Brief Training Segment for 2006/02/22 Net
Although there are a number of sources of back-up power for an amateur radio station to be used for emergency communications, generators are among the most versatile. They are fairly reliable, and if properly refueled, can run for an extended period.
A disclaimer is in order here. I will be mentioning specific technologies, brands and prices in this training. I am not qualified to, nor do I intend to, recommend any particular type, brand or model of generator, nor any vendor. I mention brand names and prices simply to give some data points to make the training a little more concrete. If you're interested in buying a generator, please do your own research, and where appropriate, consult an engineer, electrician, or other qualified professional for advice.
There are a variety of available generator types and sizes.
Some generators are designed for permanent installation at your home or business. These are typically driven by an internal combustion engine, and most are fueled by diesel oil, natural gas, or propane, and may have power outputs starting around 5KW and going up to whatever your application may demand and your wallet can afford. As an example, a 10.5KW natural gas generator from Kohler is advertised at around $4000. You might consider what fuel is appropriate for your specific location, including such factors as durability of generators using that fuel, cost of the fuel, your ability to store fuel safely and without deterioration, and your ability to acquire fuel in an emergency when your supplies run out.
Some of these generators come with enclosures to reduce operating noise. In most cases, for a number of reasons, it is not feasible to connect a generator in parallel with the commercial power mains. Thus, uou may need a transfer switch with one of these generators to allow your home to be powered from the generator instead of the commercial power mains.
Other generators are designed for application in a vehicle, such as a motor home. These generators operate independent of the vehicle's propulsion engine, and tend to be fueled with diesel, gasoline, or propane. Vehicle-application generators seem to be relatively expensive. For example, a 4KW gasoline fueled generator, specified for motor home applications, sold under the Onan brand, is advertised for around $2700.
There are also a number of trailer-mounted generators, used in construction, for temporary power requirements at fairs and festivals, and by emergency service agencies. These tend to be rated at higher power and are quite expensive, and are probably out of reach to most of amateur radio emergency communicators. However, you might encounter one if an agency you are working with owns or rents one.
Most amateur radio emergency communicators will be interested in "portable" generators of one sort or another. The term "portable" needs to be taken with a grain of salt. Some of these generators are wheeled, so they can be moved around relatively easily, but are quite heavy, and require a couple or a few people to lift into a vehicle.
Typical generators in this category supply 1KW to 8KW of power, and are fueled with gasoline or propane. Diesel-fueled generators are available, but usually cost significantly more than a equivalent gasoline-fueled generator for relatively low-power-output categories. Most of these generators employ 4-stroke engines, but some generators powered by 2-stroke engines are available. In the case of gasoline-fueled engines, 2-stroke engines may be a little more efficient, but usually require that fuel and lubricating oil be mixed in a prescribed ratio before fueling.
Portable generators start as low as $200 for bare-bones, gasoline-fueled, 2KW models, and go up. 4KW, manual recoil start, gasoline models are available in the $400 range, but some well-known brands with additional features can be double or triple this amount. A typical 4KW generator of this type weighs 140 lbs and includes an engine in the 8 HP range. Some generators are available with electric start, which may be a convenient feature. Some generators are equipped to use multiple types of fuel. For example, there are generators which may use either gasoline or propane, or natural gas. This is a great feature, but it can add 30% to the cost of the generator.
Most of the portable generators are open-frame, which means that they are quite noisy--in the range of 65-75 dBA It is possible to purchase enclosed generators, which are generally heavier, but quieter, than the open-frame style.
Conventional portable generators employ single-phase alternators which directly produce alternating-current power. These alternators must spin at a constant speed to provide a relatively constant frequency for use by motor-driven appliances and such. As a result, the engine is always running at a constant, high, speed, and making a lot of noise, even when the load on the generator is minimal. There are a number of voltage regulation schemes available. Some generators control the output voltage by simply trying to maintain a constant rotational speed. There are some other voltage regulation systems available for conventional generators, but it would take too long to discuss them all, so if you're interested, I suggest you consult an internet search engine.
Finally, there is a class of small, portable generators that use an advanced alternator design and an inverter to provide a generator that is very quiet, small, and lightweight compared to ordinary generators of the same capacity. These inverter generators are ideal for amateur radio emergency and public service communications, and will be the topic of our training next month.