Diplex OTA and RF Modulator

[408SJC]

I am looking for a cheap way to add my security system to all my TV's. I have all Hr20's w/ OTA connected. Is it possible to use a rf modulator from my surveillance DVR to a diplex into my OTA distributer ( not use another dipex on the other end) set the rf modulator to channel 4 since my DMA (Sacramento) has channel 3. Rescan for a secondary local channel market ( San Francisco since they have channel 4) and get a signal available in the guide.

I would hate to have to get another signal distributer and run another line to each tv and use a separate tv input.

It would be great to use the guide in the reciever, just tune into a ota channel and there it is. When I lived in an apartment as a kid they had the access gate on one of the channels on the cable system, so there is probably something I can buy if my cheap way won't work... any suggestions

[texasbrit]

I am looking for a cheap way to add my security system to all my TV's. I have all Hr20's w/ OTA connected. Is it possible to use a rf modulator from my surveillance DVR to a diplex into my OTA distributer ( not use another dipex on the other end) set the rf modulator to channel 4 since my DMA (Sacramento) has channel 3. Rescan for a secondary local channel market ( San Francisco since they have channel 4) and get a signal available in the guide.

I would hate to have to get another signal distributer and run another line to each tv and use a separate tv input.

It would be great to use the guide in the reciever, just tune into a ota channel and there it is. When I lived in an apartment as a kid they had the access gate on one of the channels on the cable system, so there is probably something I can buy if my cheap way won't work... any suggestions

No, you can't do this. The HR20 has a DIGITAL (ATSC) tuner and the signal from the modulator is analog NTSC. There are no consumer-level ATSC "modulators".

[harsh]

As the HR20 cannot tune a conventional RF modulator, you'll have to send the surveillance feed directly to the televisions.

Two problems:

1. The HR20 (or any other current DIRECTV OTA solution) cannot tune arbitrary channels.

2. The tuners are ATSC only and the modulators are analog only.

I would suggest you consider a line level distribution amplifier over a modulated solution.

[jdspencer]

I use one of these.
http://www.amazon.com/Channel-Plus-Multiroom-Distribution-Modulator/dp/B00006JPED

It modulates two sources on any channel your want and can add in your OTA for distribution.

[carl6]

You can modulate and send cameras to the TV, but the HR20 or AM21 can't tune them, as others have noted.

I've got a 20 channel in-house system with cameras, DVRs, etc. all modulated and fed to all TV's.

[408SJC]

Thank you for the replies. I was just hoping for an in guide solution, but oh well. jds's solution looks like a viable one. But one other question, since I have a couple modulators already from a couple older ( now recycled tv's) would it be possible to diplex it in my existing OTA cable, connect it to the tv and expect the tv to pick up analog channel 4 with the camera's, since my dma doesn't use that frequency. or if that is not possible, diplex it in and then diplex it out.

if that won't work then I will just pick up the same thing that jdspencer has but I want to try to use what I already have first.

[jdspencer]

You wouldn't use a diplexer to combine existing modulated channels with OTA. You use regular splitters/combiners, but you have to be sure that you don't overlap frequencies. Once you get that working, then you can use the 3025 for modulating any additional sources onto the older stuff.

[carl6]

You use regular splitters/combiners, but you have to be sure that you don't overlap frequencies.

And therein lies the biggest problem or issue with doing this. You need a full one channel buffer on either side of your modulated channels (e.g., if you have 4, 5,7 and 9 as local OTA channels you would not be able to use 3,6,8 or 10). Further, with the digital transition you might think there is nothing on a particular frequency, but there in fact could be a digital carrier with the "logical" channel being something else entirely. Only way to find out is to try it.

[BkwSoft]

And therein lies the biggest problem or issue with doing this. You need a full one channel buffer on either side of your modulated channels (e.g., if you have 4, 5,7 and 9 as local OTA channels you would not be able to use 3,6,8 or 10). Further, with the digital transition you might think there is nothing on a particular frequency, but there in fact could be a digital carrier with the "logical" channel being something else entirely. Only way to find out is to try it.

That is true to a point, but the example is somewhat flawed. Channels 4 and 5 are not adjacent as there is about a 5Mhz gap between them. Neither is 6 and 7 as that transitions between VHF low and VHF high.

[harsh]

Neither is 6 and 7 as that transitions between VHF low and VHF high.While there is a notable gap in TV frequencies, don't forget about the FM radio band that goes in here. If there is an opening, you can rest assured that if they haven't already auctioned it off, they're working on it.

[bobnielsen]

While there is a notable gap in TV frequencies, don't forget about the FM radio band that goes in here. If there is an opening, you can rest assured that if they haven't already auctioned it off, they're working on it.

Also you will find Public Service, Military, taxicabs, hams, etc. There isn't much of the spectrum which isn't used by something.

[carl6]

That is true to a point, but the example is somewhat flawed. Channels 4 and 5 are not adjacent as there is about a 5Mhz gap between them. Neither is 6 and 7 as that transitions between VHF low and VHF high.

You are correct, and I probably should have used either UHF or cable UHF channels as examples, which is where virtually all multi-channel consumer modulators function.