Message-ID: <000501cadcd8$53ef5180$6402a8c0@e7010>
From: "Walter und Marianne Staubach" <wum.staubach@t-online.de>
To: <rsgb_lf_group@blacksheep.org>
References: <4D95FB39404AA04CA998E7F63B1A2E5F0432C756@esealmw110.eemea.ericsson.se> <4BC71C8D.1000508@iup.uni-heidelberg.de> <4D95FB39404AA04CA998E7F63B1A2E5F0432C7CF@esealmw110.eemea.ericsson.se> <4BC74643.1030802@iup.uni-heidelberg.de>
Date: Thu, 15 Apr 2010 22:15:00 +0200
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Subject: LF: Re: 8,97kHz / dreamers band grabber, another one...
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Lieber Stefan,
          woher kommt die recht starke Linie auf 8971,5 auf Deinem Gra=
bber?
Ich dachte schon, Du w=FCrdest mit Deinem Grabber QRSS machen.
Vorn sieht das aus wie "DE".
73   Walter  DJ2LF / DI2AG

----- Original Message -----
From: "Stefan Sch=E4fer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Thursday, April 15, 2010 7:00 PM
Subject: VLF: 8,97kHz / dreamers band grabber, another one...


> Der VLF dreamers, LF,
>
> I am glad to present you my new (and first) grabber for the dreamers
> band! It is running (in the web) not even one hour!
>
> Take a look at:
> http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html
>
> Next, i will add a ALPHA beacon window as well.
>
> The grabber accuracy is that of the soundcard (one time calibrated=
 with
> SpecLab to the ALPHA stns).
>
> Many thanks to Markus/DF6NM and Wolfgang/DL4YHF for the support to
> become QRV. Also tnx to my professor who allowed me to host the page
> directly on our institutes server (makes it easy and secure to uploa=
d
> the pictures).
>
> The grabber works with an active E-field antenna (Daniele, i can giv=
e
> you the circuit if you want) using 2x BF862 and a 500Hz band filter
> arround 9 kHz.
>
> BTW: The input had a 1 MOhm Resistor to prevent static overvoltages=
 to
> the gate. Therefore the highpass edge frequency of the input C (abt=
 3pF)
> and R=3D 1MOhm was about 55kHz. This afternoon i changed this resist=
or to
> 22MOhm, giving a edge frequency of abt 2,4 kHz. The difference can=
 be
> seen now on the upper picture. In the left side you can see the sign=
al
> of yesterday, in the middle i shut down the preamp to charge the bat=
tery
> and in the right part you see the signal with the 22MOhm resistor.=
 I
> have not changed the volume level or QTH, just the supply voltage by
> <1V. So, using a high R resistor, well above 1MOhm makes sense on VL=
F!
> On LF(137), 1MOhm is fine!
>
> The preamp is fed by a 3,4 Ah battery. This has to be charged each=
 2
> days. So, i will take a solar cell ( i have many 21V/55Wp) to keep=
 the
> supply decoupled from the local earth. I use RG174 and a AF decoupli=
ng
> transformer. Now, the antenna is placed temporarely in the 2nd floor=
.
> Since everything seems to be OK i will place it on the roof of the
> building, in the 7th floor. Then, i will probably use the fiber opti=
cal
> cable to further reduce the local noise and prevent HV problems due=
 to
> lightnings!
>
> Distance to my /p QTH is abt 37km, so i think i can write a message=
 in
> DFCW60 without any problems.
>
> BTW: This weekend i wanted to do the next experiment but the wind
> forecast is not very promising! But we will see... The 600W PA is re=
ady
> to use! So, 1000km could be cracked? :-)
>
> Wish you fun and motivation to improve everything in the LF/VLF worl=
d :-)
>
> 73, Stefan/DK7FC
>
>
>
>