[time-nuts] BG7TBL 10 MHz OCXO

[Andy Backus]

More complete evaluation of the BG7TBL from eBay:

One week continuously powered up.
19-23 degrees ambient temperature, 55-65% humidity.
Output 10 MHz at 4 volts p-p.
Frequency measured by phase drift rate when compared to a Thunderbolt GPSDO 10 MHz standard using a scope.

Precision --
   +/- 0.5 mHz over two days (50-200 sec runs) with the caveat that the oven seems to regulate over a 100-second cycle
                         with a hysteresis of +/- 0.5 mHz so the "instantaneous" frequency could be +/- 1 mHz
Accuracy --
   limited by the resolution of the calibration pot to about +/- 1 mHz

Gravity effects (looking at the front panel) --
   rotation 90 degrees counter clockwise causes a 5.8 mHz decrease in frequency
   rotation 180 degrees causes a 5.3 mHz increase in frequency
   rotation 90 degrees clockwise causes a 12.5 mHz increase in frequency

Andy Backus

________________________________
From: time-nuts <time-nuts-bounces at lists.febo.com> on behalf of Bernd Neubig <BNeubig at t-online.de>
Sent: Monday, June 3, 2019 3:26 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] BG7TBL 10 MHz OCXO



 2.  interesting observation: turning the unit 90 degrees onto its right
hand side immediately increases the output frequency by 10 mHz (reversible);
turning the unit 90 degrees onto its left end immediately decreases the
output frequency by 10 mHz (also reversible)

This meant that the g-sensitivity is in the order of magnitude of 1 ppb/g
which is quite a normal order of magnitude.
Correctly doing the 2g-flipover would tilt the OCXO by 180° an divide the
observed relative frequency change by 2.
But also this simple test is not necessarily an accurate measure of the
g-sensitivity. As the extremes may now occur at 180° tilt.
Also care has to be taken to distinguish between the frequency shift caused
by the g-sensitivity and a frequency drift (usually slower) by thermal
effects, as the internal temperature profile is also reversing.

Have fun
Bernd DK1AG


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