472kHz earth electrode antenna: nothing in the air

Today, I took my experiments with an earth electrode TX antenna for 472kHz to new levels by placing the connecting wires on the grass i.e. not elevated at all.  The theory developing is that the earth electrode antenna works by forming a buried loop in the ground with the earth return path being in the soil and rock beneath the structure. If this is so, then even with the wire sitting on the grass there should still be a loop within the ground, so some radiation from it. Results this afternoon prove this is indeed the case. The following are the results with a 20m baseline between the far earth rod and the copper pipe ground at the home end and with the connecting wire just laying on the grass lawn.

472kHz WSPR reports with earth electrode antenna with wire on the lawn

TS990 Press Release

The new TS990 from Kenwood

Readers here will know I'm not a great fan of expensive transceivers: I cannot see the point of spending huge amounts of money on what is, after all, meant to be just a hobby. On top of the expensive transceiver some people go out and spend a fortune on towers, linears, big beams and other expensive accessories. Each to their own: although not my choice it is not for me to say how others spend their hard earned wages.

I see today that the modern cashbook amateur has a new toy to covet: the TS990 from Kenwood. With a price tag likely to be around £9000 it has to be SOME radio. Looking at the spec it does look very impressive. See http://www2.jvckenwood.com/en/news/2013/20130108.html .

Just one slot of WSPR - 15 reports on 472kHz!

Reports in just one 2 minute WSPR time slot with 100mW ERP on 472kHz

With the improved performance from a 9m long Marconi antenna on 472kHz, these were the reports I just got in one single time slot just now. 15 unique stations reported me! It is too easy, even with just 100mW ERP.

How far down is my 472kHz earth electrode antenna on a Marconi?

This evening I have been noting my WSPR S/N reports from stations across the country and nearer Europe using my 9m long Marconi antenna and comparing these with the reports last night when I was using just the 15m baseline earth-electrode "antenna". I crudely plotted the "improvement factor" in dB on a polar plot. Each dot represents a station reporting my signal with the dB improvement over the earth-electrode antenna plotted on a 0-20dB scale out from the centre.

Although in some directions the difference is very little, in other directions the reports are up to 14dB better on the (omni-directional) Marconi.

Stations with dB improvement using the Marconi antenna

M0BMU 10dB
G0KTN 6dB
G3ZJO 5dB
G3WCB 10dB
DL-SWL 2dB
G4HJW 6dB
M1GEO 14dB
G7NKS 6dB
M0LMH 11dB
G0MQW 10dB
G0MQW 10dB

My conclusion is that the earth electrode antenna is behaving somewhat like a loop with directionality along the line of the earth-electrode baseline and a null off the sides. With stations receiving me off the sides there is most improvement with the Marconi, and less difference with stations end-on who were getting a reasonable signal with the earth-electrode antenna.

CONCLUSION: the simple, stealth, earth-electrode antenna is a VERY useful antenna on 472kHz as long as one is prepared to accept a 2-14dB loss compared with a reasonable Marconi.

RFID chips and credit/debit cards

Many credit and debit cards now have embedded RFID chips to allow contactless transactions in cafes. bars etc. Did you realise that your card's RFID chip could be a way of cloning your card's number and expiry date? Neither did I.

Watch this video to see a demonstration of just how easy it can be to someone with the right technology at his disposal.Sounds like a security loop hole that needs fixing fast.

UPDATE: I am reliably informed that this is not an issue in the UK.

A Marconi antenna on 472kHz

So that I can better quantify the performance of my various earth electrode "antennas" I have today erected a 9m long top loaded Marconi vertical for 472kHz. Initial antenna current measurements suggest the ERP is up around 10dB to around 100mW. My plan is to run this overnight again and then tomorrow compare the signal reports against those with my smaller compromise Marconi and my two earth electrode antenna configurations.

Even more fascinating 472kHz experiment

Following on from yesterday's tests, today I started a further test using an earth electrode "antenna" on 472kHz WSPR.

This time I used 2 ground rods in the soil separated by 15m of wire (fed directly from the transverter output at 50 ohms) and powered entirely from a battery supply - PC, FT817, transverter, SignaLink interface - so that there was no connection whatsoever to the house mains earth or copper pipes in the house. The power out would have been slightly lower (lower supply voltage) and the baseline 25% shorter.

472kHz earth electrode "antenna" system in garden

So far, results are almost identical to those obtained yesterday when one side of the earth electrode system was connected to the copper pipes in the home on one end.

My best DX WSPR report this evening with 10W RF out from the transverter into the 15m separated electrodes is G0KTN at 210km. ERP is in the low mW region at best. On RX DJ8WX has been copied at 643km.

Although a large Marconi antenna will be far better, this set-up certainly works and gives highly credible results. Considering just how simple this is I hope others experiment with the earth electrode "non antenna" and see how they get on.

UPDATE: Best DX report of my few mW ERP signal with 15m spaced earth electrodes was from DL-SWL at 701km. I am copying lots of signals including SM6DHZ and DK7FC even after breakfast time. Amazing.

Analysis of 472kHz antenna tests today

With several hundred WSPR spots of my QRP signal received today on 472kHz, I have tried to do a crude analysis of the difference in performance between my short (1/100 wavelength long) Marconi and my earth electrode (ground) antenna. I did this using MS Excel. Now I have forgotten most of the things I knew about Excel, so this is basic stuff here!

I plotted the maximum and minimum signal reports for each type of antenna for a number of different reporting stations and plotted a graph showing the difference and the angle the station is from me to see if there was a clear directionality in the earth electrode system.

Analysis of signal levels with short Marconi and Earth Electrode antenna at 472kHz

Conclusion? I'm not sure, although the difference between the 2 antennas varies from as little as 0.5dB (PA3ABK) up to 16dB (M1GEO) with an average additional loss of around 7dB. Can you see any indication of directivity in the earth electrode antenna? I am assuming the Marconi is omni-directional, which of course may not be the case.

Not bad for an antenna that is invisible to the neighbours and still is capable of getting reports (so far) to 701km away with a few milliwatts ERP.

Codar AT5 transmitter

Image on G3XTZ's Radio Museum website

Way back when I was first licenced for VHF/UHF only in early 1967 as G8AWG, I used to operate under supervision at the HF station of Bill Honeywill G4PJ in Salcombe on 160 and 80m. Bill Had an old KW Viceroy TX and a Codar AT5, which was "state of the art" in its day.

The AT5 was a small valve TX producing around 10W on 160m and 80m. Using the AT5 we could work right up the English Channel in daylight on AM and CW over a mostly sea path.  I noticed a page about the AT5 on the W3EEE website and it took me back 45 years.

Image on G3XTZ's Radio Museum website

There was a companion RX called the T28 which I owned at one time - I got it as a university prize for writing one of the better final year theses - which was made using a couple of Mullard modules. The T28 was nothing special, but did make a useful tunable IF for my 2m converter used to copy signals from Oscar 6 and Oscar 7 amateur satellites.

Nowadays in a volume less than half that of these rigs one can have a complete multi-mode HF-VHF-UHF transceiver with performance far exceeding the AT5 and T28. We forget how much our hobby has changed.

Earth electrode TX/RX antenna at 472kHz

Signals received on 472kHz WSPR using the earth electrode "antenna"

This afternoon I've been experimenting with my 20m spaced earth electrode system (used at 8.97kHz VLF), but this time on 472kHz WSPR. One electrode is an earth rod at the bottom of the garden and the other is a connection to the copper pipes in the home. Although I need to analyse results more carefully after an overnight run, the system certainly works with spots of my TX already received across England and from Holland. G4HJW 9km away is as nearly strong on the earth electrode system as on my vertical Marconi.

UPDATE 1715gmt: just been spotted by DL-SWL at 701km!!!

I honestly do not understand why this system - with wire no higher than 1.5m in the air running along the fence between the earth rods - works as well as it does. This is a short video showing the system in operation.

The ERP with the earth electrode system cannot be more than around 5mW which makes the performance all the more remarkable.

Some of the TX reports this afternoon with the 472kHz earth electrode system