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Re: LF: TX > RX isolation test

To: N1BUG <[email protected]>, [email protected]
Subject: Re: LF: TX > RX isolation test
From: "Roelof Bakker" <[email protected]>
Date: Mon, 16 Jul 2018 16:16:35 +0200
In-reply-to: <[email protected]>
References: <[email protected]>, <[email protected]>, <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Hello Paul,

Noise received on your TX antenna is re-transmitted and this is responsible for 
the increase 
in noise level on your RX antenna. One way to get rid of it is to detune your 
TX antenna on 

I have been using an active E-probe antenna since 2004 with very rewarding 
results on LF / MF, 
albeit mounted just 6 meter from my house. The band noise from the antenna at 
477 kHz is 14 dB 
over the noise floor of my PERSEUS, so sensitivity is more than needed. 

There is no need for a good radio earth with this type of antenna, due to the 
capacitances involved, typical 3 pF. 

This antenna is prone to common mode problems. I have solved this by connecting 
the shield of 
the coax to a ground stake at the bottom of the mast and near the house. 
Requirements for this 
ground are modest. On poor soil one square metre of chicken wire will work 
already. A suitable 
common mode choke, e.g. 20 turns RG174 on a FT-140-77 toroid can help as well. 

To achieve best results some experimentation is on order, which is time well 

Roelof Bakker, pa0rdt

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