[time-nuts] May I ask for your advice on a faulty 5370B?

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Jul 4 09:24:44 EDT 2007

S McNamara wrote:
> Thanks Bruce,
> I used a HP5335A counter to measure the ref out at 10.000,000,3MHz and the 200MHz test point-1
> on the multiplier board as 200.000,007 MHz
> The HP5335 is not calibrated but it looks like the multiplier is working O.K. I have no way to measure the harmonics as I do not have a RF spectrum analyser.
> The test point has a nice 200MHz sine wave as tested with my eye and a 150MHz CRO.
> I also adjusted the DAC voltages on A18 although they were close enough.
> BTW I think the "set test switch" settings for the DAC module A18 may have a error.
> I think the OA cal switch settings should be the same as the OO cal settings.
> Could the harmonics from the multiplier be causing the problem?
> Thanks & Regards Scott
With a 150MHz scope almost anything at 200MHz will appear to be a 
reasonable sinewave.
How clean is the 10MHz output?

The subharmonic content of the 200MHz output is well known to be a cause 
of excessive jitter should the frequency multiplier chain filters not be 
correctly adjusted.
The sidebands around the 200MHz output have to be 65 dB or more down for 
correct operation, an oscilloscope is inadequate for checking this 

Other causes could be faulty chips in the count chain.


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