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