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FAQ - Signal Leakage Between CATV and OTA

15680 Views 14 Replies 12 Participants Last post by  hugh
If anyone is contemplating running a combination of Cable TV and OTA to the same TVs or receivers, there are specific safeguards you must take to isolate the two signals from eachother. This is not a casual concern, its very important that you do it correctly!

Likewise if you are getting Cable TV channels on your OTA tuner, a neighbour may have a signal leakage problem.

Satellite and OTA into the same TVs or receivers are not a problem.
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Gladly! Here is the situation: you have two signal sources that are feeding your TV using essentially the same frequency ranges. OTA antennas feed VHF Low, FM Radio, VHF High, and UHF to your TV, but so do CATV systems, albeit with their own sub-channel maps over the same frequencies. They do not get along with eachother.

This frequency overlap is due to historic reasons because in the 1950s-60s there were no Set Top Boxes yet for cable channel tuning, so the CATV providers had to overlap the regular 13 VHF channels and later the UHF channels with their own signals in order to feed your TV. This is why CATV gear is so heavily shielded to this day - there is a direct conflict with OTA. If we could redo CATV all over again I'd advocate assigning a third range of frequencies apart from TV and Satellite.

So, if you simply connect the antenna and the CATV with a splitter you will cause signal leakage of the CATV signals through your antenna and vice-versa, which will cause garble and interference not only for yourself but for your neighbours too. Connections like that are ILLEGAL. Industry Canada and CATV providers constantly check for signal leakage and will come down really hard on you if you let it happen. The leakage problem does not happen with Satellite because its incoming signals are way off in another part of the frequency spectrum from TV.

What is the solution then? An A-B input switch is one method, or if your TV has 2 coax inputs you could test to see if they are discrete (separated inside to prevent leakage). Some people run the OTA lead right into the TV and the CATV lead into the VCR and then over Composite or SVHS into the TV. There are a few solutions like that if you think about it. I think there might be remote control capable A-B CATV/Antenna coax switches out there too.

Check out previous posts in the OTA Forum by HDTV101 and others about this issue.
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Quick Method of Checking for CATV/OTA Leakage

The easiest way to check for leakage between 2 sources is to disconnect the regular TV's CATV and OTA inputs and put a portable TV with rabbit ears right beside it. On the portable TV do a full channel scan of both TV and CATV and make note of which channels you receive and also which other ones are really garbled.

Next, hook up the regular TV's inputs again and turn it on as well as any set top boxes needed, then on the portable TV do a full channel scan of both TV and CATV. If you are now receiving more channels than the with the first scans on the portable TV (even if they are garbled but strong signals) then you have leakage. If not, your TV is properly isolating the inputs.

Another thing you can do if you're not sure is check your TV's manual or contact the manufacturer to find out if they're isolated.

macker, let us know the make/model of your TV and what you find out. :)
RF Modulators and OTA Can Also Cause Leakage Too

Be aware that if you use an RF Modulator to connect a DVD player, VCR, XBox, or other electronic gear to your TV because it only has a coax (RF) input, you must not put your RF Modulator and your OTA connection on a splitter feeding into the TV. If you do, you will cause signal leakage that will mess up everything you try to view and maybe that of your neighbours too. Industry Canada might even fine you when they triangulate in on your location.
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