[ARC5]

[Gordon White]

    The question as to whether the Command Receivers were "state of the 
art" when they were built begs the question.  They were built to a 
military requirement, and, for their day, certainly were the top of the 
art for what they were.

    While Armstrong invented the superhet design in 1918, it had not 
gotten into general use for another dozen or so years and was not 
commonly used in military avionics until the Type K prototype of 
Aircraft Radio Corp., the forerunner of the Command receivers.

    The Command Sets were designed to be light and compact, and to be 
modular, with units easily substituted in the system racks.  An 
SCR-274-N command receiver was three quarters the size of the SCR-183 
receiver it replaced. They had to survive in the aviation environment, 
from the cold of 20,000+ feet to the heat of desert air fields.  The 
lower air density at altitude posed problems of high voltage leakage, 
etc. Use on shipboard and in the tropics involved high humidity and 
mold.  The tests made on the equipment by the Aircraft Radio Laboratory 
at Wright Field and the Naval Research Laboratory at Anacostia involved 
heat, cold, vibration, altitude chambers, salt spray and other tortures, 
which the Command Sets passed.

    The Command Sets were not, originally, vhf because the military had 
no vhf channels in 1940.  They did not have crystal control because (1) 
the Navy tried crystal control in the early 1930s and had so much 
trouble with it they ruled it out until that science was greatly 
improved, and (2) crystals were in short supply and synthesizers had not 
been invented.

    The Command sets in my opinion did not have to have all the 
refinements of much larger and heavier equipment to be "state of their 
art," any more than an F-16 should have all of the attributes of the 
Concorde to be state of its art.

- Gordon White