If I remember correctly it uses a double balanced mixer as the frequency
doubler, and only works at high output levels from the 8640 (+10dBm), so you
would require an external attenuator to get lower levels.

The HP part No is 08754-60057.

73
Jeff
G8HUL


"Scott" wrote in message
.. .
I recently picked up an HP 8640B Opt. 323 (8640B in a can) and wonder if
anyone has information on the external frequency doubler so that it can use
it's upper frequency position (512-1024 MHz). I want to get 902 MHz out of
it to test the feed for my parabolic dish's return loss (SWR).

I can build a diode doubler to generate harmonics and then put a 1/4
wavelength of shorted-end coax across its output to select the 902 MHz
harmonic, but I'd like to be able to tune all freqs between the 512 and
1024 MHz without building a lot of shorted stubs. How does HP do it with
their doubler? Bandpass filtering? Could one bandpass filter cover that
much range?? Maybe something as simple as a low pass filter with an Fco
of 1050 MHz or so, but with this, how would I keep the fundamental freq
(256-512 MHz) out of the output??

Thanks for any leads!

--
Scott N0EDV
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)