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Re: Helix and pre-amp



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.

73,

John
KD6OZH

----- Original Message ----- 
From: "Andrew Rich" <vk4tec@people.net.au>
To: "Amsat-Bb@Amsat. Org" <amsat-bb@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@people.net.au
> http://www.tech-software.net
>
>
> _______________________________________________
> Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
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