Page 1 sur 1

DK7FC's 11th VLF kite experiment

Publié : 27 mars 2011, 01:52
par F4DTL
Dear LF/VLF group,

Back in Germany i want to announce my next VLF kite experiment, as soon
as possible. If the wind will be suitable next weekend, i will go out
again. Wind conds looks promising so far but changes cannot be excluded
until friday. So i'll keep an eye on it...

I've made a new tap on my coil. It is for transmitting on 6470 Hz when
using the 300m antenna (before it was just possible if the 200m wire was
used). I expect a signal improvement of about 4 dB from that. So my
focus will be on 8970 and 6470. Maybe i can reach 4X1RF and TF3HZ on the
46km band :-) This is one of my goals :-)
Furthermore i will try to borrow the 4 kVA generator. This would allow
an antenna current of nearly 3A and a ERP of 500mW. Compensating QRN by QRO!

73, Stefan/DK7FC

Re: DK7FC's 11th VLF kite experiment

Publié : 01 avril 2011, 13:05
par F4DTL
Unfortunately i have to delay my 11th experiment due to bad wind
situations here. Next week i'll run a 1/2 marathon, so maybe in 2 weeks.

BUT: I found that we have 2 generators here at the institute and i can
get both ;-) The small one has 1 kVA and the big one has 4.5 kVA. The
small one is very light weight (about 14 kg) so i will start with that
one in my next experiment. This means about 3 dB more power which
finally allows exceeding 100 mW ERP on 8970 Hz :-)

vy 73, Stefan/DK7FC

Re: DK7FC's 11th VLF kite experiment

Publié : 18 juin 2011, 17:29
par F4DTL
Dear VLF group,

Since more than 4 months the wind and rain situation looks promising for the weekend on my /p QTH in JN49IS36VH. So i plan to do my 11th VLF kite experiment this weekend, either on Sat 18th or Sun 19th June 2011, will be announced on friday. I already announced it at the German air traffic control and just got a phone call were the permission was granted.

The plan is to come on air at about 6 UTC.

The antenna will be the 300m vertical kite antenna. I'll plan to serve the bands 33km and 46km, i.e. 8970 Hz and 6470 Hz. Since i made a new tap on the TX coil i can now resonate the 300m antenna on 6470 Hz too. This should give a about 4 dB stronger signal on 46km.

Since the gap of low QRN is much smaller now, the experiment will not take many hours, maybe just 4 or 5.

Maybe i can get the 4 kVA generator and will produce a 6 dB stronger signal but this is not clear so far. Otherwise i am limited to 550 W TX power. I will limit my antenna current to 2 A in order to prevent a HV breakdown on the coil and due to thermal losses. At 2 A antenna current i should have up to 250 mW ERP!

The program is to start a longer dash, about 40 minutes, GPS locked on 8970.00000 Hz, then a message in DFCW-600. Depending on the feedback of receiving stations i will try to send DFCW-60 or DFCW-10 or DFCW-3 and CW.
Then i'll move to 6470 Hz, transmitting a 40 minutes dash and a "K" in DFCW-600 or so.

As usual the signals will be visible on my grabber in 40 km distance: ... abber.html for 8970 Hz and ... bber2.html for 6470 Hz (spectrogram still not available)

but surely visible on many other grabbers too ( see for a list of available Dreamer Band grabbers).

Some new VLF receivers appeared since my last experiment. Two of them are: (1435 km) (598 km)
Leaving a trace on these and all other new and old VLF stations is the goal! Despite high QRN and the longest days in the year (here in EU) i am optimistic.

Maybe Markus/DF6NM or Marco/DD7PC or someone else in DL wants to be available on the phone for QSP to the reflector?

Looking forward to the weekend and hope all works well and we'll have much activity.

Best 73, Stefan/DK7FC

Re: DK7FC's 11th VLF kite experiment

Publié : 18 juin 2011, 17:30
par F4DTL
Dear VLF group,

Now, the wind forecast shows excellent wind for tomorrow and unstable and poor wind for sunday. So i will do the 11th experiment tomorrow, Saturday, 18. June 2011.

Tnx in advance to Markus/DF6NM who will be available on the phone to make QSP to the LF reflector.

Vy 73, Stefan/DK7FC

Re: DK7FC's 11th VLF kite experiment

Publié : 18 juin 2011, 17:32
par F4DTL
Réception très mouvementée ce matin de DK7FC sur 8970 kHz.
En compagnie de Michel WK et Christian à Soignolles.

Réception avec ma nouvelle antenne active E-probe à 4 m du sol.
Activités en portable interrompue par la pluie et les orages, dommage.

Ci-jointes quelques photos, fallait en vouloir ce matin.

F4DTL Nicolas


Re: DK7FC's 11th VLF kite experiment

Publié : 18 juin 2011, 17:35
par F4DTL




Re: DK7FC's 11th VLF kite experiment

Publié : 19 juin 2011, 11:47
par F4DTL
Hello Nicolas,

Thank you for doing the effort and receive my transmission! Tnx for the report and picture.

You have been the only French VLF RX station in this experiment, so hope you'll stay tuned in the next experiment. Not sure if its due to the season of if the interest in VLF is generally decreasing...

Vy 73, Stefan/DK7FC

Re: DK7FC's 11th VLF kite experiment

Publié : 19 juin 2011, 14:16
par F4DTL
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: ... ations.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


Uploaded with

Re: DK7FC's 11th VLF kite experiment

Publié : 19 juin 2011, 14:27
par F4DTL