[Milsurplus] BC-344

[WA5CAB at cs.com]

BC--314(*) was part of SCR-177-B.  I've always assumed that BC-344-(*) 
performed the similar function with SCR-188-A, although it isn't listed as such. 
 Either would have been used when the associated Radio Set was issued with 
any of the MF tuning units (except not with the TU-5).

At the beginning of WW-II, the relatively new LS-3, LS-7 and HS-23 were 
expected to be the standards for the next several years.  They are all either 
7000 or 8000 ohm input units.  The output impedances of the newer receivers 
(BC-224, 312, 342 and 348) were all 4000 ohms.  The idea was that from one to 
four of any mix of those audio loads would work with no more than a 2:1 
mismatch.  When headsets and eventually loudspeakers went to 500 ohm, the 
output transformers were tapped at 250 ohms.  Same scenario as with the High-Z 
accessories.  How/why 500 became 600 I don't know.  Typo on an order, maybe.

In a message dated 8/29/2010 7:08:12 PM Central Daylight Time, 
telegrapher at q.com writes: 
> What system might have the 344D been associated with?  Since it's powered 
> by 120Vac, perhaps a tower environment tuned to one of the A-G channels?  
> What speaker was associated with it.  Neither of my Tm 11-850-N nor TM 
> 11-850 address the issue as i can see.
> 
> In the chart in front of TM 11-850 the 314 (12V) and 344D (120Vac) are 
> standalone units, not associated with anything in particular.  Must be more 
> info out there someplace.   Why the 250 ohm speaker/phones tap?  
> 
> Larry
> W0OGH
> 

Robert & Susan Downs - Houston
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