Earth-electrode antenna for 472kHz in the new garden - not too brilliant

After trying a number of different orientations of earth-electrode pairs in my garden, I have come to the conclusion that this antenna structure does not work very well here in the new QTH. I am a little surprised as the earth-electrode antenna worked well just 350m away at the old QTH. Whatever orientation I try I seem to be always in the -22 to -28dB S/N region with G6AVK 78km away.

Why is it not so good? Well, the most likely answer is that the effective distance between the far and near ground rod electrodes is smaller, even with a similar physical separation. This could be because of buried water pipes and utilities criss-crossing the garden, although I wasn't aware of any, or different soil/rock conditions, although the chalk layer is about as far down here as at the old QTH and the soil is a similar alkaline sort. The fact that the 8.97kHz earth-mode results were so poor last week rather hinted at a problem that was not present at the old QTH.
 
I haven't quite exhausted every layout possible in  my strange shaped back garden, so there are more things to try with earth-electrodes, but it is looking like I shall have to erect a short Marconi or a fully in the air loop antenna to get better ERP on 472kHz. On my previous tests at the old QTH, a full in the air loop with 1mm diameter wire and an enclosed area of around 80m sq was around 8dB better than the earth-electrode antenna, but far more critical to tune and match because of the hi-Q. If my earth-electrode antenna is several dB down on the performance of the same structure at the old QTH then I could be expecting >10dB improvement or even more.

Half the fun is the testing and finding out what does and does not work.  The coming week we have visitors staying, so not too much time to experiment. I shall have to stick to WSPRing on 20 and 10m.

Portuguese Lesser Chirpy 10m transceiver

CT5JZX version of the Lesser Chirpy transceiver for 10m CW

In an email from CT5JZX, Pedro tells me he has made a version of my Lesser Chirpy 10m QRP CW transceiver. He has already received some beacons with it - he only has a crystal in the beacon part of the band at present - and hopes to TX with it soon when he has some other crystals. He has made a neat job of it in the plastic casing.

It is some time since I fired mine up and currently it is in a box in the loft after my recent QTH move.

VK on 20m WSPR this morning

5 VK (Australian) spots in the very first transmission slot

Whilst waiting for the bathwater to fill, I went on 20m WSPR this morning with the Par 40/20/10 end-fed antenna to see what was about. To my amazement I got no less than 4 VK reports (Australia) in the first transmission plus a lot of other reports too. The little antenna down the garden is certainly working just fine.

2m contest this weekend

After several PSK31 QSOs on 20m, I returned to 2m SSB to see what was doing in the contest running this weekend. First impressions are there are far fewer stations active than last Tuesday evening in the UKAC contest. I have worked a few stations using 5W and the halo but so far only JO01, JO02 and IO92 squares i.e. not that far away.

.....me thinks it is time to QSY to 472kHz WSPR and watch the TV, HI.

First PSK31 QSO from new QTH

E74DO in his shack

After a little while on WSPR I decided to try PSK31 on 20m running 2W to the Par antenna. I replied to a CQ from E74DO and got a 599 report. PSK31 is not a mode I too much like, but it does work when the band is busy and with QRP.

A little later (1646z) I had a nice PSK31 QSO with Svan TF3FIN in Reykavik on 20m.

HF antenna erected at new QTH

This afternoon, I strung out my Par 40/20/10 horizontal end-fed HF antenna for 40, 20 and 10m from the base of my V2000 vertical to a tall branch of the silver birch tree at the end of my garden. Being a bungalow, the height is nothing great at around 4m above ground average. Match is excellent on 10m and 20m but the end wants trimming a few cm to improve the match on 40m.

I have just started WSPR beaconing at 1W on 20m to see how it performs and on the first transmission was spotted by N6RFM, LA6TPA, LA9JO and 4X1RF with reasonable reports. So, initial results look OK.

This now means I have the following TX capability from the new QTH:

(1) 630m - earth-electrode antenna
(2) 40, 20 and 10m HF - Par 40/20/10 antenna
(3) 6, 2 and 70cm - VHF/UHF V2000 vertical
(4) 2m - horizontal halo antenna
(5) 481THz optical - 110mm lens TX

All these antennas are unobtrusive and neighbour friendly. Now let me see how soon I can achieve QRP DXCC from this new QTH.

Experimenting will mean these antennas will come and go.

472kHz - next steps

Ok, so after several more hours I am still getting WSPR spots from just G4KPX and G6AVK. Clearly the ERP with the present earth-electrode set-up in the new garden is in the low uW region only.

I'm going to try to string up a full wire loop for TX and see how this performs. I have a couple of options: (1) a thickish wire loop along the fence made from coax cable about 10m x 2m, or (2) a 1mm diameter PVC coated wire loop with a larger enclosed area. The former would be totally hidden and, because of the higher Q, may perform as well as the larger loop with thinner wire. The former is worth trying as it would be a very "stealth" antenna, totally invisible to neighbours ....and the XYL.

472kHz experiments continued

In my narrower, but wider, garden, I am still trying to work out the best layout for an earth-electrode antenna for 472kHz.

Today I started by trying to find out about the ground connections at the house end, measuring the resistance between various radiators and the mains ground to see which ones had a direct copper connection to a good ground. The answer is none! All the radiators seem to be connected with plastic pipes in the roof. The only direct "copper to ground" connections found in my water system were in the airing cupboard, the kitchen taps and the utility room taps.

The other tests (ongoing) are to a different remote ground further up the side of the garden, further from the shack but not further from the house. I am trying to see if this gives, effectively, a longer earth-electrode baseline between ground points.

So far this evening, with the (perhaps) slightly longer baseline, I am getting consistent reports from G6AVK (78km) but no-one else yet. As best I can judge, reports are very similar to those with the earlier grounding arrangements.  PA3ABK is a very strong signal at -6dB S/N.

First 8.976kHz VLF earth-mode tests from the new QTH

This evening, I did a couple of tests on 8.976kHz earth-mode from the new QTH with my 5W beacon TX. Initially I used the far earth rod about 12m from the house paired with a mains ground and set out on my travels with my loop to my usual first test site just outside the village. This is a car park for the Devil's Dyke walk. Unfortunately the car park has been invaded by gypsies, so I decided to move on to my next test site in the village of Reach (2km). Nothing at all was copied of my beacon.

Then I returned home and used the mysterious copper rod that goes into the ground just outside my shack as the local ground and still keeping the ground rod 12m away as the "far" electrode. I think this may have at one time been an oil pipe from a central heating oil tank. I have no idea where it goes. This earth-electrode pair has launched my 472kHz WSPR signal which has been copied in Belgium and Holland, but results have been disappointing, so I was not expecting much on 8.976kHz.

Rather than travel 2km, I parked outside my old QTH about 0.35km away in the village. My 8.976kHz signals were copied, but not very strongly. I suspect that this was true earth-mode without any real assistance from utilities as I do not believe either ground rod at the TX end is coupled to utilities grounds or copper pipes going into the road.

Weak signals over a 0.35km path

Path tested this evening plotted with Google Earth

Conclusions so far are that both for VLF earth-mode work and for 472 and 136kHz radiated work I need to much improve the earth-electrode arrangement in my garden to get credible results. I need to do some sort of mapping of the garden to see where would result in a good solid connection to copper water pipes going into the road (probably at the outside copper tap) and the best place to locate the "far" electrode as far away from the house (and other houses) and buried pipes as possible.

Loop preamp

After some thought I'm almost certain now to buy a Wellbrook RX loop for use on 136 and 472kHz receive. This loop will also be useful for a number of other applications such as 160m and 80m monitoring and possibly some VLF work.

The ALA1530LF looks perfect for the task being able to cover 20kHz to 30MHz with excellent IP2 and IP3 performance. One concern is that a receiver is being hit with signals from right across the spectrum: although the loop preamp itself will not fall over, the receiver after it might. So, I think a small, high dynamic range tuned preamp with a few dB of gain may be needed ahead of the receiver.  The additional gain may be needed as many HF rigs have poor LF and VLF sensitivity.

A simple preamp is easy to design for either 136 and 472kHz bands. Something along these lines (see below) should be suitable for 472kHz reception. I'm not actually sure that the ceramic filter will be needed: just the single hi-Q tuned circuit on the input may be enough to protect the subsequent RX from being blasted with everything.