[ARC5] Command Set Antenna Relay Series Capacitor Use

[David Stinson]

----- Original Message ----- 
From: "Henry Frederick "Meils" Meiseles" <meils at get2net.dk>

I have two BC-342A (sic) units....


> The relay casing/cabinet has a 3/4" high, red
>..."MI" below a ½" red square;       seems to be
>6094   inside (hardly legible)
>both immediately to the right of the riveted label. ...

The red marking (other colors sometimes used),
which is actually "M1," indicates that
an official modification was done to the unit.
This mark is usually free-hand applied.
The "M1" modification was the answer to decades
of work, trying to eliminate static-electricity build-up
on aircraft antennas, which caused an overpowering
hissing sound in the received audio and occasionally
did damage.  Many complex "Rube Goldberg" contraptions
were tried.  The "M1" answer was a 1/2 watt, 1-megaOhm
resistor from the antenna lead to ground, which drained-away
the static charge without effecting the radio.
You see the mark on all kinds of aircraft radio equipment.

The orange square with numbers and/or letters in it
is the mark of a specific U.S. Army Signal Corps inspector,
indicating the item has been inspected and passed.
In pre-war USAAC equipment, this marking is usually in yellow.