[mythtv-users] Attic antenna

[David Brodbeck]

On Fri, August 28, 2009 2:46 pm, Tom wrote:
> The TV and the inputs on the TV cards are 75 ohm impedance. Twinlead is
> 300
> ohms and won't work. Not without a matching transformer-- another place
> you
> can lose signal. Most antennae for UHF are already 75 ohm F-connectors, so
> why transform the signal from 75 ohm to 300 and then back again when you
> get it into the house?

I don't think I've ever seen an antenna with a 75 ohm feed -- usually
antennas are balanced and need a balun anyway to connect to coax, although
sometimes the balun is internal to the antenna if it's in a housing.

Loss in the balun will probably be less than 1 dB.  Making an efficient
one is not much of a trick.

> Yes, coax has loss, but it's so far simpler than using twinlead...

No argument there.

Twinlead has more loss than the "window line" used by hams but is still
quite a bit less lossy than RG-6.  Adding an amp would make the point
moot, of course.