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)
Sent: Saturday, November 13, 2010 2:19 PM
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)
Sent: Saturday, November 13, 2010 2:08 PM
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
Sent: Saturday, November 13, 2010 1:50 PM
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)
