APR4/APR4Y Search receiver

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ARP4/APR4Y Search receiver

This equipment was a Search Receiver for use on aircraft or naval vessels. When supplied with all tuning units the system was used to:

1. Determine the presence and measure the frequency of any radar or radio signals within the frequency range of 38 - 4000 Mc/s.

2. Determine what modulation may be present on these signals.

3. Give an indication of the relative field strength of these signals.

4. Monitor a transmitter.

Technical Data

The equipment was first used in 1944 as APR4, using octal tubes and acorns, but over the years the equipment was modernized, using miniature tubes (APR4Y) and a multi-band tuning head (CV253/ALR). The APR4Y had reached U.S. disposal sources by 1965. (See CQ October 1965 p33)

The APR4 utilized a 115/80v AC supply at 60-2000 cycles and also required 28vdc @ 900ma to drive the tuning head motor.

The APR4Y required 115vac at 380-1000 cycles as well as 28vdc.

The receivers are improvements on the former APR1 (Air Force) and RDO (Navy) receivers. Plug in tuning units are used to cover the wide frequency range used: TN-16 38-95MHz, TN-17 74-320MHz, TN-18 300-1000MHz, TN-19 975-2200 MHz and TN-54 2150-4000MHz. (A later unit CV253/ALR covers 38-1000MHz)

The main receiver features a 30MHz IF channel, with provision for wide or narrow passband. There is provision for panoramic and video outputs for signal analysis. A BFO is provided for weak carrier detection and CW. The set has a calibrated IF gain control. High (8000 ohm) and low (600 ohm) audio outputs are provided. The APR4 has AM and CW detectors, while the APR4Y also demodulates FM.