ISOTRON Antennas.
 

After reading many review of the Isotron antennas (the ones which look
like birdfeeders!) I had bought a 40 meter version as well as the
10/15/20 combo.

Put the 40 meter version up on a 12 foot mast, super easy to tune,
worked great, 1.2:1 SWR across the 40 Meter CW portion of the band
without the use of a tuner. Made better 40 meter CW contacts on the
Isotron than on my dipole, I still can't believe how good that
"birdfeeder" works.

Well I'm putting the 10/15/20 combo version together and its been more
of a problem. Can't get a good SWR, about 2:1 is the very best I can do
on any of the bands.

Each antenna has an SO259 connector and each antenna is connected in
parallel via short piece of twinlead. So I don't know which antenna I
really should connect my coax to, the 10, 15, or 20? Anyone have
experice with the 10/15/20 combo who can offer some suggestions....

George - KI4FIA - Daytona Beach, FL
http://www.MilAirComms.com

Hello,

Just a simple dumb question: is it the "birdfeeder" that radiates or the
coaxial cable used between the transceiver and the miraculous antenna?

73 de F8BOE Olivier ...-.-


"GeorgeF" a écrit dans le
message de ...
After reading many review of the Isotron antennas (the ones which look
like birdfeeders!) I had bought a 40 meter version as well as the
10/15/20 combo.

Put the 40 meter version up on a 12 foot mast, super easy to tune,
worked great, 1.2:1 SWR across the 40 Meter CW portion of the band
without the use of a tuner. Made better 40 meter CW contacts on the
Isotron than on my dipole, I still can't believe how good that
"birdfeeder" works.

Well I'm putting the 10/15/20 combo version together and its been more
of a problem. Can't get a good SWR, about 2:1 is the very best I can do
on any of the bands.

Each antenna has an SO259 connector and each antenna is connected in
parallel via short piece of twinlead. So I don't know which antenna I
really should connect my coax to, the 10, 15, or 20? Anyone have
experice with the 10/15/20 combo who can offer some suggestions....

George - KI4FIA - Daytona Beach, FL
http://www.MilAirComms.com

F8BOE wrote:

Hello,

Just a simple dumb question: is it the "birdfeeder" that radiates or the
coaxial cable used between the transceiver and the miraculous antenna?

73 de F8BOE Olivier ...-.-


I belive its the two metal places, one above and one below the coil
which are to form a capacitor.

George

"GeorgeF" wrote in message
...
After reading many review of the Isotron antennas (the ones which look
like birdfeeders!) I had bought a 40 meter version as well as the
10/15/20 combo.


did any of the reviews test out how well the manufacturer supports their
product? maybe you could try that route and report back on how responsive
they are to problems?

"GeorgeF" wrote in message
...


F8BOE wrote:

Hello,

Just a simple dumb question: is it the "birdfeeder" that radiates or the
coaxial cable used between the transceiver and the miraculous antenna?

73 de F8BOE Olivier ...-.-


I belive its the two metal places, one above and one below the coil
which are to form a capacitor.

George

I seem to recall an indepth analysis on the AntennEx site showing that it
was the shield on the coax that did the majority of the radiating. A simple
proof would be to change the coaxial feeder length or how it is physically
run and look for VSWR changes.

Dale W4OP

I seem to recall an indepth analysis on the AntennEx site showing that it
was the shield on the coax that did the majority of the radiating. A simple
proof would be to change the coaxial feeder length or how it is physically
run and look for VSWR changes.

Dale W4OP

Originally where I had the 40 Meter Isotron located I was using about a
50' coax run (RF-9913). I the moved the antenna to a different position
and had to add about 25' more of coax. The additional coax caused SWR
to jump from about 1.2:1 to 1.4:1. A quick returning of the "tuning
rod" on the antenna brought it back to 1.2:1

Last night I was doing more playing with the 10/15/20 combo, was able
to get the 20 meter size down to 1.2:1 and had about a 300 KHz bandwith
to say under 2:1 SWR so I'm happy with that. But still can't get the 10
& 15 meters to do any better than 3:1. It possibly might be the
location of the ant as its pretty close to some electical house wiring?

George

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"Dale" == Dale Parfitt writes:

[... GeorgeF asked about Isotrons ...]

Dale I seem to recall an indepth analysis on the AntennEx site
Dale showing that it was the shield on the coax that did the majority
Dale of the radiating. A simple proof would be to change the coaxial
Dale feeder length or how it is physically run and look for VSWR
Dale changes.

So if someone tells me about a crazy antenna that "just works" but
which relies on the feedline being straight and not coiled, I should
suspect it to be Isotron-like in design and effect?

Dale Dale W4OP

Jack.
(figuring someone with field-strength meters could solve this)
- --
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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F8BOE wrote:
Just a simple dumb question: is it the "birdfeeder" that radiates or the
coaxial cable used between the transceiver and the miraculous antenna?

Translation: Isotrons make pretty good top hats. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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Oh good... If you want to be sure, you should clamp some RFI ferrites on the
coaxial cable to see what happens then.
The results may be surprising... But it's worh trying, just to protect your
shack's equipment.

73 de F8BOE Olivier ...-.-



"GeorgeF" a écrit dans le
message de ...


F8BOE wrote:

Hello,

Just a simple dumb question: is it the "birdfeeder" that radiates or the
coaxial cable used between the transceiver and the miraculous antenna?

73 de F8BOE Olivier ...-.-


I belive its the two metal places, one above and one below the coil
which are to form a capacitor.

George