[Milsurplus] BC-221 types

[WA5CAB at cs.com]

FWIW, the actual impedance of an HS-30 is 256 ohms (128 for each R-30 
receiver).  The complete headsets were issued with one of four different cords, 
two short with PL-54 Bailout plugs and two long with PL-55 plugs.  The short 
and the long cords came in direct (256 ohm) low impedance and transformer 
coupled (8000 ohm) high impedance.

The RA-133 through RA-133-B were built for all be two models (and will fit 
in either the aluminum or the wooden cases.  The BC-221-B, BC-221-Q and 
TS-173/U use PP-79/UR.

Also, when used with either supply, the battery compartment was supposed to 
stay open whenever the set and supply was operating.  In most cases, you 
can tell whether a BC-221 has or had a homebrew AC supply in it without 
looking at the back by simply opening the front cal book door and sniffing for the 
odor of burned transformer insulation.  The military supplies have 
hermetically sealed transformers so the sniff test doesn't work for them.  You look 
at the battery compartment door and see whether it has been notched for a 
line cord.  If it has, and there is still an RA-133 or PP-79 inside, it is 
suspect.

In a message dated 07/29/2013 15:13:10 PM Central Daylight Time, 
mharmon at att.net writes: 
> Oh, BTW, you 
> really need to use a (relatively) high-Z headset like an HS-30 with 
> these meters.  You won't hear anything if you plug in a modern 8 ohm 
> headset.  Hallicrafters made a tube-type AC supply called the RA-133 
> that fits in the back of one of the big metal-cased BC-221s

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480