitlow]

How about measuring variations in propagation delay for WWV on various
frequencies, or WWVB,
using GPS ticks as a reference.

DanaK8YUM


On Fri, May 11, 2018 at 9:41 AM, Van Horn, David <
david.vanh...@backcountryaccess.com> wrote:

>
> Measuring the speed of light (Fizeau or Michelson method? Other ways)
>
>
> I saw a great demo of this at the Exploratorium in SF.  They had a long
> spool of fiber optic, a disc with holes, and a light source.  When static,
> if the light shines through the hole in the disc into the fiber, then you
> can see the light coming out the other end of the fiber through a different
> hole.   When rotating, you increase speed and the fiber output gets dimmer
> and dimmer till it's gone.   At that point, the light going into the fiber
> arrives when the other end is blocked, and vice versa.  High tech, but
> simple.
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
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Re: [time-nuts] Question about frequency counter testing

[Dana Whitlow]

I'm a bit fuzzy, then, on the definition of ADEV.  I was under the
impression that one measured a series of
"phase samples" at the desired spacing, then took the RMS value of that
series, not just a single sample,
as the ADEV value.

Can anybody say which it is?   The RMS approach seems to make better sense
as it provides some measure
of defense against taking a sample that happens to be an outlier, yet
avoids the flaw of tending to average
the reported ADEV towards zero.

Dana   (K8YUM)


On Thu, May 10, 2018 at 9:21 AM, Bob kb8tq  wrote:

> Hi
>
> If you collect data over the entire second and average that down for a
> single point, then no, your ADEV will not be correct.
> There are a number of papers on this. What ADEV wants to see is a single
> phase “sample” at one second spacing. This is
> also at the root of how you get 10 second ADEV. You don’t average the ten
> 1 second data points. You throw nine data points
> away and use one of them ( = you decimate the data ).
>
> What happens if you ignore this? Your curve looks “to good”. The resultant
> curve is *below* the real curve when plotted.
>
> A quick way to demonstrate this is to do ADEV with averaged vs decimated
> data ….
>
> Bob
>
> > On May 10, 2018, at 4:46 AM, Oleg Skydan  wrote:
> >
> > Hi
> >
> > I have got a pair of not so bad OCXOs (Morion GK85). I did some
> measurements, the results may be interested to others (sorry if not), so I
> decided to post them.
> >
> > I ran a set of 5minutes long counter runs (two OCXOs were measured
> against each other), each point is 1sec gate frequency measurement with
> different number of timestamps used in LR calculation (from 10 till 5e6).
> The counter provides continuous counting. As you can see I reach the HW
> limitations at 5..6e-12 ADEV (1s tau) with only 1e5 timestamps. The results
> looks reasonable, the theory predicts 27ps equivalent resolution with 1e5
> timestamps, also the sqrt(N) law is clearly seen on the plots. I do not
> know what is the limiting factor, if it is OCXOs or some counter HW.
> >
> > I know there are HW problems, some of them were identified during this
> experiment. They were expectable, cause HW is still just an ugly
> construction made from the boards left in the "radio junk box" from the
> other projects/experiments. I am going to move to the well designed PCB
> with some improvements in HW (and more or less "normal" analog frontend
> with good comparator, ADCMP604 or something similar, for the "low
> frequency" input). But I want to finish my initial tests, it should help
> with the HW design.
> >
> > Now I have some questions. As you know I am experimenting with the
> counter that uses LR calculations to improve its resolution. The LR data
> for each measurement is collected during the gate time only, also
> measurements are continuous. Will the ADEV be calculated correctly from
> such measurements? I understand that any averaging for the time window
> larger then single measurement time will spoil the ADEV plot. Also I
> understand that using LR can result in incorrect frequency estimate for the
> signal with large drift (should not be a problem for the discussed
> measurements, at least for the numbers we are talking about).
> >
> > Does the ADEV plots I got looks reasonable for the used "mid range"
> OCXOs (see the second plot for the long run test)?
> >
> > BTW, I see I can interface GPS module to my counter without additional
> HW (except the module itself, do not worry it will not be another DIY
> GPSDO, probably :-) ). I will try to do it. The initial idea is not try to
> lock the reference OCXO to GPS, instead I will just measure GPS against REF
> and will make corrections using pure math in SW. I see some advantages with
> such design - no hi resolution DAC, reference for DAC, no loop, no
> additional hardware at all - only the GPS module and software :) (it is in
> the spirit of this project)... Of cause I will not have reference signal
> that can be used outside the counter, I think I can live with it. It worth
> to do some experiments.
> >
> > Best!
> > Oleg UR3IQO
> > <Снимок экрана (1148).png><Снимок экрана (1150).png><Снимок экрана
> (1149).png>___
> > time-nuts mailing list -- time-nuts@febo.com
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> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
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Re: [time-nuts] WWVB: measuring local 60 KHz noise

[Dana Whitlow]

Alex- how many turns on that loop?

Dana


On Sat, May 5, 2018 at 2:35 PM, Alexander Pummer  wrote:

> tuned,[ fine-tuning with vari-caps remotely] large size frame antenna 1
> meter dia provides mV size 60kHz in the Livermore area in California from
> the Colorado WWVB TX
> 73
> KJ6UHN
> Alex
>
> On 5/5/2018 6:17 AM, Ulrich Rohde via time-nuts wrote:
>
>>   I am trying to use the 60 KHz for synchronization of a Rb receiver. The
>> local NJ noise and the signal in dBuV are about the same with an active
>> antenna, electric field.  A better solution might be a ferrite selective
>> antenna, H field , if I find one.
>>   73 de N1UL
>> In a message dated 5/5/2018 4:09:25 AM Eastern Standard Time,
>> hmur...@megapathdsl.net writes:
>>
>> Review/background: I have an UltraLink 333 WWVB receiver. It didn't
>> work.
>> Several weeks ago. a discussion here mentioned that the phone cable
>> between
>> the main box and antenna needs to be straight through rather than the
>> typical
>> reversed. That was my problem. With the correct cable, the meter shows
>> signal and bounces around such that with practice, I could probably read
>> the
>> bit pattern. But it didn't lock up.
>>
>> That was several weeks ago. I left it running. When I looked last night,
>> it
>> had figured out that it is 2018. I wasn't watching or monitoring, so I
>> don't
>> know how long it took.
>>
>> I assume the problem is noise. Is there any simple way to measure the
>> noise
>> around 60 KHz? How about not so simple?
>>
>> Extra credit for a way that others nuts can reproduce so we can compare
>> the
>> noise at my location with other locations.
>>
>> Can any audio cards be pushed that high? I see sample rates of 192K, but I
>> don't know if that is useful.
>>
>> I'd also like to measure the propagation delays on WWV so a setup for HF
>> that
>> also works down to 60 KHz would be interesting.
>>
>> --
>>
>> The UltraLink documentation says the display has a slot for a C or H. The
>> C is for Colorado and the H is for Hawaii. Did WWVH have a low frequency
>> transmitter many years ago? The NIST history of WWVH doesn't mention it.
>>
>> My guess is a cut+paste from a version that listened to WWV/WWVH.
>>
>>
>>
>>
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Re: [time-nuts] WWVB: measuring local 60 KHz noise

[Dana Whitlow]

Hal,

Some SDRs can tune that low and should provide a means to determine
if noise is really the problem as well as give some clues as to the
character
of said noise.  But they are much less likely to help with delay
determination,
unless you can figure out a practical way to ascertain the latency in both
the
SDR's HW and its SW.  The latter component will also vary considerable
depending on what computer you are using with the SDR, as well as with
random variations due to the vagrancy of typical operating systems.

I recently did a crude delay estimation for WWV (not WWVB) using my
Sony ICF-2010 receiver, a 2-channel DSO, and an Adafruit "Ultimate GPS"
module's PPS output.  The combined (receiver + propagation) delay was
very close to 5 msec in Kerrville, TX.  The precision was mostly limited by
my inability to decide precisely where each WWV tick started on the 'scope's
display due to distortion arising from multipath and the receiver's
filters.
The actual received waveform varied considerably from second to second.

Dana


On Sat, May 5, 2018 at 3:08 AM, Hal Murray  wrote:

> Review/background:  I have an UltraLink 333 WWVB receiver.  It didn't
> work.
> Several weeks ago. a discussion here mentioned that the phone cable
> between
> the main box and antenna needs to be straight through rather than the
> typical
> reversed.  That was my problem.  With the correct cable, the meter shows
> signal and bounces around such that with practice, I could probably read
> the
> bit pattern.  But it didn't lock up.
>
> That was several weeks ago.  I left it running.  When I looked last night,
> it
> had figured out that it is 2018.  I wasn't watching or monitoring, so I
> don't
> know how long it took.
>
> I assume the problem is noise.  Is there any simple way to measure the
> noise
> around 60 KHz?  How about not so simple?
>
> Extra credit for a way that others nuts can reproduce so we can compare
> the
> noise at my location with other locations.
>
> Can any audio cards be pushed that high?  I see sample rates of 192K, but
> I
> don't know if that is useful.
>
> I'd also like to measure the propagation delays on WWV so a setup for HF
> that
> also works down to 60 KHz would be interesting.
>
> --
>
> The UltraLink documentation says the display has a slot for a C or H.  The
> C is for Colorado and the H is for Hawaii.  Did WWVH have a low frequency
> transmitter many years ago?  The NIST history of WWVH doesn't mention it.
>
> My guess is a cut+paste from a version that listened to WWV/WWVH.
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] nuts about position

[Dana Whitlow]

It is true that most handheld GPS receivers have WAAS capability these
days; however the accuracy is more like 3 to 4 meters even with several
minutes of averaging.  I've always been puzzled by why it is so much
worse than good professional equipment can apparently achieve with
similar "features".  Perhaps it has something to do with the simple antennas
that handheld units use.

A day or two ago I had related the story of our survey at the Arecibo
observatory done with professional equipment.  Soon after that was
done, I took my handheld Garmin GPS60CX up on the roof and used it
to make the same measurement with WAAS corrections turned on and
about 10 min of averaging.  I don't remember the exact numbers for
the discrepancies between the two measurements, but they were in the
neighbor hood of 4 meters.  In fairness to the handheld, I should mention
that the position involved did not offer complete sky visibility- it was in
sort of a canyon such that the sky was visible only down to about 30
or 40 deg elevation to the east and west but with excellent low-elevation
visibility to the north and south.

Incidentally, Puerto Rico does have a WAAS ground station fairly close
to the observatory site, just off the San Juan airport roughly 50 miles
away from the observatory.

Dana


On Wed, Apr 25, 2018 at 8:21 PM, jimlux  wrote:

> On 4/25/18 11:18 AM, Brooke Clarke wrote:
>
>> Hi Tom:
>>
>> As part of a FireWise community mapping process I'd like to get GPS
>> coordinates of the fire hydrants (Lat, Lon, Ele). Is there a civilian GPS
>> receiver that makes use of WAAS and/or DGPS corrections?
>>
>
> I think almost all handheld receivers these days use WAAS for improved
> performance.  WAAS should give you 1 meter kind of accuracy, particularly
> if you compare a known location in the area.
>
> DGPS was a thing back in the 90s (I fooled with a Trimble Scout with a pod
> that received corrections over FM broadcast SCA) - I'm not sure it's widely
> used today.
>
> The USCG DGPS transmits corrections on MF beacons, but is being
> decommissioned.  Most of the inland stations have been shutdown.
>
>
> If you're a surveyor, you get corrections from a network (CORS or
> something similar), or you're primarily interested in "relative" position -
> you set up your base station and your RTK rover tells you where it is
> within 1 mm + 1ppm of distance from base.
>
> http://www.xyht.com/ has regular features on the latest GPS survey gear.
>
> You might be able to convince the local survey equipment rental house to
> come out and demo the gear (or give you a good price on a rental)
>
> Or, why not just do the survey optically (!) - none of this new fangled
> GPS stuff.  Rod, level, theodolite.  If Everest could do it in the 19th
> century in India, you can do it too.
>
> If you can find a couple benchmarks to work from, you can get accuracy of
> 1 part in 1000 with a decent 200 foot tape measure and something to sight
> with (a cheap laser level at night works pretty good to keep your line
> straight).  You're doing a series of triangles - SSS completely defines it,
> so no angles need be measured.
>
> With decent survey gear 1 part in 10,000 or so is straightforward.
>
> 1 ppm is hot stuff with conventional optical gear - you're going to be
> making multiple measurements, compensating for refraction, etc. It's like
> GPS at 10cm accuracy - lots of things cause errors of that magnitude.
>
> A nice theodolite (like a Wild T2) is readable to 1 second of arc. That's
> about 5 microradian.  At 100 meters, the horizontal uncertainty would be
> 0.5mm.   Yeah, not quite 1ppm, although you could probably do multiple
> setups and average in on 1ppm.
>
> Of course, you'll then need to go out and get a decent tripod, a rod and
> target, and a rod person to wave the rod, etc.
>
> But another poster did comment on "why not use the telescope" you could
> precision point to a series of stars and calculate using celestial nav
> where you are.  Although, that might be painful to the 1 meter sort of
> accuracy - the "tables" probably don't really account for deviations from
> ellipsoid and so forth.
>
>
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Re: [time-nuts] nuts about position

[Dana Whitlow]

While I was at the Arecibo Observatory it became desirable to get a good
surveyed position
for a new GPS antenna we had installed for the NIST TMAS system.  We found
a resource
at the Univ of Puerto Rico who had a Trimble (I think) unit.  He set it up
on the site, "turned on
the bubble machine", then left it alone for about two hours.  He returned
the estimated
position a few days later, expressing high confidence that it was good
within about 8 inches.

I'm sure I asked him if this machine used both L1 & L2, but don't recall
his answer.   I suspect
it was "yes".

Dana


On Wed, Apr 25, 2018 at 9:56 AM, Tom Van Baak  wrote:

> List -- I had a recent query by a researcher who would like to pinpoint
> the location of his telescope(s) within 0.3 meters. Also (he must be a true
> scientist) he wants to do this on-the-cheap. He may have timing
> requirements as well, but that's another posting.
>
> So I toss the GPS question to the group. Surely some of you have crossed
> the line from precise time to precise location?
>
> How easy, how cheap, how possible is it to obtain 0.3 m accuracy in 3D
> position?
>
> When we run our GPSDO in survey mode how accurate a position do we get
> after an hour, or even 24 or 48 hours? And here I mean accurate, not
> stable. Have any of you compared that self-reported, self-survey result
> against an independently measured professional result or known benchmark?
>
> Do you know if cheap ublox 5/6/7/8 series receivers are capable of 1 foot
> accuracy given enough time?
>
> If not, what improvement would -T models and RINEX-based web-service
> post-processing provide?
>
> It that's still not close enough to 0.3 m, is one then forced to use more
> expensive multi-frequency (L1/L2) or multi-band (GPS, GLONASS, Galileo) to
> achieve this level of precision? If so, how cheaply can one do this? Or is
> the learning curve more expensive than just hiring an survey specialist to
> make a one-time cm-level measurement for you?
>
> Something tells me 1 foot accuracy in position is possible and actually
> easier than 1 ns accuracy in time. I'm hoping some of you can help
> recommend solution(s) to the researcher's question or shed light on this
> interesting challenge.
>
> Thanks,
> /tvb
>
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Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)

[Dana Whitlow]

According to my book, each magnetic pole of some pulsars is more
like a rotating circular array of sub-poles, where the direction of induced
radiation varies from sub-pole posetion to sub-pole position.  And only a
small range of sub-pole positions out of the group happens to point in
the direction of the Earth.

A reason for a general slowdown is energy lost to the radiation.  But
the glitches, in the case of the Vela pulsar at least, involve steps upward
in spin rate, although nowhere near enough to cancel the overall
slowing trend.  The authors of "Introduction to Radio Astronomy" do a
much better job of explaining the sawtooth effect than my clumsy attempt.

Robert L. Forward, I suspect.

Dana


On Sat, Apr 14, 2018 at 12:04 AM, Bill Hawkins <bill.i...@pobox.com> wrote:

> It seems that pulsars are rotating stellar objects that have no reason
> to change their rotation, except to decay.
> Ruling out causes from the stellar object, one is left with things that
> might be orbiting the object and their ability to absorb the pulse that
> is aimed at us. One could move further out to the extremely low
> probability that some interstellar object absorbed the pulse. This
> doesn't explain the sawtooth, unless one of those orbiting bodies is
> affecting the rotation rate of the pulsar, such as a binary star.
>
> Disclaimer: I know very little about radio astronomy, but I've read a
> lot of hard science fiction.
>
> Bill Hawkins
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Dana
> Whitlow
> Sent: Friday, April 13, 2018 8:39 AM
> To: Tom Van Baak; Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)
>
> Tom's discussion about pulsars brought back some memories...
>
> Many pulsars exhibit skipped pulses.  And one curiosity that I didn't
> see mentioned in Tom's discussion is that some pulsars even exhibit
> behavior reminiscent of the "sawtooth jitter" so evident in the PPS
> outputs of most GPS receivers.  See figures 12-11 & 12-12 in "An
> Introduction to Radio Astronomy" (2nd edition) by Burke and
> Graham-Smith.  The first ed also contains the basic plot (as figure 12-8
> in this case), but whose explanation is not as up-to-date).
>
> For a deeper treatment of pulsars, also see
>   https://www.cv.nrao.edu/course/astr534/PDFnew.shtml
> by Condon and Ransom (both of NRAO).
>
> The above two references are the best Radio Astronomy tomes I've yet
> seen..
>
> Pulsar timing has been (and still is) a very big deal in radio
> astronomy, as it is key to verification of certain points of Einstein's
> General Theory of Relativity.
>
> Here are two web sites in which audio recordings of various pulsar
> sounds (made with larger radio telescopes) are presented.
>
> https://www.youtube.com/watch?v=uHEVo-LkDrQ
> (You may ignore the video part, even though it's "cute", but the audio
> portion is a fine example of the pulse to pulse variations exhibited by
> many pulsars, all wrapped up in one pulsar)
>
> http://www.jb.man.ac.uk/pulsar/Education/Sounds/0329_stack.mp4
> (I think this is the best overall site, giving quality recordings of a
> fair number of different pulsars)
>
> Dana
>
>
>
>
>
>
> On Fri, Apr 13, 2018 at 2:54 AM, Tom Van Baak <t...@leapsecond.com>
> wrote:
>
> > Amazing news... 1.2.3.
> >
> > 1) Many of you know that pulsars are weird astronomical sources of
> > periodic signals. Some are so accurate that they rival atomic clocks
> > for stability! True, but I don't have a 100 foot antenna at home so
> > I'll take their word for it. Plus, you have to account for a myriad of
>
> > PhD-level
> > corrections: from earth's rotation to general relativity. And, like
> > quartz or rubidium clocks, pulsars drift (as they gradually slow
> > down). Precision timing is not easy. If you poke around the web you
> > can find numerous articles describing their detection and measurement
> > and exploring their use as reference clocks, both here and potentially
> for deep-space timekeeping.
> >
> > 2) If you do a lot of clock measurement at home then you know the dark
>
> > side of working with precision clocks. There are signal quality
> > issues, measurement resolution issues, reference stability
> > limitations, offset, drift, phase jumps, frequency jumps, missed or
> extra cycles, glitches, etc.
> > For example, quartz oscillators (depending on make / model / luck) can
>
> > exhibit frequency jumps; i.e., without warning they just change
> > frequency without your permission. Ok, maybe not by a lo

Re: [time-nuts] getting accurate timing on RTL-SDR output

[Dana Whitlow]

Hi Jim,

Good for you!  I love to hear about backyard radio astronomy projects.

With your sample rate your GPS PPS spikes should be in the neighborhood
of 1 uS duration.  It's hard to say just how accurately you can glean the
timing
from that, but then I suspect that you're mainly interested in effectively
comparing
the outputs of the two receivers, not so much in absolute timing.  Try your
best
to keep the two receivers identical.

Dana


On Fri, Apr 13, 2018 at 2:15 PM, jimlux <jim...@earthlink.net> wrote:

> On 4/13/18 10:33 AM, Dana Whitlow wrote:
>
>> Jim,
>>
>> I'm curious:In what RF bandwidth will you be recording?
>>
>
> 1 MHz for now.. the RTL-SDR isn't a super flexible device - there are
> apparently good and bad rates - it does a DDC with 28.8 MHz I/Q NCO (with
> who knows what kind of performance), and then filter and decimate. There's
> a set of taps published for a FIR filter in the thing.
>
> Ultimately, it comes out as 8 bit I and 8 bit Q, so I figure if I do some
> more decimation on the 1MHz stream, I can get a few more effective bits.
>
> It will run at 2 MHz sample rate without dropping samples.. I could
> probably modify the rtl utility to run at a higher rate and do a first
> software filter/downsample to get the data rate down..
>
> I'm really only interested in fairly narrow detection bandwidth.
>
> For telescope use, Jupiter is pretty bright.
> For "phase array to listen to HF signals" 20kHz is probably plenty (it's
> not like I'm going to be developing a 3D CWSkimmer, yet)
>
> Mostly it's because I'm managing a project at JPL where we're flying an
> interferometer to look at CMEs from the Sun
> http://adsabs.harvard.edu/abs/2017EGUGA..19.5580L
> and I'm intrigued by whether I can do it in the backyard..
>
>
>
>
>
>> My first thought would be to search for a cross-correlation peak
>> between the two antenna outputs, but quickly realized that this
>> does not tell you anything about the timing differences between
>> the two receivers.   I think you need to determine that independently
>> (else why bother with the interferometry in the first place?)
>>
>
> That's a clever idea..
>
> Each node has its own GPS receiver, but they should all (within the
> tolerance of the receiver) be "ticking" at the same time.
>
>
>
>
>
>> The receive bandwidth in conjunction with your S/N on the PPS
>> spikes will conspire to limit your timing accuracy, although you
>> can improve on that by averaging over a few minutes as you
>> plan.
>>
>> Dana
>>
>>
>>
>>
>> On Fri, Apr 13, 2018 at 11:52 AM, Jim Lux <jim...@earthlink.net> wrote:
>>
>> I'm building a phased array receiver (actually, an interferometer) using
>>> RTL-SDR pods, where the elements are isolated from each other - there's a
>>> common WiFi network connection, and each node has a BeagleBone Green, a
>>> uBlox OEM-7M-C, and the RTL-SDR V3 (which works down to HF, since it has
>>> an
>>> internal bypass around the RF front end).
>>>
>>> In general, I have the RTL-SDR set up to capture at 1 Megasample/second.
>>> I
>>> fire off a capture, record it to a file in the BeagleBone's flash, then
>>> retrieve it from my host computer using scp over the network.
>>>
>>> What I'm trying to do is capture data from all the nodes at
>>> (approximately) the same time, then be able to line it all up in post
>>> processing. The GPS (or NTP) is good enough to get them all to start
>>> recording within a few tenths of a second.
>>>
>>> So now the challenge is to "line em up".  An obvious approach is to
>>> transmit an inband pilot tone with some sync pattern, received by all,
>>> and
>>> I'm working on that too.
>>>
>>> But right now, I have the idea of capacitively coupling the 1pps pulse
>>> from the GPS to the antenna input - the fast rising and falling edge are
>>> broad band and show up in the sampled data.
>>>
>>> The attached pulses1.png shows the integrated power in 1 ms chunks (i.e.
>>> I
>>> sum the power from 1000 samples for each chunk) and it's easy to see the
>>> GPS edges.  And it's easy to create a estimate of the coarse timing (to 1
>>> millisecond) - shown as the red trace.
>>>
>>> But then, I want to get better.  So for the 20 edges in my 10 second
>>> example, I plotted  (drift1.png) the raw I/Q output of the RTL.  The
>>> pulse
>>> isn't too huge (maybe 10 DN out of the ADC's -128 to +128 range), but is
>>&

Re: [time-nuts] getting accurate timing on RTL-SDR output

[Dana Whitlow]

Jim,

I'm curious:In what RF bandwidth will you be recording?

My first thought would be to search for a cross-correlation peak
between the two antenna outputs, but quickly realized that this
does not tell you anything about the timing differences between
the two receivers.   I think you need to determine that independently
(else why bother with the interferometry in the first place?)

The receive bandwidth in conjunction with your S/N on the PPS
spikes will conspire to limit your timing accuracy, although you
can improve on that by averaging over a few minutes as you
plan.

Dana




On Fri, Apr 13, 2018 at 11:52 AM, Jim Lux  wrote:

> I'm building a phased array receiver (actually, an interferometer) using
> RTL-SDR pods, where the elements are isolated from each other - there's a
> common WiFi network connection, and each node has a BeagleBone Green, a
> uBlox OEM-7M-C, and the RTL-SDR V3 (which works down to HF, since it has an
> internal bypass around the RF front end).
>
> In general, I have the RTL-SDR set up to capture at 1 Megasample/second. I
> fire off a capture, record it to a file in the BeagleBone's flash, then
> retrieve it from my host computer using scp over the network.
>
> What I'm trying to do is capture data from all the nodes at
> (approximately) the same time, then be able to line it all up in post
> processing. The GPS (or NTP) is good enough to get them all to start
> recording within a few tenths of a second.
>
> So now the challenge is to "line em up".  An obvious approach is to
> transmit an inband pilot tone with some sync pattern, received by all, and
> I'm working on that too.
>
> But right now, I have the idea of capacitively coupling the 1pps pulse
> from the GPS to the antenna input - the fast rising and falling edge are
> broad band and show up in the sampled data.
>
> The attached pulses1.png shows the integrated power in 1 ms chunks (i.e. I
> sum the power from 1000 samples for each chunk) and it's easy to see the
> GPS edges.  And it's easy to create a estimate of the coarse timing (to 1
> millisecond) - shown as the red trace.
>
> But then, I want to get better.  So for the 20 edges in my 10 second
> example, I plotted  (drift1.png) the raw I/Q output of the RTL.  The pulse
> isn't too huge (maybe 10 DN out of the ADC's -128 to +128 range), but is
> visible. Bottom trace is the first, and they're stacked up
> 0, 0.1, 1.0, 1.1, 2.0, 2.1, etc.
>
> And you can see, no surprise, that the sample clock in the RTL isn't dead
> on - over the 10 seconds, it looks like it drifts about 30- 50 microseconds
> - that is, the RTL clock is slow by 3-5 ppm.
>
> SO here's the question for the time-nuts hive-mind...
> What's a good (or not so good) way to develop an estimator of the
> timing/frequency error. Post processing minutes of data is just fine..
>
> I'm not sure what the actual "waveform" that is being sampled is (and it
> will be perturbed by the quantization of the ADC, and probably not be the
> same depending on where the RTL is tuned).  That is there's some sort of
> LPF in the front of the RTL, the edge is AC coupled, and then it goes into
> some sort of digital down converter in the RTL running at 28.8 MHz sample
> rate.
>
> But it seems that there might be some way to "stack" a series of samples
> and optimize some parameters to estimate the instantaneous time error-
> given that the frequency vs time varies fairly slowly (over a minute or
> so).  It's fairly obvious from the plot that if one looked at the "single"
> sample when the edge comes in, not only does the time shift with each
> pulse, but the phase rotates as well (totally expected)
>
> this is one of those things where you could probably lay a ruler on it and
> estimate it by eye pretty well, but I'd like an automated algorithm.
>
> It would be nice to be able to estimate the timing to, say, a few
> nanoseconds over a minute or so ( - that would allow a phase estimation of
> 1/10th of a wavelength of a 20 MHz signal (e.g. Jupiter's RF noise, or
> WWVH's transmissions)
>
>
> Ideas???
>
>
>
>
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Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)

[Dana Whitlow]

Tom's discussion about pulsars brought back some memories...

Many pulsars exhibit skipped pulses.  And one curiosity that I didn't see
mentioned in Tom's discussion is that some pulsars even exhibit behavior
reminiscent of the "sawtooth jitter" so evident in the PPS outputs of most
GPS receivers.  See figures 12-11 & 12-12 in "An Introduction to Radio
Astronomy" (2nd edition) by Burke and Graham-Smith.  The first ed also
contains the basic plot (as figure 12-8 in this case), but whose explanation
is not as up-to-date).

For a deeper treatment of pulsars, also see
  https://www.cv.nrao.edu/course/astr534/PDFnew.shtml
by Condon and Ransom (both of NRAO).

The above two references are the best Radio Astronomy tomes I've yet seen..

Pulsar timing has been (and still is) a very big deal in radio astronomy,
as it
is key to verification of certain points of Einstein's General Theory of
Relativity.

Here are two web sites in which audio recordings of various pulsar
sounds (made with larger radio telescopes) are presented.

https://www.youtube.com/watch?v=uHEVo-LkDrQ
(You may ignore the video part, even though it's "cute", but the
audio portion is a fine example of the pulse to pulse variations
exhibited by many pulsars, all wrapped up in one pulsar)

http://www.jb.man.ac.uk/pulsar/Education/Sounds/0329_stack.mp4
(I think this is the best overall site, giving quality recordings of a
fair number of different pulsars)

Dana






On Fri, Apr 13, 2018 at 2:54 AM, Tom Van Baak  wrote:

> Amazing news... 1.2.3.
>
> 1) Many of you know that pulsars are weird astronomical sources of
> periodic signals. Some are so accurate that they rival atomic clocks for
> stability! True, but I don't have a 100 foot antenna at home so I'll take
> their word for it. Plus, you have to account for a myriad of PhD-level
> corrections: from earth's rotation to general relativity. And, like quartz
> or rubidium clocks, pulsars drift (as they gradually slow down). Precision
> timing is not easy. If you poke around the web you can find numerous
> articles describing their detection and measurement and exploring their use
> as reference clocks, both here and potentially for deep-space timekeeping.
>
> 2) If you do a lot of clock measurement at home then you know the dark
> side of working with precision clocks. There are signal quality issues,
> measurement resolution issues, reference stability limitations, offset,
> drift, phase jumps, frequency jumps, missed or extra cycles, glitches, etc.
> For example, quartz oscillators (depending on make / model / luck) can
> exhibit frequency jumps; i.e., without warning they just change frequency
> without your permission. Ok, maybe not by a lot, but enough to notice;
> perhaps enough to cause trouble to any naive GPSDO PID algorithm that
> assumes steady state from the oscillator you thought was stable.
>
> 3) Now the exciting part! Fellow time-nut Jim Palfreyman studies pulsars.
> You've seen postings from him now and then over the years. It turns out Jim
> is the first person to catch a pulsar in the act of a frequency jump. After
> 3 years of continuous searching! This is really cool. Just amazing. You
> can't get more time nutty than this. And it just got published in Nature.
> It's a perfect never-give-up, i-eat-nanoseconds-for-breakfast, time nut
> thing to do. I am so impressed.
>
> To quote Jim:
>
> On December 12, 2016, at approximately 9:36pm at night, my phone
> goes off with a text message telling me that Vela had glitched. The
> automated process I had set up wasn't completely reliable - radio
> frequency interference (RFI) had been known to set it off in error.
>
> So sceptically I logged in, and ran the test again. It was genuine!
> The excitement was incredible and I stayed up all night analysing the
> data.
>
> What surfaced was quite surprising and not what was expected. Right
> as the glitch occurred, the pulsar missed a beat. It didn't pulse.
>
> Here is a very readable description of his discovery:
>
> http://theconversation.com/captured-radio-telescope-
> records-a-rare-glitch-in-a-pulsars-regular-pulsing-beat-94815
>
> And also the official Nature article with all the juicy, peer-reviewed
> details:
>
> https://rdcu.be/LfP0
>
> So congratulations to Jim. I will think of him next time my 10811A quartz
> oscillator does a frequency jump or next time my 60 Hz mains frequency
> monitor skips a cycle...
>
> If you have comments or questions feel free to send them to Jim directly
> (see Cc: address). Perhaps he can summarize the questions and his answers
> in a posting to time-nuts soon.
>
> /tvb
>
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Re: [time-nuts] Cheap jitter measurements

[Dana Whitlow]

Pity the poor man who has (n>1) clocks, for he knows not what time it is.

Dana


On Sun, Apr 8, 2018 at 4:29 PM, John Ackermann N8UR  wrote:

> I want to jump on Tom's post, and Bob's note at 1:14 on Saturday (that
> begins with "Just to be very clear..."  They both raise an important point
> about measurements.
>
> With both NTP and GPSDO measurements a lot of folks focus heavily on what
> the "black box" is reporting about itself.  But self-contained measurements
> are really unrelated to actual performance.
>
> As Bob mentioned, in a GPSDO you can look at tempco, humidco, voltageco,
> and all sorts of other things but the overall point of the system is to
> make those meaningless: the control loop(s) compensate for them.  If those
> internal error generators are reduced, it may make the system's work
> easier, but that improvement will have no effect on the quality of the
> output if the control loop is already properly compensating for it.
>
> And in NTP, the software reports all sorts of interesting measurements,
> but none of them really tell you how close the computer's clock is to a
> local reference.  As Tom said, the real test is how the time tick coming
> out of the box compares with the time tick going into it.
>
> The bottom line is that no self-contained measurement can tell you actual
> performance.  The *only* way to do that is to compare your box with an
> external reference whose error bounds are known.
>
> After all, this is why we're time-nuts -- every time you acquire a clock,
> you also need to acquire a better clock to test it with. :-)
>
> John
> 
>
> On 04/08/2018 03:36 PM, Tom Van Baak wrote:
>
>> What do you mean by "jitter" and what do you really want to do?
>
 I mean jitter as NTP defines jitter.  Whatever that is.

>>>
>>> I think you need to figure out what you want to do so you don't fool
>>> yourself.
>>>
>>> ntpd is a PLL.  There is a low pass filter in the control loop.  It will
>>> track the low frequency wander of the source.
>>>
>>
>> Gary, Hal, Leo,
>>
>> My mental model of a black box computer running NTP is that I should be
>> able to give it a pulse (e.g., via parallel, serial, GPIO) and it tells me
>> what time it was. Use a GPSDO / Rb / picDIV to generate precise pulses.
>> Compare the known time of the pulse with the time the box says it was.
>> Repeat many times, collect data, look at the statistics; just as we would
>> for any clock.
>>
>> Similarly, the box should be able to give me a pulse at a known time. In
>> this case it records the time it thinks the pulse went out, and your GPSDO
>> / Rb / TIC makes the actual measurement. Again, collect data and look at
>> the statistics; just as we would for any clock.
>>
>> Imagine the black box has two BNC connectors; one accepts an input pulse
>> to be timed; one outputs a pulse at certain times. This allows a complete
>> analysis of NTP operation. Should be true for both client or server. If you
>> get down to nanosecond levels make sure to use equal length cables.
>>
>> To me this better than relying on NTP to tell you how NTP is doing, which
>> as far as I can tell from live plots on the web, is all that most people
>> do. Instead use real, external, physical measurement. The internal NTP
>> stats are fine for tracking the performance of the PLL, but don't confuse
>> that with actual timing.
>>
>> So this is why I'm excited to hear Gary wants a Rb timebase and a sub-ns
>> counter. Someone will finally measure NTP for real, not rely on the
>> internal numbers of NTP measuring itself. Or at least I hope that's what
>> Gary is up to.
>>
>> /tvb
>>
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Re: [time-nuts] quartz / liquid nitrogen

[Dana Whitlow]

Many years ago, circa 1977, I was moved to try some crude tests on a few
semiconductor devices at LN2 temperature (77K).

These tests were very crude, involving dunking the parts into the LN2 bath,
and
many failed outright.  Most of the devices tested were in plastic packages.

Here are the results as I remember them, applicable only for the survivors:

Silicon bipolar transistors:   The DC beta fell to very low values.
Junction
forward voltages rose considerably.

Silicon JFETs:  Seemed to continue working reasonably well.

Silicon MOSFETs:  Same as JFETs

Red LEDs:   The junction forward voltages rose considerably, to about  5V as
I recall.   The light output per unit current rose truly spectacularly.

My first experiences with seriously-cryogenic RF amplifiers were at the
Arecibo Observatory beginning about 11 years ago.  These were all either
GaAs- or InP-based and we cooled them to ~15K, generally leading to
input-referred amplifier noise temperatures of ~3K.  Many of the devices
needed continuous exposure to light to work properly when cold, and the
metal block amplifier packages had holes in the lid directly over the active
device chips. Small red LEDs in ordinary plastic packages were inserted
in the holes and were driven at a few mA, generally in a series string.
Since cool-down was fairly gradual over a span of at least a couple hours,
there was little problem with thermal shock and almost all LEDs survived
cooldown and warmup for the several cycles they experienced during
my 10 years at the observatory.

RF amplifier biasing was invariably done with opamp circuits to maintain
set drain currents and drain voltages, with said bias control circuits
outside
the dewar at room ambient temperature.   Failures were not too uncommon,
largely attributed to connector misbehavior at low temperature.  Formation
of "ice" (really frozen air) inside the dewars was suspected because fine
wires
inside the dewar were often found to have fairly sharp bends at improbable
locations upon warmup for diagnostic purposes (or due to cooling system
failure).

Cooling was done with a closed-cycle gaseous He system, using the
Gifford-McMahon cycle.  Note that He does not liquefy (at reasonable
pressures) until around 4K.  All dewars for this kind of work depend on
high vacuum inside for thermal insulation, with black body radiation
and direct conduction through wires and mounting structures being
the principal remaining heat leaks.

At these temperatures, maintenance of high vacuum inside the dewar was
essentially automatic because all components of the inward-leaking air
were known to freeze out.  This could lead to a hazard because over time,
months or years, enough air could freeze out to result in dangerously high
internal pressures upon "thawing" when the dewar was warmed for any
reason.  For this reason, all dewars were equipped with blowout plugs
to avoid high pressure's damaging the dewars themselves.

Dana


On Tue, Apr 3, 2018 at 12:26 AM, Mark Sims  wrote:

> And you want your semiconductors to be in ceramic/lided packages with the
> bond wires flapping in free air.   Bond wires embedded in epoxy like to
> break...  don't ask how I found this out  ;-)   ... it brings back bad
> memories... and makes bad memories...  Quantum chips have very
> elaborate/specialized bonding to survive liquid helium... even with that,
> thermal cycling still breaks them.
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Re: [time-nuts] quartz / liquid nitrogen

[Dana Whitlow]

Is the thermal noise generated in the loss in a quartz resonator a
significant part
of the overall phase noise picture?  I would have not thought so.  I'd
think that a
greater benefit ought to be derived from chilling the other parts in the
oscillator,
such as the active devices.  Unless, of course, chilling the quartz
actually improves
the Q significantly, which I don't know about.

If cooling (whatever) by just a modest amount helps much, then one could
consider using Peltier cooling.  It doesn't really get things very cold,
but is a
lot more convenient than either dry ice or LN2.  But then you don't get the
fun
that you do when playing with LN2, either.

Dana


On Mon, Apr 2, 2018 at 2:46 PM, Tom Van Baak  wrote:

> Has anyone tried running a quartz oscillator at liquid nitrogen
> temperatures: -196 C (-321F, 77K)? It's probably impractical commercially,
> but maybe something of value to a time nut. Would that dramatically lower
> temperature improve phase noise & short-term performance? Is there a
> crystal cut that could be optimized for 77 K instead of ~25 C (room) or 60
> C (oven)?
>
> If not Nitrogen, how about dry ice (-109F -78C)?
>
> /tvb
>
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Re: [time-nuts] TV Signals as a frequency reference

[Dana Whitlow]

I'e always been curious as to why TV stations did not lock at least
their in-house equipment to the network feed as  a means to avoid
spending money on frame syncs.  Remote coverage, on the other
hand, would of course open a new can of worms.

But compared to the cost of building and powering a TV station and
associated studios etc, a Rb or three cost a mere drop in the bucket
to buy and maintain, so I'm baffled as to why stations in general did
not at use them on a regular basis.

Dana


On Sat, Mar 31, 2018 at 12:43 AM, Hal Murray 
wrote:

> > As noted earlier, color burst references were a big deal a long time ago.
>
> Thanks.  I was fishing for something modern, maybe a bit clock out of the
> digital receiver.
>
> I'm assuming that the digital stream is locked to the carrier.  That may
> not
> be correct.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] What does determine the short term stability of an Rb vapor cell standard?

[Dana Whitlow]

Could it be that with the narrow-band laser emission the dip in
light transmission of the Rb cell is significantly improved?   I know
that diode lasers are generally not paragons of virtue when it comes
to intensity noise, so I'm wondering what accounts for the claims of
better SNR with laser illumination.

Dana Whitlow

On Sun, Mar 25, 2018 at 8:18 AM, Attila Kinali <att...@kinali.ch> wrote:

> Moikka moi,
>
> In the past, it has been again and again claimed that the HP 5065 has
> such an outstanding short term stability because of its large vapor cell.
> But the more I read, the less I believe this. E.g. if you look at the
> papers by the group around Gaetano Mileti and Christoph Affolderbach
> from University of Neuchatel, you'll see that they get an ADEV well
> below 1e-12 with a vapor cell that is just 3x3cm (actually smaller
> than that... but details). Yes, they use a laser instead of an Rb lamp,
> which increases SNR. But that would mean it's not the cell size per se
> that limits the short term stability, but the pumping of the atoms
> and the light noise on the photo cell. Hence it should be, theoretically
> at least, be possible, to take one of the telecom Rubidium standards,
> replace the lamp with something better, and come close to the performance
> of an 5065 So, what part of this is wrong and what am I missing?
>
>
> Attila Kinali
>
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
>  -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] EFTF 2018

[Dana Whitlow]

Speaking of forums etc, does anybody in Time-Nuts attend anyof the
NIST Time and Frequency Seminars?  I'm wondering if I'd get
much from it.

I've thought about doing so for years, but never got around to
pushing for it while employed.  Now it's looking awfully expensive.

Dana


On Fri, Mar 16, 2018 at 8:38 AM, Magnus Danielson <
mag...@rubidium.dyndns.org> wrote:

> Hi,
>
> As I just registered for EFTF 2018, just wanted to check if any fellow
> time-nuts would join me there.
>
> I can also be expected to show up on the IFCS-EFTF 2019 conference, as I
> will serve on the JTPC for it.
>
> Cheers,
> Magnus
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Re: [time-nuts] Need a Watch Recommendation

[Dana Whitlow]

Most of the quartz watches I've owned were off by about 1-2 minutes per
month,
which I consider inexcusable.

Agreed, the mechanical trimmer is rather problematical, but I'd sure like
to see
*something *that the sophisticated user can tweak at home. Measurement of
the
current rate error is probably not much of a problem; I once tried seeing
the
32kHz signal in the watch by capacitive coupling to the face, and could
detect
the signal.  I just tried a token attempt on my current watch and failed,
but it
was a crude, unshielded attempt by merely laying a 'scope probe against the
watch face.  I was being severely jammed by the local 1230 kHz AM station.
Anyway, the idea is to observe the signal's phase drift while triggering
the 'scope
from a trusted 1PPS source.

So now all that's needed is an alternate way for trimming the watch's
frequency
without opening the case.  There must be a way...

Dana


On Thu, Mar 15, 2018 at 8:13 AM, Bob kb8tq <kb...@n1k.org> wrote:

> Hi
>
>
> > On Mar 15, 2018, at 1:33 AM, Dana Whitlow <k8yumdoo...@gmail.com> wrote:
> >
> > I concur with Bill.  And even if one keeps tabs on the current watch
> error,
> > as is the usual practice by celestial navigators, once that error reaches
> > or exceeds more than a minute the process frankly gets more clumsy and
> > error prone.  And if a watch drifts in time very rapidly, one loses faith
> > in its
> > ability to coast at a known rate between checks against WWV, which
> > opportunities are not always available when one wants, due to
> > propagation issues.
> >
> > Whatever happened to the quartz watches with trimmer capacitors
> > for setting the rate?
>
> Trimmer caps to set watch crystals are problematic. They are a source of
> error
> as well as a set mechanism. You bump this or that and the trimmer moves.
> They
> also cost money to buy and install properly (no flux in-between the plates
> …).
> Once that is all done you need a way to set them in the factory. Back in
> the day,
> yes, we hat line workers who did that sort of thing. We also sold the
> crystal in the
> watch module (not the whole module) for $2 once upon a time.
>
> How close do you want to set it? In our case, the set was supposed to be <
> 0.5
> ppm of the target. Ideally you needed a design that would do a small
> fraction
> of a ppm in a typical situation.
>
> If the trimmer is a normal device, you get about 120 degrees of travel for
> the
> useful part of the tuning curve. A tune range of 30 ppm for the crystal
> and another
> 20 ppm for the other parts would not be unusual. Even taking the 0.5 ppm
> number,
> you are into 120 / 100 = 1.2 degrees sort of set on that little trimmer.
>
> Bottom line: They went away because they weren’t good enough and they were
> to expensive …. Setting a modern “shoot the chip” register based module is
> way
> more accurate and reliable. It’s silicon so the cost is whatever sand is
> selling
> for ….
>
> Bob
>
> >
> > And radio controlled?  No way!
> > The process is to delicate and marginal to rely upon.  Give me a
> > good stable free-running watch any day.
> >
> > I don't like the solar watch concept mainly because one sometimes
> > has to go for weeks without an opportunity to expose his watch to
> > direct sunlight (or some indoor equivalent) for the requisite period
> > of several hours.
> >
> > Yesterday I was reading the manual for the Citizen ECO series,
> > and that thing requires far too much effort and complication to keep
> > it working and on time.  A good watch must simply work, with no
> > maintenance beyond occasional battery replacements (and possible
> > gland replacement at battery-change time), and accurately enough
> > that the time need never be reset between battery replacements.
> >
> > I use an old quartz diving watch I bought just under 10 years ago,
> > (brand no longer distinguishable), which has never drifted more than
> > about 30 sec (usually less) between battery replacements, and I never
> > take it off between batteries except when compelled to do so at TSA
> > checkpoints.  Aside from its LCD's failing I'd be happy to use if
> forever,
> > but it's getting awfully hard to read these days.
> >
> > Dana
> >
> >
> >
> > On Wed, Mar 14, 2018 at 10:54 PM, Bill Byrom <t...@radio.sent.com>
> wrote:
> >
> >> On Wed, Mar 14, 2018, at 6:53 PM, Dr. David Kirkby wrote:
> >>> What is the most demanding task one would use a wrist watch for?
> >>
> >> It depends on your job or hobby.
> >>
> >> During the Apollo 13 rocket burn before their emergency re-e

Re: [time-nuts] Need a Watch Recommendation

[Dana Whitlow]

I concur with Bill.  And even if one keeps tabs on the current watch error,
as is the usual practice by celestial navigators, once that error reaches
or exceeds more than a minute the process frankly gets more clumsy and
error prone.  And if a watch drifts in time very rapidly, one loses faith
in its
ability to coast at a known rate between checks against WWV, which
opportunities are not always available when one wants, due to
propagation issues.

Whatever happened to the quartz watches with trimmer capacitors
for setting the rate?

And radio controlled?  No way!
The process is to delicate and marginal to rely upon.  Give me a
good stable free-running watch any day.

I don't like the solar watch concept mainly because one sometimes
has to go for weeks without an opportunity to expose his watch to
direct sunlight (or some indoor equivalent) for the requisite period
of several hours.

Yesterday I was reading the manual for the Citizen ECO series,
and that thing requires far too much effort and complication to keep
it working and on time.  A good watch must simply work, with no
maintenance beyond occasional battery replacements (and possible
gland replacement at battery-change time), and accurately enough
that the time need never be reset between battery replacements.

I use an old quartz diving watch I bought just under 10 years ago,
(brand no longer distinguishable), which has never drifted more than
about 30 sec (usually less) between battery replacements, and I never
take it off between batteries except when compelled to do so at TSA
checkpoints.  Aside from its LCD's failing I'd be happy to use if forever,
but it's getting awfully hard to read these days.

Dana



On Wed, Mar 14, 2018 at 10:54 PM, Bill Byrom  wrote:

> On Wed, Mar 14, 2018, at 6:53 PM, Dr. David Kirkby wrote:
> > What is the most demanding task one would use a wrist watch for?
>
> It depends on your job or hobby.
>
> During the Apollo 13 rocket burn before their emergency re-entry, Jack
> Swigert used a wrist watch to time the retrorocket burn which was
> manually controlled by Jim Lovell. Their normal capsule chronometer was
> inoperative. This was mostly a differential (time interval) timing
> measurement.
> If you needed to determine your location (longitude) and all you had
> was a wristwatch and a sextant (and software or a table with certain
> information), the accuracy of the distance calculation would depend on
> the absolute time accuracy of the watch. At the equator the longitude
> error due to time error is (40,075.16 km/day) / (86,400 sec/day) =
> 463.8 m/sec.
> Amateur astronomers need to know time accurate to about a second or
> better for accurate osculation observations.
> Amateur Radio nets and phone, Skype for Business, or WebEx conference
> calls usually start pretty close to the scheduled time. In some cases
> people start wondering if the organizer is delayed after about 15 to
> 30 seconds.--
> Bill Byrom N5BB
>
>
>
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Re: [time-nuts] Recommendations for Mains Power Monitor / Logger

[Dana Whitlow]

Now I'm getting interested in this.  My concept is to take the 60 Hz in, do
reasonable
HW filtering to knock off the HF junk that commonly rides on the sinewave,
then use
an RC quadrature phase splitter to yield I & Q signals.  Then sample at
1PPS with
my Rb's PPS as the sample trigger,  and capture the result with a 2-channel
data
acquisition gadget of some sort.  It's that last item that's holding me
back.

I'll have to take a look around to see if there isn't something cheap that
can run
standalone so I don't have to tie up (or wear out) a whole PC for the
acquistion
process.

Dana


On Sun, Mar 11, 2018 at 1:49 PM, Didier Juges  wrote:

> I like the sound card idea. However I believe it's much better to use the
> two channels. At least under Windows, it is much easier to track the
> relative phase of the two channels of one sound card than the absolute
> phase of one channel compared to the system clock.
> I have written an audio VNA in Visual Basic that has all the building
> blocks.
> Unfortunately, it is harder and harder to develop VB 6.0 under Windows 10
> so I am not doing much of that anymore.
> Since I am doing it using FFT, filtering (and harmonics measurements) come
> for free.
>
> On Mar 10, 2018 10:47 PM, "Tom Van Baak"  wrote:
>
> > > I've done some Googling and have found any number of designs.
> >
> > Pat,
> >
> > 1) Safety. I usually use a low voltage step-down transformer. This gives
> > isolation and safety. Anything from 3 VAC to 24 VAC is fine.
> >
> > 2) Trigger. There are dozens of schematics on the web for capturing the
> > zero-crossing of a low-voltage sine wave. You can easily go overboard on
> > this. Or just keep it simple and feed the signal through a resistor
> > directly into a microprocessor input. The internal clamping diodes do
> their
> > thing. A Schmitt trigger input is helpful but not necessary depending on
> > how your software makes the measurement.
> >
> > 3) Timebase. Given the long-term accuracy of mains (seconds a day,
> seconds
> > a year) you don't need an atomic timebase. If you collect data for a
> couple
> > of days any old XO will be fine. If you plan to collect data for months
> you
> > may want a OCXO. Most of us just use cheap GPS receivers.
> >
> > 4) Measurement. There are many ways to measure the signal. You can
> measure
> > frequency directly, as with a frequency counter. You get nice data but it
> > may not be perfect long-term due to dead time or gating effects in the
> > counter.
> >
> > So what most of us do is measure phase (time error) instead. One way is
> to
> > make time interval measurements from a given mains cycle to a GPS 1PPS
> tick
> > or vice versa, from each GPS/1PPS tick to the very next mains cycle.
> Either
> > way you get about sample per second. If you're in search of perfection it
> > gets a bit tricky when the two signals are in a coincidence zone.
> >
> > The other approach is not to use a frequency or time interval counter at
> > all. Instead you timestamp each cycle, or every 60th cycle. Unix-like
> > systems have this capability. See Hal's posting. I use a picPET, a PIC
> > microcontroller that takes snapshots of a free-running decimal counter
> > driven by a 10 MHz timebase (OCXO or GPSDO).
> >
> > The advantage of the timestamp method is that you don't ever miss
> samples,
> > you can time every cycle (if you want), or throw away all but one sample
> > per second or per 10 seconds or per minute, etc. And best of all,
> > timestamping avoids the hassles of the coincidence zone.
> >
> > 5) CPU. A plain microcontroller, or Arduino, or R-Pi can be used. Or if
> > you're on Windows and have a native or USB serial port try this simple
> tool
> > as a demo:
> >
> > http://leapsecond.com/tools/pctsc.exe
> > http://leapsecond.com/tools/pctsc.c
> >
> > 6) An assortment of mains links:
> >
> > http://leapsecond.com/pages/mains/
> > http://leapsecond.com/pages/mains-cv/
> > http://wwwhome.cs.utwente.nl/~ptdeboer/misc/mains.html
> > http://leapsecond.com/pages/mains/mains-adev-mdev-gnuplot-g4.png
> > http://leapsecond.com/pages/tec/mains-clock-ani.gif
> > http://leapsecond.com/pages/ac-detect/
> > http://leapsecond.com/pic/picpet.htm
> > http://leapsecond.com/pic/pp06.htm
> >
> > 7) Final comments.
> >
> > It is tempting to worry about the design, as they are so many out there
> on
> > the web. Which is best? What are the pitfalls? What about noise immunity?
> > What about precision and accuracy? My recommendation is not to over-think
> > this. Just throw something together and see what you've got. Most of the
> > work is with handling the data you get, doing the math, making plots,
> etc.
> > If after the first day you see odd-looking 16 ms jumps in your data then
> > you know you need to pay more attention to trigger level or noise issues.
> >
> > 8) A sound idea.
> >
> > We need someone to try out the sound card method. Send the isolated low
> > voltage AC into the L channel 

Re: [time-nuts] Assorted replies, and request for info

[Dana Whitlow]

In connection with ground loops, why not put "ferrite beads" on coaxial
cables in the system?

In this case where the offending frequencies would be in the 60 Hz regime
one would probably
need large toroids with multiple turns, but the approach ought to do some
real good, without
introducing the problems associated with leaving on end of a coax shield
unconnected.

Dana


On Mon, Feb 26, 2018 at 8:45 PM, John Miles  wrote:

> Request for data from an off-list friend who is looking for info on an
> Ovenaire OCXO and/or the instrument it was used in:
>
> > Could you send a post on my behalf asking if anyone else has an
> > Ovenaire 42-15 or if not, a Spectracom 8131 Frequency Standard
> Oscillator.
>
> This is from Dennis Tillman, who can be reached directly at dennis (at)
> ridesoft.com.
>
> > Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot.
> What
> > do you think that is? On a hunch I opened the front panel and reset the
> > blinking amber battery alarm lamp, and voila, that noise went away. Makes
> > sense when you think of the power variations associated with a blinking
> > incandescent lamp.
>
> I hadn't heard of that one, but some other examples include 1-pps
> crosstalk on the 10 MHz output of some of the HP GPSDOs (which I've run
> into myself), and the inadvertent ~5 MHz comb generator that drives the
> indicator LED on the HP 5370's reference clock interface PCB that Bruce
> Griffiths noticed several years ago.  Presumably neither of these faux pas
> were bad enough to be noticed by the original designers or their paying
> customers, but they probably would have been fixed if they had come to the
> attention of the people involved.  Goes to show how improved
> instrumentation can be a curse as well as a blessing.
>
> Poul-Henning's observation on the 5065A integrator cap highlights the risk
> of erring too far in the opposite direction:
>
> > When I experimented, I could hardly find *any* property that mattered
> > for that capacitor, not even the exact capacitance, because the
> > adjustment procedue handles that.
>
> I have a feeling this is true of most of the components in that circuit.
> The nice thing about an integrator is that it's also a low-pass filter.
> And the nice thing about a closed loop is that it's, well, closed.
>
> Before spending too much time arguing about whether the opamp should be
> replaced with an LT1012 or an AD797 or a cryocooled tunnel diode or
> whatever, I'd suggest replacing it with a 741 and seeing how much *worse*
> the performance gets.  It is easier to measure the effect of that kind of
> change.  If there is little or no harm in using the crappiest opamp you can
> find, that means that you can safely stop worrying about what the best one
> might be.
>
> > One of the TimePods that I had access to in the past was particularly
> good
> > at telling you it was sitting on top of a power transformer. It didn’t
> matter a
> > lot which instrument the power transformer was in. For some weird
> > reason it was a good magnetometer at line frequencies. I never bothered
> to
> > send it back for analysis. Simply moving it onto the bench top (rather
> than
> > stacked on top of this or that) would take care of the issue.
> >
> > As far as I could tell, it was just the one unit that had the issue.
> None of the
> > others in the fleet of TimePods seemed to behave this way. Given that
> they
> > normally are very good at rejecting all sorts of crud and ground loops,
> it was
> > somewhat odd to see.
>
> I've seen similar behavior here, not only with respect to units responding
> differently to 60/120 Hz magnetic interference, but also at higher offsets
> in the absence of an obvious coupling mechanism.  There was one case where
> a TimePod I was working with picked up an unstable low-level spur near 25
> kHz from an LED aquarium light fixture several meters away.  Other units
> swapped into the same position did not show the spur at all, and I was
> never able to narrow down the cause with any certainty.  I don't have a
> good explanation for any of the above, unfortunately.
>
> That being said, Phil Hobbs posted something on sci.electronics.design the
> other day that I thought was subtly insightful, even though he was just
> stating an obvious point.  Namely, ground loops are inherently very low
> impedance phenomena, often occurring in the milliohm range.  Especially
> when dealing with anodized aluminum hardware like the TimePod's enclosure,
> the difference between a test setup where all the coax shields act as a
> near-perfect shorted transformer turn versus one with significant loss
> might come down to small differences in fastener torque, or perhaps a
> missing star washer.  So it's possible to envision a scenario where
> tightening up all the proverbial loose screws actually makes a
> magnetically-coupled spur worse.
>
> Lifting a coax shield is usually not the best solution to ground loops,
> but Phil's offhand comment made 

Re: [time-nuts] HP 5065A super

[Dana Whitlow]

Keep in mind that soldermask will also change the field distributions
around a
microstrip line, and will somewhat mitigate the microstrip's dispersive
behavior
as well.

I once worked with some miccrostrip couplers at around 2-4 GHz and found
that
directivity was significantly improved by adding two layers of thin kapton
tape
on top of the coupled region, a solution that went into production.  I
expect that
the usual soldermask layer would have about the same effect.

Dana


On Thu, Feb 22, 2018 at 8:15 PM, jimlux  wrote:

> On 2/22/18 12:29 PM, Leo Bodnar wrote:
>
>> Here is ENIG fact that is not widely known at the moment but which some
>> might find useful.
>>
>> I could not understand why I get better TDR and insertion loss results
>> from solder-mask covered microstrip transmission lines than from otherwise
>> identical microstrips on the same substrate with soldermask removed and,
>> therefore, covered with ENIG.
>>
>> Gold can't be bad, right? As it turns out, even gold coin has two sides
>> to it.
>>
>> I have found that Shlepnev and McMorrow conducted extensive research and
>> published data, some of which is presented here
>> http://www.simberian.com/Presentations/NickelCharacterizatio
>> nPresentation_emc2011.pdf
>>
>>
> the ever useful http://www.microwaves101.com/ site has an excellent
> discussion of this under the "skin effect" heading.
>
>
>
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Re: [time-nuts] The "NAKED" 5065A optical unit

[Dana Whitlow]

I'm curious:

Is the lamp RF-excited, or by DC going to internal electrodes?

And if by RF, is the energy coupled in magnetically by a loop,
or by capacitive electrodes?

Thanks,

Dana




On Mon, Feb 19, 2018 at 7:08 PM,  wrote:

> Here is a PIX of the optical unit from a 5065A totally removed from the
> shield assembly.
>
> Left to right:
>
> Lamp assy
> lamp oven cylinder
> lamp reflector/convection block/diffuser
> Rb85 filter cell
> cell oven cylinder/cavity
> Rb87 resonance cell
>
> Enjoy!
>
> Cheers,
>
> Corby
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Re: [time-nuts] eBay GPS antenna test results.

[Dana Whitlow]

I would surmise that the antenna has (or rather had) a protection network
to protect against voltage spikes or surges.  Your description of events
seems consistent with an triggered SCR crowbar circuit, and the 2nd
attempt at the higher current limit shorted the SCR.  Note that this may
not have been a regular SCR, but perhaps a NPN/PNP pair hooked up
to emulate an SCR.   If you can find evidence of such a circuit, it may
be replaceable or simply removable, leaving the antenna fully functional.

Assuming this works, do keep the supply voltage down to something
reasonable like 5 or 6 volts.   Excess voltage will result in unneeded
heat generation in whatever regulator the antenna uses, shortening
its life.

Dana



On Fri, Feb 9, 2018 at 5:00 PM, Dr. David Kirkby <
drkir...@kirkbymicrowave.co.uk> wrote:

> On 9 February 2018 at 21:43, John Green  wrote:
>
> > To those who doubted that the antenna was actually a 3.3 to 18 volt
> design,
> > it seems you were correct. Today, I hooked it up to a variable power
> supply
> > and slowly raised the DC voltage fed to the antenna. It began to pull
> > current at about 2.9 volts and at 3.3 volts, took about 40 mA. I
> continued
> > to slowly raise the voltage. At about 7.5 volts, the current suddenly
> > dropped to 10 mA. At just below 12 volts, it suddenly increased to 80 mA
> > and the supply went into current limit. I increased the current limit to
> > 130 mA and repeated the exercise. Everything went as above until I
> reached
> > 12 volts and the current went to 130 mA and the supply went into current
> > limit. Lowering the voltage didn't lower the current. I disconnected it,
> > waited a minute, and tried again. Yep, shorted. It would have worked well
> > with the T bolt, but would have blown anyway if I tried to use it with my
> > 12 volt supply and bias T. I guess I will get inside it somehow to see if
> > it can be repaired. My first attempt ended in failure. I guess I need a
> > bigger screwdriver with which to pry the top off. I am going to contact
> the
> > seller and tell them it was not as advertised. I kind of doubt that will
> > get me anything, but it won't hurt to try. There is a saying about
> > experience being a cruel teacher. You get the results first, and the
> lesson
> > after. Oh well.
> >
>
>
> You should not open it up, but open an eBay case for item not as described.
> If it said it would do 3-18 V, but does not, then its not as described, and
> you should get your money back. The chances are the seller will not want to
> arrange collection, so you will probably get to keep it anyway. But you
> should get a refund before opening it up.
>
> Dave
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Re: [time-nuts] minimalist sine to square

[Dana Whitlow]

Tom,

I recently built such a device using a couple of stages of a 74HC04,
with the RF input to the 1st stage AC coupled and the input biased
by a high-value (a couple of megohms) resistor feeding back from
the output of the first inverter stage to the input of that stage.  It's so
dirt simple, it's hard to beat.

I was not particularly concerned about jitter, so if you're not already
familiar enough with the circuit to know whether or not it's good
enough, it might be worth a try.  BTW, I am running at 10 MHz from
a PRS-10 Rb, and just wanted something to drive a count-down
chain. And there's always the 74AC04 if you wanted faster edges.

Dana Whitlow


On Fri, Jan 19, 2018 at 1:31 PM, Tom Van Baak <t...@leapsecond.com> wrote:

> John's TADD-2-mini [1] uses the Wenzel sine-to-square converter. It
> performs very well but requires +10 V.
>
> I'm looking for a solution that works at 5 V (e.g., USB powered) and also
> uses fewer parts. Wenzel also mentions using a differential line receiver
> [2]. That would be an ideal single-chip 5 V solution for me but the two
> parts he mentions, MC1489 [3] and SN55182 [4], don't appear fast enough for
> a 10 MHz input.
>
> Can any of you circuit experts suggest some line receivers that would
> work? Maybe DS9637 [5]? This isn't for cesium work so it doesn't have to be
> quite as good as the TADD-2.
>
> Thanks,
> /tvb
>
> [1] http://www.tapr.org/~n8ur/T2_Mini_Manual.pdf
> [2] http://www.wenzel.com/documents/waveform.html
> [3] https://www.onsemi.com/pub/Collateral/MC1489-D.PDF
> [4] http://www.ti.com/lit/ds/slls092d/slls092d.pdf
> [5] http://www.ti.com/lit/ds/symlink/ds9637a.pdf
>
>
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Re: [time-nuts] PBS, Tue evening, The Secret of Tuxedo Park

[Dana Whitlow]

I could only afford a single Accutron, so I got in the habit of storing it
overnight in an orientation
estimated to correct bedtime error by wake up time.  I got pretty good at
it.

BTW thanks very much for the tip on the book- I must definitely get a copy.

Dana


On Tue, Jan 16, 2018 at 9:04 AM, Tom Van Baak  wrote:

> I can't stress enough how important Loomis was to the history of precise
> timekeeping in early radio, telephone, pendulum clock, quartz oscillator
> era. And for those of us who still have Loran-C receivers can thank him
> (Loomis Radio Navigation -> LRN -> Loran).
>
> So I highly recommend the 2003 book "Tuxedo Park" by Jennet Conant:
> http://www.simonandschuster.com/books/Tuxedo-Park/Jennet-
> Conant/9780684872889
>
> Our kind of guy. In the "Palace of Science" chapter she writes: Loomis
> would remain a "time nut" for the rest of his life, according to Luis
> Alvarez, who recalled that Loomis always wore "two Accutrons--one on his
> right wrist and one on his left wrist." He would check them every day
> against WWV (the standard frequency broadcasting station of the National
> Bureau of Standards), and if one was gaining a half second on the other, he
> would wear it on the outside of his wrist instead of the inside, so that
> gravity changed the rate of the tuning fork and the two watches tracked
> each other, and WWV, "to within less than a second a day."
>
>
>
> Some other Loomis links of interest:
>
> https://en.wikipedia.org/wiki/Alfred_Lee_Loomis
> https://en.wikipedia.org/wiki/LORAN
> https://timeandnavigation.si.edu/navigating-air/navigation-
> at-war/new-era-in-time-and-navigation/alfred-loomis
> http://www.ob-ultrasound.net/loomis.html
> http://leapsecond.com/pages/loomis/
>
>
> And the clever way to do time transfer and compare precision clocks to 1
> ms in the 1930's...
>
> http://leapsecond.com/pend/shortt/1931-RAS-Precise-
> Measurement-Time-Loomis.pdf
>
>
> Also the classic "The Evolution of the Quartz Crystal Clock" by Warren A.
> Marrison:
>
> https://ieee-uffc.org/about-us/history/uffc-s-history/the-
> evolution-of-the-quartz-crystal-clock/
> via https://ieee-uffc.org/about-us/history/uffc-s-history/
> and original at https://archive.org/details/bstj27-3-510
>
>
> If someone knows how to record any time/clock/navigation parts of PBS show
> for non-US viewers let me know, off-list.
>
> /tvb
>
>
> - Original Message -
> From: "Hal Murray" 
> To: 
> Cc: "Hal Murray" 
> Sent: Tuesday, January 16, 2018 1:42 AM
> Subject: [time-nuts] PBS, Tue evening, The Secret of Tuxedo Park
>
>
> > (Sorry for the clutter to those of you outside the US.)
> >
> > http://www.pbs.org/wgbh/americanexperience/films/secret-tuxedo-park/
> > Two of the shorts mentions time.
> >
> > Many thanks for the Tuxedo Park book suggestion many years ago.
> >
> >
> > --
> > These are my opinions.  I hate spam.
> >
>
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Re: [time-nuts] AM vs PM noise of signal sources

[Dana Whitlow]

One point about oscillator design I've not yet seen mentioned is this: the
limiter
must not degrade the resonator Q when in action.  Hence, a pair of diodes
connected in parallel back to back, across a shunt resonator, would be a bad
thing to do from the perspective of low phase noise. A differential
amplifier
that limits by running out of current on peaks, driving a shunt resonator,
is
a much better way even though one pays a price in having more transistor
noise in the circuit.

I've long wondered if a very slow AGC might avoid the nonlinear mechanisms
issue except, of course, for things happening within the AGC loop's
bandwidth.
Is anybody reading this aware of what the truth really is?

Dana


On Sat, Jan 6, 2018 at 4:29 PM, Magnus Danielson  wrote:

>
>
> On 01/06/2018 10:31 PM, Joseph Gwinn wrote:
> >> --
> >>
> >> Message: 2
> >> Date: Sat, 6 Jan 2018 09:19:31 -0500
> >> From: Bob kb8tq 
> >> To: Discussion of precise time and frequency measurement
> >>  
> >> Subject: Re: [time-nuts] AM vs PM noise of signal sources
> >> Message-ID: 
> >> Content-Type: text/plain;charset=utf-8
> >>
> >> Hi
> >>
> >> The key point missing is the fact that any real oscillator must have
> >> a limiter
> >> in the loop. Otherwise it will “create one” by going over the max
> >> output of this or
> >> that amplifier. To the degree that the limiter has issues (limits
> >> poorly) you will get
> >> AM noise.
> >
> > Hmm.  Not strictly true.  One can also use an AGC loop, like a wein
> > bridge oscillator.  That said, some kind of softish limiter is commonly
> > used.
>
> Regardless what non-linear mechanism in play, this remains a non-linear
> mechanism that achieves the goal. Choose wisely.
>
> Cheers,
> Magnus
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Re: [time-nuts] AM vs PM noise of signal sources

[Dana Whitlow]

But what I'm wondering, because this is important to the discussion, is the
tone at a frequency encompassed on both sides by the noise band?  Or
is the tone outside the noise band?

Dana


On Fri, Jan 5, 2018 at 1:35 PM, Bob kb8tq <kb...@n1k.org> wrote:

> Hi
>
> The audio (or RF) tone is summed with “baseband" noise. 1/F noise seems
> to be the flavor of the day in recent postings. The only reason to use
> audio
> in the example is that it is really easy to demonstrate things at audio
> with
> a sound card.
>
> Bob
>
> > On Jan 5, 2018, at 1:42 PM, Dana Whitlow <k8yumdoo...@gmail.com> wrote:
> >
> > Is this an audio tone, summed with audio noise whose spectrum surrounds
> > that of the tone?
> >
> > Dana
> >
> >
> > On Fri, Jan 5, 2018 at 9:56 AM, Bob kb8tq <kb...@n1k.org> wrote:
> >
> >> Hi
> >>
> >> If I pass both a sine wave tone and a pile of audio noise through a
> >> perfectly
> >> linear circuit, I get no AM or PM noise sidebands on the signal. The
> only
> >> way
> >> they combine is if the circuit is non-linear. There are a lot of ways to
> >> model
> >> this non-linearity. The “old school” approach is with a polynomial
> >> function. That
> >> dates back at least into the 1930’s. The textbooks I used learning it in
> >> the 1970’s
> >> were written in the 1950’s. There are *many* decades of papers on this
> >> stuff.
> >>
> >> Simple answer is that some types of non-linearity transfer AM others
> >> transfer PM.
> >> Some transfer both. In some cases the spectrum of the modulation is
> >> preserved.
> >> In some cases the spectrum is re-shaped by the modulation process. As I
> >> recall
> >> we spend a semester going over the basics of what does what.
> >>
> >> These days, you have the wonders of non-linear circuit analysis. To the
> >> degree
> >> that your models are accurate and that the methods used work, I’m sure
> it
> >> will
> >> give you similar data compared to the “old school” stuff.
> >>
> >> Bob
> >>
> >>> On Jan 5, 2018, at 6:27 AM, Attila Kinali <att...@kinali.ch> wrote:
> >>>
> >>> On Tue, 2 Jan 2018 23:34:18 +0100
> >>> Magnus Danielson <mag...@rubidium.dyndns.org> wrote:
> >>>
> >>> [About AM noise being of equal power as PM noise]
> >>>
> >>>> Now, for actual sources this is no longer true. The AM noise can be
> much
> >>>> higher, which is why it can be a real danger to the PM noise if there
> is
> >>>> a AM to PM noise conversion. One source of such conversion can be the
> >>>> amplification stage, but another could be a mistuned filter, which
> have
> >>>> different amplitudes of the side-bands, which can create conversion as
> >>>> the balance does not balance the same way anymore.
> >>>
> >>> Yes, exactly. I am currently trying to understand how noise affects
> >>> circuits an how input and circuit noise get converted to output noise.
> >>> First assumption that needs to be dropped is that the noise processes
> >>> is purely additive and independent of the signal. This means that a
> >>> noise process does not anymore produce equal AM and PM power.
> >>>
> >>> I think I have a 90% solution of the noise processes and conversions
> >>> in a sine-to-square converter (aka zero-crossing detector, aka
> >> comparator).
> >>> But there is one process that keeps puzzling me. I think I know where
> in
> >>> the circuit it must come from, but I have no explanation as to how it
> >> happens.
> >>>
> >>>
> >>>  Attila Kinali
> >>> --
> >>> It is upon moral qualities that a society is ultimately founded. All
> >>> the prosperity and technological sophistication in the world is of no
> >>> use without that foundation.
> >>>-- Miss Matheson, The Diamond Age, Neil Stephenson
> >>> ___
> >>> time-nuts mailing list -- time-nuts@febo.com
> >>> To unsubscribe, go to https://www.febo.com/cgi-bin/
> >> mailman/listinfo/time-nuts
> >>> and follow the instructions there.
> >>
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> >> and follow the instructions there.
> >>
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Re: [time-nuts] AM vs PM noise of signal sources

[Dana Whitlow]

Is this an audio tone, summed with audio noise whose spectrum surrounds
that of the tone?

Dana


On Fri, Jan 5, 2018 at 9:56 AM, Bob kb8tq  wrote:

> Hi
>
> If I pass both a sine wave tone and a pile of audio noise through a
> perfectly
> linear circuit, I get no AM or PM noise sidebands on the signal. The only
> way
> they combine is if the circuit is non-linear. There are a lot of ways to
> model
> this non-linearity. The “old school” approach is with a polynomial
> function. That
> dates back at least into the 1930’s. The textbooks I used learning it in
> the 1970’s
> were written in the 1950’s. There are *many* decades of papers on this
> stuff.
>
> Simple answer is that some types of non-linearity transfer AM others
> transfer PM.
> Some transfer both. In some cases the spectrum of the modulation is
> preserved.
> In some cases the spectrum is re-shaped by the modulation process. As I
> recall
> we spend a semester going over the basics of what does what.
>
> These days, you have the wonders of non-linear circuit analysis. To the
> degree
> that your models are accurate and that the methods used work, I’m sure it
> will
> give you similar data compared to the “old school” stuff.
>
> Bob
>
> > On Jan 5, 2018, at 6:27 AM, Attila Kinali  wrote:
> >
> > On Tue, 2 Jan 2018 23:34:18 +0100
> > Magnus Danielson  wrote:
> >
> > [About AM noise being of equal power as PM noise]
> >
> >> Now, for actual sources this is no longer true. The AM noise can be much
> >> higher, which is why it can be a real danger to the PM noise if there is
> >> a AM to PM noise conversion. One source of such conversion can be the
> >> amplification stage, but another could be a mistuned filter, which have
> >> different amplitudes of the side-bands, which can create conversion as
> >> the balance does not balance the same way anymore.
> >
> > Yes, exactly. I am currently trying to understand how noise affects
> > circuits an how input and circuit noise get converted to output noise.
> > First assumption that needs to be dropped is that the noise processes
> > is purely additive and independent of the signal. This means that a
> > noise process does not anymore produce equal AM and PM power.
> >
> > I think I have a 90% solution of the noise processes and conversions
> > in a sine-to-square converter (aka zero-crossing detector, aka
> comparator).
> > But there is one process that keeps puzzling me. I think I know where in
> > the circuit it must come from, but I have no explanation as to how it
> happens.
> >
> >
> >   Attila Kinali
> > --
> > It is upon moral qualities that a society is ultimately founded. All
> > the prosperity and technological sophistication in the world is of no
> > use without that foundation.
> > -- Miss Matheson, The Diamond Age, Neil Stephenson
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
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Re: [time-nuts] TAPR "PulsePuppy" Pot Selection

[Dana Whitlow]

I think I need to clarify what I mean by "backlash".  It is not simple free
play in
the adjustment mechanism- it is something much more irritating, as follows:

I sneak up on the desired result, but manage to overshoot slightly.  So I
back
off on the screw, and find that at first the result continues to change in
the
*original* direction (making the overshoot even worse) for a bit before
finally
reversing as I wanted it to.  This behavior is not conducive to having a
good
time making critical adjustments, nor does it lend any confidence in the
stability
of the adjustment in the face of handling.

Dana


On Sun, Dec 24, 2017 at 4:06 PM, Charles Steinmetz 
wrote:

> John wrote:
>
> I didn't really notice much backlash, though when setting oscillators I
>> try to approach (slowly) from one direction until it's "good enough" and
>> then stop, to avoid that problem.
>>
>
> The hot tip is not to just "sneak[] up on the sweet spot and then walk[]
> away," as Dana put it.
>
> Anytime you have an adjustment with some hysteresis (classic example is
> setting a d'Arsonville movement to zero), you want to sneak up to the
> perfect setting and then run the adjuster *back* the way you came just a
> touch, to leave the adjusted part on its own without any mechanical
> connection to the adjustor mechanism.  Such contact is almost always the
> culprit if the adjustment drifts after you set it.
>
> This takes some "feel" for the motion of the adjuster mechanism, but it is
> well worth investing the time to learn it by repeated trials of the
> adjuster before you leave it alone.
>
> Dana is spot on with his advice to tap the board (or whatever mechanically
> supports the adjusted part) to make sure it doesn't drift.  If it does, you
> either failed to pull the adjuster out of contact with the moving adjusting
> part, or the adjusted part just can't hold its setting.  In either case,
> better to know that now than after you button the instrument back up.
>
> Best regards,
>
> Charles
>
>
>
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Re: [time-nuts] TAPR "PulsePuppy" Pot Selection

[Dana Whitlow]

I should comment that my bad experiences were in trimming out opamp DC
offsets.
As I recall, the amount of backlash was equivalent to a fair fraction of
one turn
of the shaft.

I never fully trusted the philosophy of sneaking up on the sweet spot and
then
walking away- I felt it was necessary to tap the board a few times to
verify that
the thing was going to stay trimmed during normal handling, temperature
excursions,
etc.

These trimmers were the 3/4" Cermet variety, made by Bournes and such.

Dana


On Sun, Dec 24, 2017 at 11:26 AM, Mark Goldberg 
wrote:

> I am using a Bournes 3224 and I do see backlash issues. I do come from one
> direction to set it and if I overshoot, I go way past and come back from
> the other direction. I also see non-monotonic sections. If one of those is
> where you want to set the frequency, it is pretty hard to do. I chose one
> with significantly lower impedance than the input impedance of the TCXO
> control port. The 3296 datasheet has Adjustability specs and the 3224 does
> not. The 3269 is only 12 turns but does have an Adjustability spec on the
> datasheet. Maybe I will consider that. I would have to change my board to
> use a throughole part.
>
> Thanks for the info.
>
> Mark
>
>
> On Sun, Dec 24, 2017 at 8:58 AM, John Ackermann N8UR  wrote:
>
> > I'm glad that the PulsePuppy post spawned some good discussion!
> >
> > The pot I'm using is a Bournes 3296W-1-103LF which is a 25-turn, 10K,
> > cermet pot, spec'd at 100ppm/degree, so it's not anything super fancy.
> The
> > number of turns provides decent setability, and it seems to be a good
> match
> > for the class of oscillator the PulsePuppy is designed for -- I found
> that
> > I could trim the Isotemp oscillator without problems.
> >
> > I'll admit up front that the PulsePuppy wasn't designed as a host for
> > ultra-stable oscillators.  I tried to keep the circuit board size and
> cost
> > down, as well as the number of components that users would have to
> > install.  And since the EFC trimmer is one of those user-installed parts,
> > it's possible to substitute as nice a pot as you'd like.  I have one unit
> > that's hooked up to an external precision pot with a turn-counter dial
> > (just because it was there).
> >
> > John
> > 
> >
> > On 12/24/2017 03:57 AM, Mark Goldberg wrote:
> >
> >> Can you specify what pot you have used? I am using some for my TCXO
> boards
> >> and am not quite happy with the settability or mechanical stability.
> >> resulting in noise and higher Allan Deviation.
> >>
> >> A low noise regulator driving it also helped.
> >>
> >> I subscribe to the opinion to not use any extra resistors. When the pot
> is
> >> used as a voltage divider, theoretically it should have the same TC
> >> throughout, so temperature effects should not affect the divide ratio or
> >> the output. Only the input impedance of the control voltage input to the
> >> oscillator relative to the effective resistance of the pot will provide
> >> some effect with temperature.
> >>
> >> Mark
> >>
> >>
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Re: [time-nuts] TAPR "PulsePuppy" Pot Selection

[Dana Whitlow]

John,

Do you notice a backlash effect when homing in on the desired setting with
those
tripots?  I last used such things back in the 1980's, and remember often
having
enough backlash to make close trimming rather difficult.

I wonder if they have gotten better in that regard.

Dana

On Sun, Dec 24, 2017 at 9:58 AM, John Ackermann N8UR  wrote:

> I'm glad that the PulsePuppy post spawned some good discussion!
>
> The pot I'm using is a Bournes 3296W-1-103LF which is a 25-turn, 10K,
> cermet pot, spec'd at 100ppm/degree, so it's not anything super fancy. The
> number of turns provides decent setability, and it seems to be a good match
> for the class of oscillator the PulsePuppy is designed for -- I found that
> I could trim the Isotemp oscillator without problems.
>
> I'll admit up front that the PulsePuppy wasn't designed as a host for
> ultra-stable oscillators.  I tried to keep the circuit board size and cost
> down, as well as the number of components that users would have to
> install.  And since the EFC trimmer is one of those user-installed parts,
> it's possible to substitute as nice a pot as you'd like.  I have one unit
> that's hooked up to an external precision pot with a turn-counter dial
> (just because it was there).
>
> John
> 
>
> On 12/24/2017 03:57 AM, Mark Goldberg wrote:
>
>> Can you specify what pot you have used? I am using some for my TCXO boards
>> and am not quite happy with the settability or mechanical stability.
>> resulting in noise and higher Allan Deviation.
>>
>> A low noise regulator driving it also helped.
>>
>> I subscribe to the opinion to not use any extra resistors. When the pot is
>> used as a voltage divider, theoretically it should have the same TC
>> throughout, so temperature effects should not affect the divide ratio or
>> the output. Only the input impedance of the control voltage input to the
>> oscillator relative to the effective resistance of the pot will provide
>> some effect with temperature.
>>
>> Mark
>> ___
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Re: [time-nuts] TAPR "PulsePuppy" Pot Selection

[Dana Whitlow]

Mark is correct, but with a caveat:  Unless the pot slider sees a load
impedance that
is much much larger than the pot's end-to-end resistance, contact resistance
variations can also play a big role, especially when the pot gets old.  For
this reason
alone I favor sticking with the 3-terminal "ratiometric" configuration, AND
using a
high-Z buffer amplifier between the pot slider and the load whenever
appropriate.

The downsides are noise and drift contributions from the amplifier, but
these can often
be held to acceptable levels with careful selection of the amplifier type
and model.

It all depends on the specific situation.  But in any event, I cringe when
I see a design
using a pot as a 2-terminal variable resistor, especially in situations
when an open
condition could cause damage.

Dana


On Sun, Dec 24, 2017 at 2:57 AM, Mark Goldberg 
wrote:

> Can you specify what pot you have used? I am using some for my TCXO boards
> and am not quite happy with the settability or mechanical stability.
> resulting in noise and higher Allan Deviation.
>
> A low noise regulator driving it also helped.
>
> I subscribe to the opinion to not use any extra resistors. When the pot is
> used as a voltage divider, theoretically it should have the same TC
> throughout, so temperature effects should not affect the divide ratio or
> the output. Only the input impedance of the control voltage input to the
> oscillator relative to the effective resistance of the pot will provide
> some effect with temperature.
>
> Mark
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Re: [time-nuts] End of Range Oscilloquartz 8600-3

[Dana Whitlow]

I looked at the photos, but can't make any sense of your comments about the
multivibrator.  Was this a joke?

Dana


On Tue, Dec 12, 2017 at 11:37 AM, Bob Albert via time-nuts <
time-nuts@febo.com> wrote:

>  You found the secret.  There is no RF wiring to the crystal.  The
> oscillator frequency is determined elsewhere, with a free running
> multivibrator that is approximately on the right frequency.  All this talk
> about precision is baloney; the circuit is stable enough to fool even the
> experts.
> And it's not even April 1 yet.
> Bob
> On Tuesday, December 12, 2017, 9:32:44 AM PST, Ed Palmer <
> ed_pal...@sasktel.net> wrote:
>
>  It sounds like yours is different from my 8601.  How old is yours? From
> the label inside it looks like mine is from 1983.
>
> Internal pictures are here:
>
> http://s701.photobucket.com/user/edpalmer42/library/Oscilloquartz%208601%
> 20Oscillator
>
> If you click on 'view as story' you'll see some comments that I added to
> the pictures.
>
> Ed
>
> On 2017-12-12 11:00 AM,   wrote:
> > Emailed Oscilloquartz that now has another name: Advaoptical... This in
> my capacity as aresearch engineer at Onsala Space Observatory.And the
> oscillator is at my work bench. Nothingprivate/hobby about this.
> > The answer was that since we do not have a service agreement,they would
> not disclose any information.
> > (Compare this with Keysight who has a free downlad area for oldmanuals.
> IMO the Keysight approach benifits their businessin the long term).
> > So...
> > I went along and started to dissassemble the 8600-3.
> > The outer case was easy. Inside is a PCB with RF buffersand temperature
> regulation circuitry.
> > Then there is a thermo bottle with the ovenized oscillator.This unit is
> connected to the PCB using two flex cables.
> > The oscillator unit can simply be extracted from thebottle using an
> Metric 3 mm screw lightly screwed inone of the holes in the oscillator
> assembly.
> > The assembly can be accessed by carfully unscrewingthe flex-cable end
> from the other mechanics. No needto touch the three small screws at the lid.
> > Now it is starting to get intersting. I have not foundthe RF wiring into
> the crystal. The PCB in this unitseems to deal only with temperature
> regulation.Possibly, the RF is routed together with some heaterwinding.
> > Or the crystal and the oscillator parts is sealedin such a way that
> there will be no wayto dissassemble it. There are several thermistorsglued
> inside to various parts of the oscillator/ovenassembly. That will make any
> further attemptsdifficult as the connecting wires are thin and delicateif
> they needs to be unsoldered.
> > The construction is a nice piece of engineering.I'll give them that.
> > Right now, I cannot see any typical oscillatorcircuitry (pF, nH, RF
> transistors) etc.
> > I think I'll contemplate on the next movefor a day or so...
> >
> > Ulf Kylenfall
> >
> >
>
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Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

[Dana Whitlow]

Checkhttps://en.wikipedia.org/wiki/Earth_tide

According to that, a foot of motion is easily plausible.

The Wiki article says that displacements around a meter in the solid
crust can be seen over the right intervals.  This must wreak havoc in
VLBI geodesy work, except that for some in the field this would be the
"signal" and most everything else the noise.

Dana


On Sat, Dec 9, 2017 at 7:42 PM, Tom Holmes  wrote:

> Mark...
> You're place really moved a foot in 48 hours? Impressive and scary!
>
> From Tom Holmes, N8ZM
>
> > On Dec 9, 2017, at 8:19 PM, Mark Sims  wrote:
> >
> > Which gets real fun with things like solid earth tides getting
> involved.   Lady Heather can now calculate and plot solid earth tides.
>  Over the last 48 hours my place moved up/down 315 mm and gravity changed
> 186  microgals... and that was a rather stable period.
> >
> > --
> >
> >> A 1 meter change in elevation corresponds to a frequency offset of
> about 1e-16. So for 1e-18 levels of performance you "only" need to know g,
> or your elevation to 1 cm accuracy.
> > 
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Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

[Dana Whitlow]

I saw that about the N atom trapped inside a C60 molecule, but also
took note of the present cost of the material.  I wonder how much is
going to be required to make a good standard.

Dana


On Fri, Dec 8, 2017 at 11:40 AM, Tom McDermott  wrote:

> There's an interesting article in the December 2017 issue of IEEE Spectrum.
>
> Researchers at Oxford U. have fabricated an atomic reference based on
> a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene").
> The cage of carbon isolates the nitrogen from external electric fields,
> and they've developed a method to also isolate it from external magnetic
> fields.
>
> They have not incorporated the material into a working standard, but have
> licensed the chemical fabrication technology to at least one manufacturer.
> The idea is to make a chip-scale atomic frequency reference.
>
> -- Tom, N5EG
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Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

[Dana Whitlow]

Use of a smaller opening would be the first strategy for getting higher Q.
Making sure that the walls of the vessel were solid reflectors would be
an important factor, too.

I noted that several of his sustained oscillators were basically either
relaxation or blocking oscillators, neither of which is noted for good
phase noise performance.  Even the pendulum clock mechanism
was interfering severely with the pendulum's motion- if you look
closely you can see that the pendulum bob's position versus time
function was a severely clipped waveform.

The flex hose demonstration was interesting in that different regimes
of swinging speed resulted in oscillation in different modes.  I wonder
why.  But in hearing people learning to play different musical instruments,
mostly wind instruments but also including the violin, I was once
moved to say that playing these devices the art was in making an
oscillator run in a resonator mode other than the "natural" one.

For an  interesting look at oscillating modes and a really oddball
sustained oscillator, view  https://www.youtube.com/watch?v=m6631u7d4E0.
and/or google "mercury beating heart".  The electrochemical effect
makes the blob oscillate between a hunched-up shape and a flattened
shape.

If given time, this hunching oscillation "pumps" a degenerate parametric
oscillation between the two triangular shapes at nominally half the rate
of the original oscillation.  I first saw this demonstrated in high school,
but the demonstrator also could  not get a sustained oscillation.  I
thought about that for a while and decided to try a little external stimulus
in the form of low voltage DC from an external supply.  After a little
optimization it worked beautifully and could run for hours on end with
little of no attention, giving me the luxury of trying a range of different
blob sizes.  With different sizes I could get sustained parametric
oscillation in four different modes: 2-sided, 3-sided (as seen in the
You-Tube clip), 4-sided, and with difficulty even 5-sided.

Of course I didn't really understand what was going on at the time,
and didn't arrive at the parametric oscillation theory until years later.
BTW, I used a baking soda solution instead of a chromium-based
chemistry, and an electrode coming down from the top center, with
a large ring surrounding the mercury blob as the other electrical
connection.

Solution concentration, voltage, electrode tip height, and electrical
polarity were the parameters that had to be adjusted for best
performance.  A mercury blob about one cm across in its resting
state seemed to be a good starting point.  For polarity, use the
one that results in the blob's hunching up when the electrode tip is
gradually lowered into contact with the blob.  If the other stuff
is not too far off, it will quickly take off oscillating at that point.

I've been wondering whether this could be made to work with
Galinstan obtained from modern-day clinical thermometers,
instead of that dreaded mercury.  A worthwhile experiment
to try.

I never did get around to measuring the Alan Variance of one
of these oscillators; indeed, I didn't even hear of the concept
until years later.  It's probably not up to Time-Nuts' standards.

Dana

On Fri, Dec 8, 2017 at 4:59 AM, Hal Murray  wrote:

> What's the Q of a Helmholtz Resonator?  What do I do to make a high(er) Q
> version?
>
> With a narrow band filter, it might make a neat demo/toy to pull an audio
> signal out of the noise.  With 2 at different frequencies you could
> demonstrate FSK.
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] New ISO8601 ?

[Dana Whitlow]

I believe the phrase "circa 1967" fits the bill pretty well, although
it may fall a little bit short of "...but it’s all a bit of a blur”.

Dana

On Thu, Nov 23, 2017 at 7:18 AM, Poul-Henning Kamp 
wrote:

> 
> In message <4bec82c4-583e-4632-8589-d898cc2bd...@n1k.org>, Bob kb8tq
> writes:
>
> >I had never realized there was a format for expressing “I think it was
> 1967 but it’s
> >all a bit of a blur”.
>
> I think that is one of the major reasons for the revision.
>
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Next upgrade

[Dana Whitlow]

I once did make a token attempt at tweaking the disciplining parameters in
that SRS-10, but seemed to be getting nowhere and gave up on the effort.

Dana

On Wed, Nov 22, 2017 at 8:12 PM, Mark Sims  wrote:

> The PRS-10 does have disciplining parameters that you can tweak.   But the
> documentation is rather spotty on how to go about choosing good values.
>
> Also, I doubt that putting a Rb in an OCXO Lucent box would work well.
>  Rb loop parameters (like time constant) are rather different for the two
> classes of oscillator.
>
> ---
>
> > the disciplining loop seems to be a bit aggressive so that the poor
> oscillator
> gets jerked around quite a bit by the GPS
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Re: [time-nuts] Next upgrade

[Dana Whitlow]

For the most part the SRS-10 is a nice choice, although I'd always be wary
of buying a
used one.

My only real beefs are that the tuning granularity is rather coarse, about
2E-12, and the
disciplining loop seems to be a bit aggressive so that the poor oscillator
gets jerked
around quite a bit by the GPS.  This makes for rather ugly-looking plots of
time error
over time.

The above comments are derived from about 3 years of operating one as a hot
emergency spare at the Arecibo Observatory against the day when the H-maser
crashed abruptly.  In this case the SRS-10 was embedded in an FS725 which we
bought new.

Dana


On Wed, Nov 22, 2017 at 4:16 PM, Jerry Hancock  wrote:

> Three questions:
>
> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
> both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
> some other technique to improve the short and/or long term performance?
>
> 2) I’ve become interested in Rubidium Disciplined Oscillators recently and
> was now thinking of purchasing one of the PRS-10 that I see on Ebay. If I
> did that and replaced one of the DOCXOs from one of the Lucent boxes, what
> impact would this have on the overall performance both with and without
> (when in hold-over)?  Basically, is it worth the money to upgrade one of
> the boxes to a Rubidium disciplined oscillator assuming the GPS signal is
> rarely lost?
>
> 3) Figuring the PRS-10 will cost around $250 when all is said and done, is
> there a better option to improve my GPSDO system?
>
> I basically use the GPSDO as a reference for any equipment that takes an
> input. I have no monetary need for a reference, just an interest.
>
> Thanks.
>
> Jerry
>
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Re: [time-nuts] H-maser drift

[Dana Whitlow]

Thank you John.  That was most informative.

dana


On Tue, Nov 21, 2017 at 2:26 PM, John Ponsonby 
wrote:

> There seem to be a lot of misunderstandings about H-masers. To set the
> record straight note:
> 1. The flow of hydrogen is generally controlled using a palladium
> membrane, though a palladium-silver alloy is to be preferred because it is
> less likely to crack. Only hydrogen will diffuse through the
> palladium-silver membrane, so as well as being a temperature controlled
> regulator it is also a filter. Indeed it is an isotopic filter through
> which even deuterium doesn’t pass. The protons are thought to migrate
> through the membrane and recombine on the output surface first into atoms
> and then into H2 molecules. I used thin walled palladium-silver tubes which
> had roughly the dimensions of a match stick. Hydrogen on the inside was at
> about twice atmospheric pressure with output into “vacuum” on the outside.
> Control is by heating with a large current flowing along the rather low
> resistance tube. Russian H-masers use nickel tubes rather than the more
> expensive palladium-silver. Such a “palladium leak” requires only a few
> seconds on Turn-On to settle to a steady flow.
> 2. Hydrogen from the "palladium leak” passes to a “dissociator" which is a
> small bulb made of heavily boronated glass, e.g. Pyrex, in which the H2
> molecules are dissociated into H atoms by a non-contacting RF discharge.
> Atomic hydrogen recombines very readily on any metal surface so the
> discharge is either by magnetic or electric field acting through the glass
> wall. Metals are charactersised by having conduction bands full of free
> electrons. Boron is an electron acceptor, so Pyrex is very unlike a metal
> and it has a low surface recombination rate. Not as low as FEP120 (See 5.
> below) but one can’t line a discharge bulb with it.
> 3. The very high Q RF cavity (loaded Q ≈ 36000), which is tuned very
> exactly to the hydrogen frequency of 1,420,405,751Hz, operates in the TE011
> mode in which the oscillating RF magnetic field is toroidal, going up the
> middle and down the outer part of the cavity. The resonant frequency is
> much more sensitively dependent on the cavity diameter than on its length.
> 4. Inside the cavity is the "storage bulb" which is made not of glass but
> of fused quartz. It is typically about 1mm thick. Fused quartz is chosen
> for its exceptionally low RF loss tangent. But of course it has a
> dielectric constant which results in its loading the cavity which is thus a
> little smaller than one first thinks. Since it is very difficult to
> manufacture quartz bulbs to normal engineering tolerances it is not
> possible to calculate how much the cavity will be loaded. So it is not
> unusual to manufacture the cavity to match the given storage bulb.
> 5. The inside of the storage bulb is coated typically with a layer of
> FEP120, a Dupont product akin to Teflon. An H atom can make of the order of
> 10,000 bounces off its surface without change of quantum state. Also H
> atoms won’t stick to the coating. (Non-stick frying pans are coated with
> FEP120 and what is true for an egg is true for an atom.)
> 6. The shape of the storage bulb should be chosen to maximize the “filling
> factor”. This is defined as: η’=Vb^2b/Vcc  Here the numerator is
> the product of the storage bulb volume Vb times the square of the mean of
> the z component of the RF magnetic field Hz averaged over the internal
> volume of the bulb b, and the denominator is the product of the cavity
> volume Vc times the mean of the square of the magnitude of the RF magnetic
> field Ha averaged over the entire volume of the cavity c. A spherical bulb
> is non-optimal though may early masers had spherical storage bulbs.
> 7. The RF discharge generates UV. This shines up the beam path and
> illuminates the bulb coating in the region where the incoming atoms first
> make contact with the bulb coating. This UV undoubtledly damages the FEP120
> coating. The deterioration of the coating may be one of the causes of long
> term drift.
> Cheers
> John P
>
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Re: [time-nuts] H-Maser drift (was: Why discipline Rubidium oscillator?)

[Dana Whitlow]

Hi Ole,

What does 'EFOS' mean?  I hadn't heard the term before.

I think I've heard the one-second lifetime figure before.

I do hear mixed reports about where the conversion to atomic H
occurs, and consider the jury to still be out on that question.

I had thought that the volume of the storage bulb was much
smaller in out maser, perhaps in the pint to quart range.  For a
frequency of ~1420 MHz, I guess it would take a cavity that is
operating in a somewhat higher than fundamental mode if the
volume is in the gallon regime as you suggest.  But with the
narrow gain profile width of this transition, I supposed there'd
be no risk of the thing running in the wrong mode.

Dana


On Tue, Nov 21, 2017 at 8:14 AM, Ole Petter Ronningen  wrote:

> On Tue, Nov 21, 2017 at 2:50 PM, Attila Kinali  wrote:
>
> > [...] The advantage of the platinum valve
> > system is that it "generates" single atom Hydrogen, as required
> > by the maser.
>
>
> Picking nits here.. It was my understanding that the splitting of molecular
> hydrogen into atomic hydrogen happens using RF in the dissociator - not in
> the platinum leak valve. Is my understanding incorrect?
>
>
> > Within the cavity there is a small glass bulb that keeps the atoms
> > in the right position of the cavity field.
>
>
> 4.5 liters in EFOS type masers - so not *that* small. I believe other
> masers are the same order of magnitude.
>
>
> > Yes, IIRC normal numbers are several 10s to 100s of wall collisions
> > before the atom loses its state due to wall colisions and without
> > contributing to the signal.
> >
>
> Lifetime ~1 second I think
>
>
> > > I've long wondered what causes the slow frequency drift, typically
> > amounting
> > > to about 3E-14 over a time span of several months.
> >
> > Mostly changes in the wall coating leading to a different wall collision
> > shift and mechanical changes of the cavity dimension (think air pressure
> > and creep) leading to a different cavity pulling. To a lesser extend
> > it's the changes in the quality of the vacuum and number of Hydrogen
> atoms
> > in the cavity.
>
>
> Also aging of electronic components - coarse tuning of the cavity is done
> by temperature, and any drift if the temperature-sensor/amplifiers etc will
> result in drift. At least for EFOS type masers.
>
> Ole
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Re: [time-nuts] ***SPAM*** Re: Why discipline Rubidium oscillator?

[Dana Whitlow]

Oops, I should have mentioned:  The unit was a Symmetricom MHM-2010 (I hope
I got that right), except that it was built before the company was bought by
Symmetricom (which was later bought by Micro-Semi in turn).

This is an active maser, meaning a self-sustaining oscillator whose gain
medium
was a volume of hydrogen atoms (at low pressure) maintained in a population-
inverted state by squirting a thin stream of state-selected H atoms into a
glass
bulb, and simultaneously pumping on the bulb to maintain a low pressure.
The
inside of the bulb was treated so that the collisions with the surface did
not
usually cause a quantum state change of the H atom involved.  I've read that
the average excited atom typically "survived" a large number of such wall
collisions before being "consumed" by contributing a quantum of energy to
the oscillating mode; this has always amazed me.

So the primary frequency-determining mechanism is the collision-broadened
line width of the gain mechanism. However, the cavity resonance exhibits a
noticeable frequency-pulling effect, and our maser has a feedback loop that
strives to keep the cavity tuned to the center of the medium's gain
profile.
But I think this loop is not a tight loop, ergo not completely successful.

Anyway, a small amount of RF power (a fraction of a pW as I understand it)
is extracted from the cavity as the useful output.  This drives a frequency
synthesizer to make a useful standard frequency output.  The "divide ratio"
of that synthesizer is adjustable in fine steps, with one step being a
fractional
frequency change of about 7E-17.

I've long wondered what causes the slow frequency drift, typically amounting
to about 3E-14 over a time span of several months.

Dana


On Tue, Nov 21, 2017 at 1:39 AM, Mike Cook <michael.c...@sfr.fr> wrote:

>
> > Le 20 nov. 2017 à 20:53, Dana Whitlow <k8yumdoo...@gmail.com> a écrit :
> >
> >
> >
> > In my pre-retirement job I rode herd on an active Hydrogen maser
> system,and even
> > that has a clear drift tendency.  Generally a couple or three times per
> > year I had to make a frequency adjustment in the neighborhood of 3E-14.
> And still being
> > privy to its performance, I was amused to note that its drift tendency
> was
> > interrupted by the hurricane Maria.  On the day of eye passage over the
> site the frequencysuddenly
> > decreased by a few parts in 10^14, held about constant for roughly a
> week,then
> > resumed almost its original value and drift rate thereafter.  If anybody
> inthis group
> > can explain* that* behavior (that is, held for a week before resuming old
> > habits), I’d love to learn about it.
>
>   You don’t mention the make of the instrument, but I suspect the same
> basic technology is used by all.
> To quote from the Oscilloquartz page on their CH1-76A product:
> «  The quantum device is used as a frequency discriminator in an automatic
> frequency tuning system of a crystal oscillator. »
> They don’t however quote stability relative to air pressure. However…..
> It is known that atmospheric pressure changes can induce OCXO frequency
> changes due to deformation of the crystal envelope causing stray
> capacitance changes.
> As the eye of a hurricane has greatly reduced air pressure than normal, by
> as much as 15%, it could be related.
>
>
> >
> > Dana
> >
> >
> > On Mon, Nov 20, 2017 at 1:40 PM, Bob kb8tq <kb...@n1k.org> wrote:
> >
> >> Hi
> >>
> >> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what
> >> have a direct relation.
> >> Even then, the qualifier is “under standard conditions”. They are
> >> sensitive to magnetic field. Rb’s
> >> also are sensitive to magnetic field. Both can be tuned by varying the
> >> field. In the case of an Rb
> >> that also takes care of a multitude of other issues.
> >>
> >> In the case of Rb, there is a distribution of cells coming out of the
> >> manufacturing process. Some
> >> are pretty close to the “right” frequency. Others are way off (as in
> 100’s
> >> of KHz or more). All of them
> >> are capable of meeting the required specs. DDS techniques allow those
> >> cells to be used in a
> >> production part. That increases the yield and thus drops the production
> >> cost.
> >>
> >> Since you now magically have a DDS in the Rb, you can do all sorts of
> >> interesting things. If you
> >> suddenly need a 9.99900 MHz standard …. here it is … If you need to do
> >> temperature compensation
> >> via a lookup table … it just takes a bit of testing and some code to
> make
> >> it happen. Indeed, th

Re: [time-nuts] Why discipline Rubidium oscillator?

[Dana Whitlow]

As far as I knew, the highest level steps *actually on the market* are
the Cesium beam clocks and the active hydrogen masers.  Are any
of the newer technologies available for purchase today?

Dana


On Mon, Nov 20, 2017 at 6:13 PM, Hal Murray  wrote:

> > aren’t too many steps after that
>
> Your imagination is broken.
>
> There are lots more steps.  Most of them are very expensive.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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Re: [time-nuts] Why discipline Rubidium oscillator?

[Dana Whitlow]

And even without problems like external magnetic fields, Rb oscillators do
drift with
age. Over a period of several years they may drift as much as ~1E-9, which
is a *huge*
error for serious time nuts.

In my pre-retirement job I rode herd on an active Hydrogen maser system,
and even
that has a clear drift tendency.  Generally a couple or three times per
year I had to
make a frequency adjustment in the neighborhood of 3E-14.  And still being
privy to
its performance, I was amused to note that its drift tendency was
interrupted by the
hurricane Maria.  On the day of eye passage over the site the frequency
suddenly
decreased by a few parts in 10^14, held about constant for roughly a week,
then
resumed almost its original value and drift rate thereafter.  If anybody in
this group
can explain* that* behavior (that is, held for a week before resuming old
habits), I'd
love to learn about it.

Dana


On Mon, Nov 20, 2017 at 1:40 PM, Bob kb8tq  wrote:

> Hi
>
> There is no direct relation for an Rb to 10 MYz. Cs beam tubes are what
> have a direct relation.
> Even then, the qualifier is “under standard conditions”. They are
> sensitive to magnetic field. Rb’s
> also are sensitive to magnetic field. Both can be tuned by varying the
> field. In the case of an Rb
> that also takes care of a multitude of other issues.
>
> In the case of Rb, there is a distribution of cells coming out of the
> manufacturing process. Some
> are pretty close to the “right” frequency. Others are way off (as in 100’s
> of KHz or more). All of them
> are capable of meeting the required specs. DDS techniques allow those
> cells to be used in a
> production part. That increases the yield and thus drops the production
> cost.
>
> Since you now magically have a DDS in the Rb, you can do all sorts of
> interesting things. If you
> suddenly need a 9.99900 MHz standard …. here it is … If you need to do
> temperature compensation
> via a lookup table … it just takes a bit of testing and some code to make
> it happen. Indeed, the DDS
> does also give you some issues. Without some sort of cleanup oscillator,
> you will have spurs and
> phase noise on the output.
>
> Lots of fun ….
>
> Bob
>
>
> > On Nov 20, 2017, at 1:34 PM, Jerry Hancock  wrote:
> >
> > I know this is going to sound dumb as I know many GPSDOs had rubidium
> oscillators in them.  I can see why, in that during holdover, they would
> tend to be more stable vs others, but given that there is a direct
> mathematical relationship between the rubidium frequency and potentially
> the 10Mhz desired output frequency, why do they have to be disciplined or
> better yet, what advantage does it bring?  Also, I can see how you
> discipline a DOCXO with the external voltage, how do you discipline a
> rubidium?  Pulse stretching?
> >
> > I guess I don’t understand how the technology works, but it seems like
> an RF signal is swept that would be used to detect a dip at a pretty well
> defined frequency.  This dip can be used to discipline the oscillator to
> something like 9Ghz or a factor of what, 900+ times better than 10Mhz.  So
> wouldn’t that be able to get your desired 10Mhz to 10,000,000.001 or pretty
> much my level of measurement?  Or does is the dip not quite that precise?
> If you can point me to a write-up on this I’ll go away.
> >
> > Thanks to Gilbert for providing me with at least one rubidium oscillator
> that is working out of 5 though 2 others seems to stay locked for a few
> hours during my testing.
> >
> > Jerry
> > ___
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Re: [time-nuts] Recommendation for cheap GBIP adapter for Linux

[Dana Whitlow]

Beware-

Many GPIB-to-Ethernet adapters are also very prolific RFI generators-
learned the hard way at Arecibo.

Dana


On Sat, Nov 18, 2017 at 5:03 PM, Bob Bownes  wrote:

>
> All GPIB to Ethernet adapters are not created equal.
>
> The NI GPIB-E is no longer supported for example, only the 100 & 1000.
>
> Which is very annoying to those that have one.
>
> Bob
>
>
>
> > On Nov 18, 2017, at 17:45, Bob kb8tq  wrote:
> >
> > Hi
> >
> > Given all the nonsense with USB drivers / “fake" serial chips / OS
> restrictions ….
> > The ethernet solution makes a lot of sense.
> >
> > Bob
> >
> >> On Nov 18, 2017, at 4:45 PM, jimlux  wrote:
> >>
> >> On 11/18/17 11:04 AM, Attila Kinali wrote:
> >>> Hi,
> >>> I have a need for a GBIP adapter that I can use with Linux.
> >>> It shouldn't be too expensive, but I rather spend a few bucks
> >>> more for ease of use. Where "ease of use" means I don't have
> >>> problems with weird drivers on Linux (Windows doesn't matter at all).
> >>> I do not mind writing my own read-out software (that's quickly and
> >>> easily done). What would people here recommend?
> >>
> >> I use the Prologix GPIB to Ethernet converters.
> >>
> >> Makes it "platform independent" since it's just an IP socket to the
> outside world
> >> ___
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> >
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Re: [time-nuts] Absolute phase

[Dana Whitlow]

Hello Arthur,

Might be interesting to try the same experiment both with the two
receivers on the same antenna and on the two different antennas.
In an ideal world I'd expect the time output(s) to track as well
either way, but it would be interesting to know how well this works
out in practice.

Dana  K8YUM


On Fri, Nov 17, 2017 at 4:15 PM, Arthur Dent 
wrote:

> I have 2 antennas mounted on opposite ends of a roof and both of them feed
> commercial GPS DA/splitters and I can have as many as 10 receivers running
> at one time for testing. I have also used one of the high frequency type F
> TV passive splitters with one D.C. feed through and added 200-300 ohm
> resistors from the other outputs to ground. All this has seemed to work
> just fine but one of the older receivers apparently radiated its L.O. out
> the antenna coax and would interfere with a couple of other receivers I
> connected to the same DA.
>
>
>
> Connecting one 10 Mhz references to the external trigger on my scope and
> feeding 2 other GPS receivers to the input channels (all from the same
> antenna DA), I can watch the slow drift at 2 ns/div with respect to the
> trigger and sometimes one receiver drift one way as the other receiver
> drifts in the opposite direction and sometimes they drift the same way.
> The
> drift is generally less than 2 ns but it is there and I assume it depends
> on what the internal ‘housekeeping’ of the receiver is doing and what birds
> they are using. So bottom line, they aren’t ‘locked’ to each other but are
> generally close.
>
>
> -Arthur
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Re: [time-nuts] Oscillators and Ovens

[Dana Whitlow]

Bob,

This discussion is getting really interesting.  In thinking about the
crystal Q versus
tuning range conundrum, two (presumably-overlapping) concerns come to mind:

1. The motional parameters of a high-Q crystal are such that the external
network
needed to pull it very far would be wholly impractical.

2. Varactors themselves probably have pretty limited Q over much of their
range.

Is my thinking on the right track at all?

Dana  K8YUM

On Wed, Nov 1, 2017 at 5:13 PM, Bob kb8tq  wrote:

> Hi
>
> A high Q crystal by design is very difficult to tune. Putting it in a
> circuit that will
> swing it far enough to compensate it degrades the Q. In addition, thermal
> noise
> will come into the compensation circuit (even if it is noise free) and
> degrade things.
>
> Bob
>
> > On Nov 1, 2017, at 4:38 PM, Hal Murray  wrote:
> >
> >
> >> In general, OCXOs have crystals with high Q -> low phase noise,
> especially
> >> compared to a TCXO, which *can't* have high Q, or the  temperature
> >> compensation circuit can't do it's work.
> >
> > I don't understand that.  Why can't I build a high Q TCXO?  I don't need
> to
> > change the compensation very fast.  Are good crystals high enough Q that
> it
> > would take too long?
> >
> > What's the time constant?  I'd guess it's Q/freq, maybe with factors of
> 2pi
> > or e or ???
> >
> > That seems small relative to how fast temperature changes.  (but maybe
> fast
> > relative to FCC smearing or things like that)
> >
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
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Re: [time-nuts] Thunderbolt - Lady Heather altitude does report abt 240m too high

[Dana Whitlow]

Remember that GPS normally displays altitude with respect to the WGS84 datum
geoid, not with respect to MSL.  There can easily be a hundred feet or so of
difference.

Dana


On Wed, Oct 25, 2017 at 9:18 PM, Arnold Tibus  wrote:

> Hello fellow time nuts,
>
> after the thunderbolt roll over problem I run the survey control in Lady
> Heather (48h).
> Since then I am getting always a wrong elevation number for my qth.
> Does anybody know the reason for that behavior?
> Is there a solution to get again the correct value?
>
> Kind regards
>
> Arnold, DK2WT
>
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Re: [time-nuts] I've been thinking about a GPS receiver experiment

[Dana Whitlow]

What "naughty schoolboy"?  How else is one supposed to learn feedback
theory?

Dana

On Wed, Oct 25, 2017 at 6:30 PM, Mark Sims  wrote:

> >  No, you set up an oscillator so that is why you have that problem.
>
> I hooked the two rubidiums together just to see what would happen.   It
> pretty much did what I expected... chaos...   the time-nut equivalent of a
> naughty schoolboy putting a microphone up to the speaker of the public
> address system.  I't's a tough job, but somebody gotta do it  ;-)
>
>
> >  No, not really. The rubidium would be the real hold-over clock.
>
> Symmetricom calls the disciplining state where it can't lock to the 1PPS
> signal the "holdover" state.  It's sort of like a GPSDO holdover state.
> Their discipline firmware does let you set the time constant and damping
> values.  I tried a little playing around with them, but never found any
> settings that worked consistently well with the LEA-5T.
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Re: [time-nuts] I've been thinking about a GPS receiver experiment

[Dana Whitlow]

Hello Skip,

I have a theory, but it will be interesting to see what others say.
Assuming that the
1 PPS error to which you refer is the so-called "sawtooth" error, I've come
to suspect
that the rate at which the individual PPS pulses walk across the sawtooth
is related to,
and likely proportional to, the error of the internal (or in this case, the
external) clock
oscillator.  If I'm right about its being proportional, then it seems to me
that having
the GPS's clock oscillator right on would freeze the PPS error at some
fixed value,
not necessarily zero.  If true, you'd experience a constant bias error to
the timing of
the PPS pulses.

Now you would seem to be in the perfect position to refute or verify my
thinking,
provided you have the means to vary an external clock's frequency in a
controlled
way, by watching how the PPS error behavior changes as a function of the
clock
frequency.

If you manage to try the experiment, I'd greatly appreciate hearing the
outcome.

DanaK8YUM


On Tue, Oct 24, 2017 at 5:17 PM, Skip Withrow 
wrote:

> Hello time-nuts,
>
> I've been thinking about a GPS receiver experiment and just wondering
> if there are any opinions or prior experience that might save me a lot
> of time.
>
> What I have been thinking about doing is taking a GPS receiver
> (Novatel OEM4-G2) that has provisions for an external clock (5 or 10
> MHz) and driving it with a rubidium oscillator (that has 1pps
> disciplining, (such as the X72 v5.05 or SRS PRS-10).  The GPS even has
> settings for OCXO/rubidium/cesium dynamics.
>
> Then, (and here is the unknown part) what if the GPS receiver 1pps is
> used to discipline the rubidium?  This basically forms a feedback
> loop, so could either hurt or help - depending.  Supposedly the better
> oscillator would give a better GPS solution.  And the better solution
> (1pps) should provide a better oscillator frequency.
>
> We know that GPS receivers using asynchronous clocks have 1pps errors
> and hanging bridges (OEM4 is spec'd at 20ns rms), If the oscillator is
> on 10MHz and disciplined will the 1pps error be reduced such as the
> Thunderbolt?
>
> Comments appreciated.
>
> Regards,
> Skip Withrow
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Re: [time-nuts] Spice simulation of PSRR and phase noise

[Dana Whitlow]

Hello Attila,

It seems to me that an AC simulation could never work since the
very generation of phase noise by the mechanisms that matter is
a modulation process at heart, automatically forcing one into the
realm of transient simulations.

But I am surprised about the simulation times that you speak of.
Would you be willing to post some information detailing your
methodology and an example "simple" circuit?

Dana

On Sun, Oct 22, 2017 at 7:53 AM, Attila Kinali  wrote:

> Hi,
>
> I have been looking into spice simulations of circuits, in particular
> trying to extract PSRR and phase noise information. Unfortunatelly,
> the obvious way of putting AC sources at the right places does not
> work, as the (ideal) input signals are not small and drive the circuit
> into non-linearities. Hence I have to do transient simulations.
> But extracting PSRR and phase noise information out of a transient
> simulation is cumbersome at best and takes a lot of simulation time
> (we are talking about hours to days for simple circuits).
>
> I am looking for guidelines and hints how to speed things up.
> Maybe even being able to use standard DC and AC analysis for the
> circuit instead of transient. Unfortunately, my google-foo was not
> strong enough to find approriate documentation.
>
> Does someone have any hints what I should read or search for?
>
> Thanks in advance
>
> Attila Kinali
>
> --
> It is upon moral qualities that a society is ultimately founded. All
> the prosperity and technological sophistication in the world is of no
> use without that foundation.
>  -- Miss Matheson, The Diamond Age, Neil Stephenson
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