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.