[Boatanchors] Modern AM Modulation techniques

[w5jo at brightok.net]

Are those RF modules so expensive to preclude their use in Amateur 
equipment?   The commercial digital AM stuff for Amateur radio seems to have 
component problems and using those modules might take care of the problem.

Jim
W5JO

-----Original Message----- 

All of the AM medium wave broadcast rigs are solid state with class D
RF modules producing various power levels that are stepped on and off
by a streaming binary coded signal derived from an A to D circuit
sampling the program audio.  This is fed to a logic board that steps
on and off needed combinations of RF modules that are paralleled with
each other to provide the needed RF level at any instant.  A 50 KW rig
will have 50 to 100 modules, each using two FETs in power blocks of
500 to maybe 2 KW.  The modules are hot swapable.   Harris can make
rigs up to one or two megawatts by simply building bigger boxes with
more FET modules.
The master mind for this design was now deceased Harris engineer
Hilmer Swanson.  These rigs are about 90% efficient.

here's a brief description of how it works:

http://hawkins.pair.com/wabcnow.shtml#digmodsect

73

Rob
K5UJ