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Message-ID: <00a601cd315a$ba5babc0$4001a8c0@lark>
From: "Alan Melia" <alan.melia@btinternet.com>
To: "RSGB LF Gp" <rsgb_lf_group@blacksheep.org>
References: <4FAFEA71.8030700@iup.uni-heidelberg.de>
Date: Sun, 13 May 2012 23:36:25 +0100
MIME-Version: 1.0
Subject: LF: Re: Cardioid RX antenna for LF...
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Hi Stefam I am not sure about what you are doing so my comments may be way
off target. If the loop is not tunes yes it will be high impedance like a
short wire (much less than 1/4 wave) BUT Finbar did some experiments with
K9AYs for NDB listening. He tuned the loop to resonance at the opposite end
to the resistor, then he matched the feeder by tapping he tuning coil. I
have buried on my machine somewhere Finbar's notes. You will be told "its
not necessary to tune a K9AY but these are people who are looking at notes
or using it on MF/HF where the pick-up is a lot better and the impedance is
lower. For narrow band reception tuning is always an advantage.

As Roelof says Hartmutt used a K9AY, a two turn version, I think

Alan
G3NYK

----- Original Message ----- 
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, May 13, 2012 6:08 PM
Subject: LF: Cardioid RX antenna for LF...


> Hello Group,
>
> I've just started to play a bit in EZNEC, trying to simulate a receive
> loop antenna for the new YV7MAE grabber.
> http://dl.dropbox.com/u/74746618/LF/YV7MAE_LF_Grabber.html ... still
> using a wire receive antenna with excellent results but now a
> directional antenna is needed.
>
> So i modelled a loop with a possible shape and a ground connection. Then
> i added a R on the far end of the source. The results of the elevation
> and 3D plot are surprising good. Maybe i have done a mistake in
> modelling? Optimal performance was obtained at R = 8 kOhm. This resulted
> in the best F/B and beamwidth... Results of ZENEC are here:
> http://dl.dropbox.com/u/19882028/LF/Cardioid%20for%20LF.png
>
> Any ideas, experiance or advice?
>
> I guess a preamp is needed when such a antenna is used. The typical 1:9
> un-un does not look useful for me...
>
> 73, Stefan/DK7FC
>