[amsat-bb] Re: Helix and pre-amp

John B. Stephensen kd6ozh at comcast.net
Mon Dec 10 06:31:46 PST 2007

I had a triple helix antenna several years ago and a preamp certaininly 
helped that and all other antennas that I used. You need to get the noise 
figure below 1 dB on 70 cm and the relationship is non-linear when pointing 
the antanna away from earth -- going from 6 dB to 1 dB improves the signal 
to noise ratio by up to 10 dB. The noise figure of a receiving system 
without a preamp is the noise figure of the receiver plus the feedline loss 
so preamps are most effective if they are mounted at the antenna.



----- Original Message ----- 
From: "Andrew Rich" <vk4tec at people.net.au>
To: "Amsat-Bb at Amsat. Org" <amsat-bb at amsat.org>
Sent: Monday, December 10, 2007 09:14 UTC
Subject: [amsat-bb] Helix and pre-amp

>I am keen to hear from others that may have added a pre-amp to a helix.
> Does it help ?
> I have made a 9 turn on 70cm - thinking of going to 16 turns.
> ----------------------------------------------------------------------------
> Andrew Rich VK4TEC
> vk4tec at people.net.au
> http://www.tech-software.net
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