The World of LF


73kHz Expedition to GW

by Mike Dennison G3XDV


I have operated on 73kHz several times from South-west Wales and had QSOs with my Novice licensee sons crossband to 432MHz as early as 1997. The distances were a few tens of km. Later I heard G3LDO in Sussex at 449 at a distance of 330km.

More recent attempts to work into south-east England have failed, despite using a kite-borne antenna. Easter 2000 saw an attempt to work GI8AYZ at a Decca site. The GI was heard at a distance of 331km, but only a kite antenna was available to me, and there was insufficient wind - even on top of a mountain - to fly the kite.

Although I have a holiday home in the area, a local power line makes LF operation impossible. |The activity has all been portable from a vehicle, using a battery or petrol generator. SM has been worked on 136kHz but nothing outside GW on 73.

When G3YXM, G3XTZ and G0MRF announced they were going to Guernsey, plans were made to activate GW3XDV on 73kHz, and to try for the first GW-GU QSO. To improve the chances of success, I asked Mike, GW4HXO, if I could operate from his established 136kHz station using my own 73kHz gear. He readily agreed, offering accommodation as well. Since I did not have to operate portable, this meant a reliable antenna, a permanent power supply and no chance of getting cold and wet.

At least that's what I thought!


Whilst driving to Wales from the London area, I heard weather forecasts talking about severe gales, winds of 80MPH (130kph) on the West coast. And guess what? Mike's QTH is on the west coast, on a hill a few hundred metres from the Irish Sea. The rain was so heavy at one time that the motorway traffic almost stopped. Travelling through Tenby, an hour's drive from Mike's house, I saw people barely managing to stand up in the wind. Half an hour later there was a huge thunder storm. I smiled at my wisdom in not going portable like the boys on Guernsey.

Arriving at Mike's QTH, I found gales force winds and torrential rain. A pint of Guinness later, the rain had stopped and we unloaded the gear from my car. This was quite difficult as the wind threatened to tear the car doors off when opened. Three quarters of an hour later, we had set up the complete station, Tx, Rx, computer and several loading coils to retune Mike's 136kHz antenna. We were over an hour ahead of schedule so had no worries sitting down to a leisurely dinner before our sked with GU0MRF. Then the lights went out! Fortunately, the dinner table was already candle-lit and extra candles were brought into use. Looking out of the window revealed no lights anywhere. I was beginning to think that my 1000km round trip would be wasted. I phoned G3YXM to say we may be delayed. He replied that they were in the pub and didn't mind any delays. There was little else for us to do but drink more Guinness and chat about amateur radio.

We let out a cheer when, after an hour, the electricity supply returned. We rushed into the shack and proceeded to tune up the antenna. Much to my surprise, Mike's system needed only about 4.5mH extra to get onto 73. My system at home needs 9.5mH extra! His 'T' with a 60m top section, must have much more capacitance than my 'L' with three 20m wires a metre wide. On receive, the noise was not moving my s-meter, Rugby was 9+40 (10dB less than at home) and HBG was 9+10dB (10dB greater that at home). A call on QRSS showed that the transmit side was working OK with nearly 2A into the antenna from my 200W Tx. Another phone call to Guernsey persuaded them to drink up and get wet again (somehow I thought their response lacked enthusiasm).

Then disaster number two happened. We lost all transmit current and the receiver became insensitive. Ten minutes of checking all connections produced only one conclusion - the antenna had gone faulty and we would have to brave the weather ourselves. Fortunately, Mike lives on a very quiet rural road because one end of the antenna was found in a hedge with the rope support dangling across the road,. Never ride a motorbike near this QTH! The wind was colossal, it was very dark and the rain cut into your face. Nevertheless we reconnected the wire and hoisted it back again. The wind pushed it into a large sideways arc and kept it high in the air.


Back in the shack, the antenna tuned up again and we could see GU0MRF on the screen, though by now the local QRM had increased greatly with bursts of S9 'electrical appliance' noise and heavy static. When the noise was low we could just receive the Guernsey station by ear and could see them very clearly on screen. When it was at its worst, it blotted everything out. By 2220 we had received an 'O' report and given 'M'. Jim, M0BMU was seen at a similar strength calling GU0MRF. We celebrated with a glass of brandy. We called Jim but got no reply, and despite several CQ calls, we heard no-one else on 73 or 137kHz QRSS. During this period we had to make a running repair when sparks were seen just outside the shack window. The antenna wire was flashing across to some plastic rope holding it away from the tower. A short length of fishing line fixed that. We wondered whether the earlier antenna failure had also been due to sparking.

Problem #3

The next morning, Mike woke me with the news that the other end of the antenna had come down during the night. The wind had dropped to about 40MPH so, after breakfast, he climbed onto the chimney of the bungalow and restored the connection. We noted burn marks on the rope and sea salt on the insulator, so it seemed that our theory from the previous night had been correct. This had never been a problem before but obviously the greatly increased voltage present at 73kHz was enough to break down the insulation, and the high winds did the rest. Mike then raised the wire we had repaired the previous night, as this had sagged to a few feet above the road because the gale had reduced. We got on the air at 0920 and put out several calls over the next hour, checking both 71.605 and 137.1 for replies, but the only station seen was ON7YD using DFCW and plainly not calling us. It is a pity that no-one was on as the noise level was much less than the Saturday evening, and the lack of crossband interest (apart from OK1FIG - thanks Petr) was particularly disappointing.

It was then time to dismantle the gear, load it into the car - a pleasure to do in daylight and with no wind or rain - and set off for home again. My mobile phone was outside its service area for the first few miles (note that unlike major towns, this sparsely populated area of several hundred square miles is served by just one large mast). When it could 'hear' again, I got a voice-mail that Jim had left the previous night to say that he had heard and called us. This was a disappointing near miss and the first GW- G QSO is still awaited.

Back home

500km later I unloaded the car, noted that my antenna had withstood the storm, and rebuilt the station once more. It was getting easier with practice and only took 30 minutes. A call to G3YXM revealed that they were just about to re-tune to 73kHz. They kindly agreed to stay on 136 for a minute to work me and we rapidly exchanged 589/579 reports.

Twenty minutes later, I had the 73kHz station running and was receiving GU0MRF a little weaker than in GW, and with much more local noise, but no QRN. I saw them work Jim rather higher in the band than I expected (71.650, not 605!) and also saw G3LDO calling. I called but got no reply. Dave then phoned me to check I was still on. I had managed to hit a Loran line but with a bit of fiddling I found a frequency that was clear for them. Reports of 'O' and 'M' were exchanged and you could sense the relief of the storm-swept Guernsey boys that they could at last close down and get back to that pub. Elated with the success of the weekend - a first for GW, and a new country at home on both bands - I went to say 'hello' to the family.

This was an exciting and interesting weekend, and as usual several lessons were learned by all concerned. What was not new was the confirmation that if anything can go wrong it will go wrong. My enjoyment was made possible by the hospitality of Mike, GW4HXO and his wife, Ingrid, and by the two Daves and Graham who generated the interest in the first place. Thanks to all. Where to next lads?

Mike, G3XDV (IO91VT)


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