Have two satellite receivers, one putting out on channel 3 and the other on channel 4...simply want to combine both onto a single cable. Cheapie combiners don't work. Do I have to do with something like Channel Plus DA-550HHR?

Thanks..........

Did this once for a retail store. You need to remove the lower sideband from the channel 4 signal until only a vestige of it is left (hence the term vestigial sideband). Then you can mix them together. When I needed to do this ten years ago, I found a filter that had about a $350 wholesale cost.
It will cost you less to buy a UHF modulator for one of the receivers.
Just a note -- this setup will be useless with a surround system because channel 3 and 4 outputs, and under $200 modulators, combine the left and right audio to mono, so there will be no stereo, so there will be no ProLogic.

Try one of these:

[Link: system-high.com]

This might be helpful:

[Link: channelplus.com]

hey, that pdf is a great confirmation of the problems that I had with the unit described at system-high.com! It even mentions that the modulators are mono....

You have to spend major bucks to make this work on channel three. The modulator is the right approach. And if it is terribly important to have stereo sound, both Channel Plus and Channel Vision have stereo modulators, although they are pretty pricy.

Ernie

their still alot cheaper than the pro stuff

two modulated channels combined on the same coax will work with a simple splitter however the channels need to be at least 2 channels apart, prefferably 3 channels apart. A simple digital modulator will be affordable and work well. Use channel 4 on your box and take right,left, and video into your modulator from the other box. This is how we do every house like that.

TONY,
why do you say use channel 4 on your box? do you mean cable box? we have an over-the-air channel 4 here in L.A., so we use channel 3 to avoid interference from accidental ingress.

For a moment I thought you were talking about modulating two channels a couple of channels apart in the VHF band, then i realized you probably did not.

Even this has problems: if the house has an antenna system, you have to know what actual UHF channels the local DTV stations are on. You can get this by going to www.antennaweb.com and pretending you need an antenna for that site. If it is cable, digital cable signals will muck up the upper cable channels, so you will have to modulate channels above 100 or get a filter, as from Channel Plus, that kills the digital cable signals.

By the way, your post and this one do not address the subject of this thread, combining channels 3 and 4. Hey, Albert, did you want to know what we would do if we could not combine channels 3 and 4, or did you just want to know about your initial subject?