UPDATE November 15th 2020
In the last few months I have not updated these pages. I am sorry. There is a new "release candidate" version of WSJT-X that may have application at VLF.
See https://physics.princeton.edu/pulsar/k1jt/wsjtx-doc/wsjtx-main-2.3.0-rc1_en.html
UPDATE July 9th 2020
News of the first Hellschreiber 8.27kHz QSO between G3WCB and G4IUG over 1km has been received.
"First 8.270Khz Ground/Earth Antenna Hellschreiber Contact ?
Dave John G3WCB and Dave Cawley G4IUG made a contact using the 100 year old modulation method Hellschreiber on 8.270Khz using ground antennas.
The transmitting equipment used by G3WCB is a QRP Labs “Ultimate 2” beacon transmitter running in “Slow Hell” mode. The output from the U2 is divided by 100 and drives a 30W audio amplifier through a 8.27 kHz low pass filter. The earth antenna consists of two 1-metre copper earth spikes separated by 20 metres and fed by a 6:1 balun wound on a ferrite toroid core. The antenna current is 150 mA, which equates to about 12W going into the ground.
The reception equipment used at G4IUG was two 1.2M copper coated earth spikes separated by 25 metres and fed by balanced and screened audio cable into the workshop. A 1:1 600 ohm balanced to unbalanced isolating transformer with an interwinding earth screen fed into a high Q resonant and capacitively tapped inductor stepup. The into a 2SK170 audio JFET. An elderly RME DIGI 96/8 PAD professional sound card was pressed into use running into Spectran software by Alberto I2PHD. Test gear included a Agilent 33220A Function Generator and Keysight DSO-X 2004 scope. Initial testing was with audioTester by Ulrich Müller with encouragement and inspiration from Roger Lapthorn G3XBM.
The distance between the G3WCB transmitting location and the G4IUG receiving location is about 1km and now that we have proof of concept the challenge it to get further, much further !"
UPDATE May 15th 2020
Jean Marie Polard F5VLB is doing some tests with his earth-electrode antenna on 8.27kHz from Brittany. Although Tom DK1IS is looking on a German grabber, he has, so far, failed to detect him.
A reminder that the Yahoo sub-9kHz group has moved to groups.io .
See https://groups.io/g/sub9khz
If I miss items always check out https://groups.io/g/rsgb-lf-group/topics for sub-9kHz tests.
How good is your German? You may like to see this video