VLF 8.2KHz Dreamers Band

I recently returned to doing some VLF monitoring. DK7FC has been improving his loading coils on his fixed TX antenna and testing on 2.7KHz. I tried receiving his test to no avail although he was received in Cumnia North Italy by IK1QFK 3 wavelengths distant, another Amateur Radio first ! The UK at 5 wavelengths seems to be impossible at the power levels available.

Attention was focussed back on 8.2KHz. I had never seen DK7FC on his fixed antenna. I improved my chances by using 1PPS GPS to Calibrate my soundcard. My first line resulted even copyable in 424uHz FFT.

dk7fc_8.2khz_424uhz.jpg

DK7FC was also testing Data messages using EbNaut and RN3AUS managed to get a 2 symbol decode, yet another first, data at 0ver 900kM distance, this was also received by SQ5BPF and of course Paul Nicholson. By the time I got the necessary set up initialised the outrageous step of attempting a 7 symbol message was the next step.

Next morning my first file was ready to attempt a decode (I had practiced on the files from RN3AUS but this was at another level), I concentrated my attention on decoder, in just 7 Seconds, flash, the 7 symbol message :-

DREAMER

I was expecting a dry radio identity, what an apropriate word DK7FC had chosed for the first real text message on the band where we are “all dreamers who will never get a signal further than our own garden fence”.

RN3AUS also copied the message as well, as did Paul, there has been no news of a decode from SQ5BPF yet and apart from DF6NM who was transmitting at the same time, so not receiving, that is the full complement of those able to receive and decode EbNaut at the present time.

Oh yes ! In the excitement of the 7 symbol decode I had almost forgotten DF6NM was also transmitting EbNaut on 8.27KHz and I had my file. Was there any chance that I could decode his 2 symbol message, considering the greater distance, over 900kM and the fact that I have never detected his signal on my spectogram. Well we are out to attempt the impossible, we are Dreamers, so I went ahead. This time in 9 Seconds came the decode, an ident, NM.

ebnaut_df6nm

What else can be achieved at VLF using what is after all QRP, what more firsts, DK7FC said of TX’ing on 2.7kHz “it is like walking on the moon”. No no, that has been done several times before.

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ZEVS 82Hz is Off Air

Someone the other side of the world asked on a group if the ZEVS 82Hz transmission was still active, thinking there would be a flood of replies I left it to the others. After a couple of days it seemed everyone else was doing the same, so I fired up my VLF set up and took a look, a carrier of the usual strength was there. Its operational I replied.

There were some queries, ZEVS shows on G3ZJO’s Grabber from June 2016 but not elsewhere. I looked again live there was the line, on frequency. I then thought back to June 2016 when the Capture was left on screen. I went over to Windows7 at that time because K1JT’s latest WSJTX was not just crashing and failing to upload but locking up XP totally every time it was shut down. Naturally I did a test of the VLF set up on Win7 all looked normal. The Grabber screen had recorded the results.

This is what the capture looks like now (no carrier at 82Hz)

zevs_off

I investigated the line at 82Hz it was so convincing as the ZEVS carrier it showed changes as if from propagation, but there was no usual DATA ever, there were tones of several seconds length at times which I suspected coud be a new keying scheme. I went back to Windows XP the phantom ZEVS was not present.

So it seems my sound card when used on Win7 produces a weak carrier, where, bang on 82Hz. Cunningly produced to mislead the world.

From some research it seems that although there are Win7 drivers for the Delta44 sound card it will never perform correctly on Win7 and up. Increasingly software won’t work on XP anymore, so another expensive piece of kit bites the dust.

QRP Power Measurement

First a realisation. The other day I moaned about the Media elsewhere.
You know, how if you know anything about the subject being discussed it is often riddled with errors.
I have been aware of this for years so why did I get caught out by a 2004 Shortwave Magazine article about QRP power measurement.

The piece described an adapter, two SO239 sockets with 50 Ohm resistive load, diode and capacitor. It gave the formula for deriving Power from Voltage across 50 Ohms, this is the method used for any Practical Wireless QRP contests, it read.
There was also a chart of Voltage and Power from 250 mW up to 20 Watts.

I accepted the article without any further thought, why oh why did I cut that page out and put it in a folder for future reference. Bah #!#!

Only when I saw a power measurement from voltage by G0UPL with my figures fresh in my mind did I puzzle over how there was such a vast difference, not explained by the Oscilloscope Peak to Peak value from G0UPL and mine derived from Rectified Peak value.

That article gives correct values of RMS Power in the chart. Use the formula given and you end up with Peak Power. There is no mention of the published circuit reading Peak value and no mention of RMS.

For each MEPT I have built I used that SWM page for reference, for QRP tests the same, my 10mW is really 5mW by everyone else’s standard.

G3ZJO you should have known better.