Antenna coupler for 50-900MHz
 

Should be simple for you guys,
I'd need a schematics for building 2 input antenna coupler for TV antennas.

Thank you!

GGap

Antenna coupler for 50-900MHz
 

Should be simple for you guys,
I'd need a schematics for building 2 input antenna coupler for TV antennas.

"Insufficient data". You need to be more precise about what you're
trying to accomplish.

I can think of at least five possible interpretations for "2 input
antenna coupler":

- A power divider, which allows two separate TVs or radios to be fed
from a single antenna, over that antenna's full frequency range
(a.k.a. a "splitter")

- A power combiner, which the signals from two identical (or similar)
antennas to be combined and fed to a single output (e.g. to allow
"stacking" of antennas for increased directional gain).

- A "duplexer", which allows the outputs of two dissimilar antennas,
which handle different frequency ranges (e.g. VHF and UHF) to be
fed down a single feedline.

- A "channel combiner", which allows the outputs of two (possibly
similar) antennas, pointed in different directions to pick up
different stations, to be combined without interference.
[Single-channel combiners are available commercially; more complex
combiners can be made but they aren't trivial.]

- An impedance matcher, which allows an antenna of one impedance to
be used with a feedline of another impedance (e.g. a balun which
goes from a 75-ohm coax to a 300-ohm twinlead-type antenna).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Antenna coupler for 50-900MHz
 

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.


"Dave Platt" wrote in message
...
Should be simple for you guys,
I'd need a schematics for building 2 input antenna coupler for TV
antennas.

"Insufficient data". You need to be more precise about what you're
trying to accomplish.

I can think of at least five possible interpretations for "2 input
antenna coupler":

- A power divider, which allows two separate TVs or radios to be fed
from a single antenna, over that antenna's full frequency range
(a.k.a. a "splitter")

- A power combiner, which the signals from two identical (or similar)
antennas to be combined and fed to a single output (e.g. to allow
"stacking" of antennas for increased directional gain).

- A "duplexer", which allows the outputs of two dissimilar antennas,
which handle different frequency ranges (e.g. VHF and UHF) to be
fed down a single feedline.

- A "channel combiner", which allows the outputs of two (possibly
similar) antennas, pointed in different directions to pick up
different stations, to be combined without interference.
[Single-channel combiners are available commercially; more complex
combiners can be made but they aren't trivial.]

- An impedance matcher, which allows an antenna of one impedance to
be used with a feedline of another impedance (e.g. a balun which
goes from a 75-ohm coax to a 300-ohm twinlead-type antenna).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Antenna coupler for 50-900MHz
 

"GGap" wrote in message ...
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.

Use a phasing harness or an antenna coupler.

http://www.kyes.com/antenna/stackluge.html

You COULD build a coupler with a few inductors and capacitors, but... why
bother? A good quality vhf/vhf combiner (aka splitter) or uhf/vhf combiner
(aka duplexer) is about $5 US.

Antenna coupler for 50-900MHz
 

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
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Antenna coupler for 50-900MHz
 

Thanks, all of you!

"Dave Platt" wrote in message
...

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
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!