Brief Training Segment for 2006/03/22 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.

Last month, we discussed the basics of generators. This month, we will discuss a special class of generators: the small, portable, lightweight, inverter-based generators.

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.

To review from last month, there are a variety of available generator types and sizes. Some generators are designed for permanent installation at your home or business. For emergency communications use, many of us will desire to use portable generators.

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.

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. training next month.

As I mentioned above, many of the benefits of this class of generators arise from an innovative combination of an advanced alternator and an inverter that produces stable AC power. Conventional alternators used in portable generators generally have two "poles", and produce AC power which is directly supplied to a load without additional conditioning. There are a number of consequences that result from this design. The frequency of the AC power provided by the alternator is proportional to the rotational speed of the alternator, and because the alternator is directly driven by the engine, the alternator speed is the same as the engine speed. In many cases, the output voltage is also proportional to shaft of engine speed. Thus, the engine speed must be carefully controlled to provide a stable output frequency and voltage. Also, the engine speed must run at a constant high speed, regardless of whether the generator is called on to provide maximum rated load, or no load.

The inverter-based generators use a multi-pole alternator to produce an intermediate high-voltage, high-frequency AC output. The intermediate output is fed to an inverter, which provides near-sine-wave AC, at a stable frequency and voltage, independent of the rotational speed of the alternator. Because the alternator operates at a relatively high frequency, the alternator need not be as large or heavy as an alternator of equivalent output power operating at 60 Hz. Because the inverter output frequency and voltage is independent of the alternator rotational speed, the engine can be throttled down, to save fuel, and reduce noise, when the generator is not required to provide high output. Because the output waveform is synthesized, the output of 2 or more generators can be synchronized, permitting the generators to be operated in parallel. This allows additional fuel savings and noise reduction.

Further considering the issue of noise reduction, these generators tend to be enclosed and have effective mufflers.

For example:

Yamaha EF1000iS 1000 0900 050 2.2 28 47dBA

Yamaha EF2400iS 2400 2000 171 5.5 70 53dBA Tw

Yamaha EF3000iSE 3000 2800 171 5.5 152 51dBA

Honda EU1000i 1000 0900 050 1.8 29 53dBA

Honda EU2000i 2000 1600 099 3.5 46 53dBA

Honda EU3000iS 3000 2800 196 6.5 135 49dbA

Rated at 7 meters.

Brushless, multipole alternator.


Pulse width modulation.

Load-dependent throttle.

Voltage stability +/- 1%.

Frequency stability +/- 0.1%.

Four-stroke engine.

DC output for battery charging only.


Don R. Burman KB9WBM reports a good source for relatively high-capacity rechargeable batteries.

Universal Battery BB-12350, a 35 Ah, AGM battery

Using SEP, I got 2 batteries for $79.90 total

($39.95 each) - less than the price of 1 battery

from Batteries America BEFORE shipping charges.

Free shipping over $50.