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Re: Question "nesting Helix antennas" (was ) JavaScript Axial-Mode Helix Calculator



Joe,

You can nest helix antennas.  Several older Hughes satellites used this
method for mounting two long helix communication antennas and even had a
metallic boom in the middle.

 I also made a dish feed with a 2.4 Ghz helix inside a 1.2 Ghz helix with
the goal of combining a 1.2 Ghz uplink antenna with a 2.4 Ghz downlink.
They both worked OK individually or for dual receive but there was too much
coupling of the 1.2 Ghz uplink signal  to the s-band helix and it totally
de-sensed the S-band downlink (they were separated by less than an inch
after all so the result was predictable).

I think you can make it work as long as you don't want to transmit on one
while listening on the other (especially if you will be listening near the
2nd harmonic of the Tx frequency).

Good luck with the project.

Larry - W7LB



----- Original Message -----
From: "Joe Leikhim" <jleikhim@nettally.com>
To: "Frederick M. Spinner" <fspinner@hotmail.com>
Cc: <amsat-bb@AMSAT.Org>
Sent: Sunday, December 10, 2000 2:34 PM
Subject: Question "nesting Helix antennas" (was )[amsat-bb] JavaScript
Axial-Mode Helix Calculator


>
>
> If I wanted to build a helix for each of the bands:13cm, 23cm and 70cm.
Could I "nest" them
> together and use a single groundplane for 70cm?, Would there be any
negative interaction? I
> would use a separate feed for each.
> --
> Joe Leikhim K4SAT
> Jleikhim@nettally.com
>
> "tv dinner by the pool,
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