I don't have much experience with Satelite systems, But have done both alarm and closed circuit camera systems. I have not heard of a sensor that you are speaking of, I don't think one would be practical. Surely something like that would degrade the signal. Signals that travel over the coax cable are at such a low voltage range that they need to be amplified very significantly to be turned into the image you see on your screen. Depending on what your problem, you might look into another alternative. Is someone stealing your satelite dish or just disconnecting it? Maybe you can put a motion alarm towards the point that is getting disconnected.

b

So far, someone has disconnected it at the dish itself, but it would seem that is the first step toward stealing it. The dish is mounted right below an exterior light so they would be working pretty much exposed to either disconnect it or steal it. I figured that they might have started out to steal it and got scared off by a passing car or something. The dish installer had strongly recommended keeping it low enough so that I could brush off snow in the winter time, I put it under the light because I thought it would scare off anyone from tampering with it.

As far as a motion detector, I was afraid that a bird landing on it or snow blowing by may trigger it. If I point it downward from the roof, might even a dog walking by trigger it? I don't know how sensitive those things are.

[This message has been edited by Vic (edited October 20, 2000).]

Yes, a dog will trigger a motion detector. But snow will not. They are made to register a combination of motion and body heat. That way, they don't get set off every time the wind blows and moves the trees and bushes. I have a couple and have found that dogs, cats,
possums and deer set them off. (I doubt if birds would.)
Also, they only work in low light, so if you wanted to use one to power an alarm of some kind, it would only work at night.
I think it's still not a bad idea. Anyone who is about to steal something and has a light come on in their face isn't likely to stick around. You can use a flood light bulb that shines right on the spot.
Some of them can be set for a fairly narrow range, so the person or animal that sets it off would have to be in just the right place.

Ive been working security for 16 years now.
Motion detectors work on heat patterns, but cold is also a heat pattern. Some motions work on microwave technology, and some on a combination of both, and even others have both and a micro prossesor. Regaurdless none of these will do what you want without false alarms. What may work is an out door duel Beam. Less expensive would be a siamese coax cable. This is a cable used in CCTV installs, it has a pair of 18 gau wires running in the same insulation as the coax that could easily be tied to the dish as a tamper circut without any signal loss.