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 cle
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 i
ue, Nov 21, 2017 at 1:39 AM, Mike Cook wrote:
>
> > Le 20 nov. 2017 à 20:53, Dana Whitlow 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 thr
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 b
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 palla
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 th
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
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:
>
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
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 201
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 fiel
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 i
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 "rati
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
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 ta
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 continu
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 si
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, D
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 differenti
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,
ount-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 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
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 be
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 fro
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 tw
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 pr
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 captur
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 i
ning the case. There must be a way...
Dana
On Thu, Mar 15, 2018 at 8:13 AM, Bob kb8tq wrote:
> Hi
>
>
> > On Mar 15, 2018, at 1:33 AM, Dana Whitlow wrote:
> >
> > I concur with Bill. And even if one keeps tabs on the current watch
> error,
> > as is the
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, 20
laser illumination.
Dana Whitlow
On Sun, Mar 25, 2018 at 8:18 AM, Attila Kinali 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 b
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
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
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
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
> abou
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.
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 t
erested 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 wrote:
> On 4/13/18 10:33 AM, Dana Whitlow wrote:
>
>> Jim,
>>
>> I'm cu
> -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
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", th
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".
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
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
>
>
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 bet
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?
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 vecto
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
; 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 wrote:
> >
> >
> > It may be that a nicely-written request to Corning could yield the loan
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 5
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,
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 spea
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
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
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 i
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
gh 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
> > err
ve 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
>> '
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@fe
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 ch
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 o
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 sp
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
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
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
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
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.
Da
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 &
66 matches
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