Colchester DF 17/04/09

Operator Roy G4 JAC
Location Alresford

Since this was a Colchester event my main focus had to be on providing a good single TX event. However, I was keen to see how difficult it would be to set up 5 time multiplexed minis (three newly completed ) and also to let my 'local guinea pigs' hear what 5 Txs on one frequency sounds like. Competitors were informed the week before that there would be an opportunity to carry on DFing (just for fun!) after the main event.

The following gets rather detailed because I hope this account may prove helpful to locals experimenting with minis on their Chelmsford events. If you are not involved feel free to scan read and look at the pictures!

A walk the previous weekend allowed me to check out areas with some cover but the main planning was done using an aerial map from the net. The red letters show the the final locations of the main TX and five minis H, I, J, K, L. Only J was moved from its planned position where the bright green dot is when I found a group fishing close by.

Access was via Ford Lane on the right, with footpaths running under H and from CAR to J. My first visit had indicated that people walked dogs pretty much over the whole area but in view of the scale of my plan I decided that it might be wise to warn the police that torches and 'strange people with headphones' may be seen on the Friday evening. The day before the event I decided to return and explain my plans to a few of the locals too - just as well I did, as at a house by the L of Ford Lane, the occupants informed me that they kept watch for the local land owner and frequently called him or the police when 'strange goings on' were spotted! With the landowner informed by them of just what non destructive, truly green, wonderful people DFers were, I felt much happier about putting the plan into operation.

Friday was not the most pleasant day, cloud and drizzle did not inspire me to leave home. It did have the benefit of making me stay by the teapot penciling out a strategy for setting up far more equipment than I had ever attempted before.

This was my plan:

1 Put up main station aerial.
2 In car, check time to start time for minis, set all to the same delay.
3. Switch on H so that after delay it would start at 8:30, I one minute later, then after another minute J ..etc.... L.
4, Take car to top of footpath and set up H
5. Drive down and set up I.
6. Drive down track to fisherman's car park at he junction of the two paths and set up K, L and J.
7. Return to car and take main TX to location.
8. Program keyer with delay to give 7:30 start.
9. Tune up Tx and leave it powered up with Keyer plugged in.
10. Park car on car park, return on foot with polythene sheet, torch, drink.

Amendment - see below. Before going to set up a station check you have:
a) Tx with aerial attached, b) Tickets in clear plastic) Black plastic bag for Tx

The latest generation of mini uses an ATU with a variable inductor made from a bit of ferrite rod driven in and out of a tube by a brass bolt. (Thanks to the ever inspirational Paul Clark for the design - This is much cheaper than a big variable C). Screwed fully in it will load a 3 m wire, fully out about 15 m. With a good earth and 15 m of wire it can be heard about 5 Km away. Just laying on the ground with 3 metres of wire it will load and can still be heard several hundred metres away.

Before setting out I decided to test all the minis in my garden and preset their ATUs with appropriate bits of wire. I put around 5 m on each TX and called local amateur Paul G4IZX to see if he could hear them from his house about a 1 Km from mine. During this test dear old 'not so mini' H (the first ever built) did not start as expected but did at second attempt - I would have liked to have checked it over but time was now short. The latest 3 built, and not used previously, seemed fine. Paul reported all 5 were getting to him.

Photo below shows the minis with aerials wound around them. Near centre is the Maxi keyer to be used on the Main TX set to 2 in 10 mode.

I eventually arrived on site just after 5 pm. I decided to travel light on the aerial front, no long pole just a hammer as a sling weight. A random long wire was run out and thrown with the help of the hammer over several small trees. The last section was thrown into first one high tree then another 'Oh Bother' the wire has snagged high up and the 2 lb hammer was dangling way out of reach. For a moment I contemplated the safety implications of the suspended hammer over the search area - no I couldn't leave it there! Right, I heave on a section of wire that was in reach, yes its coming, snap, no it isn't, and Oh Double Bother, the hammer is still up there with all attached wire too high to reach. OK seasoned DFers will have encountered the joys of aerial erection many times but possibly not with six transmitters to set up and now two hours to start time. Well eventually after much rotten branch throwing the hammer did descend and a much joined bit of wire was in place.

Back at the car it is now 5:45 pm. The next job is to start the clocks. The maximum start delay programmable in to the minis is two and half hours. I decided to switch H on at 5:50 this would mean that it should start transmitting at 8:20 pm (50 mins after the main TX).
I set about moving all the delay switches to the correct positions. At 5:50 H was switched on, 5:51 I was started etc. While I was waiting for each minute I checked that my callsign was selected and hoped that no dog walkers would interrupt my train of thought. Fortunately none did and by 5:54 all TXs were ready.

OK guys (and gal) it's your turn now ...... the main event

By the time I get back to the TX it has just started sending the Morse intro for the 7:40 transmission. A smug operator picks up the microphone as the transmit light goes solid red...." This is G4JAC/P and I have a few extra treats for you this evening ........ "

Around 8:14 Ian does a complete circuit of me and the aerial system and disappears.
8:17 Tim also does a three quarters of a circuit but then spots me.
8:19 Ian returns and this time sees me.

After completing the 8:20 transmission on 1901 I retuned my DF set to see what the minis were up to. Yes I can hear I, J, K, L on 1960 all in sequence but where is H? There is dreadful QRM on 1963 where this one crystalled mini is supposed to be (all the other minis sitting on 1960 are synthesised). Sounds like I am not the only person who found a source 1963 crystals on eBAY.

Just as I finish the 8:30 transmission Gary and Tanya are heard walking past me on the other side of the bank .... It's strong here, can you see any wire? Another ten minutes goes by and I hear Larby complaining that "From this side of the lake the signal says go to the other side but when you get there it tells you to come back" Previously mentioned smug operator feels a chuckle welling up!

It all goes quiet until at 8:54 Philip arrives via Fingeringoe.

The main Tx is now on continually and Larby is doing a moth and light impression, the only difference is that the moth usually bumps into the light bulb. Finally he makes contact at 9:03 and disappears after the minis.

A couple of minutes later and Gary turns up, this time on the right side of bank. He comes straight towards me, set gyrating and then a torch blast from Tanya hits me straight in the face 9:07. Certainly the most impressive arrival, pity they didn't try my side of the bank 40 minutes earlier.

Minis

So that's it, 5 teams in., I switch off the main TX and leave the hide to see what the minis are doing. What has happened to H? In fact, it is on, but a minute and a half late - very strange, should have checked it out when it played up at home. At the time of writing I still haven't taken the lid off. It could have been a cracked capacitor that I had spotted when I took the PIC out for reprogramming but didn't have time to fix. Perhaps I introduced a bug into the PIC code when I last updated it. However, I reckon the most likely explanation is that an irate rabbit got to it..

At this point I should explain that each competitor had been allocated a mini to find as their last mini, with instructions to turn it off after 9:30 and bring it back to the pub.

To my relief I could see a torch by station H so someone had been able to DF it. Walking along the bank I bumped into Philip - he told me that he was supposed to retrieve J but couldn't hear it. As it was now late I gave him a vague direction thinking that the battery was low and he would hear it as he got closer.

Thank heavens I, K and L are still on time and chirping loudly. A quick visit to H and I had that back on time for the last part of the competition.

Meeting up with various competitors I began to realise that I had hidden the tickets too well (particularly H in the gorse bushes), they were DFing to the right area but with no long aerial to guide them in they were struggling. Others reported being drawn to fences and power lines ... (and I didn't even mean it!). The little B....s seem to be achieving Triple B...... status.

At 9:30 I took my Tx back to the car where I found Philip. He had still not heard J. Fortunately they had not closed the gates beyond the the car park and I was able to drive almost to it. The LEDs indicated that the timer was still running but the synthesiser was not locked on to 1960 - strange (but see later).

In the pub the competitors look seriously DFed but start to revive as liquid reaches the parts that have been reached so many times before.

Results

The Main Event

The rest was for fun only, some had more than others!

Had this have been a Chelmsford event where the minis counted, this tie would have been resolved by 'who handed in their tickets to the operator first?'.

Analysis

1. My original concern that the minis with short aerials would be too easy to find seems unfounded!
   It would appear that the A4 sheet/tickets don't need to be particularly well hidden, so future operators please note.
   
   
2. Previously people have complained about not being able to identify stations but most seem to have got the hang of it now, they just can't find them!
   
   
3. Setting up five minis was remarkably easy.
   They need so little cover to hide; with a short aerial a single tree or bush is enough.
   You don't need to stray far from a path, this opens up sites that would be useless for a conventional Tx.
   I suspect that few operators will attempt to set up five (particularly since we also need micros to give a range of difficulty) but at least we now know it is possible in a surprisingly short time, also competitors have had a chance to hear a full set of five Txs running.
   
   
4. Asking people to retrieve a mini was a big help. However with everyone DFing right up to 9:30 and then having to clear up did reduce time in the pub. I think the two hour event is spot on for Sundays but perhaps needs a tweak for any Chelmsford event run on a Friday evening. I have an idea for a refinement to the rules for unattended stations which may help - more when I have had time to think it through.
   
   
5. This was never intended to be a model for future Colchester events, only a testing session for Chelmsford style equipment and procedures. However, look at the spread of results for the main event. Was this due (at least in part) to moving people away from the main Tx? Perhaps future Colchester operators may wish to consider having an 'amusement only' mini or micro just to move people well away from their hide.
   
   
6. Theft has been a concern, but after some experience I am becoming less worried. Perhaps a fake Tx (blob with a wire coming out) could be hung with the tickets.
   
   
7. My contacts with the public suggest that it is worth being more open. Mentioning orienteering always seems to get a good reception. We may even find a new DFer somewhere!
   
   
8. 1960 seemed much clearer than 1963 at least on this night event Plus of course minis should be on 1960 according to the band plan. I hope to replace station H with another synthesised mini. The existing one can then either be used as a spare or beefed up for use as Chelmsford Maxi.
   .
9. The battery on J was not flat. The next day the unit was run for a further hour with no problems. It appears that the oscillator lost sync and stopped. Fortunately, the synthesiser has an output which I should be able to link to the PIC controller, so if this happens again, the PIC can resend the start up commands to get it going again automatically - at least that is the theory.

Thanks to all for putting up with this experimental evening - I learned a lot from it. I hope that you leaned something that will help you come a little closer to the sparkling performance that I shall doubtless put in when I try it from the other side of the mini airwaves.

Any constructive comments on the above welcomed.

You can now relax, I am not scheduled to run another DF until November! Of course one spare Sunday ...........

Speaking of Sundays, Andrew is running the next Chelmsford event on Sunday May 10th. I don't know what he has planned but last time I saw him he had a really mean look in his eye. Hope to see you all there (wherever 'there' is).

Roy 21/04/09