In answer to your questions below, I would expect to only use one antenna at
a time, switching between them when wanting to use a different antenna or
directivity.

I would expect to use banana plugs to short the unused antennas to ground
just outside the shack, hooking up only the one to be used. I don't like the
idea of having an ungrounded feedline...lightning/static discharge hurts!

The open wire/coax question is a good one. Some of my antennas will be open
wire (vee beam, center fed 80 meter dipole for 80-10 meters), but others,
another dipole for 80 at 90 degrees and 150 foot separation is resonant and
fed with coax, while I have two verticals fed with coax, plan to experiment
with wire LPDAs, etc. So I am trying to think this thing through now,
especially in buying a tuner, as I can't afford both a Balanced tuner (ala
Palstar BT1500BAL) and an Unbalanced L tuner (TenTec 238B).

I feel like I have gotten a college education on balanced feeds and it's
caused me to reevaluate if that is really the easiest way to go. I started
out thinking about using just ONE antenna (80 or 160 dipole center fed with
600 ohm line) up about 75 feet on a 45 foot light weight tower and 30 feet
of mast above that. I liked the gain on the higher (20-10 meter) bands, but
the patterns wouldn't all be in the directions I want given the orientation
I have available for the antenna. So I started thinking about TWO such
antennas, with the second one on a 40 foot pushup mast. The I thought about
adding the Vee Beam I used to have long ago...really worked well on
20-10...definitely a good antenna with the 2 acres I have. And so forth. As
most of these antennas would be for multiband use, a balanced tuner would be
ideal, but then I had the questions of how to route the feedlines to keep
them out of the other antenna fields and away from each other. Having
always used coax, this is starting to seem like a nightmare. I almost think
the best is to do as one gent suggested, just put in an 80 meter or 160
meter loop, feed it with 450 or 600 ohm, and all it a day.

As I am no longer an avid DXer (used to have stacked beams for 10 through
40), but enjoy chatting on all modes on all bands, with reasonably good
signals, I think perhaps at the end of the day maybe the two 80 meter
dipoles at right angles (roughly forming an L from a top view) but about 100
feet apart, with one at 75 feet and the other at 40 feet might be the
solution, fed with 600 ohm to EITHER a balun-coax-L tuner or direct to a
balanced tuner. Good enough is good enough. Of course, I just know I'll
throw back up the 300 foot Vee Beam for 20 through 10 at some point, health
permitting.

Oh, so many choices and dreams! I think I am going to start small, probably
the dipole at 40 feet 350 feet away. That will satisfy until I get the tower
refurbished and up in September. The reason I have had so many questions is
because I am trying to foresee what my needs will be a year from now...I
don't want to say, gee, I should have thought of that!

73,

Greg, N6GK



I probably have more questions than answers.

1. Are the antennas to be operated independently? Is this a duplex or
diversity system?

2. Will the unused lines be terminated in the shack?

3. Are these multiband antennas with tuned feeders or could they just
as easily be coax-fed?

4. What do you consider to be detrimental interaction?


As others have suggested, there will be coupling between the antennas,
so feedline-to-feedline isolation will not necessarily be a figure of
merit.

If you consider the impedance change of a single pair of wires
operated over ground as a proxy for interaction, then with separation
by 3 or 4 times the wire spacing, you are probably okay for all but
the most critical situations.

One test would be to excite one line and measure the power in an
adjacent line, remembering that some (a lot?) of the coupling will be
antenna-to-antenna and will also be frequency dependent.