[Amps] Big Solid State Amplifiers

[Rob Atkinson, K5UJ]

<<<The guys designing MF AM broadcast transmitters using arrays of switch 
mode power amplifiers are commercially driven. Modern transmitters in this 
field offer much greater efficiency, and
thus lower running costs, than traditional tube designs. And I'd be prepared 
to bet that the modulation linearity is better, too!>>>

It is a mistake to apply a commercial broadcast economic model to a ham 
radio station.  If you are transmitting every day for 18 - 24 hours to make 
money, a completely different set of demands is in place:  high reliability 
(hot switchable solid state rf modules, high margin CCS components), and 90% 
efficiency from solid state are desirable.  If you tx 50 kw 24/7 the expense 
of this kind of efficient advanced gear is justifiable because it will pay 
for itself after a few years of service in savings on the power company 
bill.  There are also other cost reductions.

A ham is just some guy transmitting for fun infrequently out of his house 
(comparatively speaking, with phone patches, traffic, and other service work 
the exception).  He is mostly concerned with the up-front one-time cost 
since he isn't making money on his station.  For hams, tubes continue to 
offer the best watt/<unit of currency> value today.  The operating costs of 
tubes are not that punishing for a ham unless he's running his amp on the 
air for hours every day (I wonder what that's like--I should live so long to 
find out).  This may all certainly change in the near future however.

Rob Atkinson
K5UJ

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