[ARC5] ARR2 info

[Ray Robinson]

Hi Francesco,

The AN/ARR-2 is the combined version of the ARR-1 (also called the ZB-3)
and the BC-946 command set. Used for homing, mainly US Navy.
Highly secret, they weren't declassified until 1949.

The ARR-1 was a small TRF set covering 234-258mhz, using acorn tubes,
the output was 800-1000khz. This set then connected to the BC-946
which took the signal and demodulated it to recover a morse signal.
The ARR-1 was also used with ARB and RU-18 receivers, there were 2 studs
on the top of these so it could piggy back, and be powered from the ARB
accessories connector. Also powered from the power adaptor on the BC-946.

The ARR-2 was a combination of these, in a Command set sized box,
which tuned fixed channels, and used minature valves in the font end.

An aircraft carrier had a rotating aerial, which sent out a different
morse character depending on the direction. When you received that character,
the aircraft knew which direction to turn to locate the carrier.

To prevent the enemy using this system to loacte the carrier, several
ideas were used. The range was small, only a hundred miles at 50,00 feet.
The codes were changed daily, so the pilot needed a new code sheet every mission.
The frequency was high, the enemy had few receivers capable of tuning
this frequency. The transmitter was only on when aircraft were returning.
The signal was double modulated, so if you had a single conversion receiver,
the output signal would be 1mhz, with modulation on that. Difficult for 
an audio stage to amplify, and to hear. The dial was
engraved with the wrong frequency, the 234-258mhz read 34-58mhz. Although
I have seen one with the correct markings, must have been post war.

73s
Ray	VK2ILV



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