[ARC5] BC-946

[Mike Morrow]

It is a useful technique to properly identify EXACTLY the equipment in question.  There are many small but important differences in the USN's 1940 ARA/ATA, the USAAF's 1941 SCR-274-N, and the USN's 1943 AN/ARC-5.
 
Just one of those differences is the impedance of the AF circuits in the receivers and modulators.
 
->ARA/ATA, ALL Units:  Low Impedance 600 ohm ONLY.
->SCR-274-N, Unit nomenclature ending in "-A":  High Impedance 8000 ohm ONLY.
->SCR-274-N, Unit nomenclature ending in "-B":  High Impedance 8000 ohm as wired from factory.  A Low Impedance 600 ohm tap is provided with internal wiring change.  Units so modified have an external red-on-white decal indicating the wiring change to low impedance.
->AN/ARC-5, ALL Units:  Low Impedance 600 ohm ONLY.
 
You are thus in great luck.  You want low impedance AF from your ARA CBY-46145, and that is the ONLY impedance which that unit provides.  Do nothing.
 
Mike / KK5F
 
-----Original Message-----
From: Waldo Magnuson 
Sent: Jan 2, 2022 7:53 PM
To: 
Subject: [ARC5] BC-946
 
Yes, black wrinkle. Actually it is not a BC-946 but a Navy type CBY-46145, s/n is 1593, so it’s probably an early one.
Skip W7WGM