Message-ID: <2FFEE227229C4963B0D56511C36E2BA7@PCCasa>
From: "Daniele Tincani" <daniele.tincani@alice.it>
To: <rsgb_lf_group@blacksheep.org>
References: <71A8DF2CFC0B4036B2664789F2AC98E0@PCCasa> <BA1F5018451046159131B4F4A3ADD679@JimPC>
In-Reply-To: <BA1F5018451046159131B4F4A3ADD679@JimPC>
Date: Sun, 28 Mar 2010 22:12:53 +0200
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Subject: LF: Re: Re: Balun for tuned loop antenna
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Thank you very much James for your comment which greatly clarifies this 
subject to me.
Best regards
Daniele

----- Original Message ----- 
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, March 28, 2010 9:21 PM
Subject: LF: Re: Balun for tuned loop antenna


> Dear Daniele, LF Group,
>
> The high impedance input of your portable should be a good match to the
> loop. It may be an advantage to have 2 or 3 turns coupling winding instead
> of a single turn, but this is best found by experiment.
>
> It is probably the high impedance tuned winding that could benefit most by
> being balanced, rather than the receiver input. The best way to do this is
> to make a centre tap in the main loop winding, and connect this to ground.
> The tuning capacitor must not be grounded, of course. If you prefer, you
> could make a balun with a single centre-tapped winding. The centre tap 
> would
> connect to ground, while the two ends of the balun winding connect to the
> two ends of the loop winding. The balun should have much higher inductance
> than the loop (at least 5 times, say), or it will significantly increase 
> the
> minimum tuning frequency of the loop. The stray capacitance of the balun
> will also reduce the maximum frequency of the loop.
>
> Personally , I have found it makes little difference to pick-up of
> interference, whether the loop is balanced or not. It is probably just as
> effective to leave the tuned winding floating. It is usually more 
> effective
> to move the loop to a different position (often only a few metres will 
> make
> a big difference) if QRM is a problem. Again, experimentation is the best
> way to find out.
>
> Good luck with LF,
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>


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