Date: Wed, 24 Mar 2010 09:46:01 +0100
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
In-Reply-To: <op.u909m21cyzqh0k@pc1>
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Subject: Re: LF: Re: DK7FC's 3rd VLF transmission
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Hello Roelof,

thanks for the circuit diagram. It looks pretty simple.
If I "read" the circuit diagram correct it is a buffer amplifier (the 
voltage gain maybe even less than 1, however due to the impedance 
transformation the power gain is huge).
It seems a bit of overshoot to me to buy a perseus (just checked, 
they ask 850 Euro for it), so my first option would be to go to the 
PC soundcard.
Do you (or others) have any experience with that ?

73, Rik ON7YD


At 19:29 23/03/2010, you wrote:
>Hello Rick,
>
>Michael Oexner has had good results with a mini-whip E-field probe I build
>for him.
>The circuit diagram is in the attachment.
>The feedline is CAT5 network cable.
>
>Note that the RF-isolating transformers in the signal path are not correct.
>I have used MCL TT 1-6 parts, rated for 0.004 - 300 MHz at the -3 dB
>points.
>The common mode chokes are not optimum, as I used the parts I had on hand.
>Type 75 or 77 ferrite should be better.
>
>Michael used a PERSEUS SDR, which has a noise figure of about 25 dB at 9
>kHz.
>This is due to the fact that there is also a RF-isolating transformer in
>the signal path.
>
>It is amazing that with this not optimized set up it was possible to have
>good reception over a 72 km path.
>The actual capture area of the antenna is 30 x 40 mm single sided copper
>clad PCB.
>
>There are quite a few people around with a PERSEUS SDR, who are probably
>interested in receiving Stefan's signal.
>So a simple antenna design might help.
>
>I have the parts for an optical link active E-field antenna, as suggested
>by Stefan.
>Due to other more pressing matters, I have not yet put them to good use.
>
>I hope this helps,
>
>Best regards,
>Roelof, pa0rdt
>
>
>
>