Another C band puzzle

[tonydix]

I have been experimenting with a prime focus Ku LNB on my C band dish.
Results so far have been disappointing. The only signal I have managed to get so far on my Coolsat 6000
is MTY1,MTY2,MTY3, MTY4 which turn out to be scrambled channels and default whcih seems to ne a spanish religious program and first which seemed to be a stationary camera of a political event possibly in Cuba.

I am not sure which satellite I am looking at but the real puzzle for me is as follows :-
If I move the dish a few clicks east I lose the signal as you would expect but when I move the dish a little further east I pick up the same 6 channels !!

Does this tell you experts someting about the dish. Is the dish distorted ?
Is the polarity wrong ? Is the lnb not at the focus of the dish ?

Any help much appreciated ?

Thanks

Tony

 

[qwert1515]

I think you are on 116.8°W SatMex 5 Ku

On the Coolsat 6000 if you have previously saved the DiSEqC position for that satellite and don't save the new DiSEqC position,
when you exit the menu it will go to the last position that was saved for that satellite.

 

[B.J.]

I have been experimenting with a prime focus Ku LNB on my C band dish.
Results so far have been disappointing. The only signal I have managed to get so far on my Coolsat 6000
is MTY1,MTY2,MTY3, MTY4 which turn out to be scrambled channels and default whcih seems to ne a spanish religious program and first which seemed to be a stationary camera of a political event possibly in Cuba.

I am not sure which satellite I am looking at but the real puzzle for me is as follows :-
If I move the dish a few clicks east I lose the signal as you would expect but when I move the dish a little further east I pick up the same 6 channels !!

Does this tell you experts someting about the dish. Is the dish distorted ?
Is the polarity wrong ? Is the lnb not at the focus of the dish ?

Any help much appreciated ?

Thanks

Tony

I've seen that several times with Ku on a BUD. What it usually was for me, was that the feedhorn was not at the proper focal point. If the feed is at the proper focal point, the signal pattern will be a single spot, however as the feed moves closer or further, the signal pattern blurs out, until it begins to look like a donut. When my feed was at the wrong focal length, I'd get double reception across the arc on Ku, and yet on C-band, it wouldn't do that, and C-band would generally peak at a different point, in between the 2 Ku peaks. With my C/Ku feed, I eventually had to first locate the satellite using C-band, which would generally end up not giving very good Ku reception, THEN, I would move the feed in/out to peak the Ku, after which Ku would focus as a spot at the same point as C-band.
If you just have a Ku feed, then you can't do what I did, but what I would try would be to move the dish in the middle between the two points where you see the 2 Ku signals, then try to adjust the focal length to get maximum Ku signal.

It's basically just that signal patterns have side lobes, and when the focal distance is off the sidelobes get bigger and the center lobe goes away.

 

[1ADAM12]

I've seen that several times with Ku on a BUD. What it usually was for me, was that the feedhorn was not at the proper focal point. If the feed is at the proper focal point, the signal pattern will be a single spot, however as the feed moves closer or further, the signal pattern blurs out, until it begins to look like a donut. When my feed was at the wrong focal length, I'd get double reception across the arc on Ku, and yet on C-band, it wouldn't do that, and C-band would generally peak at a different point, in between the 2 Ku peaks. With my C/Ku feed, I eventually had to first locate the satellite using C-band, which would generally end up not giving very good Ku reception, THEN, I would move the feed in/out to peak the Ku, after which Ku would focus as a spot at the same point as C-band.
If you just have a Ku feed, then you can't do what I did, but what I would try would be to move the dish in the middle between the two points where you see the 2 Ku signals, then try to adjust the focal length to get maximum Ku signal.

It's basically just that signal patterns have side lobes, and when the focal distance is off the sidelobes get bigger and the center lobe goes away.

Brilliant

 

[tonydix]

Many thanks B.J. much appreciated
Tony