Message-ID: <4E5A9A3A.50205@iup.uni-heidelberg.de>
Date: Sun, 28 Aug 2011 21:42:50 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: Ferrite rod antenna - on-air testing
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Hello Jim,

What a surprise, i didn't expect such a story as a result of my 
spontaneous transmission ;-)

Congrats to your compact and well performing antenna which will be good 
for holidays and /p, if home QRM rises and rises with the years. This 
should be a good solution for many QRM bothered OMs. Better to take a 
walk and try it from a bank with a good view beside a forest than 
sitting at home and trying for hours without success!
Yes, 136.5 kHz would be more useful for a CW QSO. We really should try 
that ASAP. Are you ready for transmitting?

Ah and thanks for the nice report ;-)

73, Stefan/DK7FC



Am 28.08.2011 20:44, schrieb James Moritz:
> Dear LF Group,
>
> The QRN level on 136kHz has finally died away, and I was able to 
> record the attached spectrogram, showing DK7FC calling CQ around 
> 1755utc, using my prototype ferrite rod antenna. On the left of the 
> spectrogram, the rod is oriented for N-S reception, and the background 
> noise consists mainly of horizontal Loran spectral lines, plus some 
> unidentified, low-level,  local "mush". On the right of the 
> spectrogram, Stefan's signal level increases as the rod is rotated for 
> E-W reception. Here, the noise level is mainly vertical streaks due to 
> sidebands of DCF39's FSK modulation. The black area at the right hand 
> edge of the screenshot is where the ferrite rod was replaced by a 
> "dummy antenna" inductor, and shows that the internal noise level of 
> antenna and preamp is below the band noise level (by around 10dB).
>
> The band noise seen with the ferrite rod is practically the same as 
> seen with larger loop antennas under quiet conditions, so this 
> practical test does show that a reasonably compact ferrite rod can 
> give sensitivity limited only by the external band noise on 136k. In 
> fact, there is some margin for making the rod smaller still in this case.
>
> BTW, Stefan was an S4 audible signal - CW would have been a bit 
> difficult due to the bursts of noise from DCF39, but a QSO would 
> certainly be possible, especially if a quieter frequency were chosen.
>
> Cheers, Jim Moritz
> 73 de M0BMU