The Temco RA-150 (late 1940s)

The Temco (stands for Transmitter Engineering Manufacturing Company) RA-150 is a blast to operate, especially if you're into "old buzzard" long winded style transmissions. If you've wondered why some people make 10 minute long transmissions this rig will explain why. It's necessary to key the oscillator first and then the plate supply to transmit; and do the reverse to receive again. Make no mistake about operating PTT here. You can actually master it with a little practice, and the Temco people made it easy for you since the transmitter has it's own "wired" remote control box attached to a 6 foot cable - neat!

The tube lineup is a single Eimac 4-65A tetrode modulated by four 6L6's in push-pull parallel. It will make just about 100 watts output on the lower bands and a little less on 15 and 10 meters.  Each band has it's own 1614 (a metal variant of the 6L6) oscillator, and it's necessary to change grid coils when changing bands. The internal VFO does not give a direct frequency readout, which is a little different than most ham rigs. You instead use a supplied calibration chart  to determine your operating  frequency, or else an external frequency counter to measure your transmitting frequency.  Even simpler,  I tune mine to zero beat into my receiver with the oscillator on.

 Transmit audio is “communications quality” and usually a bit better than that when used with a crystal element D104 or Turner 22X crystal microphonium. The secret is the high impedance of these two mics which allows improved audio response.

The Temco weighs about 200 to 250 lbs so be prepared to have a helper help you move it around your shack if you plan to relocate it.

One very positive note: Most of the caps are oil filled with the exception of the audio coupling caps in the speech amp. You'll probably be able to rekindle the power supply just by bringing it up on a variac. B+ is handled through a pair of 866-A’s.  Everything in the transmitter is easily serviced through the rear cover and each "module" slides out to facilitate repair. Everything seems to be made of the highest quality material at the time (1947-1948).The optional FM unit (tried it on 10 meters coupled to a pre-war Hallicrafters S-27) works very well.

If you're lucky enough to find one of these transmitters it'll be a forever "keeper" in your shack.

Mod-U-Later,

 Joe Cro N3IBX

                                          Click on images to enlarge

RA-150

Inside

Temco Control Head

Rear shot of top deck

Lower deck