C-Band problem with Sparklies (1 Viewer)

[Jim Benard]

I've been having a strange problem with my big dish that I can't figure out. The sparkles start showing up on G5 and west of G5. Everything on G9 - east is perfect. I thought it was trees but now I have a good sky, next I tried replacing the LNB, no effect. It starts happening on the higher channels as listed below. What's left? I've tried all of the manual skew adjustments on the IRD menu to no avail. Listed below are some of the channels affected. I've got a TRX1800 toshiba IRD which used to work fine, it's about 9 years old.
G5 transponder 5 = 10.0 quality perfect.
G5 transponder 22,23 Cnn and A&E = 5.5 sparkles
F3 transponder 5 (i think) Lifetime 7.1
F3 23 E! 5.3
F4 1 7.1
F4 23 5.3
What I don't understand is why the satelites east of G5 don't have the same issues with higher number transponders.
any C-Band guru's out there still????

 

[Keith A]

Could there be a new microwave tower shooting through you area causing TI problems? Does your receiver have a built in TI filter?

 

[Jim Benard]

Not sure but don't think so. I'm very far from any major infrastructures , I do have a TI filter but it doesn't change the quality settings whether it's off or on.

 

[Keith A]

There's not a whole lot that might be a problem. I just had to change my pr motor. It was stuck (died) in such a position that it let me get both vertical and horizontal polarity, but the picture was only about 70-80%, so I got a lot of sparkles. Also check for weathering of coax connectors.

 

[Jim Benard]

I had another person tell me to try the TV on the roof and move the dish manually. I did that tonight and it didn't help. I was able to move it up and down easily but from side to side there isn't much play. In any case I didn't get a better signal.
I've read a little about the PR motor, I can hear it moving when I was on the roof switching channels. What does this device do in simple terms? Is it hard to switch out? I'm a little leary of switching it out because it seems like the sparkles should be behaving the same on all satelites? It's really strange how I can get all 10's on all G9 subscription channels when G5 right next to it I get poor on CNN 22 and A&E 23. Or is there enough differences with their power output, etc. that it still may point to the pr motor? Do you need any tools to do a realignment when switching out the PR Motor?
thanks for your help...

 

[Art Morales]

I had the same problem a few years ago It could be your feedhorn. You might need a service call.

 

[Keith A]

the polar rotor motor has 3 wires and 4 screws, so changing it is no big problem, you just have to do a little tuning of the receiver's polarity after you put it in. If you get no change in the picture when you tune polarity from the receiver then the motor is the problem. It doesn't sound like it though. It sounds like TI.

 

[Jim Benard]

I do get a change in picture when I tune from the receiver so maybe it's not the motor.
I've gotton some more help from another forum, but i'm starting to think it has to be either TI or the PR Motor. Based on this help below, I hope it's not TI, what a pain to solve!
"Off hand Jim, I'd wager you have a either a "TI" (Terrestrial Interference) problem or quite possibly a beamwidth/cross interference problem from an adjacent satellite more than a PR motor problem judging strictly by the symptoms to describe. TI can be caused by a huge number of things ranging from TV towers, airport radars, cell phone and microwave towers, and even high tension power lines. The ingress of TI can interfere with reception from only one or several satellites depending on the relative direction between dish, bird, and the offending source. Sometimes retweaking a dish (readjusting the AZ-EL polar mount settings), changing the video skew, or the probe polarity setting can positively affect reception but only to a small degree. If it is in fact TI causing the problem, the best way to fend it off short of moving the dish is to find the source and deflect it away from the parabolic reflector with some sort of metallic structure. IF you manage to determine that TI is the culprit and from what direction it is originating, you can email me and maybe I can help you to design something that might help. I could do it here on the board but it can be a long drawn out procedure dependant on a wide array of variables."

 

[Jim Benard]

Success! I figured out that I must have a problem with the feedhorn not being centered. From what I read, this means you effectively reduce the overall size of the dish, e.g., a 10' dish becomes only a 7' dish, thus the poor reception on weaker lower to the horizon satellites.
I started with the laser pointer and the best I could tell the feedhorn was aiming below the center of the dish. I loosened all the bolts and started trying to move it up. This is not an easy job. All four support arms don't have much play without taking each lag bolt off. I kept experimenting until I got a darn good reading, not perfect but it's in the sweet spot were the sparkles are not noticable now. My F3-23 is pulling in a 7.2 now! Not bad for someone with no proper tools or expertise.