[Test-Equipment] HP8640B Signal Generator Problem

[Jose V. Gavila]

Hello Scott,

>If I connect a cable from the rf output to an external frequency counter 
>and set it to any frequency in the 18-128Mhz ranges the frequency 
>displayed doesn't match the frequency of the signal being generated, they 
>are off anywhere from 5-12Mhz.
>
>For example, 8640B set to 50Mhz shows 62.5Mhz on the external frequency 
>counter.  Also, if I take a cable and connect the output to the external 
>counter input and tap the int/ext button the 8640B's frequency counter 
>will show 50Mhz as it should.
>
>So it appears that when you select the external frequency counter input 
>the circuitry works just fine, its the internal input that has a 
>problem.  Can anyone suggest exactly what might be the cause, because I 
>spent three days running through suggestions without any luck so far.
>
>Above or below the 18-128 Mhz ranges it operates as it should, no error in 
>frequency.

Hmmmm... I guess the 8640B is cheating you when it counts 'right'... and 
your problem could be in the band switching assembly. Please, check my WEB at:

http://jvgavila.com/hp8640b.htm

It could be a similar thing.

Regards,

JOSE
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