In an Ecosphere or Ecostar? receiver with an 11' C-band setup

it worked fine until 6 months ago, then the picture became static invaded
with crackly noise in the audio. Some channels are worse than others, odds
seem better than evens.

Location is southern California, dish is behind a house, no obvious
microwave towers at all, its a rural area

The LNB is new, didnt make any difference, tuning the dish position, pushing
the dish from various sides? didnt help, it was at the best spot. focus?
didnt do much, turning the LNB assembly slightly? again it was at the best
already

Cables check out fine, tuning the video, polarity, it was already at its
best spot. One person said it was microwave interference, now Im not from
the show me state, but.... I gotta see it to believe it.

If its microwave noise coming in at an angle, then what about putting some
sheet metal on the dish? its a wire mesh type, so if I cut strips to fill in
all the wire mesh area wouldnt it change the reflectivity and do something
to make the signal...different??

OR how to tell if there is some stray microwave coming in from the horizon?
wouldnt a big 4' x 8' sheet of plywood with some sheet metal fastened to it
serve to block the possible stray interference, if it existed???

So say the dish would have perfect reception. Its aligned with a good LNB.
but a microwave tower is messing it up. If I hold up a 4x8 blocking panel,
and find the direction of the tower, then the picture should clear up
right??

What can microwaves pass thru? or be reflected by?

thanks in advance