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Re: LF: Ferrite RX antennas

To: [email protected]
Subject: Re: LF: Ferrite RX antennas
From: wolf_dl4yhf <[email protected]>
Date: Mon, 15 Aug 2011 20:23:58 +0200
In-reply-to: <[email protected]>
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Hi Stefan,

For a resonant design (tuned with parallel capacitor) I'd use the litz wire. For the broadband design (terminated with a low-Z amplifier) it shouldn't matter too much, but 0.5 mm wire diameter would be the minimum. The thinner the wire, the larger the 'R', R is noisy, and we don't want noise ;-)

7 rods in a bundle, and two of these bundles sound good. But it depends on the material (permeability) if it makes sense to use 8 "parallel" rods - consider this: one single rod may already 'attract' enough magnetic field lines from the far field; 7 rods will not attract 7 times as much ! Anyway for backpack operation you don't have the choice to build a meter-long rod like Lubos' large antenna.

Beware that my crossed-loop antenna was built for VLF, not LF.

Cheers,
    Wolf .


Am 15.08.2011 19:26, schrieb Stefan Schäfer:
Hello Wolf,

Thanks to the link to your nice to read article. I just found it a hour before your mail and already read it ;-)

Well, i also prefer the usual configuration instead of that sleeve antenna. Also i have to keep the focus on my actual goal: Making a handy antenna for amateur LF / p operation without a car! And the 16 rods i will get (14 cm long, 8mm diameter) will be best in a 2x7 config. i think. Or do you rather suggest 3x5 or even 4x4?
2x7 is then about 30 cm long which is very fine for a backpack and should be robust enough.
I would use the same double side bonding tape, this is very useful to get a first fixed arrangement. Then putting all that in a PVC tube, 2mm thickness and add the turns above the tube.
Would you recommend litz wire or standard 0.5 mm enamelled wire?
As an E field shield i would use aluminium bonding tape, without making a shutcut turn of course.

So the newcomers should not think that this antenna is the best what one can use for LF. Just in that special case of /p i see advantages. Otherwise a well designed loop (+ preamp or a very sensitive RX, if a samll loop is used) or E field antenna such as the PA0RDT should be preferred, as Alan already pointed out.

Looking forward to a direct comparison of the DCF39 SNR that can be achieved and to the first amateur signal received with that antenna in /p...

73, Stefan/DK7FC


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