Earth-electrode "antenna" damaged?

Suddenly on 630m, the antenna current meter read 0uA. A check on 160m showed high SWR too.  It looks to me like there is damage to the earth-electrode "antenna". Maybe the feed from the far earth may be broken. I shall have to check in the morning.

Earth-electrode "antenna" in ground

As many know, this simple arrangement has given me great success on 1840kHz FT8 and 472kHz WSPR. I am sure a "proper" antenna and ground would be better, but for me, at 2 QTHs, it has worked.

On 160m QRP TX it has allowed me to be copied in North America! Although I used the mains earth at this QTH (you need to check if this is safe with your mains system), I used an external ground at my old QTH with the interconnecting wire on the ground with broadly similar results. My theory is this arrangement acts as a loop in the ground on VLF, LF and MF. At the old QTH I did not need the matching transformer.

Earth-electrode "antennas"

As you may know, I have had great success on VLF to beyond 160m with this structure. DK7FC has used such antennas down to ELF! A copy of my blog, which shows quite a bit about my experiments, is available as a .pdf. I think you have to join this Facebook group first, although the blog is also available here.

These experiments were at the old QTH, although I use this here too on 472kHz and 1.84MHz. At 137kHz it worked pretty well last year here. It has even been used on higher frequencies, although if my "loop" theory is correct it should be far less effective as the frequency is increased.

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.

New post on earth-electrode antenna coming

Although I have some urgent family matters to attend to first, it is my intention to do a new post about my earth-electrode antenna system for LF/MF, which works well for me, but is dead simple. I'll probably do it at the weekend and add photos and diagrams to make things clearer.

Mending my 630m earth-electrode "antenna"

630m transverter

Back in the spring, my brother managed to cut my 630m earth-electrode "antenna" whilst staking a tree for me. I have not got around to repairing it. If the weather is good tomorrow, I might get the extension lead and soldering iron out in the garden and try to mend it. I could use it as an "antenna" or as a ground for my current vertical Marconi (very poor!) to see if it raises the ERP a bit.

I noticed that the coax to my 2m big-wheel (used as a Marconi via an ATU on 630m) is barely 0.5m above the ground for half its length, so I am surprised it radiates anything, especially with just a mains plug earth.

630m ATU

If you want to see 630m on a shoestring, look at this setup! There should be 2 pictures attached showing (1) my transverter and (2) ferrite rod ATU.

Earth-electrode antennas at 472kHz

Some 4 years ago I posted this based on my results at 472kHz:

These were my conclusions in Jan 2013:

1. The earth-electrode antenna at 472kHz (2 earth rods in the soil 15-20m apart fed from the TX output) behaves like an H-field loop transmitting antenna. At the present QTH the spacing is less.
2. It has directivity, with strongest signals in the line of the loop and weakest signals at right angles to it.
3. It works as an effective RX antenna too.
4. In my environment the loop looks like about 50-60 ohms resistive, so a good match to my transverter directly without matching. At this QTH it looks a higher impedance, presumably because the soil and rock are different.
5. The structure works because much of the return current flows deep within the soil and rock beneath the earth-electrode antenna. In my case Rik OR7T calculated that the loop area in the ground is effectively 290m sq with a radiation resistance of 0.017 ohm and a loss resistance of 66 ohms.This is a BIG loop! I think the loop is smaller at this QTH.
6. Performance compared with my 9m high top loaded Marconi antenna averages only around 8dB down, not a bad figure at all, even with the connecting wire on the ground and not elevated at all.
7. Where no other antenna option is available, the earth-electrode antenna is well worth trying both on 472kHz and on 136kHz both for RX and TX. Although it works well here, your geology may be different and results not the same.

472kHz - earth electrode antenna

Since about 1930z I have been using the (short) earth-electrode antenna on 472kHz.  Baseline is at most 15m, probably less and it runs roughly E-W.  On RX I am seeing F5WK (436km) for the first time and reports exchanged (both ways) with G3WCB (101km) seem to be slightly stronger. Semi-local G0LRD (25km) is spotting me at much the same strength.  PA3ABK/2 is similar on the earth-electrode antenna and the Marconi.   I have yet to spot or be spotted by other stations.

I am matching the loop with a tapped 3C90 transformer and a few turns on a 110mm diameter former, although the Q is so low that this coil is probably not necessary. Antenna current is about 0.4 that with the "short" Marconi vertical. It is probably acting as a loop and I have still to try to work out the ERP.  At this QTH, the earth-electrode antenna looks like a higher resistance than at the old QTH, hence the need for a step-up transformer between transverter and "antenna". At some point, when fit again, I want to try a longer baseline earth electrode antenna and a better Marconi vertical. When fit again - oh please!

I suspect the earth-electrode antenna to be directional, so in some directions it may be better and others worse than the Marconi.  I'll leave it running overnight to see how results compare with the very short Marconi. I suspect results will be worse overall on the earth-electrode antenna, but I may be surprised.

472kHz experiments (continued)

As mentioned in an earlier post, for the last few days I have been using the 15m earth-electrode and not the same antenna with the far end as a capacitive connection to ground as used previously.  So far, I have spotted 14 unique stations (best DX DK7FC at 669km) and my own signal has been spotted so far by 10 unique stations (best DX F59706  at 570km) using WSPR.

Overall, my impression is the "proper" earth-electrode antenna is a few dB down, and more directional (?), compared with the similar arrangement but with the capacitive ground connection for the far electrode.

In the coming days I shall extend the baseline and repeat with the capacitive far ground connection. Based on results to date I would expect it to perform quite well, despite what theory might say.

15m earth-electrode

Well, because of my stroke and bad weather, a few days ago was the first chance I had to go into the garden to inspect the far grounded electrode. To my great surprise I discovered  my wire was not connected to the ground rod at all and was as my son had left it last September - the wire was just connected to  a rolled up piece of coax laying on the ground, in effect a capacitive ground connection: that was why I needed series inductance then! The feed wire is about 1.5m off the ground along a fence. Since the start of the weekend I have been using the far end grounded (as I thought it was originally) to the ground stake. Impedance is still very high (around 200-300 ohms) but I no longer need the series inductance. As for results, it seems perhaps more directional and (maybe) a few dB down on the  previous (unintentional) arrangement. Whether the antenna was working as an NVIS wire is not clear but at the old QTH running the wire back through the grass made little or no difference to performance of the earth-electrode antenna, confirming the " loop in the ground" behaviour at MF/LF.  I may next try extending the poorly grounded wire further along the fence top to compare performance. The maximum run possible is about 30-35m.

160m on 15m earth-electrode "antenna"

I have just started WSPR on 160m with the 15m baseline earth-electrode system, matching the "antenna"  with just the Z817 auto-ATU. First TX burst resulted in 5 spots in 5 countries and best DX 633km. The system will run through the night and I'll report on results more fully tomorrow.

474.2kHz TX - soon again, I hope

Up to now this winter I have confined my MF activity to receive only as I have had no suitable system of antennas for TX. Andrew G6ALB is ordering me some earth rods, so I hope to put in place a better earth-electrode "antenna" for 474.2kHz TX soon, possibly with Andrew's help. My recent stroke more or less put a stop to ladder, antenna and earth-electrode work sadly. I am improving but have a way to go still yet. I have managed to prune a few roses, but just this exhausted me! A visitor today (for 45 mins only) left me breathless.

It will be interesting to see how a longer baseline earth-electrode system works at the new QTH on MF   I had great success with the 20m baseline system at the old QTH in earlier years and the new one SHOULD be longer.  It will also be interesting to compare performance on LF and VLF. A lot depends on buried pipes and cables. The position of the new earth rods should be optimal in the space I have.