Hello Markus , LF  ,

73  qro  Jean-Pierre f1afj


Le 13/11/2010 23:04, Markus Vester a écrit :

Dear LF, Paul,

here's a short summary of today's VLF kite transmission. I'm sorry for the late 
notice, but the experiment had not been planned ahead, and I wasn't sure if I 
could get on at all. Also, the kite I am using (a 0.8 m^2 delta toy bought for 
4.99 Euro) is a bit small for this sort of activity, and really requires a good 
and steady wind.

The QTH was actually at 49.3874 N 11.1692 E, a few 100 meters from the former 
location reported earlier. The GPS-controlled carriers were on air
  11:15 - 12:15  6470.000 Hz ~ 50 uW, and
  12:30 - 13:10  8970.002 Hz ~ 200 uW (EMRP).

Getting on 6470 was easier than expected. I simply used the same "seven-bucket" 
coil, which resonates my 240 pF home antenna to 8.97 kHz. Connected to the kite wire, the 
resonance was close enough to 6.5 kHz to be tuned by the ferrite plate variometer. Then 
the drive for the audio amp was increased until the onset of corona sizzling at 0.25 A. 
At that point, the amp drew 10 A DC from the car battery and probably delivered around 50 
W. After connecting mobile internet and staring at Stefan's grabber, I was positively 
surprised to find a faint trace there!

For the frequency change, I removed the two bottom coil buckets, which brought the 
resonance to ~ 8.5 kHz. Then I had to carefully pull the remaining 5 buckets apart, 
inserting bits of plastic foam material as spacers. Going through a few iterations took 
about 10 minutes, and I got to "full power" (380 mA, 100W) at 12:30. 
Unfortunately, the wind had started to calm by then, and there were several dips during 
this transmission. Finally at 13:10, the kite landed gently in the grass, and I decided 
to close down and pack up early.

Traces from both transmissions were visible on DK7FC's 4.5 mHz "600" windows, 
and the second one also produced a nice dash on the 0.45 mHz window. It is likely that 
these signals would be useful for a kite-to-kite QSO on either frequency, using 10 minute 
dashes.

The screenshot from F1AFJ has an interesting dash before 13:00. The indicated 
frequency seems a bit high (8970.020 instead of 8970.002), which could perhaps 
be due to a small samplerate calibration error. I am also not sure about the 
time scale  - judging by the width of the noise blobs, the setting could have 
been 11 mHz and 10 seconds per pixel. It would be nice if Jean-Pierre could 
confirm the frequency calibration and scroll settings.

I also carefully inspected the OE3GHB grabber, which runs at 1.4 mHz resolution 
and seems to be very sensitive. It showed an unusually dark period of very low 
noise between 8 and 11 UT today. But no luck for my transmission there yet.

Well, in addition to the technical aspects, being outdoors in the warm wind was 
again a rewarding and enjoyable experience.

Best 73, and thanks again for the interest.

Markus (DF6NM)


From: Markus Vester
Sent: Saturday, November 13, 2010 2:19 PM
To: [email protected]
Subject: Re: VLF: TX on 6.47 and 8.97 - QRT


Sorry folks, I had to shut down at 13:10 due to lack of wind. Many thanks for 
looking!

Best 73,
Markus (DF6NM)



From: Markus Vester
Sent: Saturday, November 13, 2010 2:08 PM
To: [email protected]
Subject: Re: VLF: TX on 6.47 and 8.97


Hi Stefan, thanks for the observation! I am approximately at 49.3851 N 11.1727 
E. After a bit of fiddling with the coil, the carrier is on 8970.002 since 
about 12:25. I will try to stay on till 14:00, but there are a few lows as the 
wind has calmed down a bit.

73, Markus



From: Stefan Schäfer
Sent: Saturday, November 13, 2010 1:50 PM
To: [email protected]
Subject: Re: VLF: TX on 6.47 and 8.97


There is a trace now coming up slightly above 8970 Hz in the DFCW-600 window :-)

Markus, what is your exact locator? http://no.nonsense.ee/qthmap/  Let us see 
where you are currently :-)

73, Stefan

Am 13.11.2010 13:16, schrieb Stefan Schäfer:
   Wow! Hi Markus,

   Good luck!! Yes, the wind is very strong indeed. For my kites it is almost 
to strong...
   With your kite you should easily be visible in the 6000er window on 8970.

   OOOH! I just looked on my 2nd VLF grabber 
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html and saw 
your trace in DFCW-600!
   Congratulations Markus!!!! This is the second amateur radio station at all 
who reaches the far field within the 46km band :-) i estimate 8 dB S/N maybe 
10. Great!!!

   So DFCW-600 on 8970 should be no problem later :-))

   Who else of the group is monitoring? It would strongly interest how Markus 
is received at other locations :-)

   Best 73 and wish FUN!!

   Stefan/DK7FC

   Am 13.11.2010 12:54, schrieb Markus Vester:
     Nice wind here in Nuernberg, and I'm back on the /p QTH with my small kite 
(100m wire, kite currently about 60m up). Since 11:15 I am sending a carrier on 
6470.00, trying to generate a small peak on DK7FC's second grabber. Max current 
into the thin wire is about 0.25 A. After one hour at 12:15, I intend to switch 
to 8970.002 Hz, where I can radiate about 0.2 mW at 0.4 A.

     Best 73,

     Markus (DF6NM)