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.

Bitsbox - excellent service yet again

www.bitsbox.co.uk

A couple of days ago I realised I needed a few tools to help me: a "helping hands" clip to hold PCBs and breadboards whilst soldering, a desoldering tool, some trimming tools, more solder, switches etc. So, I placed an order with Bitsbox, a small UK supplier I've used before. The order was easy to place, a Paypal payment was accepted and the order received very quickly indeed with a low fixed price for delivery by first class post. They have a good range of parts in stock and their service has always been first class. I can highly recommend Bitsbox if you need a few bits for your amateur radio hobby.

2m UKAC this evening with QRP and a halo

Stations worked on 2m SSB with 5W and halo tonight

After 90 minutes of 2m contesting this evening I decided to QSY to 472kHz WSPR even though there was another hour to go.  The contest was my first from the new QTH running 5W into the 2m halo on the roof. In all I managed 12 QSOs with the best DX GW4FZN/P near Bala at 272km. Best DX heard was G4PPT/M in IO70 near Penzance, Cornwall.

The RSGB UK Activity Contests are every Tuesday evening on different VHF/UHF bands each week of the month. Great fun for an hour or so and well supported.

Early morning 6m Es opening

After breakfast I checked 6m beacons this morning at around 0730z and was surprised to hear IW3FZQ/B and YU1EO/B coming through marginally. I then went on to work YL3IQ in KO17OD square at 599 each way on 5W CW at 0736z. Conditions on 6m are still good at times, and surprisingly at such an early time so late in the sporadic-E season. Currently WSPRing on 6m but only UK spots this lunchtime.

3 countries now on 472kHz WSPR with short earth-electrode antenna

Limited success this evening on 472kHz with the earth-electrode antenna with the copper pipe grounding at the house end. Reports from G8HUH, OR7T and PA3ABK/2 this evening, but I am left feeling that results are still some 6-10dB down on at the last QTH. The system is far from optimised yet though.

Tomorrow evening I will have a go at the 2m UKAC contest with the halo but hope to try some different antenna arrangements on 472kHz later in the week. So far 6 unique station reports on 472kHz WSPR in 6 different QTH locator squares. I do feel that a better antenna is needed, somehow!

VHF tropo (non ducting) history

Whilst trying to locate an up-to-date list of VHF 2m beacons I am likely to be able to copy here on a halo, I chanced upon a site with a history of non-ducting tropo (NDT) going back to the work by Marconi in the 1920s and 1930s. See http://www.quercus.demon.co.uk/thistory.html. Interesting reading.

2m halo added to VHF/UHF antennas

This morning, whilst waiting for the Virgin Media installers to arrive, I added the 2m halo to the mast supporting my V2000 6/2/70cms vertical, allowing me horizontal 2m operation again. The picture shows the antenna on the gable end of the bungalow.

V2000 and 2m halo antenna installed

I have also been trying a different ground point for the 472kHz earth-electrode system at the house end. I shall have to wait until this evening to try this. Current into the loop is higher, so I hope performance will be a bit better.

The second picture was the sunset last night as seen from the shack window. It was beautiful.

GB3VHF on the halo

Removing earth rods?

At my old QTH I have 3 solid copper earth rods driven in about 0.8m into the soil. Does anyone have any recommendations on how to remove these please? They are pretty solidly embedded in the soil but it would be good to be able to reuse these at the new QTH as solid copper earth rods are not cheap.