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Gary, Markus and others,
Oil jacket heaters are also fairly good dummy loads
for LF. A 1200 watt 230 volt heater has a resistance that is a bit under
50 ohms, but there is some inductance, so simple compensation with around 2200
pF (depends on specific heater) can neutralise the reactance at 136
kHz. Polystyrene or polypropylene HV capacitors are recommended. The
low Q compensation also raises the effective resistance by way of the
series to parallel transformation (consider it to be a form of L match, with
series RL and parallel C).
I have found that 1200 watt heaters with two
elements have lower inductance (with both switches on, elements are presumably
in parallel) than a heater with a single element.
The 1200 watt rating of an oil jacket heater is of
course a steady state rating, so you wont "blow it up" like you could with a
load that is only good for short term use.
You can use a domestic heater fed directly via its
mains plug (with clip leads), it does not need to be dedicated to LF :-)
If you want to, you can make a simple interface box, with SO239 to mains socket,
and put the compensating capacitor inside the box.
73, Bob ZL2CA
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