By Dave Sergeant G3YMC
This is John G3NCN outside the camping trailer which formed our home for the NFD contest. This is the result of two months planning, and was the first time we had put on a totally battery powered station in an amateur radio contest.
This page details what the contest is all about, and how we set out to achieve our goal. And for those of you who are not familiar with amateur radio and contests, an insight into what makes us sit out in a field all the night!
NFD, National Field Day, is an amateur radio contest organised by the Radio Society of Great Britain, the national amateur radio society in the UK. The contest is arranged to coincide with a similar contest in other European countries, though the UK scoring system is slightly different. The objective is to contact as many other stations as possible, with extra points for working portable stations and stations outside the UK. In practice most of the contacts are with UK and European contest stations.
In NFD operation has to be portable, with the station power derived from a generator or batteries, not from the mains. There are three sections - Open, with no restrictions on the number of aerials - Restricted where a single aerial at 11m is used - and Low Power where the power is also restricted to less than 10 Watts. This is a CW (morse) contest - there is a SSB event in September. Operation is on all the amateur hf bands between 160m and 10m, with the exception of the 30m, 17m and 12m bands where contest operation is not permitted.
NFD is one of many amateur radio contests - the rules, operating modes and frequencies differ, but the objective is the same - to work as many other stations as possible, and hopefully to win! More details of NFD and other RSGB hf contests can be found here.
NFD is a 24 hour contest, from 1500z June 1st to 1500z June 2nd 2002. For the Low Power section which we entered, operation is limited to 12 hours, but can be in several sections over the period.
The Bracknell club has entered NFD many times in the past. We are always looking for something different, and as we are not a big club in terms of hf cw operators we are not in a position to do well in the open section, where we would be competing against much better equipped stations. Two years ago for instance we operated a single band station on 160m, and were the band leaders (though way down in the overall entries).
Initial ideas started when I bought an Elecraft K2 transceiver. This is a very compact hf transceiver with, in its basic form, up to 12W output and running off a 12V supply. With the options I have currently fitted, ie the 160m option and the KAT2 automatic ATU, it looked attractive to use in the low power section with its 10W limit. Normally we have powered all the station equipment from a 3kVA petrol generator. What would be the possibility of instead powering the complete station with all its accessories, from batteries, and hence saving the noise and significant running expense of the generator?
The K2 takes around 240mA from 12V in receive, and around 1.5A key down in transmit. If necessary the receive current can be reduced to around 150mA by turning off the LCD backlight and other measures. Rough calculations indicated that a 4AH solid lead acid battery, readily available for alarm backups, might last for 12 hours of operation, but a second one should be kept in reserve. I ran my K2 in the shack from such a battery one day as a check, and was impressed with how long it lasted. Just before Field Day John G3NCN produced a couple of 7AH units - we had enough power for several days!! Oh, and the K2 has an internal keyer, which works very well. No problems with incompatible keyer interfaces and rf feedback into them. And excellent full QSK - no clattering transmit relays.
But what about the rest of the station, in particular power for a logging computer (essential in today's contests), lighting and home comforts. The latter were solved when John offered us the use of his camping trailer as our operating position - towed as a large trailer behind his car onto site, and then magically transformed by unclipping and reclipping a few bits into a spacious caravan, complete with all the lighting, cooking and heating mod cons you expect from a camping enthusiast. And it had a copious 12V supply of its own - 65AH in fact - enough to power the rest of our gear. To maintain our aims, the K2 would still be powered separately from the gel cells.
Most modern laptops do not have enough charge in their batteries to run for 12 hours without charging, and also require unusual voltages such as 18V so cannot be run from 12V direct. By luck we still have a number of ancient Zenith laptops - no hard disks, 720k floppies, and incredibly slow - but they run off 12V at around 0.5A! We checked these out on bench supplies and found they worked OK right down to about 10V input. Software was EI5DIs Super Duper - the later versions will not run on 8086 processors, but the copy we purchased a few years ago did (take note, Paul!).
Field Day is a portable contest and a suitable site must be identified in advance, preferably one with plenty of open space for antennas and away from residential areas, permission obtained from the owners, and the site registered in advance with the contest organisers. There are several suitable sites available to the Bracknell Club, two of these are local. Our site in Dorset used for VHF NFD (and incidentally to be used by some of our club members for the 50MHz contest that weekend) was not suitable in this instance as two of us had commitments locally on the Sunday. One of our sites suffers from waterlogging in wet weather, but was kept in reserve as a possibility.
Longhill Park where we operated is a former landfill waste disposal site, which was converted into public parkland in the mid 1960s. We have operated NFD and other contests there over the years, and it is an excellent location for amateur radio - large, open, well away from housing developments, and with a low electrical noise level. It is open to the public, and a favourite place for 'taking the dog for a walk', but in general is quite peaceful. Most significantly, it is conveniently located for all our members, and is only ten minutes walk from my QTH! Longhill is owned and maintained by the local council, and permission was obtained from them to use it for the weekend. Registration details were submitted to the contest committee in early May to allow their 'inspector' to visit us if necessary to check we were operating within the spirit of the contest.
Stations in the Open section of NFD have no limit on the number of antennas they can use, apart from a 20m height limit. In the Restricted and Low Power sections however only a single antenna is allowed, to cover all the operating bands, with a height of 11m maximum, and no more than two elevated supports. If operation on all bands is required, the options for antennas are somewhat limited, and we decided to use what has become a standard for Field Day stations - an inverted vee doublet with the centre supported by a single mast and fed with open wire feeder. To give good performance on the 160m band a total top length of 204 ft was decided on - there is nothing significant in this length, but it is in fact a double size G5RV and so can be expected to give a sensible impedance match on all bands. The feeder was 40 ft long, sufficient to reach the operating position with some spare.
The internal antenna tuner of the K2 can match most antennas but for feeding balanced line a balun is required. Using the designs in the ARRL antenna book I constructed a suitable balun and arranged it to be switchable between 1:1 and 4:1 impedance ratio via a toggle switch - in fact it was used just in the 1:1 position and a match better than 1.6:1 was obtained on all bands. The K2 remembers the ATU settings for each band so instant band change was possible and it was not necessary to change the settings after the start of the contest.
In order to identify any problems with the impedance of the antenna, I downloaded a copy of the program dipole3.exe from Reg G4FGQ's site. This program is specifically written to calculate the matching impedance of dipoles fed with balanced line. Although this was an interesting exercise, the results of the simulation bore no resemblance to the performance of the antenna when erected!
Any antenna requires a support mast or tower. Initially we had planned to use the same mast as we had used two years ago - a light weight aluminium mast designed by John G3NCN. Just ten days prior to field day we heard that a former member of the club had kindly donated us an ex-army 30 ft sectional mast, brand new, for club use, and an initial check indicated this would be ideal. To check out however we needed to do a trial erection, and this was done a few days before the contest. The whole antenna and mast was erected, checked with the K2, disassembled and repacked within an hour or two. With just two of us on site it was remarkably easy to erect the mast, though we were hoping more would be available on the Saturday! We had a quick QSO on 40m just to prove it worked. Of course, to keep within the Field Day rules, everything was then taken off site again.
When operating all bands, it is important to choose what time to operate on each band in order to maximise the scoring rate. In NFD double points are given for all contacts on 160m and 10m. The operating time for 160m is from late evening until the middle of the night (by which time there will be few new stations to work). 10m is only open during daylight, and is unpredictable as it depends largely on sporadic E propagation, which may only occur for relatively short periods. It is important not to miss these openings on 10m!
In the Low Power section we are also limited to a maximum of 12 hours operating time in total. We had another problem - both myself and John have church commitments on the Sunday. On that basis an operating time of 5pm to 5am local (1600z-0400z) seemed sensible. We would have a fair chance of catching any sporadic E opening on 10m on the Saturday, and we would be able to use the whole of the night period for 160m, 80m and 40m. And by 5am it would be light, and the station could be dismantled easily allowing us hopefully be rested in time for church (or that was the theory...).
Knowing now how long it would take to erect the antenna, we aimed to get on site around 3pm which would allow us plenty of time to achieve our starting time - in fact we were there a little earlier, as John's son-in-law was keen to witness the transformation of the camping trailer! Our third operator was to be Ian G3TLH, a QRP die-hard, who cycled to the site. We were joined in due course by Steve G4AUC (our 'cameraman' who supplied the photos on this site).
The first task was to convert the camper trailer into the operating tent, which was done by John with a little assistance. We were all amazed at how large and roomy it was after assembly. Having stored all unwanted items (and Ian's bike) underneath the trailer we paused before unpacking and erecting the mast. With four on site this was erected fairly quickly, and the antenna with its open wire feeder uncoiled, pulled to the top of the mast with its halyard, and the remote ends secured in the correct places. The balun was attached, and the feeder fed through a convenient hole in the trailer to the operating position.
We then encountered our only hiccup during the weekend. When we came to check the trailer electrics we found the voltage collapsed when we turned on any load such as the lighting. Dreading a flat battery which would have seriously limited our activities (but certainly not stopped us) we investigated. We found the master fuse was not making proper contact in its holder - a small piece of aluminium foil was placed in the holder to make it firmer (no, we didn't short the fuse out...). The other problem was we were unable to light the pilot light on our propane powered fridge - so the milk had to do without.
Setting up the station itself was done relatively quickly - it was just a matter of connecting up and go. Each band was then tuned with the K2s atu, a simple case of pressing the tune button and letting it do its work (loads of clicking relays as it runs through all possibilities). In fact on most bands the tuning had not changed since the trial run, quite surprising as the antenna had been in a completely different place in the field. The logging computer was then powered up and we waited while it booted and loaded the software. A quick check and break, and we were now all set for the fray!
Here I am operating the rig, with Ian G3TLH doing the logging on the Zenith laptop. Since neither of us had used the SD program for some time, we had a few problems during those first QSOs. In particular, we had forgotten that the '-' key is used to totally delete an unwanted entry. I took a 'tea break' trip back home and returned with the SD instructions - we had no further problems with that one!
This photo shows how compact our station was - absolutely everything apart from the balun and antenna is in the picture. The gel cell is behind the K2, partially hidden by the laptop.
No, that is not a road you see out of the window - it was the newly mown grass the council had obligingly cut to allow us easier access.
As if by cue, we found the 10m band open right at the start of the contest, so we spent the first two hours down there taking advantage of the double points available. These sporadic E contacts were largely with European portables, though it was nice to work 5B4/GM3YTS/P in Cyprus who was doing very well indeed in the contest. We stayed on 10m until the band started to fade, followed by a short spell on 15m. Most of the time we kept the K2 output at 5W to maximise battery life, and we had no problem making contacts. After some successful sessions on 40m and 80m it was time to start on 160m at 2200z. I had been sceptical as to how the 5W from the K2 would perform on that band, especially since I had only had two QSOs on the band from home. I needn't have worried, we could work virtually everything we heard - time and time again John suggested we would be wasting our time calling a weak eastern European station and he was proved wrong every time when we made it on the first call! It seemed our antenna worked like a dream on that band.
It was a pleasant night. Fortunately there were no problems with thunder static which can wreck havoc on the LF bands, and even worse damage equipment if there is an actual storm. For a while we needed to use our propane gas heater, but it was by no means cold, and as always it is a thrill to see the sun slowly appearing out of the dark. All too soon it was 0400z and time to pull the plug and take down the station.
And as we drove off site early that Sunday morning, it was time now to analyse the results and work out the strategy for next year. These days preparing the logs and sending them off is a very straightforward process - the SD logging software takes care of marking all duplicates, scoring etc. and producing an electronic log file suitable for sending the the adjudicators. In fact the log was submitted by e-mail on the Monday morning. Gone are the days of laboriously copying all the contacts from paper onto the official log forms by hand, checking for duplicates with check log sheets, and adding up the scores manually - in those days this took several days, and there were always problems reading individual operator's handwriting and sorting out conflicts and errors. This is one aspect where computers score - and it also makes the adjudicator's job much easier (but doesn't mean they announce the results any earlier..).
These are our results as submitted:
Band 160m 80m 40m 20m 15m 10m Total
Valid QSOs 95 90 67 4 28 51 335
QSO Points 756 331 252 14 98 364 1815 (including band bonuses)
When the results were finally announced in October we found we were placed second in our low power section. It seems a little more time on 160m or use of 10W instead of 5W would have made those extra few points to achieve our goal. In first place were the Echelford club, operating as G3UES/P, who rather interestingly were also using a K2!
However we received a nice certificate for our efforts!
The full results of the contest can be found in the November 2002 issue of the RSGB magazine RadCom
Did our entry meet our expectations? Undoubtedly! Could we have done better? Probably!!
I have no reservations in saying that the Elecraft K2 is an ideal rig for the Low Power section of NFD. Of course now that they have introduced their 100W version, it would also make an excellent rig for the Open and Restricted sections as well. But I shall not be buying that version myself! Although we could have run the full 10W allowed, we were very pleased with its performance at 5W - certainly we had no problem making QSOs, and whether we would have worked many more with 10W is questionable. Time and time again Ian G3TLH commented on how much he liked the feel and operation of the K2, it certainly is a nice rig to use and less daunting than many of the other rigs on the market today. And the performance of its receiver is the real bonus - excellent strong signal performance and very nice CW filters. I suspect we had an advantage in hearing stations, particularly on the lower bands, which others couldn't.
And what about the antenna? I think the length we chose, 204 feet, is a good compromise. It gave excellent performance on Top Band and still gave reasonable results on the higher bands. By using the K2 internal tuner we did not need to worry at all about matching during the contest - instant band change, and a knowledge that it was always matched and working as it should be.
The advantage of powering the whole station from batteries was also well received. In the past the major expense in NFD has been the cost of petrol for the generator. We own our own generators by the way, so never had the additional expense of hiring one. There was also an absence of the generator humming away close to the tent, no worries about electrical noise from it which can make reception difficult, and there was no need to worry about keeping the fuel tank topped up (a potentially dangerous process at night). We now know that we have more than adequate capacity in our batteries, both the gel cells and the trailer batteries, though this was something of an uncertainty this year. Yes, this is the way to do it.
Conditions on the bands were reasonable as far as NFD is concerned. Not much DX about, but good propagation into Europe, a nice sporadic E opening on 10m, and no QRN (static) on the lower bands. Our choice of operating times was optimum as it happened, though we would have lost out if the 10m opening occurred on the Sunday. We missed out though on working much on 20m. When we finally went on that band around 0130z we found propagation to Europe had faded and most of the activity was from the USA who were only interested in ragchewing. But the bonus points on the other bands made up for lack of QSOs on that band.
Will we do the same next year? Maybe, but that is a decision to be made nearer the time. But those taking part in this year's event agreed that it was a most enjoyable weekend and would recommend a set up similar to ours as an excellent way of putting on a station in the Low Power section of NFD with the minimum of effort - and achieve an excellent position in the results.
Watch these pages for next year's attempt!
73s Dave G3YMC