VLF: Success with my new Ground Antenna on Dreamer's Band

[Horst Stöcker <horst.stoecker@web.de>]

Hello,
the 800m Ground Antenna Test is still a future project - transmissions planned on 23. to 25. July from the Erpeler Ley near Bonn.
But today I did the second Ground Antenna Test at my home QTH. Two copper rods of about 50cm were directed and splitted in the middle of a 100m line. 10m of RG58 connect this point with the equipment in my garage: torroid stepup transformer, 300 W car amplifier and my new communication test system as sweep oscillator betwen 8,7 an 8,9 kHz.
After my disappointing first test with the 30m base I di not expect too mauch. But the signal was audible in a range of 600m depending on the environment.
Horst DO1KHS/DI2AN

---

Von: mal hamilton <g3kevmal@talktalk.net>
Gesendet: 05.06.2010 17:16:12
An: rsgb_lf_group@blacksheep.org
Betreff: Re: VLF: Two-Way QSO on Dreamer's Band

Gary

What sort of strength are u receiving the Alpha signals

This might give u an idea how strong amateur signals are likely to be by comparison

There is not much information available from UK stations about their receiving capability

de mal/g3kev

 

 

----- Original Message -----

From: Gary - G4WGT

To: rsgb_lf_group@blacksheep.org

Sent: Saturday, June 05, 2010 2:20 PM

Subject: Re: VLF: Two-Way QSO on Dreamer's Band

Marcus, Walter, LF,

Well done for your VLF 8.97 Hz 2 - way communication.

Keep up the good work.

Monitoring most of the time here but nothing seen as yet, one day I may see something.

73

Gary - G4WGT - North West England - IO83QO

On 4 June 2010 21:59, Markus Vester <markusvester@aol.com> wrote:

Dear LF,

 

this morning, June 4th between 6 and 8 UT, Walter (DJ2LF) and myself (DF6NM) were able to successfully conduct a two-way contact (aka "QSO") on 8.97 kHz. The distance between us is 20.2 km, well outside the reactive near field zone (lamda / 2pi = 5.3 km).

 

Both of us were using our small backyard Marconi antennas at home, for transmit and receive. Walter's antenna has 260 pF at an estimated effective height of about 5 m. He achieved about 370 mA current, resulting in a radiated power of about 5 uW (EMRP). I also got 5 uW from 270 mA into 240 pF at about 7 m. I resonated the antenna using the same little "yoghurt coil" described a while ago, having 1.3 henry from 9 x 480 turns of 0.2 mm magnet wire, and a room-temperature DC resistance of 820 ohms. Walter used a scaled up version of this coil, about 25 cm diameter and 60 cm long, consisting of seven polypropylene household buckets inserted into one another. Each bucket has 460 turns of 0.4 mm wire on it, about 320 ohms total DC resistance. Each of us applied approximately 100 W of "RF" power from a car-HiFi amplifier.

 

Reception was done by soundcard, without preamplification. We set Spectrum Lab to 0.95 mHz FFT bandwidth, with noise blanking on, and samplerate tracking based on the German 23.4 kHz MSK signal. We chose to transmit 30 minute dashes, separated by 15 minute quiet intervals to allow for FFT processing delay.

 

We employed a special "micro-QSO" format, which was designed to exchange the minimum single-bit report and confirmation in only three turnovers, each containing a single dash. Station identification was by frequency alone, with preassigned pairs (8969.92 / 8970.02 Hz for DJ2LF, 8970.0 / 8970.1 Hz for DF6NM). Generally the lower frequency was assigned to a negative response (ie. "not confirmed"), whereas the upper one is positive ("received ok").

 

DF6NM started by transmitting a carrier on his lower frequency, from 4:00 to 4:30 UT. This was indeed seen by DJ2LF, who replied on his upper frequency from 4:45 to 5:15, reporting positive reception. Then DF6NM confirmed reception on the upper frequency from 5:30 to 6:00. The whole procedure took two hours.

 

Attached are screenshots from both sides. Unfortunately the QRN level this morning was much worse than we had hoped for, with active thunderstorms in South Italy, Poland and Belorussia. To my surprise, our dashes still made it through and were unambiguously visible, with an estimated SNR of 6 to 8 dB. Walter's signal can actually still be seen between my own dashes on my VLF grabber http://www.mydarc.de/df6nm/vlf/vlfgrabber.htm .

 

As far as we know, this was probably the first two-way amateur QSO on VLF, using truely radiated fields. Another dream came true...

 

Best regards,
Markus (DF6NM)

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