[ARC5] Coil Color Codes

[Mike Morrow]

Wayne asked:

> Do any of y'all have a color code info for the Command Set receiver
> and transmitter coils?

1.  Receiver Band Color Codes (Paint Dot)

COlOR    RF COIL SET MHz    IF and CW OSC kHz
BROWN      0.19 - 0.55          85
RED        0.52 - 1.50         239
ORANGE     1.50 - 3.00         705
YELLOW     3.00 - 6.00        1415
GREEN      6.00 - 9.10        2830

RF COIL SET INDIVIDUAL COIL POSITION - ALL BANDS
COLOR      COIL
RED        Antenna
YELLOW     Amplifier
BLUE       Oscillator

IF COIL POSITION - ALL BANDS
COLOR      COIL
RED        First
YELLOW     Second
BLUE       Third

2.  Transmitter Oscillator Coil

COLOR       BAND MHz
BLACK       2.1 - 3.0
BROWN       3.0 - 4.0
RED         4.0 - 5.3
ORANGE      5.3 - 7.0
YELLOW      7.0 - 9.1

Reference:  AN/ARC-5 Maintenance Instructions, AN 16-30ARC5-2, Figure 7-3.

> And has anyone checked to see if the inner and outer MO coils are swapped
> around from unit to unit to produce different frequency ranges?

The inner coil in the MO is not a frequency-setting coil.  Only the heavy main coil winding performs that function.  The inner coil may be abandoned, and often was in post-war ham hacks.

It does not even exist on the MO coils for the T-15 and T-16.  But for all other versions, one side of the MO heater is tied to the cathode, which then taps into the MO primary winding.  The inner coil connects to the OTHER SIDE of the MO heater.  This sets the cathode and both sides of the heater within the cathode at the same RF potential so that, as the manual says, "variations of cathode-to-heater capacitance within the tube will not affect the frequency of oscillation."  Elegant...but not a frequency-setting effect!

Mike / KK5F