[Test-Equipment] HP 8640A

[gil smith]

Hi Mark:

At 11:31 AM 2/5/02 -0500, you wrote:
>Gil, regarding the drop in output at the high end...
>Make sure the equipment you are using to measure the output is
>up to the task.  You might be hitting an upper limit of the
>equipment you are using.

Yeah, I've chased my tail on things like that before.  In this case I have
the 8640 plugged into a tee at the (hi-z) input of a tek-2465 scope, then
to the 50-ohm input on an HP 8554 spectrum analyzer.  The scope is only 300
MHz, so I expect rolloff there (though it still triggers nicely on a 500
MHz signal).  The SA is 1250 MHz.  Though the SA is not calibrated, I can
correlate the signal level variations between the two, so I don't think I
am seeing SA response.  Plus, I also see the same output level variation
down on the 64MHz range of the 8640, and I know the SA is flat at least to
the 110MHz limit of my 8601 gen.

The 8640 level does not just roll off either -- it goes up and down several
times through the range, much like the passband of an elliptical filter or
something.  Peak-to-valley delta is over 10 dB.  It happens on the 512MHz,
256MHz, and 64MHz ranges, if I recall correctly.

thanks,

gil


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