We sourced a couple of very fine 7.5kVA 2-cyl Lister diesel generators
from trailer-mounted lighting towers being auctioned off by the
Highways Agency and building contractors. This kind of gear is
often bought for specific road-building projects and sold off
immediately afterwards. Can someone suggest a similar source in the
States?
These 60ft crank-up / tilt-over tower and generator combos are great
for field contests. They're generally in good condition, as they've
been properly maintained and always used under constant load. I've
found that the serious engine and generator manufacturers are very
good for supplying manuals and helpful advice, and "service kits" of
O-ring seals and gaskets are readily available. Overhauls aren't
difficult. You should fire up your generator once every two or three
months and leave it running for an hour or two against a load, like a
string of heat lamps or a fan heater.
You should obviously have the generator earthed at source, in addition
to any earth in the shack. Given that they tend to be deployed in
unpleasant conditions, often in a hurry, it's a worthwhile investment
to fit a good RC circuit breaker if it doesn't already have one.
Getting a good earth is generally more difficult at good VHF sites
(cliff and hill tops) than HF ones.
You should also consider having some kind of over-voltage protection
in the shack/tent/van to protect delicate gear. If a generator loses
regulation, it is likely to do so upwards. Ouch. As Yuri points out,
some generators' flywheels have problems smoothing the rapidly-varying
load applied by large SSB and CW transmitters. Some amplifiers have
choked supplies, which generators cope much better with than the more
common capacitor-input amps. Perhaps one of our resident amplifier
gurus could come up with a list of the more common types.
73
Al, GM4BAP
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