Message-ID: <5643B24C.6090200@posteo.de>
Date: Wed, 11 Nov 2015 22:25:32 +0100
From: DK7FC <selberdenken@posteo.de>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <3EEE0BD431264721BAD95B0598D0A459@White> <55AA13A5.5090300@posteo.de> <55F6E63E.1090407@posteo.de> <5609BBA4.5030007@posteo.de> <561AD16F.2010506@posteo.de> <56226BE5.5060707@posteo.de> <56279657.2050205@posteo.de>
In-Reply-To: <56279657.2050205@posteo.de>
Subject: Re: LF: Ongoing work on the forest grabber
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Status: O

Hi all,

Just a small report again.
Did you ever solder into a tree, 18m above ground level?
I've added a deep discharge protection circuit including bash scripts 
for the Raspi today. It was a sunny afternoon.
Soldering was easy. I took my soldering iron from my solder station at 
home. It is normally running at 24 VAC and has a temperature regulation 
circuit. Amazon offers 3 EUR cheap DC/DC up-converters. So i generated 
16 V DC out of the batteries to feed the iron. This is enough to 
comfortably solder /p !!
https://dl.dropboxusercontent.com/u/19882028/MF/20151111_160546.jpg
Now there are two missing steps to get the system ready for a permanent 
MF/LF/VLF streaming: The battery charger and the solar module(s). 
Hopefully this can be finished very soon.

73, Stefan

Am 21.10.2015 15:42, schrieb DK7FC:
> 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
>