It's been a year or so since I had the analog side up on C- but I always had white sparkles in the red colors. The amount of sparkles were dependent upon the transponder I was on (same bird). I had black/white sparkles on occasion, but adjusting the skew and tweeking the LO freq would make that go away. Also, the TI (terrestrial interference) filter would help sometimes.
But the biggest help was when I adjusted the feedhorn to the correct F/d setting and distance from the dish. I never got it perfect, but there were times that it was really good.
I seems that the design of the support arms and how they screwed on the rim of the dish was the problem. I'm currently rebuilding the dish, and I thrubolted the brackets to the rim. Before, they were screwed to the outer trim piece, which caused the trim to work away from the structure. #10 stainless screws and nuts have greatly stiffened the bracket mounting, to the point that the scaler ring is quite stiff in the 4 arm support.
I'm going to an orthomode feed for
c band, and I cut a portion of the scalar ring to accept a prime focus lnbf for Ku. (that will be after I get C working.)
Tough part is that I have to attach an
actuator to a dish and inoperative HH mount. So i'm fabricating a beefy mount for the tail of the actuator.
And the real challenge will be finding the arc again- because I had to completely loosen the settings for latitude angle to get bolts to back out.
I did mark polar north on the pole, so I should be close (enough) to make it a fun exercise in hunting.
Larry