[Milsurplus] BC-348-R

[Mike Morrow]

Dave wrote:

>I use my BC-348s with 600-ohm matched speakers and
>the volume level is plenty enough to run me out of the room.
>If a properly matched speaker is low-volume, there is 
>some other problem.

Indeed, there must have been a fair amount of AF power
available from the AF output stages of the BC-348 liason
receiver, the SCR-274-N or SCR-522-A command receivers,
and the SCR-269 ADF receiver to support all the headsets
which could be aligned to them simultaneously through the
aircraft interphone system, such as the common RC-36.

The WWII-era aircraft interphone systems did NOT amplify
the AF output of the receivers that were connected to the 
interphone.  In the case of aircraft like the B-17 or B-24,
there were typically at least ten interphone stations as
part of the RC-36.  At worst case all ten of the stations
could select the same receiver, resulting in ten HS-33-type
headset coils connected in parallel to the 600 ohm output
of a receiver.  But usually, the ten stations would be
connected in parallel across the output of the single-tube
(VT-99/6F8) interphone mic amp of the BC-347 interphone
amplifier.  It's amazing that the AF output of a typical
receiver or the interphone amp itself was sufficient to 
adequately supply enough AF power to supply all those
multiple loads in noisy aircraft conditions, especially
as multiple connected stations created greater and 
greater AF impedance mismatch to the AF output stages.

WWII-era USN interphones also did not amplify the AF of the
receivers connected.

Apparently, it worked well enough.  So, it would be 
surprising if a properly working receiver could not supply
enough AF output to supply a reasonably matched speaker.

Mike / KK5F