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Date: Fri, 26 Aug 2011 12:59:39 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: DK7FC, DF6NM in YO and 4X
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Hello Jim, Piotr, Alex, Markus, Chris, Mike, LF :-)

Thanks all to this interesting observations and your reports about the 
LF ferrite antennas and propagated signals. I'm sure there will be more 
useful nights for such tests, anyway the tests have been successful, 
very happy about that.
If QRSS-60 is possible with O copy in such conds, CW should be possible 
on a quiet sunday morning. Maybe we can test that later :-)

Piotr, congrats to your successful reception. The QRM is stronger at 
home but the signal levels as well, compared to the previous antenna. So 
if you go outside with that ferrite antenna, you can easily gain 20 dB 
S/N or so. Fascinating, 800 km distance with an indoor antenna during 
QRN+QRM!! :-)

Looking forward to further tests!!

A few minutes ago, i improved my ferrite antenna a bit more: Have 
replaced the fixed 2.2 nF cap by (1+1+0.15+0.033)nF + a variable 47pF 
cap with an axis for hand adjustment + a switchable 47pF cap. This is 
rather compact than a 500 pF variable cap and reduces the volume of 
conductive materials near the ferrite rod. So this allows me now to 
easily tune over the entire amateur LF band. Even more useful: If i tune 
the variable cap to 137.7 kHz and just switch the fixed cap, i come out 
at 136.5 kHz (CW!) without the need to further adjustments. Excellent, 
isn't it? :-))
The high-Z preamp is still an open project but soon i have it completed.

What a fun!

73, Stefan/DK7FC



Am 26.08.2011 03:43, schrieb Piotr Mlynarski:
> James Moritz pisze:
>> Dear Stefan, Markus, LF Group,
>>
>> A screenshot of DK7FC and DF6NM received in IO91VR between 2230 and 
>> 0000utc, with 84mHz FFT resolution, and using the ferrite rod 
>> antenna. DK7FC seems to be about 6dB stronger than DF6NM here, on 
>> average. But not really a very good night for testing receive 
>> antennas - the QRN level is so high that the proverbial piece of wet 
>> string would be just as good!
>>
>> Cheers, Jim Moritz
>> 73 de M0BMU 
>
> Dear Markus, Stefan, Jim, LF
>
> Maybe this night is not a very good one for testing different rx 
> antennae according  to Jim observations , nevertheless, some  of us 
> decided  to do it ...   :)
> Enclosed,  there is a SL capture from my  night 'experiments' - at 
> first, i have used  my air loop antenna ( 1 sq. meter, 11t ) About  
> 2:25  a.m. local time I disconnected my air loop while SL was running 
> , then, i reconnected  SDR-IQ  to  my ferrite-rod antenna which was 
> inside the room !!!
> ( i only managed to raise it  some 40-50 cm above the floor) and to my 
> real amusement i could  still copy Markus DF6NM, also Stefan, though i 
> got some constant qrm line almost
> on Stefan.. 172 freq  i did not play with brightness/contrast etc.. 
> just to see how the noise changes.
> Anyway, i am very happy - it is my first positive observation of a 
> distant amateur signal on 136 kHz band ( if i have correct data Stefan 
> grid-loc is  JN49IK, Markus JN59NK so this makes
> 800 and 640 km , respectively)  using ferrite rod antenna ( described 
> in earlier mails). As an amplifier i have used  Roelof, PA0RDT 
> miniwhip circuit , simply
> using as a high Z-input the LC parallel network.
>
>                                                                                                 
> 73, Piotr, sq7mpj
>
> qth: Lodz /jo91rs/