Message-ID: <555DF128.50702@posteo.de>
Date: Thu, 21 May 2015 16:52:24 +0200
From: DK7FC <selberdenken@posteo.de>
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To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Subject: LF: MF loop towards UK (300/120 deg)
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Status: O

Hi MF,

Last night was quite interesting on MF for me. I'm now attempting to 
optimise the RX performance more and more.
Today it is good WX, so i spent a few hours into my trees...
I've built a RX-loop antenna out of simple loudspeaker cable, 2x 0.5 mm 
diameter wire, i.e. a 2 turn loop. 2 turns primary through a ferrit 
core, 9 turns secondary (50 Ohm side). The resonance C is still unknown, 
i have a combination out of a 1 nF variable C plus a switched C of 1 nF, 
2.2 nF and 4.7 nF. With the modified MFJ-259B i found the resonance and 
matching within minutes.
See a crazy image on: 
https://dl.dropboxusercontent.com/u/19882028/MF/MF%20RX%20loop%20into%20trees%20beaming%20NWSE.jpg
The antenna is now connected to the remote RX. Hopefully it will not 
rain in the evening, because i'm still using the good variable C shown 
on the photo. Water would move the resonance dramatically towards lower 
frequencies.
The signal levels are about 10 dB below that of the T-antenna, so i may 
need the high gain which my receiver is offering in the moment. Maybe i 
will modify the RX circuit so i can switch a preamp on and off, remotely 
via the GPIO of the Raspberry... Also i will add a relay to switch 
remotely between T and loop antenna :-)

Now i'm hoping for some signals to receive on MF WSPR, from any 
direction. :-)

73, Stefan