[time-nuts] another Ebay mixup, 5370

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Jun 9 20:17:01 EDT 2007

SAIDJACK at aol.com wrote:
> Hi Bruce,
> just found out that the 10MHz output looks very much like the  picture in the 
> 5370B service manual.
> I am not impressed. HP could have done a better job on that output :( Maybe  
> my unit isn't broken after all, maybe the 200ps RMS jitter is normal?
> I attached some pics of the 5370B 10MHz output here.
> Will send plots of the Fury sine output in separate email, then plots of  
> both Fury and 5370B 10MHz outputs on the spectrum analyzer.
> The 5370B is quite noisy, energy up to 700MHz. That's also clearly  visible 
> in the sine wave.
> Of course the 200ps RMS jitter is not visible in these pics.
> bye,
> Said
The HP5370 external output isnt taken directly from the internal xtal 
oscillator, but is squared up using a sting of ECL line receivers and 
then its fed to a longtailed pair which produces a squarewave collector 
current. An LC tank in the collector filters out the 10MHz component.
The simple output filter will off course not attenuate the higher 
harmonics as much as you may like.
However as long as the amplitude and phase of each harmonic is stable 
they will have little effect on the jitter.

A 200ps jitter from the EXT 10MHz output isnt normal.
Even the low cost oscillator option is far better than this.

Remove the 10811 and power it up externally and then check its output 
It can drive a 50 ohm load directly.
Its output waveform should be much cleaner than that of the 10MHz output.


More information about the time-nuts mailing list