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LF: Re: Re: Loop antenna problem

To: [email protected]
Subject: LF: Re: Re: Loop antenna problem
From: "J. B. Weazle McCreath" <[email protected]>
Date: Sat, 21 May 2005 13:30:13 +0100
Delivery-date: Sat, 21 May 2005 14:28:24 +0100
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Hello Niels, LF group,
 
Yes, it is a rather large loop!  I have a few pix of it if anyone would like to
see how I've built it.  Your guess of the inductance is close, I measured
it with my LCR-55 meter and it's 2150 uH. or about 2.1 mH.  According
to Reg's loop program the self resonance is about 800 kHz. and the Q
is 383, but I've no way to verify the latter.
 
At this point I'm game to try any suggestions to see if I can improve on
the performance (or lack thereof at the moment)  I think I'll try a simple
one turn unshielded pickup loop next, but I'll certainly keep your idea
of a capacitive divider in mind.
 
73, J.B. Weazle McCreath, VE3EAR - VE3WZL
 
Dr om!
Quite a big loop you have made there!
I would not recommend the use of a pickup loop at all. It is rather
difficult to predict the degree of coupling between the loop prober and
the pickup loop.
From your description I guess that your loop inductance is about 2 mH,
as for the Q of the loop I would say it lies between 20 and 50.
Why not try to scrap the heavy RG213 loop and instead use a
capacitive divider . If you try a capacitor of 10 to 22 nF in series
with your variable capacitor, you might have success.
As for the question of balancing etc. in order to avoid capacitive signal
pickup, I suggest you try to solve that problem with an isolating
transformer. But let that be a second exercise!     
73
Niels/OZ8NJ+
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