In article , GGap wrote:
Thanks Dave, by antenna coupler I meant a power combiner, but,
precisely, since channels which are emitted from tv transmitters (obviously
in 2 directions from my home) are not overlapping, nor are adjacent, I think
of pointing logperiodical antennas to transmitters and couple them into one
tv cable towards receiver.

That may work acceptably, if your log periodic antennas have a high
enough front-to-back ratio, so that each is rejecting the signals
coming from the transmitters "behind" it. Without sufficient F/B
rejection, you'll end up with some amount of cancellation/interference
between the two. And, even with high F/B rejection in the antennas,
you can still end up with ghosting and interference if the antenna
pointing "away" from a transmitter picks up a signal reflected from
buildings, trees, or mountains.

You'll have to accept some amount of signal loss, no matter what you
do... the combiner will have some loss, and (to the extent that it
doesn't isolate one antenna from the other) each antenna will act as a
load on the other and will actually re-transmit some of the other
antenna's signal.

Building an effective broadband signal combiner isn't rocket science,
but neither it is trivial. Frankly, in your situation, I'd recommend
that you just buy a commercial combiner. For example,

http://www.starkelectronic.com/cmjoiner.htm

The first item #0538 is a two-way combiner/joiner made by ChannelMaster,
which appears to be designed to do just what you want... $9.95 plus
shipping. It takes 75-ohm coaxes from the antennas (you'd need
75-to-300-ohm balun on each antenna) and feeds a 75-ohm
downlink with the combined signals.

Click on the "Winegard Combiners" link on that page, and you'll see
the Winegard CC-7870 (same idea, higher cost) as well as the SD-3700
(which has 300-ohm inputs and a 75-ohm output - no need for separate
baluns on the antennas - just run some 300-ohm twinlead from each
antenna to the joiner).

The other alternate solutions to this problem that wouldn't have the
potential ghosting problem would be: use filtering combiners
(feasible for one or two "joined" channels, probably too expensive for
more than that), or use one antenna with a rotator, or use two
antennas and two feedlines and a "which antenna?" switch at the TV set.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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