I would say try another sat recevier.

Simply put, a ground loop is caused when there are parallel grounds that, for some reason, are not at the same potential (voltage). Potential differences cause current flow. When there is undesirable current flow, it can cause unwanted audio and/or video interference.

Larry
www.fineelectricco.com (temporarily down)

A ground loop occurs when there are two different ground paths from one component to another. This becomes a problem if voltage is induced in one of the paths.

I love troubleshooting ground loops, and the master is to be found at www.Jensentransformers.com

Go to their page on Audio isolators by clicking a link on the home page, then near the bottom "Download our ISO-MAX® Hum and Buzz Troubleshooting Guide (115kB PDF)."

This troubleshooting guide explains how to solve the problems. I don't remember if it explains just what causes the problems.

This article helped me understand it alot better....and it was written by Jensen Transformer.

[Link: svconline.com]

Hope it helps.

very interesting article --thank you

Glaro,
The Channel Plus "GlassLink" will solve your problem, though you may need to adhere them with a 1/8" sheet of lucite (or something similar) in between. I was up against a wall with a particular ground loop problem where the only way I could fix the problem was by breaking the satellite coax ground. The Glasslink did the trick - the lucite was at the suggestion of a Channel+ tech. Do not rely only on the adhesive to keep them stuck to the lucite - add some sort of strap as well - or it will be a very annoying service call when one of the two halves pops off.
-Mike

Bill Whitlock of Jensen has a class at NSCA that covers this in depth. I haven't been to it but I have been lucky enough to know him and Neil Muncy personally. These two people have been what many people consider to be the front men in the industry for the past decade or two at promoting proper grounding application as well as problem solving for venues rather larger than your typical home theater. The June 1995 reprint of the AES Journal is also a great source of info but it is an engineering journal so be warned. The syn-aud-con seminars also cover grounding but only in passing. However if you are interested in doing commercial sound there is no substitute for syn-aud-con

this glass link will filter the noise?

thank you for the post michael--i just read all the specs on the "glasslink" and it seems to filter the noise through ferrite cores --very interesting....

not likely. it will break the ground loop that is inducing the noise. I would actually look at the way the dish is grounded before I did any of this. It should be bonded with the main house ground at the service entrance to the building

when i ground the dish the noise gets worse

Then your answer is certainly that it's a ground loop. How are you grounding the dish? What is the configuration? mounted on the ground or in the air? Multiswitch or not?

it's a directv multi-sat-3lnb's---I have it mounted to the roof--the wires go into the attic to the basement where there is the 4-in, 4-out multi-switch. the are three samsung recievers connected. One is on a 71 inch mits-rear projector which has no lines. the second is on a 40 inch loewe with no lines. the third is on the 61 inch zenith plasma which is where the problem is. It is set up as a 7.1 surrond with a b&k pre-pro, denon dvd, sony sacd, and mits vcr and the troublesome samsung hd reciever. all the equipment, except the plasma, is connected to a monster 5100.The plasma is connected to a small two outlet monster surge protector. I have the cable going into the samsung with a ground isolator --which cleaned up the cable problem. it's not the typical hum bar-it's more of a shadow about 10 inces wide that rolls upward. when i ground the multiswitch the plasma freakes out, lines, jitters. when i disconnect the ground the picture stabilizes but still has the rolling shadow----??????

If the cable problem is fixed - Plug the plasma into the same outlet as all the other equipment (to troubleshoot). On 6-23 you said you couldn't do this because it was on the other side of the room. If the outlet for the plasma is on different circuit or side (phase) of the breaker panel then all the other equipment - you have a typical ground noise problem. I bet if he has lighting dimmers anywhere in the house - the shadow will either get bigger/smaller or move up faster/slower when you adjust them.

[Link: svconline.com]

It sounds like you have a bad RF amplifier in the system.