Troubleshooting AFN Broadcast Reception on 4.5 Meter Dish

[Captain Midnight]

I use this calculator to figure out where the LNB needs to be. Focal distance is measured from the center of the dish to 1/4" inside the feedhorn opening. Prime Focus Satellite Antenna reflector calculation

 

[arlo]

Aiii capn', But never do the math and slap it there and call it a day.
1/4" in or out from that will make or break your day.
Always peak signal and balance skew. Polorotors made skew a day at the beach.
Right now I'm thinking it could be a slab/skewathon.

Maybe, maybe not because using post #14 for reference. And laying out the actual Norsat feed dimensions. The dielectric looks like it's actually close to 24 degrees instead of 45.
I could be very wrong. But look at the corel doodle.
Orange is what the pic. shows and is 24 degrees.
Black is a true 45 degrees with reference to the green center lines.

 

[Titanium]

1/4" inside the feed opening is an estimated starting point. The optimal convergence point also depends on how the install will be used. The optimal focal point will be different for a stationary dish on a fixed satellite/carrier, vs an FD averaged position for a motorized dish that would be exposed to different sidelobe influences as it moves across the arc.

Adjusting a servo skew on a circular polarized separates the installers from the techs! LOL

 

[Redbull-wings-]

Hey all,

Tried swapping out the cable and while the signal quality still remains in flux the signal level did come back up to previously indicated levels (58-70) so there may have been something there or maybe just a glitch in the receiver.

One thing I wanted to get some help on is whether interference could be playing a role. There are a lot of microwave point-to-point receivers and transmitters where we are and I know one for sure operates at 4.5 Ghz which is fairly close to the 4.095 Ghz signal we are trying to receive. Could interference from that microwave transmitter possibly lead to an intermittent signal like the one in my video? I only bring it up since it might also explain why one day everything came in perfectly and now we get an unstable signal. The PTP transmitter is about 20' away and 5' below our dish.

I think we have the focal distance set properly now (just a little outside the recommended measurement gave us the best quality). We haven't tried moving the dielectric plate as it's glued in place and I'm worried about snapping the plate while trying to remove it. We did try another feedhorn/LNB with a true 45-degree mounting but didn't see any difference.

Thanks as always for your help!