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  1. HP8924-Family-Spectrum-Analyzers
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HP 8935 Ext Ref Problem

 
Edited

My 8395 works fine with the internal reference and I did ti alignment with an external source.
However it does not lock with a 10 MHz external signal - shows "unlock" but once in a while it will Lock.
If I put in a 10.000.022 MHz signal it will lock to that...but of course all the signals and freq counts are off also...
I have the Temp Comp Xtl. 1813-1106
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Any Suggestions??
 

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Hi,
either your HP 8935 or the external frequency reference that you a using is off frequency. A lot of HP/ Agilent test equipment will reject the external?frequency reference if it is off?frequency, sometimes only as much as a few hundred hertz. If you are sure that the external reference is on frequency, do a frequency check of the generator output of your 8935. Sometimes just a adjustment of your 8935 to the correct frequency is all it needs, or it may have a faulty internal reference fault, eg, a faulty oven reference oscillator, which is common on high hour equipment.?
I believe the 8935 frequency adjustment is done electronically via a test function called PERCAL.?


James?
 

Problem is resolved. Unit now recognizes and uses external REF.
?
 

Wally,? good news, but please tell us how it's working again.
 

The 8935 board I have is not identical to the 8920 CLIP Schematic. So I cannot be sure.? There is a signal to the oscillator that appeared to be high when the ext ref? was plugged in. a pull down resistor of about 500 R at this point solved the problem.? There is also a big cap at this point which is not on the schematic, It was fine.? I think there is something amiss in the oscillator itself.? however works fine now.
I have the high stability OCXO not the TCXO.

Wally KC9INK


On Thursday, August 22, 2024, 12:48:47 AM UTC, Hank Riley via groups.io <n1ltv@...> wrote:


Wally,? good news, but please tell us how it's working again.

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