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

jmfranke jmfranke at cox.net
Fri Jan 15 20:14:36 UTC 2010


The 10544A is specified for a 1000 Ohm load.

John  WA4WDL

--------------------------------------------------
From: "David C. Partridge" <david.partridge at dsl.pipex.com>
Sent: Friday, January 15, 2010 3:11 PM
To: "'Discussion of precise time and frequency measurement'" 
<time-nuts at febo.com>
Subject: Re: [time-nuts] HP 10544A with dodgy output?

> 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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