[time-nuts] HP 10811 Tuning Diode
lists at rtty.us
Fri Oct 19 16:19:58 EDT 2012
The normal 10811 package has several openings in it. Light *might* get in
there. A "micro volts" level of noise can mess up your phase noise if it's
AC noise at a low frequency.
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Adrian
Sent: Friday, October 19, 2012 4:10 PM
To: richard at karlquist.com; Discussion of precise time and frequency
Subject: Re: [time-nuts] HP 10811 Tuning Diode
I didn't notice any damage, nor was there a visibly bad solder joint.
However, I couldn't reproduce the excess noise with a quick bench test
at 30V / 100k neither.
DC-wise there are a few microvolts only. Same with the SMD diode.
Exept, when the original glass diode is exposed to light. With a LED
Maglite, I got up to 50 mV (across 100 kOhm) out of it!
But there is no light shining inside of a 10811, is there?
I had first suspected a 0.1 ceramic cap, but that didn't cure the phase
The diode in the original circuit appeared to be heat sensitive,
and the excess phase noise has gone away since I replaced the diode.
The noise was clearly there, and it was also there using a test adapter
and two lab power supplies.
Rick Karlquist schrieb:
> I wonder if the glass case got a crack in it or if the kovar seal
> was failing. Maybe a failed solder joint (which gets fixed when you
> install the new diode). I've never heard of a noisy varactor before
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