[time-nuts] HP10811 problem - wrong frequency

wa1zms at att.net wa1zms at att.net
Sun Jan 13 19:39:39 EST 2008


I too had a 10811 that was off frequency by 100KHz or so
and although hard to believe, it was a defective xtal.
The xtal was dead and had no series or parallel resonance
near 10MHz.

At the same time I had a 2nd 10811 that had a failed internal
voltage regulator. While I had the two units a part, I was
able to perform an S11 measurement of each xtal to confirm
that the first unit did in fact act like an open circuit.
I even swapped xtals to confirm that it was the xtal itself.

So I guess a dead xtal is also possible.

-Brian, WA1ZMS

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Bruce Griffiths
Sent: Sunday, January 13, 2008 4:11 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP10811 problem - wrong frequency

John Miles wrote:
> Yes, I don't think a broken oven controller is going to pull the frequency
> off by 890 kHz. :-)
> -- john, KE5FX
If the oscillator is oscillating in an undesired mode, then it is likely
that the mode suppression network
(C5, C6 L2, L3 in the schematic) in the oscillator has a faulty
component or maybe a dry joint.
It probably worthwhile to check all the frequency determining components
in the oscillator at the same time.
You'll need to disassemble the oscillator to check.


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