Generators for Portable Stations

Generators are commonly used to power portable stations, and are the best option for long-term use. These may be supplemented by deep-cycle batteries to bridge over periods where the generator must be shut down for refueling, maintenance, or quiet hours.

QST magazine published a review of gasoline-powered generators back in June 2012. (You must be an ARRL members to access the review.) The information is a bit dated, but on the other hand, generator technology hasn’t changed that much in the intervening 10 years. The review considers not only the features and general usability of the generators but also their radiated emissions at HF frequencies.

Current 2 kW inverter generator models from both Honda, Yamaha, and Westinghouse (and perhaps others) have the ability to join two generators (of the same make and model) together with an optional control cable to synchronize the inverter outputs. This enables the outputs of both generators to be paralleled, yielding 3.6 kW total power. Should you do this, you will need a a suitably-sized twist-lock power cord, and a portable circuit breaker panel (sometimes called a spider box) to split the 30A circuit into several 15A and/or 20A circuits.

If you have a portable generator, it is important to drain the fuel during periods of disuse. My mechanic recommends draining the fuel from the fuel line and carburetor as well as the gas tank and spritzing a few squirts of Gumout carburetor cleaner into the carburetor. This flushes out any residual alcohol in the system that causes long-term damage. On my 14-year old Yamaha generator, there is a drain valve that makes this easy to do.

Older generators needed to run at a constant speed (usually 3600 rpm) to maintain 120 V at 60 Hz output. In the newer inverter generators, an electronic circuit synthesizes the AC waveform so the generator can throttle back when lightly loaded, reducing gas consumption, pollution, and acoustic noise. (You can easily carry on a conversation in a normal voice while standing next to any of these units.) However, when the load imposes a sudden demand for additional current, the voltage can briefly sag until the generator speed ramps up. My Yamaha EF3000iSEB generator has an electric starter that is powered from a small (7 Ah) lead-acid battery. The inverter is designed to briefly “steal” charge from the starter battery to hold up the inverter’s output voltage during such transient demands. During Field Day with three 100-watt stations in operation, you can hear the generator constantly adjusting its speed in small increments as the current demand changes. But the output voltage remains steady, and I can imagine that the boost feature reduces mechanical stress on the generator. It doesn’t appear that the smaller generators have this boost feature.

We have not had issues with RFI from my 3 kW generator. However, its size and weight is a bit of a challenge. The current crop of 2 kW models represents the sweet spot in terms of size, weight, and capacity, even without the boost feature. A number of MCACS members have the Honda eu2200I model and speak highly of it.

Another alternative is a “pup” generator. The June 1997 issue of QST carried an article describing how to pair a small lawn mower engine to an automobile alternator to produce a system that could rapidly charge one or more 12-V deep cycle batteries. W3TDH has the materials to construct a pup generator as described in the article, should anyone want to take that on as a project. Again, you need to be an ARRL member to download the article.