[mythtv-users] HD and cable
rkoblish at gmail.com
Mon Dec 31 02:43:01 UTC 2007
> > Do they make a product that will combine my HD over the air with my
> > cable from the cable company so that I can combine them on one coax
> > and then feed it into my TV?
> Notwithstanding the interference that would occur between the cable and
the broadcast TV signals, there are other technical reasons not to attempt
to combine the cable and antenna signals. Some of the frequencies used by
cable are in the gaps between the VHF LO (54..88 MHz, broadcast channels
2..6); VHF HI (174..216 MHz, broadcast channels 7..13; and UHF (470..800
MHz, broadcast channels 14..69). The cable companies are required to keep
the signal from radiating, to avoid interfering with over-the-air users of
these frequencies. Users include paging transmitters, police, fire, and
other government services, other two-way land and marine mobile services,
and also civilian and military air traffic control.
A T or passive splitter-used-as-a-combiner will not have nearly enough
isolation between the cable and the antenna, and would put the cable company
in violation of FCC regulations. If you were found to have caused the
violation, they would have grounds to seek reimbursement for any fines,
which can reach $10 000 per day. And in these litigious times I wouldn't
want to be the guy who was found to have caused Flight XXX to crash because
an air traffic controller's directive was wiped out by a cable TV signal
radiated by your antenna.
In short, don't do it.
You might be able to find a coaxial relay or switch which has the required
isolation, and rig up a way to control it with a parallel printer port
output bit from your Myth frontend. Maybe an LNB switch from the satellite
TV world would have the required (60dB?) isolation. Or maybe you could use
the coaxial relay from an old Nintendo or other video game.
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