[Milsurplus] 51J-2

[W7QHO at aol.com]

All,

I've owned a 51J (which I took to be a J-2) and currently have a 51J-4.   The 
earlier set had a box shaped LMO (I forget the number) and the osc. tube was 
a 6SJ7 mounted under a drawn metal cover.   The glass thing screwed in next to 
the tube socked is indeed filled with desiccant crystals.   I read someplace 
that the assembly was something originally designed to screw into the spark 
plug holes on aircraft engines while in storage.   The 51J-3 and J4 both used 
the later Collins cylindrical LMO with miniature tubes (osc. and buffer amp.) 
and better sealing.   The 51J-4 added the three mechanical filters.   In all 
other respects the sets were basically the same (tubes, conversion and IF 
frequencies, etc.).

The R388 is essentially a 51J-3 The meters are shaped differently, though, at 
least in several examples I've seen.   Like Robert, I've heard of an R388A 
which had mechanical filters but I've never one either.

Dennis D. W7QHO
Glendale, CA