Mid Essex DF October 12th 2008

This event is usually a double but on this occasion it was decided to experiment with a Multi-Tx Format. To encourage newcomers it was a team not an individual event, with a team allowed to use as many receivers as they wished.

There were 3 Maxi Txs, each with the operator sitting comfortably in a car. The cars were clearly identied with an A4 poster - this avoided all the usual explanations to members of the public. Each operator had located an automatic mini Tx 500 - 1000 metres away, so 6 transmitters in all.

Two trophies would be awarded one for the most Txs found in the shortest time and one for the team finding the three maxis first.

The start can be seem top left.

My site (Maxi Y, Mini R) was only about 2 KM away.

Richard's site ( Maxi I, Mini H) was out to the East.

Peter's (Maxi T, Mini M) was to the South.

All teams were issued with the Transmission Shedule

To allow for team training and for all to get used to time multiplexed Txs the Stations Y and T were started at 13:00.

By the official start time of 13:20 all 6 Txs were operating on schedule and all could be heard from my site (phew!)


Loads of signals.

Plenty of bearings to plot!

Despite each station being on for one minute in every five, all teams drove past my close in stations and headed for the distant ones!

I guess - the old 'forty minutes of silence' habits die hard!

8 of the 9 teams headed for Peter's southerly site first. Stations T and M - the 'Dah Site'! The map (2003) has the footpath wrongly marked, the new route follows the stream but since the car was parked at the beginning of it this, it caused no problems. What did cause a problem was that some competitors had not checked the schedule and set off along the path without it! The fact that they could hear all three mini Txs plus probably breakthrough from the local maxi caused some interesting behaviour. Of course those who knew they were looking for station M (dah dah!) were not confused but this mini was well hidden so proved a reasonable challenge. Sadly all who found it were so relieved they forgot to take a picture. To prevent any such confusion in future the parent maxi tx letter will be printed on the punched card along with the mini tx letter. Although I suspect those involved would not have made the same mistake a second time. 'When all else fails ......................... '
Stations Y and R (the 'Mixed dots and dashes'!) 1 hour and 20 minutes had passed and still no teams had arrived at my site near the Secret Bunker. Richard had reported that Tim had been into him. I was beginning to wish I had chosen a different deodorant, well any d.... then a car screached to a halt, it was Philip and Ray. A quick check in and they were off after my mini. Then Richard called again to say that his valve TX had flattened its battery. I told him I had a spare leisure battery and would send it with Philip when he returned from finding my mini. Meanwhile it was hooked up to the car's supply.

Twenty minutes later Philip left my site with a bit of extra ballast - well he is a former champion.

Unfortunately this is where the cunning plan went a little wrong, for instead of heading off East for about 7 Km to Richard, the Cunningham team went North to the wrong side of the river .......

The second team (well person in this case) to show up was Tim at 15:05. To my amazement I was his fifth station. Unaware that Philip had headed North I warned Tim that he would have to get a move on if he wanted to win.

My mini had been thoughtfully placed so that it was a nice downhill run from my maxi. At the tea Tim described his feelings of joy when he realized that having found the little .... he had a complementary uphill run in order to log his finish time. Still it was all worth it Tim, you only had forty minutes to spare!

What's he doing behind there? Mini spotting of course.

Below the high tech card used to record 'mini finds'.


Ian finds it too, photographing his set as proof! Interesting that he was the only one to go for the optimal strategy - mini then maxi to avoid the double maxi visit.

OK so it isn't a Tx it is a sheet of paper and 'hi tech' hole punch. Obviously the Tx has to be seriously well hidden to stop members of the public finding it, but it is within a few feet of the check in point, jammed under a thorn bush; this made adjusting the ATU a seriously painful business.


Paul Clarke's mini - all surface mount components and synthesised frequency generation - very neat. Used at Peter's site.

Underneath is my not quite so mini.

Both contain logic, Tx, ATU, bridge and battery! Both could be heard from all locations within the competition triangle. So clearly less sensitive receivers could be used - not too difficult then to equip beginners for this limited area event. Over to Richard .....

Report for Station “India” and Station “Hotel” {The Dotty Site Ed.}

The “all-new improved” DF event meant two transmitters at G4ICP/P. Extensive planning and testing resulted in much modifying my trusty main DF TX, changing frequency and installing a microprocessor control board as specially designed and built by Roy. This was station I or “India”

Because my tx is all valve construction, the micro had many functions to perform including switching the valve heaters on, HT on (at 5 seconds before transmission) then provide the Morse keying sequence, switch off, standby etc

This all sounds simple but resulted in quite a challenge what with current switching and consumption parameters to be considered. The final circuit included a number of relays, heavy gauge wiring and EMC protection and screening for the PIC board, bulb for reducing 'sleep' heater current, chassis bashing and full bench testing before starting out on the event. {You forgot the the PO rubber bands - Ed.}

Once all this was working it did feel strange listening to and watching my “manual” transmitter being totally controlled and operated by a microprocessor. This was old technology meeting new!! Handsfree!

Roy had kindly built and supplied me with another tx, this time fully solid state. This was known as the “Mini”and was to be set up at a nearby hidden location. Due to it being unmanned and easily hidden, was expected to be the main challenge at the site. This proved to be the case. Sir Alec Issignosis would have been proud.

I chose a blackberry thicket and buried station H or “Hotel” in a handy gully I discovered as I tripped over it. The TX earth stake was easily pushed into the moist soil at the bottom of the gully providing a ready-made ideal-earth connection.

The main station, station India, was then set up in the car. A simple quarter wave aerial was used.

All went well and competitor Tim kindly and promptly proved the two TXs were doing their job.

However readers, it was not all comfort and joy at my site. Station India’s battery, which had never failed me until this event, failed at approx 1420. Overcoming panic and restoring logical thought, the TX was then connected to the car battery during an “off period”. Roy sent a spare battery (no lightweight as it was 110 AH) courtesy of Philip who was expected to be with me pretty quickly. As in all DF events, nothing ever turns out as expected because poor Philip took a detour to my stations via the wrong side of the Stour, turning up rather later than expected!

With the arrival of the replacement battery, normal service was resumed but no transmissions were missed and the show carried on! (and the car started at the end of the event)

Most competitors who targeted me did find me and the lengthy debate about the “new” DF event started in depth before some of them had even got their breath back! The rest, they say, is history.

Thanks Richard

Time for tea and time for decisions - who gets prizes and who gets swatted..?

Are you ready for panoramic ...

The Results:

Tim - The Mid Essex Trophy

Philip and Ray - The Triple Maxi

Well done Tim --- remarkable performance --- and well done Ray and Philip for still being in the prizes despite the ballast and the significant detour.

Thanks to Caroline for an excellent Tea, thanks to Paul (Torbay,) Peter and Richard for all their help in getting six Txs on air, and thanks to all the competitors for trying something 'a little different'.


Did it work? Yes, I think it did. OK a few got confused in the early stages but within an hour everyone knew what they were doing and for a totally new style of event that ain't bad! A few tweaks to the signal format, perhaps 3 IDs at beginning and 1 at the end instead of 4 at the beginning; Maxis on team card as well as minis; and perhaps most important, more differential between the maxi only comp. and the full comp. I guess that means two minis with each maxi, perhaps a micro too ....... must get building more auto Txs.......

Until next year .................................... Cheers!