[Elecraft] kpa500 builders

[Ron D'Eau Claire]

In the 1950's I was an operator of an AN/GRC-26 portable radio system in the
U.S. Army. It ran phone (A.M.), digital (RTTY) and CW. The transmitter was a
BC-610 which I believe was the successor of the HT-4 transmitter shown here.


The whole "portable" system was built into a hut that was mounted on 2-1/2
ton 10-wheel truck pulling a 1-ton motor generator on a trailer behind it.

Had some real adventures climbing mountains off-road with that rig, but it
had two huge advantages over today's "pocket-portables" - we could stay
inside the hut out of the weather and it had a coffee pot. 

The Ham activity on the film has one huge missing bit: no heterodynes! When
two A.M. stations are close enough to the same frequency to hear the audio,
you also hear a loud tone whose frequency is the difference between the two
carrier frequencies. Often on a crowded band like 20 meters you might hear
three or four of these heterodynes blasting away on top of the audio of the
station you are trying to hear. Unlike today's rigs, most "phone" receivers
of the 40's and 50's had a 6 to 10 kHz bandwidth! 

In the early days of SSB, that lack of heterodynes was the most common
reason cited by Hams for leaving AM for SSB. Power efficiency, denser band
occupation, and the like were secondary reasons, at best.  

Ron AC7AC