Message-ID: <009501caba50$fb571a20$0201a8c0@Clemens04>
From: "Clemens  Paul" <cpaul@gmx.net>
To: <rsgb_lf_group@blacksheep.org>
References: <Pine.LNX.3.95.1100228212241.229A-100000@noname.nodomain.nowhere> <4B8CE312.7090904@abelian.org> <20100302110052.BFCD8F3864@smtps02.kuleuven.be> <4B8D015B.10205@abelian.org> <op.u8xyu1djyzqh0k@pc1> <4B8D5529.1060501@abelian.org> <op.u8yi7mnnyzqh0k@pc1>
Date: Tue, 2 Mar 2010 22:39:58 +0100
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Subject: Re: LF: Re: 9kHz noise level
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Hi Roelof,

>and at 8.970 kHz it is 7.7 dB.

That's pretty close to IK1ODO's meaurements some time ago,
he measured -7,9dB at 10kHz.

73
Clemens
DL4RAJ


----- Original Message -----=20
From: "Roelof Bakker" <roelof@ndb.demon.nl>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, March 02, 2010 9:29 PM
Subject: Re: LF: Re: 9kHz noise level


> Hello Paul,
>
> Thank you very much indeed for the description of your elaborate VLF
> reception station.
> There must have gone a lot of effort in building it.
>
> I am looking for a simple way to detect the proposed test signals at=
 8.970
> kHz from Germany.
> At my location loops are useless, due to local noise problems.
> Using an E-field probe has been much more productive as a building=
 acts as
> a Faraday Cage and will refrain local noise from inside the house to=
 reach
> the outdoors. At 400 kHz the attenuation is around 30 dB. How this=
 works
> at VLF has to be established yet. The main problem is to prevent loc=
al
> noise travelling over the shield of the coax cable to the antenna.=
 CAT5
> network cable and isolating transformers have been used here as well=
 to
> feed the antenna and transport the rf. An optical link will be teste=
d on
> short notice.
>
> I have a SPM-30 SLM which is fine for direct monitoring and is flat=
 down
> to 200 Hz. However my PERSEUS direct sampling SDR is a much nicer to=
ol as
> the sampled input can be recorded and processed later on. Today I ha=
ve
> been testing sensitivity at VLF. At 20 kHz the attenuation is 2.7 dB=
,
> compared to 100 kHz. At 15 kHz it is 4.1, at 12 kHz it is 5.5 and at=
 8.970
> kHz it is 7.7 dB.
>
> This is nothing dramatic as at 8.970 kHz the antenna noise is still=
 10 dB
> over the receiver noise.
>
> I have also been looking into Spectrum Lab and feeding the antenna
> directly into an external EMU 202 USB soundcard, sampling at 192 kHz=
. At
> first sight sensitivity is down compared with the PERSEUS SDR, howev=
er my
> settings of Spectrum Lab are probably not optimised yet.
>
> There is a link on the Spectrum Lab website to yours truly about VLF
> reception, but unfortunately it appears to be dead.
>
> Best regards,
> Roelof Bakker
>


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