Combining Antenna and Cable Lines

[SaurusX]

I got a new LG HDTV the other day to replace a CRT in the bedroom that we'd been holding on to. The wife and I have been using antenna for our TV watching (with the assistance of an HTPC DVR) for the past 5 years or so. Haven't paid for cable for the same time. The antenna is in the attic and has coax running behind the walls to three different rooms of the house.

This new TV, however, does not tune the local NBC station without glitching even though the signal is at full strength. No other TV in the house has this problem and I tried troubleshooting this every way I know with only one solution being found. I combined the cable from Time Warner and the antenna line using a coax splitter turned around and then plugged that into the TV.

The clear QAM local channels from the cable company and the antenna channels don't seem to interfere with each other much at all. I choose the NBC channel from the cable feed and all others from the antenna feed. The LG HDTV actually allows me to pick and choose which channels I want from both sources and combines them into one channel selecting lineup; i.e. no switching from Air to Cable.

Long setup for this question: Is this going to cause a problem? Is the cable signal going to leak out of my antenna in the attic and cause interference with anything else out there? I don't want the FCC breaking down my door and shooting my dog.

[elmo]

Rule of thumb is never to mix antenna and cable signals on the same coax. It's like putting republicans and democrats in a room and asking for a quick solution to a critical problem. Not only do you cause your tuner to go nuts, you potentially could cause localized issues which could get you a knock on the door by the cable co. The best way to combine those is thru separate inputs to the TV (Tuner 1, Tuner 2, etc) or to use something like multiple or a dual input HD Homerun, which you may know of since you have an HTPC.

[SaurusX]

Thanks for the input. I don't want to cause any problems for anyone, but at the same time I think I came up with a viable solution to my problem.

The tuner in the LG seems intelligent enough to be able to handle both types of signals on one line. During its scanning process it goes through DTV, TV(analog), CADTV(digital cable), and then CATV(analog cable) one right after the other and there is only one coax input. And like I said, I can choose which channels from all sources to be in a single combined lineup.

So with the tuner problem seemingly addressed, my only worry is the interference this may be causing via my antenna. Can the cable signal go up the other side of the combiner(and vice versa I suppose) and actually "broadcast" or am I concerned over nothing?

[ADTech]

Can the cable signal go up the other side of the combiner(and vice versa I suppose) and actually "broadcast" or am I concerned over nothing?

No, that is exactly what you must be concerned with. If you inadvertently re-broadcast cable signals via your antenna by merging them, you will be broadcasting on frequencies reserved for other licensed services including aircraft, police, and other public safety services. Once discovered, you will be held accountable for any interference.

Use an A-B switch to prevent problems. Radio Shack stores have been closing out their remote-controlled switches for under $10.

[SaurusX]

Originally Posted by ADTech

Use an A-B switch to prevent problems. Radio Shack stores have been closing out their remote-controlled switches for under $10.

Done. I'll pick one up today after work. Thanks for the help.

[elmo]

Originally Posted by SaurusX

The tuner in the LG seems intelligent enough to be able to handle both types of signals on one line. During its scanning process it goes through DTV, TV(analog), CADTV(digital cable), and then CATV(analog cable) one right after the other and there is only one coax input. And like I said, I can choose which channels from all sources to be in a single combined lineup.

Interesting. What's the model # for the TV?

I might learn something here.

[SaurusX]

Originally Posted by elmo

Interesting. What's the model # for the TV?

I might learn something here.

It's an LG model 32LN5300. There's a 39 inch and I think a 45 inch in the same line. I've never seen a TV be able to handle multiple signal types on the same coax input either.