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Date: Mon, 08 Jan 2001 11:03:56
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: LF Spurious signal on south coast
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>It is very stable and crude DF checks with a loop put it arriving north or 
>south

Hi Laurie,

There is a rather easy way to find out wether it is north or south :

1. Take minimum bearing with a loop (or ferrite) antenna, with that you get
2 possible directions (opposite to each other)

2. Sum the signal from the loop with the signal from a small electric
antenna (piece of wire). The small electric antenna has an omnidirectional
pattern, while the loop has an 8-shaped pattern. If both are summed you get
a cardioid pattern (because both lobes of the loop pattern are opposite in
phase). The null and maximum of the cardioid are far too wide to do an
accurate bearing, but it is good enough to determine which of the 2
directions (determined with the loop) is the good one.

remarks :
A. Remind that for step 2 you have to turn the loop 90 degrees (the nulls
of the 8-shaped pattern are in right angles to the loop plane while the
maximum/minimum of the cardioid pattern are in the loop plane).
B. you get the best F/B ratio on the cardiod pattern when the signal from
both antennas have (abou) the same strength).
73, Rik  ON7YD