First, what is Field Day? It is an amateur radio event that is part contest, part emergency preparedness exercise, and part public demonstration of amateur radio. In my opinion, it's also a lot of fun. After all, what could be better than combining camping and radio with plenty of food and drink in the company of friends?
Field Day is sponsored by the American Radio Relay League (ARRL) and is primarily a North American event. It takes place on the fourth full weekend in June. Unlike most ham radio events, this one encourages clubs and other groups to set up operation out in public locations, instead of at our home stations.
The first Field Day was held in 1933, when an announcement in ARRL's QST magazine prompted several hams to operate using portable stations. This was not a trivial matter, given that these were vacuum tube radios. The event was a success, so it was repeated the following year and has been running ever since (except during World War II, when all ham activity was banned in the USA).
What does it take to operate a portable ham station? The essential items for a ham station are a radio transceiver, a microphone, an antenna, a feed-line to connect the radio to the antenna, and some way to power the radio and any accessories. This doesn't seem like much, but -- like most things -- it's often easier said than done. Of course, once you have the basics, there are some other things that are really useful and nice to have, like a table and chair. Since the event lasts for 24 hours, you also need shelter, food, and lights.
Now consider that, as a club, you are going to set up several stations with a number of club members, who all have their own ideas on how things should be done. The complexity increases rapidly with the number of stations and the number of members, so the challenge is to use equipment brought by a dozen people or so to put several stations on the air simultaneously.
How does this work?
In our case, we started organizing things at the club meeting about two months before the event. The first order of business was to find a suitable location. For simplicity, we decided that we should try to use the same location at the local fairground that we've used for the past several years. Naturally, this involved getting permission, but -- since we had done this before -- it was relatively easy. One of our members also contacted the county for the use of its communications trailer. Even though we'd used the trailer for the last few years, it wasn't easy to get in touch with the right person to make arrangements. In fact, it took long enough that we started seriously considering alternatives. Fortunately, we were eventually able to get assurances that the trailer would be available and even transported to the site.
We spent most of the next club meeting (a month before Field Day) going through lists of items that we needed. This year, to make it more of a challenge, the group decided that we should put an extra station on the air. This meant we had to have at least one more radio and antenna than we'd had in the past. We would also need more power for the additional equipment. Since the rules for our classification specify that we have to use emergency power for the radios, we couldn't just run an extension cord.
How do you power several radios (in our case, three of them) along with associated accessories, laptops, lights, etc.? Conveniently, modern ham radio equipment is designed to be powered by a 12V lead-acid battery, so a large RV battery is usually the first choice. Last year, we had two radios running off batteries with a generator to charge the batteries. Even though we used an extension cord to run the laptops and lights, we still had to swap out batteries several times. Clearly, we needed a better plan for this year.
Fortunately, one member took on the task of making sure we had adequate power. First, since the local university ham club was joining our operation this year, we were able to use its fuel cell. Next, a local solar panel installer got his ham license and was persuaded to bring his trailer of equipment he takes to home shows. The equipment included an impressive array of solar panels (which he said would be added to the system on the roof of his house), a 48V battery bank, and a charge controller.
Solar panels generating full power during the day. (Click here
for a larger image.)
Since the fuel cell also put out 48 V, we had the fuel cell and the solar panels both feeding the battery bank through the charge controller. The controls were set such that the solar panels always provided what power they could, and the fuel cell operated only when the battery voltage dropped (which meant that the solar panels weren't supplying enough power).
Fuel cell generating power at night. (Click here for a larger image.)
Thus, we now had an adequate supply of 48V power, but we needed 12 V for the radios. The university ham club anticipated this need and had power converters to convert 48 V to 12 V for the radios. The result was quite an impressive setup that worked very well. It's the first time I can remember us getting through a Field Day without worrying about not having enough power. The only use that the extension cord got this year was that one of our members used it to plug in a coffee pot on Sunday morning.
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