[1000mp] Very Hot Final Heatsinks

[Adam Farson]

Hi Rob, 

To quote: "with the increased popularity of high duty cycle modes, plus a
renewed interest in AM, the finals on rigs are getting a workout they did
not receive back in the days when a transceiver was made to do ssb and cw.
i wish manufacturers could make the new rigs more like ccs transmitters, but
i guess the cost would by sky high."

It is all a matter of what most amateur purchasers as well as non-amateur
users want and are willing to pay for. It is probably true to say that the
majority of customers who purchase a given HF transceiver will operate it on
SSB and CW, and are content with the typical "100W-class" rig powered from
13.8V DC. High-powered key-down modes are probably best addressed by an
external power amplifier. If the amplifier has adequate power gain (12 dB or
better) the exciter will not need to work very hard.

The only non-broadcast HF radio service which still uses A3E emissions (DSB
AM) is the ARS. AM is no longer authorised in any of the other services in
this category. This is a disincentive to manufacturers to provide anything
more than minimal AM or "AME" support in multi-market radios. A day may yet
dawn when A3E will quietly disappear from the ARS as well.

An interesting approach would be to use a transceiver's RF transverter
interface (typically 0 dBm transmit output) to drive a high-gain,
multi-stage external PA. A 1kW PA would need 60 dB power gain, achievable
with 4 or 5 stages. Such an amplifier would be rather complex, as it would
be packed full of RF interstage and output  filters!

Cheers for now, 73,
Adam VA7OJ/AB4OJ



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