[ARC5] [Milsurplus] Question: What is a BC-688-A?

[WA5CAB at cs.com]

SCR-618 was in between SCR-518 and SCR-718.  There is some information in 
one of the Green Books.

In a message dated 8/31/2009 8:42:52 PM Central Daylight Time, 
enrpnr at erols.com writes: 
> APN-1 was a common radar altimeter in WWII but it was low altitude only, 
> 4000 ft max altitude.  Operated CW on the FM principle.  SCR- 518 was an 
> early attempt at a high altitude pulse radar altimeter made by RCA at the 
> urging of Hap Arnold for high altitude (40,000 ft) bombing of Germany.  
> However it was overdesigned, heavy and took up a lot of space, (half a dozen 
> units I believe).  Was soon replaced I think with the SCR 718 that was much 
> smaller and only a couple of units.  There are a few complete sets around, 
> mine included so drill away, no historic loss since it has already been 
> stripped.
> Ray Chase
> 

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