and-dirty check, so a months is not in the cards
> - but that second antenna/receiver is climbing on my list of priorities, in
> imminent danger of surpassing «doing nothing on the couch»! :)
>
> > 27. mar. 2021 kl. 16:52 skrev Dana Whitlow :
> >
> > Ole,
> >
>
Jim, how large is the Goldstone antenna to which you referred?
Dana
On Tue, Mar 30, 2021 at 4:01 PM Lux, Jim wrote:
> On 3/30/21 6:40 AM, Wes wrote:
> > Was a pity. China's FAST is receive only. I believe that leaves
> > Green Bank as the biggest transmitting telescope.
>
> More likely the
Hal,
The older (and probably the newer models, too) Trimble Thunderbolt GPSDOs
have
a user-adjustable time constant accessible via the serial port using a
program like
"Tboltmon.exe" (from Trimble). I suspect that "Lady Heather" may also do
this. I
am fortunate in owning a still functioning
Philip,
You and I are definitely "in sync" regarding cheating to alter the pendulum
motions!
I had a very similar thought for effectively making the pendulum based
system into sort
of a VCO, except that instead of a metal plate, use a small Nd magnet
polarized
vertically, stealthily-attached to
easurement
> setup? Is there something that will give more accurate results, given
> the equipment on hand? Certainly the Q value seems unreasonably high,
> and Rs seems quite low. However, these are large low frequency
> resonators (being 25mm in dia.).
>
>
> Thanks,
> Dan
&g
I've long understood that ionospheric delays and variations thereof lead to
*position*
uncertainties in GPS navigation receivers, to the tune of perhaps 10m
(2DRMS IIRC).,
and that these are said to constitute the single largest GPS error source.
Q1: Would this not imply timing errors of
b 27, 2021 at 9:08 AM Bob kb8tq wrote:
> Hi
>
>
>
> > On Feb 27, 2021, at 9:41 AM, Dana Whitlow wrote:
> >
> > I've long understood that ionospheric delays and variations thereof lead
> to
> > *position*
> > uncertainties in GPS navigatio
Blue LEDs under Nixie tubes might have a deeper purpose than appearance-
they can also
help the Nixie tubes get started upon turn-on (especially if they're
getting old). I once stayed
in a hotel room whose light switches had neon indicators to help one find
them in the dark,
and the one near the
Thanks for the link, Bob. I got to know both Victor Zhang and Mike
Lombardi during my
stay at Arecibo, but to my regret have never met either in person.
Dana
On Sat, Feb 27, 2021 at 6:01 PM Bob kb8tq wrote:
> Hi
>
>
>
> > On Feb 27, 2021, at 11:18 AM, Dana Whitlow
>
Dave, you just did it yourself. So there!
Dana
On Thu, Apr 15, 2021 at 7:39 AM Dave B via time-nuts <
time-nuts@lists.febo.com> wrote:
> Someone used 'php' and 'secure' in the same sentence? :-)
>
> Dave G8KBV
>
>
> On 15/04/2021 08:30, time-nuts-requ...@lists.febo.com wrote:
> > php =
C'mon guys- when you speak of a frequency error in Hz, you should also
specify "at
what frequency" *in the same breath*. Or better yet, always specify
frequency errors in
relative terms.
Hundreds of Hz at 10 Mhz is unthinkable for a Rb. Even at 8.2 GHz, 100 Hz
error is about
12E-9, which is
Thanks very much, John.
Dana
On Mon, Aug 23, 2021 at 8:52 PM John Ackermann N8UR wrote:
> In 2020 I did an extensive evaluation of the timing ability of the
> u-blox LEA-M8F, NEO-M8N, NEO-M8T, NEO-M9N, ZED-F9P, and ZED-F9T. The
> work was made possible by support from the HamSci consortium
>
he other.
>
> --- Graham
>
> ==
>
> On Thu, Aug 26, 2021 at 4:43 PM Dana Whitlow
> wrote:
>
> > Hi Jim,
> >
> > I think the best way is to view the signal as a phasor, with any
> > noise present adding a
> > random trajectory (a fuzzball) to the ti
Hi Jim,
I think the best way is to view the signal as a phasor, with any
noise present adding a
random trajectory (a fuzzball) to the tip of the signal vector.
Conceptually speaking,
this eliminates needing to worry about the distribution of power between I
& Q, etc.
It lets you view the whole
If my watch were that bad, I'd toss it out and go shopping for a new one.
I wonder if Leviton offers a version with an external ref input.
Dana
On Fri, Aug 27, 2021 at 12:12 AM D. Resor wrote:
> I inquired with Leviton as to the accuracy of the VTP24 24 Hour
> Programmable
> Timer with DST.
>
Another point should be mentioned:
Many inexpensive RF products use floating BNC connectors (those with shells
that are insulated
from the bulkhead in which they are mounted). These are virtually
guaranteed to be common-mode
leaks, and should be avoided like the plague. Nobody will admit to
This *assumes* that there is a crossover somewhere practical between
> the fiber noise and the noise on the optical gear. You should be able to
> work out what it is with some fairly normal phase noise or ADEV testing.
>
> Bob
>
> > On Aug 28, 2021, at 3:03 PM, Dana Whitlow wrot
I was looking for something similar about 18 months or so ago. Although I
haven't taken any
action yet, I concluded that one could do a nice job for under $200 per
segment, including the
transmitter and receiver modules and lots of connectorized multimode
fiber. What I *don't* know
is what the
nch of 10 MHz cables running out from here or
> there
> will impact your ability to listen to WWV at 10 MHz :) Other than killing
> all the sources,
> there is no silver bullet.
>
> Bob
>
> > On Aug 28, 2021, at 7:57 PM, Dana Whitlow wrote:
> >
> > Bob, my
8/28/2021 08:26 PM, Bob kb8tq wrote:
> >> Hi
> >>
> >> Anything you do that has a bunch of 10 MHz cables running out from here
> or there
> >> will impact your ability to listen to WWV at 10 MHz :) Other than
> killing all the sources,
> >> there
n coax for 10MHz distribution
> Removes all possibility of ground loops
>
> Andy
> www.g4jnt.com
>
>
>
> On Sun, 29 Aug 2021 at 15:22, Dana Whitlow wrote:
>
> > I believe that a significant problem in my case was not leakage through
> the shield,
> > but
&
Paul is right, and it can be difficult to figure out which cable works well
at a given
wavelength and which connector type is which. A phone conversation with an
applications person at the cable supplier ought to help avoid any of the
traps
At the Arecibo Observatory we had some bad experiences
Skipp,
Several responders have correctly referred to the "noise floor", but I
believe that
none have said what level that is. And it's not trivial to say so, either,
because it
is dependent on the extent to which the antenna under test sees the sky and
ignores blackbody radiation from the
I love Dan's idea, with one caveat. The transmission through a
powered-down LNA
is an unknown, probably even to the manufacturer. Thus comparing output
signal
levels with power on or off is pretty meaningless.
But his test with power on should be a great way to get some clue that the
antenna
is
;
>
> On 8/23/2021 3:30 AM, time-nuts-requ...@lists.febo.com wrote:
> > Message: 4
> > Date: Sun, 22 Aug 2021 10:16:56 -0500
> > From: Dana Whitlow
> > Subject: [time-nuts] Re: Efratom LPRO-101 Rubidium question
> > To: Discussion of precise time and frequency
s of a GPSDO and the Rb
> >under test using a simple quadrature demodulator, with the I & Q outputs
> >displayed on a 2-chan DSO.
>
> Can you explain what you do? Do you just connect the two 10 MHz signals
> to the input of the demodulator?
>
> Robert
>
>
> On 08/
I'm curious- is this a realtime sampler, or is it one of these things
like early sampling 'scopes used?
Dana
On Wed, Sep 1, 2021 at 1:10 PM Mike Monett wrote:
> Conventional samplers for home brewers usually go to 1 GHz. The SD-32
> sampler for the Tektronix 11801C mainframe goes to 50 GHz.
It seems to me that in order to derive much thermal stabilization, the *top*
of the space would need to be several feet underground (depending on
geographic location). And I think that the means for human access would
likely "spoil the broth" unless fairly extreme measures were taken.
Wouldn't
Tom,
Andy brings up good points, especially about water leaks.
Are you familiar with "Whitlow's 5th law" (which can be summarized
as "everything leaks")?
Dana Whitlow
On Thu, Sep 9, 2021 at 7:29 AM Andy Gardner, ZL3AG via time-nuts <
time-nuts@lists.febo.com> wro
One might also consider mounting smaller items inside the cylinders of the
engine block,
to get the most out of its thermal mass.
Dana
On Thu, Sep 9, 2021 at 11:03 AM Joseph Gwinn wrote:
> On Thu, 09 Sep 2021 03:30:35 -0400, time-nuts-requ...@lists.febo.com
> wrote:
> Re: time-nuts Digest,
It may be that the time constant of eddy current damping would be too
limited by the
inavailability of sufficiently good conductors (ar room temp, anyway). To
get really
long time constants one basically needs superconductivity somewhere in the
system.
Dana
On Sat, Sep 11, 2021 at 11:54 PM Tom
Perhaps the author is trying to include Schmitt triggers to sort of emulate
mechanical escapements.
I've occasionally used the things (Schmitt triggers) to help square up
sinewaves, but never in a case
where I was concerned about stability or jitter.
BTW, how do three inverters constitute a
Andy,
Good point, up to a point. But even if the antenna's amplifier itself has
a good return
loss, cheap cables like RG-174 are pure garbage and could be doing just
about
anything along their length. And if the bottom end connector is put on by
a person
without training and the correct
Alec,
I seem to perceive that PC clocks have gotten quite a bit better since
their early days. What do others think?
Dana
On Wed, Sep 29, 2021 at 3:10 PM Alec Teal
wrote:
> Hi there,
>
> I have a question and I cannot think of anyone better to ask, for a
> project we need to time some things
My dad worked in the absorption air conditioning field using ammonia and
water,
and he once told me that ammonia-water was hell on aluminum copper points,
or
even aluminum tubing that had impurities in the form of tiny copper flakes
in it.
As to dry ammonia, intuition suggests to me that things
I wonder what the detailed thermal model of telecom Rb's looks like. I
cool my PRS-10's
hear sink surface to ~55C with a heatsink, but parts of some other surfaces
of the package
run several degrees hotter. This rather puzzles me, and worries me.
Dana
On Tue, Oct 5, 2021 at 10:46 AM Bob kb8tq
One other thing to consider with LDOs: some types can go unstable and
oscillate with
the wrong (combination of) capacitors on input and output. So any time you
design in
an LDO, it is important to closely scrutinize the datasheet and application
note(s) and
heed their warnings. Unless you like
Bob, I seem to remember reading in the manual on the PRS-10 where they
expounded
at length about how they took great pains to make the unit work well with
typical noisy
GPS PPS input.
I'm using a CNS Clock II as my primary GPSDO, checking phase slippage with
respect
to my PRS-10 to make decisions
TVB, I'm interested in the nitty-gritty of this problem and would appreciate
it if you OK this thread's being kept on the group.
Dana
On Thu, Nov 18, 2021 at 6:58 PM Jared Cabot via time-nuts <
time-nuts@lists.febo.com> wrote:
> Hi,
> Your help is appreciated. We can keep this on-list for now
But if you can stand the ADEV hump around 2 sec, the PRS-10 is delightful.
BTW, the ordinary factory new PRS-10 does provide for direct locking to 1
PPS,
but many of the available surplus units had that feature removed. Tne new
PRS-10's sold for years for $1595, but I see that it has gone up to
I own at least two Garmin handhelds that park out-of-service sat symbols
at due north on the horizon. But they don't do anything like that finger.
Dana
On Wed, Nov 10, 2021 at 9:30 AM Bob kb8tq wrote:
> Hi
>
> Your GPS antenna does not have a clue where signals are coming from. The
> only
>
Dan, in recent years I've read that DOD (or some such agency) has been
running
spoofing tests here and there, but always in remote thinly-populated areas
(for
what should be obvious reasons).
As to why not all your receivers exhibit the "finger", I point out that the
appearance
of a GPS satellite
Dan, could it be that you have a spoofer in the area?
Dana
On Sun, Nov 14, 2021 at 4:27 PM Dan Kemppainen
wrote:
> Hi,
>
> Still trying to sort out the cause of that 'finger' of signal.
>
> Hooked up two more different GPS modules. A ZED-F9P, and a Jackson Labs
> LTE-LITE eval board.
>
> The
In fact, I believe that the satellite positions shown on screen plots are
those
calculated from almanac data. My reasoning is that most GPS receivers
seem able to put up such plots first thing after turn-on, before ephemeris
data from even a single satellite is available.
IMO, if the almanac
Poul,
You did not really answer the basic question: "Does the 2.5 Hz
(or 5 Hz if applicable) C-field reversal cause the 2-sec bump in
the ADEV plot for the PRS-10?".
BTW, some radio hams are involved with microwave and even
MMW communications between mobile stations, and I'd bet they
benefit
Hal, that looks suspiciously like the fickle finger of fate to me.
Dan, since you have good low-angle coverage I might
suggest setting the elevation cutoff as low as 10 deg or so
and taking a look at the results for a few weeks. Then
start raising the elevation cutoff and repeating the
My experiences with the T'Bolt have not been entirely satisfactory. If I
set the loop
lime constant long enough to get a satisfying smoothing of the GPS noise (a
few hundred
seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears its
ugly head and
I see a lot of my HVAC system
Bert, remember that I need a very long locking loop time constant setting in
order to smooth out GPS noise, so in a sense the GPSDo is *almost* in a
holdover state anyway, all the time.
Probably the smartest thing for me to do is to buy a spanking new PRS-10,
with the PPS locking feature present.
-10 you get that hump in the ADEV. I’m not saying that it’s
> the
> end of the world, but it really does bug me that it’s there ….
>
> Bob
>
> > On Jul 20, 2021, at 10:03 PM, Dana Whitlow
> wrote:
> >
> > Bert, remember that I need a very long locking loop time c
Hal, in cases where it is physically applicable, the temperature rating is
generally
that of the flange which is intended to be bolted to a heat sink.
Dana
On Mon, Jul 19, 2021 at 7:30 AM Hal Murray
wrote:
>
> I have one sitting on a shelf. No air-conditioning. The top plate is
> warm,
>
Agreed, Ziggy.
I'm actually thinking (a little bit) about getting a Thunderbolt E. But
the price does
kind of hurt.
Dana
On Mon, Jul 19, 2021 at 1:08 PM Ziggy
wrote:
> $650 for the _starter_ kit - $124 for the carrier board with module. So
> I'd say that's affordable. But the ±7us over a
Dave,
The usual source for old used Thunderbolts is either on eBay, or private
sales by
individuals.
I've twice now requested a quote for a new model from Trimble, and they did
not
even bother to respond. Perhaps there are distributors, but if so I
haven't been
able to identify any.
Dana
On
t;
> These guys:
>
> https://novotech.com/products/timing-modules.html <
> https://novotech.com/products/timing-modules.html>
>
> At least have a listing suggesting you can buy a Thunderbolt E.
>
> Bob
>
>
> > On Jul 17, 2021, at 3:28 PM, Dana Whitlow wrote:
> &g
I think there might be a down side to using more sensitive GNSS receivers,
which is
that such a receiver will be willing to include more impaired signals in
its time and/or
position solutions, leading to poorer overall accuracy.
Does anybody know?
I certainly concur that good antenna siting is
Most general purpose passive splitters for the L-band regime are
essentially variations
on the Watkinson splitter, which provides good isolation between the output
ports, if
(and only if) the input port is driven from a matched source.
So if your GPS antenna, whether active or passive, has a good
y rarely hit a 14 db return loss spec in any case. Indeed
> there are a lot of attenuators out there that don’t get to 14 db at 1.5
> GHz.
>
> Trimble did a *lot* of testing before they put the F connector on the
> TBolt.
> They could find no impact at all.
>
> Bob
>
Eric,
Do the observed DAC steps correspond in polarity to the observed frequency
changes, or just the reverse? That's a key determination to make in placing
blame, for it tells you whether the DAC steps are causative to the frequency
changes, or rather the PLL's reaction to problems in, say, the
Let's see if I have this correct, then:
"Decimation" refers to the two-step procedure (filtering followed by
picking every nth sample), and
"Sub-sampling" (or "downsampling") properly refers to taking every nth
sample and discarding the rest.
Is this correct?
And thanks for all the responses.
ld shorter, and compute adev from that.
>
> FWIW IIRC all the allantools examples/tests that (successfully) compare
> results against Stable32, using frequency input data, just use simple
> non-overlapping 'boxcar' decimation - nothing more fancy or elaborate.
>
> AW
>
>
>
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