The big issue with parts like the ARF-1500 is managing the heat. For
high duty cycle use, like contesting or RTTY (or worse yet, contest
RTTY :-) ), you are dealing with dissipating something like 1500 watts
of heat (assuming 50% efficiency running class AB) being generated in
an area about one inch by three inches.
That is a solvable problem, but not for most ham's who don't have a
background in thermal engineering. Notice that the HL-2.5KFX is not
rated for full power high duty cycle use - in fact it shuts down when
the heatsink reaches 100 degrees C.
It is much easier to deal with the heat if it is being produced by
lower power parts, spread over a larger physical area. NB: For the
ragchewer or DX'er this is much less of an issue, because the lower
duty cycle makes life much easier than for contesters.
Also, although people are constantly talking about transformerless
power supplies for these higher voltage parts, in the real world the
best source of power supplies for high power solid state amps is the
telecom surplus market. 48 volt switching supplies rated at 50 amps
are frequently available on eBay (e.g.) for under $100 - and they are
small and light weight.
***dan, K6IF
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