[time-nuts] About HP10544A

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Mar 7 20:48:27 UTC 2009

DO NOT use a 50 ohm termination as this may damage the output emitter
At the very least the waveform distortion will increase considerably.
The output stage isn't designed to drive 50 ohm loads.
Nor is it intended to drive large capacitances so use a 10x scope probe
to keep the load capacitance down.
Its possible that your load capacitance is too high.
If so the npn emitter follower output stage will distort on the negative
1/2 cycle.

New 10544A's have a somewhat cleaner output than that.
Perhaps something is wrong with the emitter follower.
Maybe the emitter followers dc collector current isnt large enough.
Despite the warnings its relatively easy to open them up and repair them.
As long as you don't alter anything in the oscillator circuit it
probably wont be necessary to tediously retune the oven temperature
control system.


J. L. Trantham wrote:
> I looked at your oscilloscope signal and it looks cleaner than mine but I
> looked at mine at a slower sweep and both 50-ohm termination and 1-Megohm
> termination.
> Can you look at it on the oscilloscope with 50-ohm and 1-Megohm termination
> and display several cycles?
> I suspect we are seeing the same thing.  I just don't know if it is the
> normal function of the 10544A.
> Joe
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Esa Heikkinen
> Sent: Saturday, March 07, 2009 2:00 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] About HP10544A
> Hello..
>> I tried to view the files on amigazone but was 'denied'.
> Yes there's many network bans and all thanks for this belongs to couple
> of spambots trying to scan the webserver at multiple IP's at same time.
> I just changed the IP bans based on IP address where you send your mail.
> You should now have access.
> Can you see the pictures?
>> Any way to get a look?  Am I doing something wrong?
> You are not doing anything wrong but someone else does with their
> spambots... :-(
>> I have several 10544A's and they all put out a 10 MHz signal but it is
> sort
>> of a 'ramp like' wave as viewed on the oscilloscope that looks rich in
>> harmonics.  My 10811's seem to have a pure sine wave though I have not
>> looked at it on a spectrum analyzer yet.
> Oh no.. then it could mean that 544 is no good for that project...
> --
> 73s!
> Esa

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