Circularly Polarizing C1PLL LNBF

[cyberham]

Dish tracking and skew should be reasonably OK. I can use USALS to receive signals fairly well for the Ku band though there are limited tps to receive on Ku on the eastern half of the arc. I do touch up using diseqc commands for best signals. Since I'm using a H-H motor, skew is set a 0 and left alone.

I believe the correct way to position an LNBF and conical scalar on an offset dish is to first position the LNBF for maximum signal, and then position the scalar to improve that signal. This is what I did for the western half of the arc. Unfortunately, for the eastern half, this isn't possible since I can't get any signal from any satellite I've checked until I add the scalar.

So the position of the LNBF is a guess. What I can try, with conical scalar in place, is to adjust position of the LNBF in its bracket to see if I can improve the signal and the uniformity of circular signal levels across the eastern half of the arc. This is backward but it may help to receive signals better. I won't spend too much effort since I intend to soon move the dish back again to receive the western half which doesn't have FTA circular tps. Despite the many tps I am receiving from the eastern half, the only English I can receive is from 3W and I don't want to dedicate my best dish for that alone.

 

[cyberham]

I went ahead and tried moving the LNBF/scalar assembly slightly. I was able to improve signals by moving the assembly a little further away from the reflector. I believe this improved the circular plate issue since I can now locate the plate closer to midway for the tp that previously needed the plate all the way in the LNBF. Good enough for now.

 

[Titanium]

Didn't catch until now that you are using a 1.2m dish for C-band. The wide main lobe received with the undersized reflector throws a lot of unwanted signals from adjacent satellites into the feedhorn. I am not surprised that the slab requires repositioning to optimize a transponder. I am surprised that it works as well as it does!

Are you also adjusting the conical scalar to optimize the main lobe reception, attenuate side lobes and properly illuminate the reflector to prevent off-edge terrestrial interference and noise?

 

[cyberham]

The portable dish is now positioned so it can only view the eastern half of the arc. There aren't a lot of receivable signals in this area of the arc with a 1.2m so I think adjacent satellite interference here is not like the western half of the arc. I have maximized signals by adjusting only the scalar and then the LNBF/scalar assembly.

To date, I've received tps on 55.5W, 47.5W, 40.5W, 34.5W, 22W and 3W. Overall I'm very satisfied with the LNBF performance on this small dish. I'm receiving DVB-S2 8PSK tps when some thought that was not possible on C-band on a 1.2m dish. In fact, I am receiving satellites with footprints having lower dBW values than on the western half due, possibly, to lower adjacent satellite interference on the eastern half.

Main problem is almost everything I can receive except 3W is Portuguese or Spanish.

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