[time-nuts] HP10544a Technical Info needed

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Feb 3 02:07:20 EST 2007

Gerald Molenkamp wrote:
> Hi Bruce,
> You are right. I havn't checked my unit against the schematic at all. It is 
> well secured calibrated and operating in my HP 5342 operating well within 
> the specifications. The scanned schematic came from Leapsecond a few years 
> ago, and I have not had to use it as yet. Lets hope it stays that way.
> Cheers
> Gerald

On closer inspection it would appear that to be consistent with the 
specified output R8 in the AGC cascode amplifier should be 100 ohms as 
in the output cascode amplifier that feeds the emitter follower 
otherwise the AGC detector will not develop enough output.

Some modifications to the oscillator circuit were made to improve the 
phase noise floor by about 15dB between the early and later versions of 
the 10544A.
Thus you will need to know if your oscillator is an early or later 
production unit.
I suspect the circuit schematic that Tom scanned is for the early 
production unit as the ouput cascode amplifier has an RF voltage gain of 
about 13.2x (22.4dB) and a corresponding RF input voltage at the base of 
the input transistor of about 76mV rms which is quite low.


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