C & Ku signal within one Satellite

[kelleyga]

When I am at IA6 watching Azteca (Ku) I get like 99%, but If I change to a C band channel within the same IA6 I will have to mannually move the dish a litlle to get a signal for C band channels.

My question is:

Is it normal? Or if I get great Signal for a Ku channel on Satellite X, then all of the C band channels on the same satellite should also be there without moving the dish?

 

[No Strings]

Perhaps the satellite is using a different antenna (pointed slightly different) for C-band than for Ku.

Neal

 

[voomvoom]

kelleyga,
I would say "Yes, it's normal!"

Al

 

[bryansr]

It is "normal" for me too.

 

[anik]

It's normal for me too, and the only theory I can come up with as to "why" is that the C and Ku LNB's may have a slightly different focal point, even though in theory they should be the same with a standard C/Ku feedhorn. In other words, the C-band LNB may be getting the signal coming from one side of the feedhorn throat while the Ku-band LNB is more interested in the signals falling on the other side of the feedhorn throat. Since a feedhorn throat is typically a couple of inches across (more or less), that could possibly make a difference of a positioner count or two.

I wish I knew if that's in fact the case, if so it would mean that the orientation of the feedhorn is important - if the signals are being picked up at different points on a horizontal plane you could compensate by moving the dish a couple of positioner numbers, but if they are on opposite sides of a vertical plane then one or the other signal will always be a little weaker than it could be, depending on which LNB you used when aligning the dish. This is an interesting question, anyone know any feedhorn engineers you could ask?

 

[Diamond Jim]

When I am watching analog and switch from C to Ku on the same satellite I have go to the corresponding icon or bump it a little bit to get it to come in. I check the location numbers and sometimes there is a difference of 12 to 16 digits. When I use the FTA receiver I can pick up Ku on either icon.

 

[huplink]

Try adjusting the C band LMB a little.