In my quest to keep improving my GPSDO, a simple test tool
that I find indispensable is a GPS 1PPS (or 100Hz) signal simulator
reference. Others may also find this useful because it allows testing the
PLL DO in their GPSDO to Cs type accuracy using a standard OCXO.
Warren,
There's
On Thu, 27 Nov 2008 21:55:26 +1300, Steve Rooke [EMAIL PROTECTED] wrote:
Hmmm... International Traffic in Arms Regulations, well I don't like
to poke holes in that excuse but unless the US customs are REALLY
paranoid, I can't see how most of the items I have tried to purchase
would be covered
On Sun, 30 Nov 2008 17:27:54 -0700 (MST), M. Warner Losh [EMAIL PROTECTED]
wrote:
The thing that got me was the word 'really' in Bruce's statement. It
read like someone who had tried it, had limited success, but in the
end wound up believing that while possible, it wasn't really
practical.
On Sat, 29 Nov 2008 03:32:23 -0600, Brian Kirby [EMAIL PROTECTED] wrote:
Maybe we should consider coming up with a standard voltage reference as
a TAPR project. We have a lot of good brainpower out here and it seems
a lot of experience available.
I think that this is a spectacular idea.
On Sat, 29 Nov 2008 19:27:34 -0500, Mike Monett [EMAIL PROTECTED]
wrote:
This discussion of voltage standards is very informative and useful, and my
thanks to all who are contributing.
It is clear why precise frequency standards are needed - there are
innumerable applications such as GPS, VLBI,
John,
Yes, that is a common practice. Both scale factor TC and balance TC
are inside the cell body.
Usually it is a device similar to foill strain gage, (but made of
nickel or balco alloy) and glued to the cell near the sg bridge.
Micromeasurements.com (Vishay) has a lot on that
One of those things that I've always wanted to do was to lash together a
liquid air plant from, say, refrigeration parts. Never had the time and the
funds at the same time.
Looked at that 10-15 years ago when in the SFX business and we used a lot of
LN2. You need a real high pressure
A question please . . . . .
In all the considerable exchange of useful information regarding the Trimble
GPS units, I cannot recall any mention of the actual specification of the
antenna system for these units. My old Odetics used an Active antenna which
required 12 volts DC to be supplied
Hi Roy:
I have some info on what antennas are allowable for the ThunderBolt at:
http://www.prc68.com/I/ThunderBolt.shtml#Ant
Note the earlier Trimble Trimpack receivers needed 41 dB of gain between the
antenna and receiver, but the Thunderbolt only needs 18 to 35 dB.
Have Fun,
Brooke Clarke
As far as DMM voltages standards, no need to build one for the 4.5 digit
meters. Doug Malone sells an excellent Xicor based reference that runs off a
9V battery for around $30 shipped. Mine checks out to better than 0.5V on
all my 6.5 and 7.5 digit meters. He sells them on Ebay under
Mark Sims writes:
I am a bit of a mass nut (OK I have a LOT of digital scales
with resolutions down to a nanogram and up to 60Kg with
0.01g res). Many of the industrial scales require you to
enter your lat/lon/altitude (or at least your general location)
so they can better model and
- Original Message -
From: Tom Van Baak t...@leapsecond.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Thursday, December 11, 2008 7:10 AM
Subject: Re: [time-nuts] GPS signal simulator
Tom
Thanks that should be very useful for software
Most of the industrial scales that allow location to be specified do it to
improve out-of-the-crate accuracy where you might not have a calibration
weight/cart/truck available (BTW, calibration carts are not used on the more
accurate scales... things like bouyancy of the air in the tires
Do you know of any laboratory scales that also require you to enter
the date/time so they can also model the dynamic 0.1 ppm effect on
gravity of lunar/solar tides?
It's worse than that.
Geologists measure gravity to get the density of of the underlying rocks. I
saw a neat topo map of the
One of the questions I've needed to answers is just how good is good enough
when it comes to making a high performance GPSDO.
There is no single answer to this. One man's high-performance
is another man's low-performance. It all depends on where you
are in your quest.
Some of the self build
Joe
I suspect that the phase detector characteristics stated in the NIST
papers only apply when the mixer RF port is saturated.
This is evident from the Kurtz application note:
http://www.wj.com/archive/documents/Tech_Notes_Archived/Mixers_phase_detectors.pdf
which indicates (Figure 14 and
Most of the industrial scales that allow location to be specified do it to
improve out-of-the-crate accuracy where you might not have a calibration
weight/cart/truck available (BTW, calibration carts are not used on the more
accurate scales... things like bouyancy of the air in the tires can
One of the questions I've needed to answers is just how good is good enough
when it comes to making a high performance GPSDO.
There is no single answer to this. One man's high-performance
is another man's low-performance. It all depends on where you
are in your quest.
Some of the self
The quintessential gravity meter (Worden Gravity Meter by Texas Instruments)...
still being made after 60 years or so:
http://www.mssu.edu/seg-vm/pict0246.html
--
Geologists measure gravity to get the density of of the underlying rocks. I
saw a neat
And a newer design gravity meter:
http://www.ipgp.jussieu.fr/files_lib/163_CG-3DescriptionTestResults.pdf
_
Suspicious message? There’s an alert for that.
Brooke
The NIST papers concerned were about using mixers as phase detectors:
http://tf.nist.gov/timefreq/general/pdf/112.pdf
http://tf.nist.gov/timefreq/general/pdf/971.pdf
As is all too often the case with some NIST papers the operating conditions for
which the stated phase detection
Bruce,
time-nuts-boun...@febo.com wrote on 12/10/2008 08:38:13 PM:
Joe
Joseph M Gwinn wrote:
Bruce,
Reflecting the sum frequency back into the mixer is actually
necessary
to reduce the noise at the IF port.
I believe that one of Agilent's simulation application notes mentions
The Symmetricom 5120A does something very clever to alleviate this
problem. Explained in US patent 7,227,346 and Direct-Digital
Phase-Noise
Measurement; J. Grove, J. Hein, J. Retta, P. Schweiger, W. Solbrig,
and
S.R. Stein; 2004 IEEE International Ultrasonics, Ferroelectrics, and
Ooooh, way to big, complicated, expensive, fragile, and swoopty fancy pants
for real world use...
The CG-3 type instruments and some of the the LaCoste Romberg units also have
ppb resolution and weigh around 12 kg. The Worden units weigh even less (and I
bought mine for less than $100).
Joe
Isolation from mixer RF to LO port may be too low when the mixer input
frequencies are different.
Injection locking can then occur all too easily (just ask Ulrich about
this) when the mixer RF ports are driven by 2 separate OCXOs.
Detailed in line post follows:
Bruce
Joseph M Gwinn wrote:
Joe
Attached is noise spectrum (1kHz and below) of AP192 with nothing
connected to inputs.
Sampling rate 96KSPS.
Frequency bin equivalent noise bandwidth ~ 3Hz.
Noise has similar spectrum to flicker noise with a noise corner of
around 300Hz or so.
Bruce
inline:
On my Oscilloquartz GPSDO, the 10 MHz output goes low at very close to
the same time as the 1 PPS output goes high.
On my Fury, the 10 MHz sine wave is just dropping off of its max high
voltage as the 1 PPS goes high. The 10 MHz CMOS output goes high just
shortly before the 1 PPS.
What do other
Matt
For those GPSDOs which also use the OCXO clock to generate the LO for
the GPS receiver (eg Thunderbolt) the zerocrossing transitions of the
10MHz output are accurately aligned to the leading edge of the 1PPS output.
For other GPSDOs there may be an offset between the 10MHz zero crossing
and
Hi Matt,
What do other GPSDOs do?
All over the map. A well-engineered GPSDO might choose to
align the rising zero crossing of the 10 MHz sinewave with the
leading edge of a very fast risetime 1PPS, because this is
common sense but if it isn't in the spec, it's best not to expect
it to happen.
Hi,I was wondering by chance if someone familiar with hp date coding could
tell me the date of manuf. of this 5071a
3608A01190
Thanks,
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aceamuseme...@mchsi.com wrote:
Hi,I was wondering by chance if someone familiar with hp date coding could
tell me the date of manuf. of this 5071a
3608A01190
Thanks,
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Thanks,
I just purchased this on ebay and was just wondering how bad the tube could
be(yrs left)
I have a agilent one now I got new a year ago and its ion pump current keeps
rising,the one advertised says its still pretty low @ 2.0uA ,1450emult..has
telcom options installed so I bet it
The date code is not a production date, necessarily, but the date of that
particular design revision (presumably when it was released to
manufacturing). It sets a lower bound, but your unit could potentially be
several years newer. You can get a better idea by looking for the latest
date code on
Are you using terminations or is the end equipment properly terminating
? Mismatched impedance does weird things to waveforms. Also check to
make sure you not overdriving on your source. And a bad power supplies
can induce waveform distortion.
Brian
Matt Ettus wrote:
Also, I noticed
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