[time-nuts] Don't use cheap cables -- a cautionary tale
jra at febo.com
Sun Mar 3 10:46:10 EST 2013
Yup, they are BNC (by necessity). I'm still experimenting but it may be
an ill-fitting connector on the cheap patch cable. Switching to a
better quality cable seems to have solved the problem, one way or the other.
Bob Camp said the following on 03/03/2013 10:10 AM:
> By any chance is the connector a BNC? They have been known to create similar looking issues.
> On Mar 3, 2013, at 9:59 AM, John Ackermann <jra at febo.com> wrote:
>> I was measuring two OCXO and was getting some quite unusual results -- a symmetrical frequency cycling of several more than 1e11 p-p, with a period of around 15 seconds.
>> I removed an RG-58 3 foot jumper cable that fed 5 MHz from the rear panel of another OCXO to a patch panel (where it was terminated in 50 ohms), and the noise quieted right down. See the attached frequency plot.
>> The other OXCO had a similar jumper cable in the path, and although the two cables were not parallel to each other for any significant distance, there was still enough signal radiation and pickup to cause a nasty problem.
>> Lesson learned -- use only double-shielded cable in the oscillator rack (and in any RF measurement path) from now on.
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