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From: John Rabson <john.rabson07@gmail.com>
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Date: Tue, 1 Mar 2016 15:40:36 +0100
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To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Loop antenna 77,5kHz
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Marcin,

A few years ago I built an eight-turn loop about 2.2 m square.  The unloaded Q was about 90, giving a bandwidth when series-resonated at 136 kHz of about 1.5 kHz, but it worked usefully for monitoring purposes from 75 to 183 kHz. 

The resistance at resonance was about 6ohm. The loop was fed through a 1:3.5 step up transformer on a ferrite toroid and then via a hundred metres of TV coax and a 20:20 isolation transformer wound on a Maplin N87AB toroid (this is not critical – a winding reactance of about 300 ohms at the working frequency would be good enough).

This configuration achieved a null on DCF39 of 34dB but I reoriented it to reduce the signal from France Inter on 162 kHz.  

I am at the moment rebuilding this antenna as it was severely damaged in a recent storm but I have not found it necessary to change the parameters.

Good luck with your experiments and 73,
John F5VLF

> On 27 Feb 2016, at 06:32, Marcin <bxi@go2.pl> wrote:
> 
> Thank you for so many answers regarding the depth of ground electrode.
>  
> I’d like to build a loop antenna for DCF77 time signal radio station at 77,5kHz. At the desired destination, noise around the ferrite rod antenna effectively blocks entire signal.
> Does anyone know how to build 1m x1m or 2m x 2m loop antenna?
> What to look out for while constructing?
> Thank you in advance.
>  
> 73! Marcin SQ2BXI

john.rabson07@gmail.com

Researching history of RABSON, BLACKSHAW, GAUNTLETT, VERLANDER and ROBSONNE