[time-nuts] [hp_agilent_equipment] Re: Upgrade an HP 5342A microwave frequency counter to have an oven oscillator.
Dr. David Kirkby (Kirkby Microwave Ltd)
drkirkby at kirkbymicrowave.co.uk
Sun Nov 30 10:20:21 EST 2014
On 30 November 2014 at 15:05, fjdvries at zonnet.nl
[hp_agilent_equipment] <hp_agilent_equipment at yahoogroups.com> wrote:
> I have had a 10811 in the 5342A. Not really a problem. However the thing is that while your counter is switched off the outside temp of the oven warms up, no surprise here, but when you switch it on, the outside gets cooler and takes the ref freq also down due to the fan. So the whole benefit of having the oven in there to improve the accuracy of the thing is marginal. Its just a design error to put a fan directly on an OCXO.
> I have taken it out again. I now have it run from my rubidium source, The counter is way more accurate, and depends no longer on it's warm-up time. Better invest in a good rubidium for your lab. (Or a GPSDO)
> Fred de Vries, PE1FBO
I see what you mean about the fan. But the reading is considerably
more stable now the OCXO has been put in, and the TCXO removed. Before
I mad that change, the output from a signal generator set to 10 GHz
was changing around 1 kHz or so over a time fame of a few seconds. Now
it shifted 100 Hz or so over a period of hours.
I suspect you are right about the fan being bad near the oscillator,
but the oven probably insulates the crystal far more from the effects
of temperature change compared to the TCXO. The fairly rapid
fluctuations I see before might well be the result of air flow over
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