I tried to use 1PPS as Ext. trigger for the oscilloscope. I was able to
"stabilize" signal movement. Then I tried to calibrate OCXO. However its
appeared out of range (I reach end of potentiometer limit but counter
still shows that OCXO is out of 10Mhz). Which kind of "suspicious".
Then I decide to disassemble my project to take pure 10Mhz directly from
GPSDO to measure OCXO signal. Its read totally different frequency value
now. So, using 1PPS didn't work for me. I tried using that GPSDO 10 Mhz
as Ext. Trigger. And now I got much better result. I was able to
calibrate 5386A to some extent. But my 5386 has TCXO. So, after few
minutes its moving out of "perfect" value. May be I need to wait much
longer to stabilize oscillator. I am not sure what to expect here.
Using GPSDO 10 Mhz as REF signal, I was able to calibrate OCXO. And now
its potentiometer position was nether at its both extremes. The reading
on 5386a (using 10 sec gate) fluctuate from 9.999999993M to
10.000000007M. Again, may be I need to wait much longer when OCXO will
be stable.
So, I think the best approach will be using 10Mhz GPSDO as ref. signal
for this counter. In another case, I'll need to wait to warm it up (the
manual advised only 30 minutes. But I am not sure). And then
re-calibrate it. Its time consuming.
I am curious, if its practical to calibrate something like Morion MV89A
and use it as signal reference for this counter ? Or OCXO still will
drift out of desired frequency relatively soon ?
Regards,
V.P.
On , Scott McGrath wrote:
Or feed both oscillators into a mixer and extract the difference
which will be the offset of your DUT from your standard
Content by Scott
Typos by Siri
On Apr 24, 2015, at 10:36 PM, Brent Gordon <time-n...@adobe-labs.com>
wrote:
Just feed the PPS into the scope trigger on step 2.
The low repetition rate on the PPS would make this difficult on an
analog scope; on a digital scope it is easy. You can use any
sub-harmonic that is less than or equal the counter reference
frequency (10 MHz).
Brent
On 4/24/2015 3:45 PM, d0ct0r wrote:
Hello,
The input: HP 5386A which I would like to calibrate, Well warmed
Tremble
Thunderbolt (1PPS only), 10 Mhz Datum OCXO (unknown accuracy), Rigol
1101E Oscilloscope.
The goal is to calibrate counter to read the Datum OCXO.
===========================
Reading the manual for 5386A, there is simple schema for calibration:
1. Connect HP 5386A 10Mhz OUTPUT to Oscilloscope
2. Connect Frequency Standard to Ext. Trigger on Oscilloscope
3. Adjust the frequency on 5386A TCXO for minimum sideways movement
of
10 Mhz signal
However, my Trimble TB 10Mhz output is currently in use. I have only
1PPS signal available. The HP manual do not mention what exactly
frequency needs to be on "Frequency Standard" connected to Ext.
Trigger.
Is there any method/option I could apply to calibrate HP counter ?
Thanks !
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--
WBW,
V.P.
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