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
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