You have a wiring problem or a bad LNB. This problem would occur if you had only one feed coming down from the satellite LNB, split somewhere to feed the two receivers. Or if the LNB were bad, with two outputs are acting as one (I have seen this once before).

Are there three thingies up there on the dish? One would be the DirecTV receive LNB, one the DirecPC receive LNB, one the DirecPC microwave transmitter, which is why the instructions tell you not to stand in front of the dish when everything is powered up.

The DirecTV LNB should have two RG-6 coming off of it, one going to the Philips, one going to the Sony. The DirecPC has two RG-6, going to the transmit and receive connections of the chassis near your computer. If three wires come down, then one of those comes from the DirecTV LNB and is split somewhere.

First, though, you need to know that when you "turn off" a satellite receiver, it does not go off. Its outputs go off, but otherwise it acts just as though it were on. That is why you can leave it off for a month but it has an up-to-date guide when you turn it on. That is why it stays warm, too. That is why this problem does not go away when you turn it off. If you disconnect it from the power, though, it will be what you and I consider OFF and the problem with the other receiver will go away. This will work both ways with your setup unless there is also a problem with the amplifier.

The satellite receivers send a DC voltage up to the LNB to tell it which polarity of signal to look for, which corresponds to even or odd transponders, but does not correspond to any recognizable pattern of channels.

If both satellite receivers on a signal split from one LNB are sending the same voltage up to the LNB, then both will receive a channel. If one sends the low voltage and the other sends the high voltage, the LNB will act as though only the high voltage is being sent, and that receiver will work. If they both send up the same voltage, be it high or low, they will both work.

That is why sometimes they both work, and if they are on the same channel, they definitely are sending up the same voltage. If you find a couple of channels where one receiver works and the other one doesn't, try reversing which receiver is on which channel: the other one should then be the one that works.

And please let us know!

If you really have two outputs from that LNB, and it is not the case that someone has split a single output, then your LNB is bad.

Incidentally, I have used an amplifier when I thought there was a signal problem and the measured signal number went down. The number some undefined measure of quality, not signal level, and if the amp made the signal too hot, its quality could be lower. Try your setup without the amp to see if the number increases. I have run over 200 feet of RG-6 without an amplifier with signals in the 80s. I used amps once, but those were runs over 300 feet, which DirecTV said could not work. The amps were in the middle of the run.

This message was edited by Ernie Bornn-Gilman on 10/09/05 15:04 ET.