Why is my signal bouncing around?

[bel71281]

C/P


What is Terrestrial satellite signal fade?
OR
Why dos my “Q” flicker or bounce up and down now that the weather is better?

This is a funny little problem with RF that has many different sources and very little solutions.

It starts with the area the dish is mounted in, if its hilly and has some trees around, you more than likely wont have this problem, if you live in the flat lands and your dish angle is low too the ground (30 to 15 degrees) you may be in for a signal fade, this occurs when the signal from the satellite is bounced off of something, this can be the ground, a lake, a hillside or a large building or other structure, anything that can reflect the RF signal from the satellite and is in a direct line, or at just the right angle with your dish can cause this problem.

What happens is the reflected signal is 180 degrees out of phase with the signal coming down from the satellite, to better under stand this you can reverse the connection to one of the speakers on your stereo and play a song, it doesn’t sound right does it, that is because the speaker is 180 degrees out from the other and the out of phase signals cancel each other.

Now this problem may not happen all the time, if the ground is just wet enough, or the air has just the right amount of moisture in it, or that lake is just at the right level or surface temperature, you can get a fade. The signal can even bounce off the satellite dish next door or across the street, or that metal barn roof down the road south of you, who knows where it’s coming from, and without special equipment you won’t know.

Solutions, not many, you can try mounting the dish in a different location, or raising it up higher or lower, you can even try a metal screen (3’ X 3’ aluminum window screen) mounted in a frame, move it around till the problem goes away, (if it does) (just don’t mount it directly in front of the dish) in the microwave business we used to have all sorts of problems with this and it always was something we didn’t plan on in the original site survey.

In some cases it could even be the LNB of the second dish your using, the DN and BEV LNB’s use the same LO frequencies, 11250, if one or both have a leaky shield they could talk to each other and you have a problem, the LO from one LNB bouncing off the second dish will be 180 degrees out and you will have problems, solution for this is to mount the dishes 6 to 8 feet apart or put the metal screen in-between them as a test, if the problem goes away you know what to do.

Another possible problem is related to the last one, and that’s a bad or cheap switch, using a bunky switch with two or more LNB’s could be the problem also, the two signals don’t have enough isolation between them and they mix together and cause you to pull your hair out looking else ware for the problem, to test this possible scenario, use only the LNB that the problem is occurring on and disconnect everything else (power off first) connect directly to the LNB (or dish) in question and test it out.

I hope I didn’t put anyone too sleep with this long drawn out dribble, but it may fix or explain your problem.

[jc7257]

Great info for the newer members that are setting up a dish, or even members that are having some dish problems...