How are you going to use the modulator? Will output be going into a distribution amplifier (if so, which kind)? Are you going to want IR control of the device that you're modulating?
In particular, you should watch the output db spec. You need to design a system that will deliver proper number of dbs to your TV's. Too many db's can cause a herringbone effect; too few can cause snow. Factors, in addition to the modulator spec, are: splitters between modulator & TV's; length & type of coax used; and any amplification used (need to be careful not to overdrive amplifiers with a high db input).
I have used a lot of ChannelPlus products & think they make the best modulators. They also have great tech support.
Thanks for your expertise. I am learning about this - thanks to you!
I have 4 video sources in 1 room. I have several coaxes homerun to that location, all feeding out of a ChannelPlus modulator/amplifier.
There is no off-air in the area, the modulator feeds channels 15 (C-band)and 25 (DISH PVR) mono, and channel 3 (from DISH receiver #2 or the VHS deck). Surprisingly nice pictures on all channels, except on 1 long leg with a weak signal upon which I will install a small amplifier one of these days.
The plan is to buy a cheap UHF modulator for DISH #2 so my kids can see the VHS on channel 3 fulltime. They can't figure out they have to toggle TV/Video on the DISH2 remote to see the VCR.
Your set-up sounds a lot like what I used to have. I had a Sony MRD-D1 (which, I think, is a very similar unit to your ChannelPlus all-in-one). I used it with great results to send 2 inputs/channels to 5 TV's.
When we moved, I bought a ChannelPlus 5645 so that I could get stereo capability & add four more inputs/channels. I fed the 5645 into the antenna input of my all-in-one & got unsatisfactory results. I learned from ChannelPlus tech support that their modulators put out a large amount of gain (25db) -- when this was fed into the antenna input of my all-in-one, it overdrove the amplifier of the all-in-one & distorted the picture. On tech support's recommendation, I inserted an attenuator in between the 5645 and the antenna input of the all-in-one. This fixed the problem, but was not ideal.
I recently re-did my system & used the high gain of the 5645 to my advantage rather than as a handicap. I purchased 2 ChannelPlus single channel modulators & fed the A/V inputs that were going into my all-in-one into these units. Then, I combined the output of the modulators (using an inexpensive ChannelPlus splittter/combiner). The combined signal (which now contains all 6 modulated channels), gets split into home-run coaxes that go into each room. The all-in-one unit, therefore, is no longer needed. The quality of this configuration is much cleaner, as the signal path is very direct & there is no extra amplification needed. This configuration works because I (like you) don't need to amplify an outside antenna or cable feed -- all of my sources (satellite, A/V stuff, etc.) are internal.
So... I think that you have basic 3 choices to accomplish what your looking for:
1) Get a lower-gain modulator & combine its output with the RF out from your VCR (tuned to channel 3). This combined signal goes into the antenna-in of your all-in-one.
2) If you get a higher-gain modulator (like ChannelPlus), you need to put an attenuator in between the modulator output and the combiner input going into the all-in-one.
3) The best choice (I think), get a 4 channel modulator like a ChannelPlus 5545. This model also includes IR capability. Put your 4 A/V sources into the A/V inputs of the modulator, split the output of the modulator into as many outputs as you need -- I think that 4 to 8 is probably ideal to get the gain to the appropriate point for input to TV's, depending on the length of the coax runs & the type of coax cable you're using. This would give you the most direct connection and (I think) the best results.
Unfortunately #3 above is also the most expensive alternative. The CP 5545 sells for approx. $280 at buy.com. If you go with #1 or #2, pay attention to the gain spec of whichever modulator you use -- as described above.
Sorry I didn't directly address your question re: the two different brands of modulators that you found. I, myself, have only used ChannelPlus stuff -- so I don't have a fair basis for comparison. I'd be wary of the unit that has an analog modulator tuned with a reostat -- you might get signal drift & need to adjust it periodically. You might try to do a search on this forum for the brands that you're considering to see if others have experience with them.
Hope all of this helps rather than confusing you. Please let me know if there's anything I can clarify.
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