Hi all,
The autumn makes progress:
https://dl.dropboxusercontent.com/u/19882028/MF/20151020_164144.jpg
Finished the installation of the accus on the tree:
https://dl.dropboxusercontent.com/u/19882028/MF/20151020_164131.jpg
Coupled the first MF RX-loop:
https://dl.dropboxusercontent.com/u/19882028/MF/20151020_173822.jpg
Run the first MF stream from this location ever!:
https://dl.dropboxusercontent.com/u/19882028/MF/stream2_86.jpg
The first impression isn't so good, i must admit. But the spectrogram
settings are not optimal. The RX' bandfilter obviously doesn't like the
small resonance curve of the loop, i.e. there is a nerving visible
ripple inside the band.
Currently, the resonance peak is at 479.9 kHz:
https://dl.dropboxusercontent.com/u/19882028/MF/20151020_180246.jpg I
already modified the C-pack to move the resonance peak down to 475 kHz.
Some of the QRM traces are coming from the far field. I know these
traces from the city grabber and from the garden grabber and now even
from this location, so it cannot be local.
It quickly became cold during the time i monitored the band so i haven't
had enough time to wait for WSPR traces. DH5RAE was the only active
station to that time and the "duty cycle" wasn't really high ;-)
Anyway, it's a good progress and i'm looking forward to the next tests...
73, Stefan
Am 17.10.2015 17:40, schrieb DK7FC:
Hi all,
Despite mostly overcast wx i spend 3 hours into the tree today. Now
the first of 3 accus is on the board, still not used. Also, the
(mono-) MF-RX is up and a shielded USB-soundcard is connected to the
Raspi.
Further i have completed the installation of the first loop, beaming
about 120/300 deg. It is a single turn, circular(ish) loop with a
diameter of about 5m. The feed point (the highest point of the loop)
at about 15m above ground.
Measurements with a modified MFJ259B show that i need 14 turns on a
coupling transformer, when 2 primary turns are used, i.e. the loop
losses (at 475 kHz) is about 1 Ohm. I tried to find the C that is
needed to resonate the loop at 475 kHz but unfortunately my C-network
(0...1000nF + 1nF + 2.2nF + 4.7nF, switchable) does not cover the
value prcisely, it is just below 4.7 nF and above 4.2 nF. Next time...
Some images, as usual:
https://www.dropbox.com/sh/hjnkp3a60fyqk9v/AADRX9Hv2nAu7jYdzHHdRJ4Ja?dl=0
(nothing special, just to share some RF stuff :-) ).
73, Stefan
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