Until our son accidentally cut it, I used this antenna extensively from VLF to 60m. On 630m (472 kHz) it consistently got reports from Norway with a measured ERP of just 10mW using WSPR.
My theory is that at low frequencies it acts as a loop in the ground. As you go higher in frequency the loop gets smaller, so the antenna gets worse.
If my theory is correct, the loop will get larger as frequency is lowered making it very effective for sub-10 kHz communications. Indeed, such an antenna has been used to great effect by DK2FC and others at VLF.
For use on LF and MF it has worked well for me.
See https://sites.google.com/view/g3xbm4/home/antennas/earth-electrode-antennas .
Did you find that the same turns ratio on the toroid would work equally well on all the lower bands - in particular 472kHz and 1.8MHz?
ReplyDeleteI have very limited space for antennas, so the earth electrode approach might be worth investigating.
Regards,
Keith G0RQQ
Hi Keith - The transformer was the same at 472 kHz and 1.8 MHz as I recall, although I did not optimise it for 1.8 MHz or higher. I seem to recall also trying it directly connected to the FT991A and using the auto ATU. The WSPR and JT65 tests would have been with the FT817ND.
ReplyDeleteAt the old QTH I managed some international QSOs on 472 kHz JT9, although this would have been without the transformer, but still with the earth-electrode "antenna" in the ground.
ReplyDelete