To explain how a multiswitch works, and why splitting one (the A) cable won't work:

With a normal single receiver system, and a single LNB, the receiver sends a DC voltage (14v or 18v) up the coax to switch the LNB from even to odd channels. This is necessary because even channels are polarized either clockwise or counterclockwise (I forget which), and the odd ones are polarized the other way. This allows more channels within a given bandwidth.

When you add a second receiver, you need a dual LNB, so each receiver can independently select channels. This setup behaves exactly as if there were two separate dishes. Remember, each receiver sends a DC voltage which corresponds with the desired channel, so either cable can have either voltage on it at any moment.


However, with three or more receivers, since there are only two coaxes, and there can't be three different receivers trying to send the DC voltages on two cables, you need a multiswitch, which does several things:

First, it "locks" each element within the dual LNB to one polarization, by always sending 14v up one coax cable, and 18v up the other, so from now on, one cable carries only even channels and the other only odd.

Next, it switches each receiver from one of the LNB elements to the other. There is a relay or transistorized switch for each output of the multiswitch that senses the DC voltage at that output (hence the term 'multiswitch') and connects that output to either cable A or B. If all receivers happen to be tuned to even channels, for example, then they're all receiving their signals down the same coax from the dish.

Note that dual-tuner receivers, such as my Philips DSR6000Rs, require two multiswitch outputs and two cable runs, just as if they were two separate receivers. The output from a dual-tuner receiver, however, is a single cable, and the receiver acts like it has an A/B switch in it somewhere.

Actually, an A/B/C switch would be more appropriate for a dual-tuner TiVo like mine, since you can watch a prevoiusly-recorded program while recording two, or watch either tuner's program.


So, to answer your question, a dual-tuner receiver must have two feeds. It looks like you will have to run another cable for the modulator output (rather than for the receiver feed, to keep the two existing feeds equal, mainly), or use a wireless transmitter/receiver system to feed the audio/video to the relocated modulator (moved to where its output can feed the rest of the house's coaxes).

Another possibility is, as you mentioned, a CAT-5 distribution method. In any case, I'd save the already-installed coaxes for the receiver. You want the best signal to feed the receiver.

Larry
www.fineelectricco.com

This message was edited by Larry Fine on 03/19/02 02:31.02.