Re: VLF: DK7FC's 6th VLF kite experiment

[Daniele Tincani <danieletincani@yahoo.com>]

 

Great work, Stefan. I again tried to see something from as far as Italy (and from a very noisy environment). So, no real hopes but nevertheless lot of fun and interest in your experiment :-)

Unfortunately I had to setup my "grabber" early in the morning before leaving home, so I had to make a guess about your tx frequency. I choose 6600Hz, ~4mHz FFT. Of course there was less than "no chances" to receive your signal at 6470Hz :-)

May be next time...

Best regards

Daniele

> Dear LF/VLF group,

> Many thanks to all the people who tried to catch may signal in the
> yesterdays test! Thanks for taking the time to watch the QRG on a sunny
> sunday! The RX side is an important factor in such a experiment because it
> motivates the TX side when there is no QSO but just a reception. It makes
> me glad that there is such an interest in those tests.
> Special thanks to Paul Nicholson who did the effort to re-arrange his
> antenna and software and the website with a nice overview.
> Also special thanks to Markus/DF6NM for the telephone support about the
> activity on the reflector, the lightning situation and the QRN situation.
> This is an important feedback as well and much more interesting than just having a mobile internet stick.

> Congratulations to all the successful receiving stations! It was a test
> in the middle of the summer time with heavy QRN. The QRN was on its daily
> maximum as i was able to transmit at a high kite angle. The QRN was even
> high compared to the last days during that time (still comparable in my
> DFCW-6000/8,97 window on the grabber1). So, there is MUCH potential to get
> a much better S/N in the winther period and at better wind situations.
> Thus, i am very hopefully that e.g. Jim and Paul will catch that signal!
> This makes the following experiment an optimistic challenge! I am even
> sure that it will be possible to go down in the DFCW-mode, maybe to
> DFCW-60. This makes it possible to try a cross band QSO (!) like
> 137kHz/6,47 kHz (or 8,97 first). Here i could use a small portable active
> antenna for 137 that will not be too much swayed be the TX antenna...

> As far as i can see there was a positive reception at least by the following stations:
> DF8ZR (QRSS-60 mode, 16km)
> DK7FC (grabber in DFCW-240 mode, 40km)
> DD7PC (congrats, first time! 53km)
> DF6NM (insecure, fragments, 180km)
> DL4YHF(impressive S/N!, 264km) Best DX reception of the lowest signal,
> transmitted by an amateur so far (far field)

> Paul Nicholson told me that he has recorded the siganl and will try to
> work the trace out. Let's be excited about his proffessional and nice to read report!


> Now, i want to give a detailed report of the things that happened on the TX side:

> I arrived at about 9:40 UTC. It was no problem to arrange the equipment
> and nothing was forgotten. Just before, the rain stopped but the wind was a little to weak.
> I used the 8,1m^2 kite but it took some hours until the wind was enough,
> sadly. First, the wind increased just for some minutes. In that time i saw
> that the wire was to long and was sagging to much.

> After cutting some meters i could start the generator and PA and turned
> the VFO wheel down until i saw a peak on the amperemeter. It was on 5,7
> kHz but it was due to a very low kite angle. Later, as the wind increased
> i could do more useful resonating tests. I found that i can resonate
> between about 6,4 kHz to 6,6 kHz. Maybe this is due to the fact that the
> wire has to be slighty longer than 200m since the kite braid is elastic
> and will be 20m (10%) longer at strong wind.
> After watching the 6,5 kHz sector in the last weeks i found that it is
> best to transmit not on n*50 Hz or n*16,6667 Hz (frequency of the german
> trains grid). Thus i decided to go about into the center, to 6470,00 Hz, within the 46 km band!
> First it was not possible to transmit a real "message" since the wind was
> OFF sometimes :-(. My plan was to transmit "CU" in DFCW-600.

> Than, an accident happened: Suddenly the was was off and i wasn't fast
> enough to bring the kite down on the road. So the 200 € kite dropped in a
> 15m high tree! I felt like a child that lost his parents on the airport! I
> was not strong enough to pull it out there with its braid. I saw no other
> way to try it with the car, even when the kite gets damaged with this
> attempt. So i fastened the braid on the car and drove some 10m until there
> was a heavy pull on it. The braid stopped in a beginning corner of a corn
> field and as i lifted it above the corn it sounded like a lash/whip. But
> suddenly the kite came out of the tree and before it dropped on the bottom
> it was caught by the wind and rised into the sky, hanging on my car  I
> drove back the the TX coil with the kite on the car...

> After taking too much sun and after this stress i was powerless and not
> motivated to improve the earth losses and so on but it was my absolute
> goal to produce some nice signals for the RX stations, at least a limple
> carrier! So i set up the whole arrangement and now the wind was stable,
> lifting the kite continously above 45 deg, sometimes 70 deg. In proper
> wind conditions, it is lifted to 70...80 deg.
> The antenna current was about 750mA and after connecting the copper rod i
> hammered into the soil in the 5th experiment it rised to 800mA. Then i
> reduced the primary winding number from 70 to 60. Then, the current was up
> to 920 mA, the highest current so far. Just before 16 UTC the fuel of the
> generator was empty and my fuel as well  That was the end of the 6th experiment.

> So, my overall losses are about 600 Ohm now. The ERP was about 11mW and
> the voltage just about 20 kV rms. I am sure to be able to decrease the
> earth losses to 200 Ohm and the coil losses will be reduced to 200 Ohm as
> well since i can reduce the L to come back to 8,97 kHz.

> Now i know the C of the wire and can make a reasonable tap on the coil,
> at arround 275 mH! So, in the 7th experiment i can transmit on 6,47 kHz as
> well as on 8,97 kHz. I just have to change the coil connection and the VFO
> frequency and that can be done in < 2 minutes.

> I will spend some experiments on this 200m antenna now before going to
> 300m. And i want to test it on 137 kHz  With a 300m antenna, i will
> explore the 58km band in future tests! Also, just for fun,  i want to
> transmit on 7355 Hz. This frequency is a message in it selfe for amateurs 

> So, all in all it was a hard experiment with many difficulties and the
> QRN situation could have been at least 15 dB better but it was an
> important test to find the tap for the L to come back on the Dreamers Band
> (33km) with a 200m vertical. Also we have done some new record receptions
> and can be very hopefully that this can be much improved in the next test,
> if there is proper wind and less QRN that can be assumed when going to the autumn

> Again thanks to all the group and hope cuagn in the next test! 

> Best 73, Stefan/DK7FC

> PS: Some photos and screenshots will be displayed on my QRZ.com page in some days.

> PPS: Hopefully there will come up further stations on the dreamers band within this year