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From: "hamilton mal" <g3kev.ham@virgin.net>
To: rsgb_lf_group@blacksheep.org
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Date: Sun, 22 May 2005 16:44:54 +0100
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Subject: LF: Re: Re: Loop antenna problem W1TAG suggestion
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----- Original Message -----
From: "J. B. Weazle McCreath" <weazle@hurontel.on.ca>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, May 22, 2005 12:11 PM
Subject: LF: Re: Loop antenna problem W1TAG suggestion


>
> -- Original Message -----
> From: "John Andrews" <w1tag@w1tag.com>
> Sent: Saturday, May 21, 2005 10:45 PM
> Subject: LF:Re: Loop antenna problem
>
>
> > J.B.,
> >
> > There is another approach you might want to consider. Skip the single
turn
> > link altogether. Rather than the normal parallel tuning, series tune the
> > loop into a transformer wound on a ferrite core. The turns ratio of the
> > transformer will determine the Q of the loop. You might not want a
really
> > high Q setup with a loop of that size.
> >
> > I have been using a 10 turn (on the loop side) to 20 turn transformer to
> > couple to a 50 ohm termination. This places a nominal 12.5 Ohms in
series
> > with the loop. A higher ratio would improve the Q, but this might be a
> good
> > starting point for you to play with. The core material in this case is
> #77,
> > but #43 or similar should be OK.
> >
> > The advantage of this arrangement is that the loop remains inherently
> > balanced to ground, while giving you the flexibility of playing with the
> > coupling. You may choose to put the preamp right at the transformer
> > secondary, or run a coax line back to the shack. A short write-up on
> > my arrangement is available at:
> > http://www.w1tag.com/rxloop.htm
> >
> > John Andrews
> >
>
> Hello John, LFers,
>
> Thanks for your suggestion on the series tuning setup.  Yesterday I tried
a
> simple non-shielded single turn pickup loop but it was no different than
my
> original shielded pickup.  I can't help but think that I'm getting led
down
> the garden path by something, but I'm amiss as to what!
>
> Do you suppose that because I used #12 wire, rather than the #20 that
> Steve, VE3SL, used on his loop that my Q is too high and therefore the
> bandwidth is too narrow?  I think I'll wind a toroid transformer today
> based on your info (I checked your website too) and see if I can get
> better results.
>
> Niels had suggested I try a capacitive divider, but my collection of caps
> doesn't have anything close to the values he recommended.  I'll keep on
> plugging away at it until I get it to work.
This is probably the best approach for your loop, or any series or parallel
arrangment
I use a parallel resonating approach on my 80 m perimeter vertical loop and
never had a problem.

G3KEV

>
>
>
>