Some Thoughts on Generators, Jerry Totten (K8JRO)

Jerry has put together an assortment of useful ideas and considerations for the use of AC generators in a ham environment. This article, published in Worldradio, June 2003 is used by permission of Jerry Totten (K8JRO). Click on callsign for email.


The excellent Search and Rescue column in the April issue by Jerry Wellman about emergency prepardness prompted me to submit a few thoughts about generators. I have been installing and repairing generators, everything from a 450 kW diesel to a 600 W gasoline unit, for about 40 years.

You have probably seen generators at a club Field Day site and may have thought about buying a small one for home standby and Field Day use. So, what size do you need?

If you are in a rural area, powering a deep well and a sump pump will be a priority, as well as the furnace, a refrigerator, and a few lights. You will probably need a unit with a 240 volt AC duplex receptacle. One rated at 5,000 W continuous duty should be adequate unless you have a special need such as a heat pump. Larger units are heavy, loud, and use a lot of gasoline.

If you don't need to run a deep well pump and a sump pump, you may be able to get away with a 3,500 W unit. It will still run a lot of radio equipment, too. But some generators in the 3,500 W size range are very limited as to the maximum current that they can provide to a 120V load and will not start a large motor. [Motor starting current is about 5 times the motor running current.]

Be sure to look for one that can be switched to 120V-only operation or one that has a 120V 30A output connector. You will also want a unit with a large gas tank (four or more gallons) so you won't have to fill it every few hours.

Contrary to what Jerry suggested, though, I have never seen a good used generator at a garage sale. Maybe i should do sales in Jerry's neighborhood this summer! If you do find a used generator, be sure to check it for output under load before you buy it. I use one or two 1500-watt space heaters as a load.

Discount building supply stores and hardware stores are good places to look for new units. Get a name brand that has a service shop in your area if you can. "Overhead valve" engines tend to be much quieter than the older "slide valve" units. In most of the country, a new 5,000 W unit should cost less than $500.00. That may seem like a lot of money until you are without power for a few days in the dead of winter!

Electric Start

Consider buying a unit that has an electric start. Gas engines with generators attached to the shaft can be very hard to start when cold. Some of the new electric start units also come with a 12V gel-cell battery and a small 120V charger.


Now that you have a generator, how do you use it? Always read and follow the manufacturer's safety suggestions. Never run a generator inside a building or near an open window, the wind can trap exhaust gasses inside a garage even with the door open.

For field day use you will probably need a few heavy-duty extension cords and plug strips. Be sure they are in good condition before you need them. I recommend that you ground the frame of the generator to a cold water pipe or a driven ground rod. This should prevent someone from getting hurt if the frame of the generator becomes "hot" due to a faulty power supply or light, etc.

I have found that most small generators do not put out a clean 60 Hz sinewave. This should not be a problem with most radio equipment, but may bother a computer or a TV. Laptop computers should work OK though. If your generator has an "Automatic Idle" control, turn it off. You won't want your generator going into idle mode when it is not loaded.

Additional safety considerations include ensuring that your generator outlets have GFI (ground fault interruptor) capabilities, or you mount a GFI outlet in an electrical box with a cable to plug into the generator outlet. This is an inexpensive precaution that can save your or another person's life!

A Transfer Switch

If you are planning on using your generator as a standby power for your home QTH during an "outage," you will need a generator transfer switch. That is, unless everything you plan to run can be plugged into extension cords. many of the discount building supply stores cary transfer switches and generator panels.

Never ever use a "suicide cord" to back feed power through an AC outlet. This is not only very unsafe but is also against the law. You could hurt or kill someone and/or ruin your generator.

Make sure you have a 24-hour supply of fresh gasoline. If you plan to siphon gasoline from your car or truck, try it now. Many new vehicles have a screen inserted into the filler neck to prevent siphoning. I allways have two five-gallon cans that are used to fuel the yard tractor, push mower, tiller, and snow blower. As soon as one is empty, I refill it and start to use the other one.

Most new generators come with a quart or two of thirty-weight oil for "break-in." Thirty-weight oil is OK during warm weather but is a poor choice in cold weather. Most small engines are "splash" lubricated, and thirty-weight oil is just too thick to splash when cold. I use 10W30 oil at all times of the year. I recommend switching to a synthetic 10W30 oil at the first oil change. This thin enough to lubricate at 0 degrees F and should be OK in hot weather. A lot of owner's manuals now recommend synthetic oil for year round use.

Spare Supplies

Keep an extra quart of oil, a spare spark plug, and a set of brushes on hand just in case. Run your generator for at least an hour or more at least every six months and shut the gas off at the tank and let the carburator bowl run dry. This will insure that you won't have varnish in the carburator. I keep a gallon or two of gas in the generator's tank to prevent rust and condensation from forming. A generator that won't run is not worth much in an embergency or at Field Day!

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