[MRCA] Military Antenna Tuner

[Mike Morrow]

Paul asked:


> Wondering if anyone in the group could shed some light on a small 
> military antenna tuner? The tuner is black in color, 7 inches high,
> 6.5 inches deep, and 3.75 inches wide. Here is the odd thing. the
> tuner is for only the broadcast bands 500 kc to 1500 kc. It is a
> variometer type tuner. One knob labeled "Tune To Minimum P.A. Plate"
> another knob labeled one through 7 for the tapped inductor. Text near
> the bottom provides a trailing wire would be used (500 to 1100 kc use
> 200 feet of wire; 1100 to 1500 use 1500 feet of wire). There are two
> porcelain insulted terminal posts labeled "Antenna" and " Transmitter.

There is no doubt that the unit you describe is the CU-26/ART-13, designed
for USN T-47/ART-13 transmitters with the optional six-band O-16/ART-13
LF/MF oscillator (200 to 1500 kHz).

There is an earlier (but identical) version for the ATC and ATC-1 versions
of the AN/ART-13.  It is the nt-47282.

> There are no model numbers anywhere. 

Your unit should have either one or the other of these markings.  It most
likely is a USN nt-47282, many of which used plastic nomenclature tags
that get damaged.  

> It almost looks like it could have been attached to something else...

The only "mounting" is the back cover plate, which would be drilled and
mounted on some firm metallic structure near the transmitter.  On the
CU-26/ART-13, that unmarked back plate is officially known as the
MT-162/ART-13.

The various external LF/MF tank units for the ATC or AN/ART-13* are more
than just antenna tuning coils.  The transmitter itself has **NO** PA tank
coil or other tuning reactance for LF/MF operation when the optional LF/MF
oscillator is in use.  ALL of the transmitter's LF/MF PA and antenna tuning
is performed with this tuner.  It consists of variable inductances and a
fixed capacitance.  

The most common external tank units:
CU-25/ART-13    200 to 600 kHz, usually requires SA-22/ART-13 switch unit
CU-26/ART-13    500 to 1500 kHz, usually requires SA-22/ART-13 switch unit
CU-32/ART-13    200 to 600 kHz, includes functions of SA-22/ART-13.

Mike / KK5F