[time-nuts] HP 10544A with dodgy output?

[David C. Partridge]

What impedance loading is the output specified for?  1M or 50R.

Could I suggest using a distribution amp?

Dave 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Nick Foster
Sent: 15 January 2010 19:53
To: time-nuts at febo.com
Subject: [time-nuts] HP 10544A with dodgy output?


Hi all,

I've just built a GPS-disciplined oscillator built around a 10544A, somewhat
in the style of the Brooks Shera unit, just to use around the shack. Problem
is, now that it's wired up, I notice the output is heavily distorted. It's
clipped on the negative side of the waveform, like an emitter follower
without enough headroom. The more I load the oscillator output, the heavier
the clipping. When I load the oscillator output with 1000 ohms, spec for
this unit, almost 30% of the waveform is clipped on the negative side. If I
don't load it at all and just put a probe on the output, it looks OK, but
still some flattening of the bottom half of the waveform.

I've got it wired up according to the datasheet, with +12V on the oscillator
and +20V on the heater. The grounds for the oscillator/amplifier, oven
controller, heater, and output are all tied together.

I know these are old units, and I'm wondering if this is a problem (for
instance in the output emitter follower amp) that others know about, before
I tear into it looking for a solution.

Thanks for your time,
Nick
 		 	   		  
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