Nomen Nescio wrote:
In article
ospam (Theplanters95) wrote:
I'd love to see this thread expand to answers. Many of us have the same
wants, maybe not all the bands, but a least 80-10 in the confines given
above. Many solve with a vertical but I for one, would like something
better.

This has been covered before but bears repeating. Consider a 40m
full-wave square loop of about 138 feet, about 34 ft. per side.
If an insulator is installed halfway around the loop from the
feedpoint, the antenna becomes 1/2WL on 80m. Figure out an easy
way to short the insulator out for 40m-10m operation and open the
circuit at the insulator for 80m operation. Three possibilities
come to mind.

Locate the insulator on a pulley on one of the support poles and
lower that point on the antenna for physical access. Shouldn't
take more than 5 minutes to accomplish the short/open function.

Install a 1/4WL shorted stub for 80m operation. That will give an
open circuit on 80m and a short circuit on any multiple of 3.8 MHz,
for instance.

I once rigged up a Rube Goldberg high voltage switch out of copper
tubing supported by PVC pipe. One end of the antenna was attached
to a piece of 1/2 inch copper tubing. The other end was attached
to a piece of 1/4 inch copper tubing. By tugging on one of two
strings, I could move the 1/4" tubing in or out of the 1/2" tubing.
More elegant than strings would be a small screwdriver motor powered
by +/- DC from the shack end of the transmission line.
--
73, Cecil http://www.qsl.net/w5dxp



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Yes Cec, to use a vertical 1/4-wave line is a neat way of shorting and
opening a horizontal wire at a single frequency from ground level.

I once used a sealed reed relay to do a similar job. One of the horizontal
antenna wires was in fact twin 20-gauge speaker cable to operate the relay
coil. The shack end of the twin wire required a bifilar choke wound on a
ferrite rod to separate RF from the DC relay supply.
---
Reg, G4FGQ