16 Feb 2019

Earth-electrode "antenna" further description

Earth-electrode "antenna" system - click to enlarge
As blog readers will know, over the years I have had great success on VLF earth-mode, LF and MF with a very simple "antenna" that the neighbours and XYL don't even realise is there. Now, if you have space for a real antenna you may well get better results with a proper antenna and ground system. However, if like me, you don't like big antennas this may be an answer, at least with modes like WSPR, JT9 and FT8. Every situation is different. At the old QTH I did not need a matching transformer at all. At your QTH you may need a different turns number or ratio. At 137kHz, 472kHz and 1.84MHz my theory is this forms a loop in the ground. With VLF utilities assisted earth-mode I think it behaves differently.
3C90 step-up transformer
Basically, the far end connects to a ground rod about 1m long in the soil. This is connected to the shack end via a wire (normal hook-up wire) that runs along the garden fence, not far off the ground. At the shack end I connect to the mains ground (please check that this is safe at your QTH as mains earths vary), although at the old QTH I used a separate ground spike (outside the shack) with the wire from the far ground spike run along the ground. Results were almost identical.

At this QTH I use a 3C90 42mm diameter toroid with 2t on the primary (connected to the rig or transverter) and a 20t secondary (connected to the "antenna"). This was empirically wound to give best match and best ERP. I hope the diagram and photo helps. The video was at the old QTH.

3 comments:

Keith said...

Thanks for the info, Richard - I’ll give it a try.
Regards,
Keith G0RQQ

Anonymous said...

You must have a very quiet location Roger. My earth antenna is close to a main road and the noise level on 160m is a terrible ‘roar’ at +20dB S9.
73 Ken G4APB

Unknown said...

Hello Roger,
Much appreciate you updating the information on the Earth Mode Antenna. My supply of
3C90 Toroids is at zero, so need to find a supplier. Located beside the sea here,
I have two well grounded 2 inch poles in the salt marsh,which I might be able to connect
to the system, however the connecting wires would be about 80 metres and 100 metres.
Thank you for a most interesting Blog. Keep up the good work.
Regards Finbar EI0CF Trawbreaga Bay, Malin.