"rhymer" wrote in message
...
What is the best way to use one feed line for more than one dipole?
Or, is it better to use a coax switch in the shack?

Thanks, Ron

Ron,

Connecting two *dipoles* to the same feedline works just fine. Just tie them
directly to the same balun. There will be two kinds of interaction: first,
the two are electrically in parallel, and second, the wires themselves could
have mutual coupling. The first seems to not really be a problem, and the
second is minimized if there is separation between the two dipoles. For best
results, put them at right angles to each other; if that is not possible,
have at least 15 - 30 degrees separation, either vertical or horizontal. For
instance, you could have a dipole supported at the ends, with an inverted V
hanging below it.

The most interesting case is for antennas at 75 and 80 meters. You get 2:1
SWR from 3.5 to 4 MHz in a virtually non directional antenna (if the two
dipoles are at 90 degrees).

I presently have a 40 m inverted V hanging below an 17 m dipole. (The trees
are too close to do it the other way). The 40 meter is also out of plane to
miss the trees. Works great.

Since you have to trim the lengths slightly (lowest frequency first), it is
simplest to run EZNEC or some other simulation first.

Tam/WB2TT

On Fri, 21 May 2004 10:22:20 -0400, "Tam/WB2TT"
wrote:


"rhymer" wrote in message
.. .
What is the best way to use one feed line for more than one dipole?
Or, is it better to use a coax switch in the shack?

Thanks, Ron

Ron,

Connecting two *dipoles* to the same feedline works just fine. Just tie them
directly to the same balun. There will be two kinds of interaction: first,
the two are electrically in parallel, and second, the wires themselves could
have mutual coupling. The first seems to not really be a problem, and the
second is minimized if there is separation between the two dipoles. For best
results, put them at right angles to each other; if that is not possible,
have at least 15 - 30 degrees separation, either vertical or horizontal. For
instance, you could have a dipole supported at the ends, with an inverted V
hanging below it.

That's what I wanted to hear, that it can be done without using
anything special. It sure would beat switching them at the xmitter. I
have always used separate feed lines and recently I read where someone
had 4 dipoles on the same feed line.


The most interesting case is for antennas at 75 and 80 meters. You get 2:1
SWR from 3.5 to 4 MHz in a virtually non directional antenna (if the two
dipoles are at 90 degrees).

That sounds really cool.

I presently have a 40 m inverted V hanging below an 17 m dipole. (The trees
are too close to do it the other way). The 40 meter is also out of plane to
miss the trees. Works great.

Is the 40m at a right angle to the 17m, or is the V separation
adequate?

Since you have to trim the lengths slightly (lowest frequency first), it is
simplest to run EZNEC or some other simulation first.

Tam/WB2TT

Thanks muchly for that,

Ron, W1WBV

"rhymer" wrote in message
...
On Fri, 21 May 2004 10:22:20 -0400, "Tam/WB2TT"
wrote:
.................................................. .....
Is the 40m at a right angle to the 17m, or is the V separation
adequate?

The 40 is not at right angles. Only shifted horizontally enough to clear the
tree trunks and find suitable anchors for the ends. Vertically, there might
be 30 degrees separation, since the ends of the 17 go up, and the ends of
the 40 come down

Since you have to trim the lengths slightly (lowest frequency first), it
is

That is because the 40 has more effect on the 17 than the 17 does on the 40.
I am using a 1:1 balun. Not sure if that affects anything or not.

simplest to run EZNEC or some other simulation first.

Tam/WB2TT

Thanks muchly for that,

Ron, W1WBV