Six Essentials for Field Day

It's really easy to enter field day, why not give it a go? CW field day is on the first weekend of June, VHF field day on the first weekend of July, and SSB field day on the first weekend of September. Field days are a fun way to involve club members in contest operation, and can be combined with a social event such as a barbeque. Here are the six essential components which make up a field day entry. 

FIELD 

The idea of field day operation is that you can set up an effective radio station under emergency or 'field' conditions, with no more than 24 hours' notice. You will not be reliant on an existing antenna, nor have a permanent building from which to operate, and you must not use mains power. Field day operation also gives a chance to operate from a well-sited location, which may be on top of a hill and which will be away from sources of interference and TVI hassles. 

You may be lucky enough to have a team member who has a spare field in a good location, but if not try approaching a local farmer. They often have pasture, or set-aside land and usually respond favourably to a polite approach. Even a 6 metre wide 'headland' at the side of an arable field may be sufficient to establish a small field day station. 

There is merit in choosing a location which is quite close to the club's centre of population, as you want as many members as possible to help put up the station and operate, or to attend to give their support. Make sure to give clear instructions on how to find the site, and guidance on where to park and instructions ensuring gates are left shut. 

At the conclusion of operations, when all the gear has been packed away, make sure to do a 'sweep' of the field and pick up all rubbish: discarded cable ties, PVC tape, food wrappers, cigarette butts. Be especially careful to ensure all guy stakes have been removed - the farmer will not welcome you back if his plough should happen to come across a piece of angle iron still driven into the ground. 

No more than a week after the operation, visit the farmer to thank him for use of the field. A bottle of whisky makes a good token of appreciation and normally ensures that a request to use the field in following years is received favourably. 

OPERATORS 

Although mention has been made of clubs entering field day, the rules only say that all operators must be RSGB members or members of their Affiliated Society. It is usual for field day stations to represent a local club, but this is not a requirement. Any group of like-minded amateurs may get together, think up a name, and enter as a field day group. For CW field day, some clubs have difficulty rustling up enough CW operators, and it is perfectly acceptable for two or more groups to pool resources in order to enter. 

Don't be daunted if you are not a 'hot shot' contest operator. There is room in field day for all levels of operating ability. Plenty of groups enter knowing they have little chance of winning outright, but enjoy the fun of competing from a quiet location, often with much better equipment and antennas than are available at home. Field day is also an excellent opportunity to give training to those who are unfamiliar with contesting, and many of today's top competitors started their contest careers in field day. 

How many operators should be on the team? For the QRP section of NFD, which is limited to 12 hours, one operator might be sufficient but this is hardly in keeping with the spirit of field day as a group or club event. Three operators is really the minimum, especially if use is made of the second receiver in a rig such as the FT1000 series. Choice of section may also be influenced by the number of people available, and the Open sections are only really for the larger and better-equipped groups. 

In the larger clubs, not everyone will want to take part in the operating activities but there are many other important roles to be fulfilled, such as helping to put up the antennas, filling the generator, keeping the operators fed, and finally helping with the tear-down so that everyone can get off site as quickly as possible. 

GENERATOR 

Of all the equipment making up the field day station, the generator is most often the one that gives trouble. Field day rules state that mains power may not be used, but a generator is not the only solution. For the QRP section of NFD you may well be able to get away with one or two gell cells, and it is also possible to run a 100w station for 24 hours from a lorry battery which can be kept topped up by a small 12v generator, a set of solar panels or even a wind turbine. Remember if you go down the 12v-only route that all items including keyers, computers, lighting must run from 12v. 

If the generator is stored by one of the members of the group, then it should be brought out a while before the event, oil level checked, and run up and operated under load for at least 30 minutes. An 800w petrol generator can be used to power a 100w station, though 1.5 or 2.5kVA would give more margin. 

Traditionally, the generator has been obtained from a hire shop and this is frequently where the problems start. Hire shop generators see most of their service on building sites and the voltage output and regulation must be checked to ensure that the generator will power a radio station without problem. Collect the generator from the hire yard on Friday, and run it for at least an hour under test conditions. Use an electric fire or similar load of at least 1kW, and check that the voltage does not rise above 250v when the load comes off. The reason for getting the generator on Friday is so that if any problems arise it can be taken back to the hire company with some chance of being able to obtain a replacement in time for the weekend. Whatever generator is used, it is worth applying a constant minimum load of at least 100w, and this can be done by mounting a 100w bulb on a post by the generator. 

Generator hire for a weekend should be under £50, but the cost of buying a generator has come down significantly in recent times and it is now possible to buy generators which use an inverter, and give a true sine wave output. Buying a generator is still a significant outlay for use only once or twice a year, and one of the members of the group will have to undertake to store it safely and securely. 

Site the generator as far from the operating position as possible, to keep noise levels down. A car can be placed between generator and station for this purpose, but even better is to borrow straw bales from the farmer to provide sound insulation. Just don't place them so close to the generator that the hot exhaust sets fire to the straw. An awning can be suspended above the generator to keep the rain off, especially important while refuelling. 

RADIO 

Pay regard to the rules for the particular field day and section that  you wish to enter. For CW field day, it is highly desirable that the radio include a CW filter. 

As mentioned above, a 12v radio can be run from a well-charged car or lorry battery, which can then be float charged. So long as all critical parts of the station are also powered from 12v, this will also enable the generator to be powered down before refuelling. 

The question of which radio to use ofen comes down to which group member is prepared to let their rig be used by different people in a field day situation, but modern rigs are so much more reliable than they were even 20 years ago, and this should not be a major concern. The groups which are going all-out to win have no qualms about using whatever top-of-the-line rig it takes, FT1000MP, Orion or whatever. Take a standby rig: Murphy's Law ensures that the rig will only develop a fault if no standby is available. Make sure everyone who is going to operate has a basic 'driving lesson' before the contest starts so they know the main controls of the rig. 

If different club members are bringing different items of kit, it is a good idea to try them out together beforehand. Especially if the field day site is some way from home, you need to make sure all necessary connecting cables, interfaces, adapters and leads have been checked. Always make sure to have a soldering iron and set of tools to hand. 

The operators will be wearing headphones, so in order that other members of the group or visitors can hear what is going on it is a good idea to rig up a simple audio amplifier and loudspeaker. Many rigs have an audio line output, and this can be connected to a powered PC speaker for a simple audio solution. Make sure all visitors to the site are greeted, and it may be a good idea to prepare a short briefing note about the field day, the club and amateur radio in general - you may find some new recruits to the hobby this way. 

ANTENNA 

Choice of antenna again depends on which section is to be entered, but for the group trying field day for the first time, on HF it will be the QRP or Restricted section. In this section, the antenna height on CW field day is limited. Supports can be erected using scaffold poles, and lower heights can be put up single-handedly with use of a gin pole. 

Ensure the guy ropes are firmly secured to guy stakes driven into the ground, and check the stakes if there is heavy rain or a strong wind blows up during the contest. It is always a good idea to mark the position of the stakes with a post and reflective tape, to avoid visitors driving into them especially if the grass is long. Rather than attach a wire antenna directly to the mast, always use a pulley and halyard so that the mast only has to be raised once, no matter how many times the antenna may need to be raised and lowered for adjustment. 

In practice, the antenna of choice for almost all entrants in the restricted and QRP sections is the centre-fed doublet. CW field day includes topband, so a common length is around 270ft whereas for SSB which is only on 80-10m, 135ft is a better choice. The simplest configuration is to have a 11m mast close to the operating position, and run the doublet legs out on long lines so that the wire ends are at least 3m above ground. 450 ohm lead or, even better, home-made 600 ohm open wire feeder is run to the ATU(s) at the operating position. 

The line of the doublet should run approximately east-west. If this is not possible take care, since the 20m lobes tend to be in the wrong place if a doublet runs north-south. The doublet is not the only possible antenna, but it is often the best choice. Loop antennas, trap dipoles and even longwires have also been used with success. The second elevated support may be used to raise the height of one leg of the antenna, or both masts may be used to support the centre part of the doublet and ensure it is horizontal, while the end legs are suspended on lines down to ground. If this configuration is chosen, make sure the weight of feeder doesn't lower the centre of the antenna too much. 

Once the antenna is brought to the operating position, an efficient ATU must be employed. If a multiband ATU is to be used for all six bands, it is as well to check the configuration well in advance of field day and confirm that a match can be obtained on all bands. The feeder length may need to be changed, or lumped components added, to get a match on some bands. Most multiband ATUs are of the T-match type and the 4:1 balun on the output is not always a good performer. On some bands where the feed impedance is low, an external 1:1 balun may be better, and it has been found that a 1:1 balun when used with the internal ATU in the Elecraft K2 transceiver gave a good match on all bands. The internal ATUs on most transceivers are nowhere near as good as the Elecraft design, but another option is to use an Auto ATU together with a balun. Greatest ATU efficiency comes from use of a balanced link-coupled ATU with adjustable taps. Several may be needed to cover all six bands. 

TENT 

Some entrants in the 12-hour QRP section might trust the weather forecast and brave the elements, but in practice all stations need to have some sort of shelter. While the lucky ones may have a caravan from which to operate, it must be brought onto site: a caravan which is not moved from its storage position would be a violation of the field day rules. It is possible to operate from a large car or van, though a van in particular can get very hot during the day. 

Most groups use a tent from which to operate, and someone in the group can usually get access to a frame tent large enough to accommodate two operators and a rig. The larger the tent the better, though it is best to discourage visitors and club members from talking in the operating tent and distracting the operators, so a second 'social' tent, if one can be found, is a very good idea. 

Make sure the operating tent is equipped with lighting - in the past, groups have set up during daylight and happily operated until it got dark, when they realised no provision had been made for lighting and further operation was only possible because of the dial lights on the rig. Also make sure one or more torches are to hand, in case of sudden generator failure. Bear in mind that even in June or July, it can get very cold at night so ensure the tent flaps can be closed and that there is some provision for heating. Only if a really large generator is available will electric heating be an option, but calor gas heaters of various sorts are available and can be effective while the tent flaps remain closed. Care may be needed in routing open-wire feeder into the tent, or it will be found to be impossible to close the tent up completely at night. 

There are many more detailed aspects of field day operation that could be discussed - provision of food and drink, operating rota, logging method (paper & pen or software), but no group in its first foray into field day is going to get it 100% right - that's part of the fun. Make it a club or group event, involve as many people as possible, and learn together. There probably won't be any fog and it's very unlikely there will be any rats but remember the six essentials - FOGRAT - and enjoy your first field day.