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Date: Wed, 24 Mar 2010 11:16:30 +0100
Subject: Re: Re: LF: Re: DK7FC's 3rd VLF transmission
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Hi Rik,

I prefer the SDR-IQ for VLF - it's less expensive than the Perseus, and mo=
re important, it goes down in frequency to "almost zero" (unlike Perseus,=
 as mentioned here before). Don't get this wrong, Perseus is a superb radi=
o too, but there's no easy way to bypass the input bandpass (highpass). I=
 use Perseus on HF, and SDR-IQ on LF, VLF, and to listen for bats(!) .

Most soundcard's are fine too, and for the next experiment, you will be ab=
le to use the ALPHA signals to permanently calibrate the soundcard's frequ=
ency drift (when extremely high FFT resolution is required).=20

Cheers,
  Wolf DL4YHF .

----- original Nachricht --------

Betreff: Re: LF: Re: DK7FC's 3rd VLF transmission
Gesendet: Mi 24 M=E4r 2010 09:50:19 CET
Von: "Rik Strobbe"<rik.strobbe@fys.kuleuven.be>

> Hello Roelof,
>=20
> thanks for the circuit diagram. It looks pretty simple.
> If I "read" the circuit diagram correct it is a buffer amplifier (the=20
> voltage gain maybe even less than 1, however due to the impedance=20
> transformation the power gain is huge).
> It seems a bit of overshoot to me to buy a perseus (just checked,=20
> they ask 850 Euro for it), so my first option would be to go to the=20
> PC soundcard.
> Do you (or others) have any experience with that ?
>=20
> 73, Rik ON7YD
>=20
>=20
> At 19:29 23/03/2010, you wrote:
> >Hello Rick,
> >
> >Michael Oexner has had good results with a mini-whip E-field probe I bu=
ild
> >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 ha=
nd.
> >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 ha=
ve
> >good reception over a 72 km path.
> >The actual capture area of the antenna is 30 x 40 mm single sided coppe=
r
> >clad PCB.
> >
> >There are quite a few people around with a PERSEUS SDR, who are probabl=
y
> >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 suggest=
ed
> >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
> >
> >
> >
> >
>=20
>=20
>=20

--- original Nachricht Ende ----




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