[time-nuts] About HP10544A

J. L. Trantham jltran at worldnet.att.net
Sat Mar 7 21:32:37 UTC 2009

I have been able to find schematics of the 10544A but not a service manual.
Is there a service manual available?


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Bruce Griffiths
Sent: Saturday, March 07, 2009 3:24 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] About HP10544A

Esa Heikkinen wrote:
>> New 10544A's have a somewhat cleaner output than that.
>> Perhaps something is wrong with the emitter follower.
> Sorry I forgot to say that the oscilloscope picture was taken directly
> from HP10544A output, without emitter follower but with 1:1 probe,
> output terminated with 1 kohm. resistor. With spectrum analyzer the
> emitter follower is necessary due to 50 ohm. input impedance of the
> analyzer.
> Datasheet of HP10544A claims that harmonics should be more than 25 dB
> down. Doesn't look like they are.
> Here's a spectrum measured from OCXO which is used in the Thunderbolt.
> I'm not an crystal oscillator guru but I think that this is just what an
> xtal oscillator output should be:
> http://www.amigazone.fi/files/gpsdo/tbolt-1.png
> http://www.amigazone.fi/files/gpsdo/tbolt-2.png

The capacitance of the 1x probe is too high.
Use a 10x probe with 1k across its inputs at the 10544A.
The 10544A output stage is an emitter follower.


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