Earth-electrode "antenna" in the ground

Let me say from the outset that I have no firm conclusions on how this works, but work it definitely does.

My theory is that it forms a loop in the ground, so the effective loop area increases as the frequency is lowered. If the spacing between the electrodes is increased the effective loop increases in diameter. This structure has been used (by others) for amateur radiated tests at extremely low frequencies. In my case it has proved effective with QRP up to 60m. On 630m WSPR it has proved very effective with reports from Finland with low mW ERP. It is almost invisible, with the XYL and neighbours not even aware it is there! 

If the loop theory is correct a low impedance is needed as the electrodes enter the ground, but a high impedance between the electrodes so the effective loop diameter is large.

At present, I am using a mains earth (please check your mains earth is suitable) at one end, but tests at the old QTH showed that using 2 electrodes in the ground worked just as effectively.

Before anyone says that it is the wire back from the far electrode that is doing all the radiating, I tried putting the return wire on the ground with very little difference in performance.

See https://sites.google.com/view/g3xbm4/home/antennas/earth-electrode-antennas .

Matching the earth-electrode antenna in the ground

To allow the auto ATU in the FT-710 to match the earth-electrode antenna on 80m (see the excellent results yesterday) I had to use this transformer.  As you can see, it is not pretty!!  With it, the load presented to the FT-710 was obviously less than 3:1 as it matched well.

Monday plans

My main aim today is to match my earth-electrode "antenna" on MF. I I can do this, I can try it on FT8 or WSPR TX on 160m or 80m.

Later, I may try 10m QRP FT8 again with the QDX, although it does not teach me much - I know less than 5W of FT8 can get spotted across the planet. All these stations could be worked, but I do not have the energy to chase these!

UPDATE 1021z: After adding more turns to the primary of my 3C90 transformer I can get a perfect match on 160m and 80m with my earth electrode "antenna" with the auto-ATU in the FT-710. I shall try 160m WSPR or FT8 tonight!

Earth-electrode "antenna"

My earth-electrode "antenna" has been reinstalled. 

Much to my surprise I am unable to tune it using the internal auto-ATU suggesting the impedance is greater than 150 ohms. 

I shall have to try a new matching transformer to bring it in range of my auto-ATU. This make take a few goes. I want a good match at MF.

Earth-electrode "antenna"

This has been used for many years from VLF-60m with great success. After cutting back some bushes, I want to replace this and try it on 630m, 160m and 80m. Although theories vary, I think it acts as a loop in the ground at MF. It certainly works remarkably well.

Most of the path is in the ground with just the return wire from the far electrode along the fence. Tests with the return wire on the ground at 630m made little difference, so most of the radiation is from the loop in the ground. 

If my theory is correct, the effective loop diameter gets bigger as you move LF. At 2200m it should be even better!

160m FT8

As an experiment I tried my earth-electrode "antenna" in the ground on 160m FT8. The match is very good and with QRP I have been spotted all over Europe and I've spotted plenty of stations in South America and North America. If anyone tells you that they have no 160m antenna don't believe them! My 160m antenna is invisible to the neighbours and XYL. 

See https://sites.google.com/view/g3xbm4/home/other-amateur-radio/160m-ft8 .

472kHz WSPR RX

This evening I am on the earth-electrode "antenna" in the ground. It is now 0755z and I have been on for about 15 minutes, but nothing yet spotted.

UPDATE 21020z: So far, just DC0DX (467km) spotted several times At the moment he was the same strength (roughly) as on the active loop. Does this mean they are similar in gain?

Earth-electrode "antenna" replaced

Yesterday, I replaced the wire that I used successfully on 472kHz WSPR TX with a very low ERP. 

It was also used successfully on 160m and 80m.

As yet, it has still to be tested. 

UPDATE 0940z:  Tested on 160m and 80m.  Still high VSWR. Totally puzzled.

UPDATE 1538z: I cleaned the contacts at the far end and the VSWR remained high on 80m. With the auto ATU it matches on 160m. I have not tried 630m, which needs the transverter. My conclusion is that over the years tree roots have grown and effectively shorted out across the "loop" in the ground rendering this "antenna" no longer useful. I may try 160m WSPR or FT8 tonight, but may remove it tomorrow.

Snap!

Yesterday I reported that my earth-electrode "antenna" in the ground suddenly stopped working. An inspection this morning revealed the issue: my wire had snapped.

I did an emergency repair and the SWR on 160m was back to normal. Sadly the output on 630m was still zero suggesting the output FET has been damaged. Until this can be repaired I shall have to restrict myself to RX only on this band.

Earth-electrode "antenna" in the ground

For some years now I have used this antenna system successfully on the VLF, LF and MF bands. It certainly works and has worked as high as 60m, although this high I am unsure how much is the "loop in the ground" and how much is from the wire just above the ground. If you don't have space for a big antenna and earth on 160m, 630m or 2200m, you might want to give this a try.

See https://sites.google.com/site/g3xbmqrp3/antennas/earth-electrode-antennas