Message-ID: <4FB11876.10208@iup.uni-heidelberg.de>
Date: Mon, 14 May 2012 16:36:38 +0200
From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: Re: Cardioid RX antenna for LF...
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Hello Alan, Markus, Jim, Warren, Hartmut, Ben, Laurence, Clemens,=20
Roelof, LF!

Perfect. Many thank for the big resonance to my query :-)
The page of F1AFJ and the EZNEC file from Hartmut is very helpful, also=20
the general explainations and links!

OK, we'll start in this week and will see what comes out. At least the=20
loop will be installed and a cable to the RX. Then we will build a 1:3=20
transformer and just test what comes out if a 1k pot is used. I'm=20
looking forward to the results. Maybe a preamp will be needed but=20
hopefully we will get first impressions without one...
Loop, cable, xfmr, ground rod, loop orientation, resistor, alignment...=20
These are the steps for the week...

73 to all,

Stefan/DK7FC

Am 14.05.2012 00:36, schrieb Alan Melia:
> 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 wi=
th
> 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 "i=
ts
> not necessary to tune a K9AY but these are people who are looking at no=
tes
> or using it on MF/HF where the pick-up is a lot better and the impedanc=
e 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 Sch=E4fer"<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...
>
>
>   =20
>> 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. Th=
en
>> 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 =3D 8 kOhm. This resu=
lted
>> 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
>>
>>     =20
>   =20