I had no idea what to expect, so the first experiment was not publicly announced. Dale, VK1DSH, was monitoring the frequency and we had communications via the Mt Ginini repeater on VHF. I drove to my block of land near Murrumateman QTH locator QF44nx (22 km from VK1DSH) and set up my MEPT to a couple of electrodes (galvanized rods, 1 m long) about 27 m apart. The MEPT is configured to send QRSS3 but I can force it to transmit a continuous signal.
The electrodes were connected with crocodile clips and insulated cables to the impedance matching transformer.
The "antenna" seemed to be behaving as a mostly resistive load, confirming the previous experiments done in the UK. The impedance matching transformer showed an impedance in the neighbourhood of 500 Ohm. The antenna current was measured and it was 200 mA, confirming the 500 Ohm impedance. What is displayed in the scope in the photo below is the current and voltage through a "Scopematch". They are almost at 0 degrees difference, which is what one should expect from a resistive load.
To my surprise, Dale reported that the signal is clearly visible!
I decided to change to a longer base, this time about 100 m. The impedance transformer did not indicate any major change in the impedance of the "antenna" but Dale reported an impoved S/N. The fuzzy bit at the start of the QRSS3 transmission is normal Morse code ID, which Dale reported as being almost copyable by ear!
My signals were captured also by my own grabber which was setup for QRSS90/QRSS120. Of course, the oscillator used in this MEPT is not suitable for that mode, so the picture doesn't look all that pretty :-)
The activity was also captured by Ian, VK1IS through his grabber. Ian is in QF44mp which is about 35 km away, which is the best DX achieved on the day.
So, where to from here? I think I can improve the electrode setup. I can experiment with different electrode distances, and maybe different electrode dipole orientations. A more stable oscillator will be required for QRSS30 transmissions which will have a 10 dB gain over QRSS3.
If you find all that interesting, I recommend to visit the links in the top of this page.
Go back to the main earth antenna page.
Dimitris Tsifakis, VK1SV