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Re: LF: Re: DK7FC's 3rd VLF transmission

To: [email protected]
Subject: Re: LF: Re: DK7FC's 3rd VLF transmission
From: "Roelof Bakker" <[email protected]>
Date: Tue, 23 Mar 2010 18:29:16 -0000
In-reply-to: <[email protected]>
References: <[email protected]> <38A51B74B884D74083D7950AD0DD85E82A1B81@File-Server-HST.hst.e-technik.tu-darmstadt.de> <[email protected]> <56800827A5644E1BB3F320CB51E2300E@Black> <26E279AD762E44FB937A8A7DF8F934BC@Black> <8C7F2923D86B4517B1C156BA499E96E4@Black> <F277E8E705B545489E6506C9E10C1225@Black> <bd8.4bf8185f.38d7802a@UNKNOWN> <B25CA16D1AFD4B7E889CB2E75FC2F8FE@White> <29746320.1346347.1269244849281.JavaMail.fmail@mwmweb078> <[email protected]> <[email protected]> <38A51B74B884D74083D7950AD0DD85E82A1B87@File-Server-HST.hst.e-technik.tu-darmstadt.de> <0A742B5B9F6A4E84A802D1F98B670E79@JimPC> <[email protected]>
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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





Attachment: pa0rdt-Mini-Whip CAT5.JPG
Description: JPEG image

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