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Message-ID: <B6744C828D0E46809F88181F89342AEE@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <memo.20090610114023.3260A@Jodan.cix.co.uk>
In-Reply-To: <memo.20090610114023.3260A@Jodan.cix.co.uk>
Date: Wed, 10 Jun 2009 22:00:42 +0100
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Subject: Re: LF: Re Welbrook Loops
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Dear Tim, LF Group,

I tried some expeiments with measuring loop antennas at LF and MF a while 
back - changing the height above ground from 0 - 10m made virtually no 
difference. The only thing that made a lot of difference to signal levels is 
if the loop is very close to big metal objects, but even then the difference 
is only minor unless the metal thing is big compared to the loop, and within 
a loop diameter, say.

I would agree with G3YXM about overloading - if you have an oscilloscope, it 
is worth connecting it to the loop output to see if any huge signals are 
present. I have used elliptic low pass filters here to reduce the signal 
level from the local medium wave broadcast stations to a reasonable level.

Cheers, Jim Moritz
73 de M0BMU

----- Original Message ----- 
From: "Trevor Smithers" <tsmithers@cix.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Cc: <tsmithers@cix.co.uk>
Sent: Wednesday, June 10, 2009 11:40 AM
Subject: Re: LF: Re Welbrook Loops


>I use a 1530 as well, its mounted on a rotator about 2ft above ground level 
>on a Barenco
> socket/spike. Works well 80m down to 500khz but being so close to the 
> ground its a bit deaf
> above 80m as you would expect. My understanding is that for hf it should 
> me mounted high up but
> for lf its better low down near the ground.
>
> A rotator isn't really necessary as the beamwidth is quite broad but where 
> I do find it useful is
> nulling out the local qrm, switch modes etc.
>