I have a channel master 7777 pre amp and was wondering where most people have there internal switch set to separate or combined VHF and UHF inputs?

I would assume that it would be left on UHF since the most HD channels are transmitted there.

But if a combined VHF and UHF input is selected does it reduce the over all signal strength of one or the other?

I some times use my antenna just for analog reception.

This preamp is designed to be used with one or two antennas. Let's say that, in your area, the VHF antenna needs to be pointed differently from the UHF. This preamp will separately amplify the two sets of signals and combine them. In such a location, you could not take a single VHF/UHF antenna and get good signal.

Consider this same location problem, but that you have two VHF/UHF antennas. Consider also that the antenna pointed correctly for UHF stations picks up godawful ghosty signals on VHF.

You could combine the antenna signals with a splitter wired backwards and used as a combiner. Then you would have clean UHF and a combo of good VHF and ghosty VHF. That will equals ghosty VHF. And if the antenna pointed at the VHF stations gives you ghosty UHF reception, the splitter approach will ALSO give you ghosty UHF.

Now, these same two antennas, connected to the proper UHF and VHF inputs on the preamp, and with the switch set to "separate," will amplify only the good UHF signal and only the good VHF signal, then combine them.

So you would choose the switch position depending on what you are doing.

The preamp has one amp section inside it for VHF and a different one for UHF. Switch position with just one input will make no difference at all. There is a very large gap of unused frequencies between UHF 13 and UHF 14, so it is just reasonable to have two amplifiying sections, each optimized for its part of the spectrum.

Edit: from channelmaster.com in quotes:

"...designed for...deepest fringe applications and MATV headend applications.
...high signal handling...mast mounted, ultra low noise distribution amplifier..."

We think of distribution amplifiers as having several outputs, not just one, but that is video or audio. Because we have 2, 3, 8, and even 16 output RF splitters, but no such animal for video or audio, an RF distribution amp will have one output, allowing you to choose the correct splitter for your need.

"Three models are available:

– Model 7775 is a UHF only model.
– Models 7777 and 7778 cover both VHF and UHF bands with separate amplification in each band for maximum signal handling. They may be configured for either separate or combined VHF and UHF inputs. They include a switchable FM trap."

The FM trap is used to keep FM stations from going through the amp. If there are a lot of powerful FM signals on the VHF signal, the maximum signal level that can go through the amp cleanly will be reduced. The FM trap should be IN in general; switching it OUT will give you FM on that cable but might also give you distortion of the TV channel signals.

This message was edited by Ernie Bornn-Gilman on 07/28/05 15:51 ET.