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Message-ID: <5.1.0.14.0.20020501113247.00afbda0@gemini.herts.ac.uk>
Date: Wed, 01 May 2002 12:27:43 +0100
To: rsgb_lf_group@blacksheep.org
From: "James Moritz" <j.r.moritz@herts.ac.uk>
Subject: LF: RX sensitivity
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Dear LF Group,

I have been doing some work recently on a preselector/convertor design for 
LF - The idea is an easy-to-build project to get started on LF that does 
not require test gear, alignment, or coil winding. I have a breadboarded 
circuit working quite nicely at the moment - the preselector has a tuned 
input circuit which can be adapted to a wide range of antennas without 
requiring a specially made antenna loading coil. A RX that covers LF can 
use the preselector output directly, or an oscillator/mixer circuit can be 
used to mix the signal up to HF. Although the up-convertor is fine for many 
applications, for the narrow band modes it is obviously better if you can 
use the circuit as a preselector with the main receiver tuned to LF, 
because this reduces drift.

The problem is to know what gain is required from the preselector. I know 
several people have measured the sensitivity of their receivers, which 
varies a lot at LF - so I would be very grateful for any figures anyone has 
to hand for typical amateur receivers, so that I can design in gain levels 
that will suit the majority of peoples' equipment.

Cheers, Jim Moritz
73 de M0BMU