Trying to add Ku

[drifter-dewar]

I Am interested

Please let me know how you are doing with this project. I live in central Florida and am having the same problem(s). All advice is appreciated, especially advice on how to make sure a LNB is functioning. I have a relately new one and an old one (Ku) with no way to know if either is actually working. Oh and I hope this isn't highjacking the thread as my problem is identical and so far the things I have tried to fix it are the same. Oh and if the loaner LNB is available I would very much like to try one that I know works. I would also consider sending my LNB(s) to have someone with access to a corotor II to check them for me. Thanks, Ross

 

[truckracer]

When you use a large dish to receive KU band the pointing and tuning of a large dish for such a short wavelength is touchy. The parabola (dish) is physically tuned to provide a certain beamwidth for a given frequency.

For instance on C-band (3.7-4.2 Gigahertz) the beamwidth of my 7.5' Sami dish is 2.5 degrees. This means that in any given direction or position my dish can "see" 2.5 degrees of space. This means that I can be somewhat sloppy with my aiming on C-band frequencies.

On Ku band (11.2-12.?? gigahertz) the beamwidth is 0.5 degrees on my dish.
My dish can see within a 1/2 degree on KU band making it move out of focus very easily.

A 10 foot dish would be more prone to be off aim since the beamwidth is even tighter as the dish diameter increases.

tighter beamwidth is better for cleaner signals especially with digital tv.
You can watch channels with very low signal and low forward error correction rates with a large well tuned dish that others with smaller reflectors can only wish they could receive.

Be patient and you will get it. It is just very precise tuning.



I can only imagine what it is like to aim a 1.2 meter (4 foot) on Ka band for the commercial hughes data systems. Ka band is even higher in frequency than KU and would be very touchy on aiming.

 

[gabshere]

i agree its a fine tuning of all the dishes i've checked this year (4) none were correct for FD but all except 1 was c band only so didn't need to be spot on.
one was a c/ku setup and FD was off about 1 1/4 inches. so i would start with the basics and work up from there . do the strings across it and make sure its all in the correct shape then get your FD and check that then tune the feedhorn.
yeah just PM me for the LNB . And Welcome to the group Drifter

 

[drifter-dewar]

Hi, Thanks very much. I will try again to adjust and also try the older Ku-lnb. I kind of messed up the dish a little by trying to adjust it when it really didn't need to be adjusted. So I will have to start from scratch. Basically I have good signal with C-band but that's because it really doesn't have to exactly right. So I will start by checking as far East as I can go and manually stress the dish to see if an improvement can be made. I have mapped most all the birds. One thing, I don't get a very strong signal on T5 and T6 with PBS. Only in the high 20s. Does that seem right? Also I never always get a 0 on quality and a 10 on signal. Seems like I should get a little something on the Ku birds. I have checked the cables by swapping and I have a volt meter that pegs right on 20.0 volts at the co-rotor. Also, I read in this thread where you have to have mesh that is the thickness of a pencil lead. First I heard of that. I though it was a pencil. Lead is very thin almost like not having any mesh at all. That's all for now. Thanks to Monkeygirl for letting me highjack her thread........DO NOT CUT DOWN THE TREE....that's a last resort please. lol.

Central Florida...8'6'' dish with 920 receiver (new battery). Old dish unknown brand.