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Date: Wed, 21 Oct 2015 15:42:47 +0200
From: DK7FC <selberdenken@posteo.de>
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Subject: Re: LF: Ongoing work on the forest grabber
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Status: O

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