[time-nuts] Frequency Counter Errors

Eric Lemmon wb6fly at verizon.net
Thu Mar 22 00:32:52 UTC 2012


Jerry,

My guess is that the amplitude of the reference signal may be on the ragged
edge of what the counters require- either just barely adequate, or much too
"hot" and being distorted.  Also, check to see if the source and load
impedances are matched.  I once corrected a similar problem by inserting a 2
dB attenuator in line with the reference signal.  And check to be sure that
the reference signal is not riding on a DC level.

73, Eric Lemmon WB6FLY
 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jerry Mulchin
Sent: Wednesday, March 21, 2012 5:06 PM
To: time-nuts at febo.com
Subject: [time-nuts] Frequency Counter Errors

I have a question for the collective group.

I have a HP 5372A and a HP 5328A frequency counters. Both counters use the
same
PRS-10 Rubidium frequency standard driving a 6 channel reference
distribution amplifier
to each counters reference input port. The problem is this;

When I measure the same frequency on both counters, (done one at a time) the
frequency
is generally off by about 300 Hz or so between the counters. Now I would
expect an error 
of +/- 1 digit, but 300Hz seems a bit strange to me. I can not find the
problem and the 
difference exists even if I use the internal timebases of each counter, give
or take the timebase errors.
The frequency is always at least >200 to 300Hz off between the two counters
and I don't know
which one to believe. You know the "man with 2 clocks" problem.

Anyone have any idea what may be causing this?

Thanks
Jerry


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