Dear VLF group and further observers and interests,
After another very succesful 11th VLF kite experiment i want to give a
final report and summarise the observations.
First, a big thank you to Markus/DF6NM and Marco/DD7PC who have been in
phone contact to me, keping the contact to the LF reflector and gave me
feedback about the receivers side.
Thanks and congratulations to the RX stations in this experiment!
Activity has been relatively poor, relatively. This may be caused by
the holiday season and expected lower chances for a successful
reception due to the high summer QRN? ;-)
The best DX seems to be 2404 km, to Halldor's / TF3HZ VLF grabber in
Iceland, with amazing SNR despite the summer season and its significant
higher QRN. The first time my signal was received in Romania
(Bucharest, KN34AL) by YO/4X1RF (grabber). An overview of the
successful RX stations (including grabbers) can be found here:
http://dl.dropbox.com/u/19882028/VLF/11th_VLF_exp_RXstations.png
Further overview will come soon.
Also thanks to those who tried without success: 4X1RF, RN3AUS, DL4RAJ,
VE2IQ ... as far as i know. Don't give up, i'm sure it is worth to try
in the next experiment! I definitely will improve things the next time.
Furthermore it have been less than optimal conditions in this
experiment, see in my report below.
Now a report what happend on the TX side:
I arrived on the hill about 5:30 UTC (7:30 local). Since the sky
was overcast i called Marco/DD7PC to inform me if there are lightnings
detected in DL. I waited some time with a decision if i should start
building up or aborting the experiment. Then it started to rain and i
had to wait about 1 hour. But then i remembered that i have to be
optimistic, since it is the Dreamers Band! So i started to build up the
station, while the rain stopped.
Unfortunately the
coil dropped on the bottom and got a strong
scratch on the upper part of the winding. Some turns may cause a short
cut now :-( I will have to replace 100m wire or so :-( Anyway, the
upper turns are needed for transmissions on 5170 Hz but not for 6470 Hz
and 8970 Hz and so i was able to start anyway.
I started to come
on air at about 9 UTC on 8970 Hz. Since its
summer here, the fields are coverd by corn so things were a bit more
difficult and lossy. But it was raining just before and so i seemed to
have a low earth resistance and got
up to 1 A antenna current (900
mA average) on 8970 Hz. Again i used 2 massive earth rods (about
0.5 m into the soil) pus the copper plate and got earth losses of about
100 Ohm and coil losses of about 185 Ohm on 8970 Hz.
The cheep generator
just gave about 250 W TX power. This is
very annoying. I will definitely use another generator the next time
which will give a stable 900 W or even 4 kW.
Unfortunately the wind was unstable with strong blasts. So i had to use
the "small" kite (3.6 m^2). Often, the kite line and so the wire was
sagging much and so the resonance and thus the antenna current often
changed. Thus, the average ERP must have been significantly lower,
maybe about 10 dB. But the
peak ERP must have been in the range of
50 mW which sounds good for just 250 W TX power!
But despite the summer time (QRN) and suboptimal wind conds there was
good reception in Iceland, and UK, Germany, France, Italy, Romania,
Austria, Czech Republic and Poland! Since there was no copy in
Israel/4X i decided to transmit a longer carrier, maybe to appear in
the DFCW-2400 grabber window of 4X1RF. I got the feedback that some
stations receive me in DFCW-60, e.g. G3ZJO, DF6NM, OK2BVG, G3KEV. Thus
i sent "73 DK7FC" in DFCW-60 after that. Thanks for the screenshots!
A new old notebook was used for this experiment, completely new WinXP
installed and nothing except SL V2.76_b18. The soundcard samplerate
drift was compensated within SpecLab, that did an essential job again
(TNX Wolf/DL4YHF). The reference was the 10 kHz signal of my GPS
receiver. No phase glitches seem to have occured. Partly there was a
somewhat broader signal appearing on the grabbers. This may be caused
by the kite movement, causing some kind of AM of the signal. Paul
Nicholson determined my TX frequency to be: "
Frequency:
8969.999945Hz ± 1uHz
".
After that i changed to
6470 Hz which was done i a minute or
so. I achieved
about 750 mA average antenna current (850 mA peak)
at 250 W TX power,
about 21 mW ERP peak but average ERP maybe 10 dB
lower too.
In the afternoon the clouds and wind blasts became stronger again. So i
transmitted about 1 hour, a stable "carrier" on 6470Hz (Paul says:
"Frequency: double peak 6469.999706Hz ± 1uHz 6470.000086Hz ±
1uHz6470.000086Hz ± 1uHz
"). Then some rain drops started to fall down and i decided to stop
transmitting.
As usual it took about a hour to bring down the kite and all the stuff
in my car. During that time another radio amateur arrived there and
build up his 2m/70cm equipment to participate in a local VHF/UHF
contest ;-)
_______________________
So, that was the 11th experiment. I'll start again in September or so,
depending on the interest, new stations and antennas on ideas. Maybe we
can go lower in frequency if i have repaired my coil and got a visit of
DF6NM who brings his coil on the hill to switch it in series to come
down to 4 or 3 kHz...
I'm definitely looking forward to a experiment/project in cooperation
with EA1PX and RN3AUS and others!! There was no detection of an amateur
generated VLF signal in Spain or Russia at all (far field) so far i
think!?
Tnx agn to all those who do and did the effort to try to receive such a
weak signal, especially to the grabber runners who make their
receptions available in the web for all! Thanks to Roger/G3XBM for
keeping his sub9kHz webpage up to date!
Best 73, Stefan/DK7FC
