You might google for "waveguide vane attenuator". That is the device
used to measure fade margin on microwave links. A company called ARRA
makes them, so did HP at one time. There is a lossy vane which rotates
into the waveguide, turned by a calibrated knob and scale. Might be
worth your while to check e-bay to see if you can find exactly what you
want. Also some old microwave radios had these attached to the output
waveguide. Of course you need to find X-band.
The-RFI-EMI-GUY

gudmundur wrote:

Hi folks,

I needed to produce some referance power levels that were 'down' from
my calibrated 0DbM generator. (It's output power is auto leveled, and
non-adjustable) 9445mhz, center of one of the maritine radar bands.

I built two little aperature plates that look like a waveguide cover,
but have a hole drilled in the exact center. A .185" hole provides about
45db of reduction, and a .310" hole provides about 25db of reduction.

There are some differances of exact gain reduction depending on where
in the waveguide system I place these plates. (Close to source, or close
to receiver) Perhaps up to about 3 db differance, not a big worry for me.

Do the numbers sound correct? Should I have attenuated in a differant
way? Like perhaps a slot, instead of a round hole??

If I want to make some more of these plates, is there some math to help
me predict the size of the hole for 10db?

Thanks for your help and comments. I am exploring some new areas here.





--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.