[Milsurplus] Re: Beauty in the SCR-508 beast

[Unserviceable but Repairable]

Mike, you're not alone - sic

} Under current FCC rules, Signal Corps "Armor-band" radio sets 
} operating in the 20.0 to 27.9 mc range have value only as static 
} relic displays.  That's too bad.  When they were still in service 
} and the solar cycle was good, there must have been some very 
} surprising long range[*] contacts possible with, say, units like the 
} BC-603/604 combo.  (I'm probably one of few who see the SCR-508/528 
} as a thing of beauty.)

We have a 603/604/FT-241 running here in 12V on 29.04 mhz using a
"channel 38" 440kc '604 xtal.  Channel 38 supposed to be 23.8 mcs.

How?

Tune "peterson coil" comb generator to 11th rather than 9th harmonic on
604.  Downstream tripler & doubler tuned as usual.  The '603 here by
Colonial in fact goes up to around 29.3

Note 'artillery' BC-684 does just this 11th harmonic process & it's not 
wierd science.  Don't know why this invention of a pal's wasn't 
discoverd a half century back.

'508 here runs with Link SCR-298 that was a "govt appropriated" 6V
police FM 2-way fm '41 & '42.  Chassis has tube IDs rubber-stamped 
"JAN 7C7, JAN 7A8, etc."  Apparrently these hadn't yet been assigned "VT"
ids.

Link used Armstrong-licensed balanced modulator xtal-controlled phase
modulation.  I surmise that Galvin evolved xtal-AFC-lock direct FM &
WECo came up with the xtal/comb-generator to bypass Armstrong.[**]  But
Armstrong released his license for the war effort &, to my knowledge,
the Galvin & WECo methods became so entrenched that nobody noticed

Do try the 604 11th harmonic tune & surprise urseffs w. band-plan legit
"tank" 2-ways.

Love those shiny buttons.  US Army 1943 bling-bling which was used up
thru Korea.

   Marty


 *fleet tugs had 620s & 659s aboard.  I've a collected tale from
  a perky W5 OT at Shelby Hamfest, '1997.  Story of a 36mc 659-659 
  sporadic-E contact from the Sulu sea to the Phillipines in late '44.
  1500 mi.

**remarkable story in 'Green Book 1" on how army got into FM. In 
  there appeared note about success of Link eqpt. but concern over 
  ability to deliver huge quantities.  Hence a design competition ensued
  wherein Galvin was unable to demo their xtal-AFC-lock (as in BC-620
  & 659) so WECo got the contract