Only one HDTV. I want to receive Both OTA and 'cable', without having to remove (change) coaxial connections.

[ITclimber]

I need to share an (input to the TV) coax cable with both my OTA antenna and directTV "cable". There's only one hole drilled through the garage wall for a cable, and it's not big enough to squeeze both coaxials through (only the [DirecTV] input cable goes through, now [to the T.V. set-top box]). And, there is an amplifier with my outdoor HDTV antenna, which I need, way out here.

I was hoping I could just use a coax A-B switch in the garage, with two inputs, and one output. But:
A) If it is switched to Antenna, it needs to be input, into the "amplifier" of the antenna (then, from there to the tv), but
B) If it is switched to cable, this line from the garage needs to go directly to the tv (as far as my brain can think), without the antenna's amp. in the middle (even if I need to combine [or unsplit] the output from the antenna amp with the straight line to the TV [when bypassing the antenna]).

So, can you reverse an A-B switch? Will it be possible to take the one input from the garage (that will be carrying either "over-the-air", or "cable" signal, and switch it to one of two outputs? (either the amp/antenna input, or the TV input [and I will make sure that if the directTV box Is on, that the antenna amp is off])?

{Can I just use a coax A-B switch backwards?)

The direcTV set-top box has an "off-air ant." input, but I'm not sure it's going to work....if I wanted to pick up Lexington, KY HDTV (ota) channel 36, and hook up the output from the antenna amp to the "off-air ant." coax input on the set-top, then when I turn the TV to channel 36, will the direcTV box try to find a "DirecTV Channel 36"? What if there were no DirecTV 36? If there were both an ota channel 14, and a directTV channel 14, wouldn't it just multiplex both the ota signal and the directTV signal, and superimpose both channels onto the screen at once? I was hoping all I needed to do, then, was to turn off the set-top (to let the ota signal pass-through [but I can't get anybody that sounds like they know what they're talking about at DirectTV]).

Anybody ever heard of a coax A-B / "x-y" switch (with both a switchable input, and a switchable output)? Or, just a coax x-y switch?

It's nuts trying to get a tech. support rep. from DirectTV to understand the need that arises from both the single input cable into the living room, and the fact that I either need an input into amp, or I don't.....(into the TV, instead)... depending upon whether it's (the single input from the garage into the living room) carrying "cable" or "air".

 

[Alabalcho]

Any switch you are going to use will degrade the quality of the signal. Moreover - unless you have very old TV, connecting your DirectTV box to the antenae input further degrades the quality of the picture.

Find a way to get two cables inside the house. There are almost-flat cables designed for under-the-door passage, may be you could use two of these to squeeze thru the hole.

 

[ITclimber]

Any switch you are going to use will degrade the quality of the signal. Moreover - unless you have very old TV, connecting your DirectTV box to the antenae input further degrades the quality of the picture.

Find a way to get two cables inside the house. There are almost-flat cables designed for under-the-door passage, may be you could use two of these to squeeze thru the hole.

Good point; but, I didn't know they made flat coax. 1 tv is old crt (the "cable" tv), 1 is flat (off-air tv). I guess I might try to widen the hole through the garage, but it's a plaster on cinder-block wall....worst of all, I'll have to move a piano (with junk piled all around it).

Thanks, Alabalcho.
-=-=-=-=-=-=-
By the way: In addition to an A-B switch out in the garage, I'm using a splitter, backwards near the tvs, and it hasn't fried the antenna's amp-unit box, for now, but I'm careful to only have EITHER the cable set-top ON, OR the off-air TV ON---only 1 at a time. If I can find another reasonably priced coax A-B switch, I'll try it backwards, near the tvs, to isolate the amplified antenna signal (from getting into the set-top).

 

[americanaudiophile]

If you DTV box has an over the air antenna input then you should try it and see if it gets the channels you want. It should not mix the channels (you would have to select sat or air). You could use two passive coax switches together but adding all kinds of complicated and lossy switching make less sense than just running another cable.

 

[ITclimber]

OOUCH! Someone (finally) forgot to turn off the DirecTV set-top...
the antenna got fried! That's what I get for trying not to use the Di-plexer at the DirecTv box's off-air coax. port, and make do with what I had with me.

I wasn't sure it would do any damage to the antenna, especially since the antenna amplifier box was turned off; but, leaving the set-top on fried the actual antenna, somehow.

With the splitter, the two 75 ohm cables were "in parallel", I think--making too much voltage go into the antenna. Two 75 ohmers in parallel is 1/[(1/75)+(1/75)] = about 38 ohms, effectively doubling the voltage through the antenna cable.
Ouch! There goes a good $40 antenna.