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From: hajo.brandt.dj1zb@t-online.de
References:<4F9E695F.4010901@iup.uni-heidelberg.de>
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To:  <rsgb_lf_group@blacksheep.org>
Date: 30 Apr 2012 11:10 GMT
Message-ID: <1SOoVC-23D2lE0@fwd14.t-online.de>
Subject: Re: LF: 137 kHz SWL report from a tube Audion
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Dear all,

a real audion receiver usually contains an adjustable rf feedback so
that the rx can oscillate. Therefore a pitch of 800 Hz should be
obtainable without the reception of any other transmitter close to the
wanted signal.

73 Ha-Jo, DJ1ZB   


"Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de> schrieb:
> Hello group,
> 
> Since yesterday in the afternoon, i'm running a CW beacon again at 137.0 
> kHz. Speed is about 25 BPM i guess.
> It was intended to generate a test signal for my antenna tests here in 
> the holiday camp in JO41.
> After seeing two interesting spots in the DX cluster ( 
> http://www.dxsummit.fi/CustomFilter.aspx?customCount=50&customRange=137 
> ) i decided to run it some days longer, knowing that many LF listeners 
> can cross the way (=spectrum) and note that there is something going on 
> in the LF amateur band.
> 
> This time i got a mail from Horst/DL2SAV near Stuttgart (JN48 i think). 
> He gave me a very interesting report. He is using no amateur radio to 
> receive LF but an old tube radio from the 60's (Schaub-Lorenz) and a 
> homemade tube Audion. He tells that DCF39 seems to work as the BFO, so 
> he can hear me in normal AM mode, like a NDB. Today he sent me 3 
> recordings which sound very fascinating for me. If you want to listen, 
> here the link:
> http://dl.dropbox.com/u/19882028/LF/DK7FC_137kHz_30Apr12_amTag_mit_Audion.mp3
> http://dl.dropbox.com/u/19882028/LF/Dk7FC_137kHz_30Apr_12_mit_Radio_Schaub_Lorenz.mp3
> http://dl.dropbox.com/u/19882028/LF/DK7FC_137kHz_30_Apr_112_mit_Audiion.mp3
> 
> What i don't understand: If DCF39 is the BFO and i am transmitting at 
> 137.0, then the CW sidetone should be 1830 Hz (LSB, 138.83-137.0)? But 
> the tone from the Audion sounds rather like 800 Hz for me. Maybe someone 
> has an explanation.
> 
> BTW the beacon is stilll on the air...
> 
> 73, Stefan/DK7FC
> 
> 
>