[BC] The ultimate radio?

[Lewis Munn]

Willie,
   
  28D7 was one I recall.  I think they were mostly used in the aircraft radios..ARC5 series sticks in my mind but not sure.  Little boxes about 4" square in the front and a foot long.  Apparently interchangeable in shelf racks with captive connectors.
   
  I do not think you'd want a portable radio with 18 D-cells in it!
   
  The 1.5 (and 3V that would run on 1.5 in a parallelled filament connection) were around a long time.  I recall the first FIM I used back in the 50's or 60's used 1T4's as amplifiers.  Since the filament required only 1 zinc-carbon cell, it was economical and light.  And they would work with a not too beavy 67.5V plate battery that lasted a long time.  D-cells were popular in flashlights, so the filament cells were easy to get.  And we had no transistors to make efficient inverters for plate supplies.
   
  3A5's made nice QRP transmitters.  Or audio outputs.
   
  The 28D7 was a fairly large GT octal, not good for really portable uses, same with the others in the series.  Took an airplane to lift them!  And to power them.  I think they went out in the '50's.
   
  I think the miniature 12V auto radio tubes just got shoved out by transistors.
   
  Transistors used one small 9V battery, whereas 12-V tubes would have required 8 D-cells, and and so lost out.  Size and weight, and eventually cost.  Could not make a vacuum tube for 25 cents.
   
  Aside from solid state, the 1.5V filament tubes were the best combination of size, lightness, cost, and battery consumption and availability that came along.
   
  And I recall a radio that used the 1-series tubes so it could be battery, but had a 117Z6 rectifier for running off the AC line!
   
  Looey Munn
  Roundup, MT
  

WFIFeng at aol.com wrote:
  The thing that I am very curous about, though, is why these didn't make it 
into portable sets?
		
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