[mythtv-users] OT: OTA HD

Richard Shaw hobbes1069 at gmail.com
Wed Dec 24 01:47:36 UTC 2008

On Tue, Dec 23, 2008 at 7:43 PM, Brian Wood <beww at beww.org> wrote:
> On Tuesday 23 December 2008 18:30:31 David Brodbeck wrote:
>> Travis Tabbal wrote:
>> > I had not considered the interference issue before I posted about setups
>> > like this. You might be able to use a diplexer, those are used in
>> > satelite/OTA installs. I have no idea how they would behave with CATV
>> > setups though.
>> A diplexer won't work.  It works for satellite because satellite and OTA
>> TV use different frequency bands, making them easy to separate.  Some of
>> the cable frequencies overlap the OTA frequencies, so that trick doesn't
>> work for mixing OTA and cable.
> Quite correct, a diplexer separates signals of different frequencies. This is
> what allows you to talk and listen at the same time with your cell phone,
> though those have a 45Mhz. separation in the signal frequencies, to make
> duplex operation cheaper. Diplexers for two-way radios that use 4.5Mhz.
> separation are big, bulky and costly.
> A channel elimination filter, or band-stop filter, might do what the OP wants,
> but a high-quality one is extremely expensive. Microwave Filter Corp. makes
> some nice ones, but they are custom built-to-order, and you could buy several
> nice MythTV systems for what they cost. I have seen cavity type diplexes that
> look like several garbage cans (cavity resonators).
> Best answer is to not try to combine the cable and OA signals at all, just too
> risky, and use an A/B switch, coaxial relay or other very high isolation
> solution.
> Assuming you need to have Myth control the switching device, there are
> controllable A/B switches, or you can use coaxial relays made by Dow-Key,
> justmake sure to terminate any unused inputs.

Easy solution. Get a HDHomerun and hook one tuner up to cable and the
other to a good antenna.


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