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Old March 3rd 04, 06:35 AM
Theplanters95
 
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Default Perfect Antenna

Hi All,

I am looking for my "perfect antenna". It should work on 75m-6m, with NVIS on
75m & 40m and good DX for 20m and above. Above all it must fit in my backyard
which is 34 by 50 feet. The use of a tuner and/or balanced line is fine.

By perfect, I mean an antenna that gets the RF out (reasonable efficiency as a
percentage).

At first, I considered a random loop of 34 ft by 50 ft, at about 20 to 30 feet
high, with window line, but am having second thoughts.

Any ideas or suggestions?

Randy KA4NMA
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Old March 3rd 04, 04:03 PM
denton
 
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try putting up the loop anyway...and opening it opposit of the feedpoint for
use on 80 meters. I will probably work just fine.
"Theplanters95" wrote in message
...
Hi All,

I am looking for my "perfect antenna". It should work on 75m-6m, with

NVIS on
75m & 40m and good DX for 20m and above. Above all it must fit in my

backyard
which is 34 by 50 feet. The use of a tuner and/or balanced line is fine.

By perfect, I mean an antenna that gets the RF out (reasonable efficiency

as a
percentage).

At first, I considered a random loop of 34 ft by 50 ft, at about 20 to 30

feet
high, with window line, but am having second thoughts.

Any ideas or suggestions?

Randy KA4NMA



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Old March 3rd 04, 06:53 PM
Cecil Moore
 
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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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Old March 3rd 04, 09:55 PM
Reg Edwards
 
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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


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