[Doug Houston]

High frequencies were known before WW II in several places. For home radios, FM broadcasting began in 1940, and used the frequencies from 42-50 Megacycles.

Then, television channels picked up after the FM band, and prewar channel 5 became postwar channel 4 (66-72 Magacycles). I'd need to look it up, but there six prewar channels, so the TV spectrum went a tad higher than the old channel 5.

Now, Hallicrafters made two models (actually the same set, cepackaged) the models S-27, and S-36. Both covered from 27 Megacycles to 155 Mc. Both sets had AM or FM reception.

Then, the Halli. S-37 picked up after the S-36, and went all the way to 216 Megacycles, which was the top of old TV channel 13 (210-216 Mc).

Tube technology was the key to high frequency performance. The first 7 pin miniature tubes were beginning to appear just prior to WW II for us, the tubes that made high frequency use possible were the "acorn" tubes: 954, 955, and 956. These were in the front ends of those Hallicrafters sets just mentioned.

The front end of the TV sets had to be content with a 1852 (6AC7) mixer,, and 6J5 Oscillator. They worked, to the surprise of many, even RCA, we can bet.

The new 7 pin jobs were: 9001, 9002, 9003. there was also a good little RF tube: 6AK5, before the war.

Loktal tubes, pioneered by Sylvania, proved to have superior performance to many (most) octal based tubes at high frequencies, because of their revolutionary new interior design. But RCA would never have been caught dead, using another company's tubes, so they never used Loktal based tubes.