1955 CONELRAD Receiver

1955ConelradRXUnder the headline, “Are You Ready For CONELRAD?”, the April 1955 issue of Radio News carried the plans for this small CONELRAD receiver which could be easily carried in a pocket or glove compartment. The circuit is very similar to the Conelrad receiver carried by Boys’ Life the following year.  This receiver also consists of a crystal set followed by a one-transistor audio amplifier.

The article describes CONELRAD, and notes that “the responsibility of the individual citizen and particularly of the electronic technician and experimenter would be to provide themselves and their families well ahead of time with some means for receiving Conelrad broadcasts under any or all emergency conditions.” The article noted that receivers should be exactly calibrated, to avoid losing valuable seconds fumbling around trying to find 640 and 1240 on the dial. The article suggests using a signal generator to calibrate and mark the dial before an emergency.

1955ConelradSchematicIt then offers the circuit shown here, since it would be “highly advisable to have available at all times a portable battery-operated radio. The average portable radio is fairly cumbersome to carry about over any appreciable distance and its power requirements are high enough to make it impossible to keep in operation continuously.

The author notes that his original plan was to have one transistor serve as the detector, but had some difficulty in designing the circuit, due to the low input impedance of most transistors. Therefore, like the author of the Boys’ Life design, he settled on a diode detector, with one stage of audio amplification.

Unlike the Boys’ Life model, which was mounted in a cigar box, this one is mounted snugly in a small plastic box. The author notes that “as most old crystal set men will recall, a fairly long antenna and a good ground are required for best results.” Therefore, he recommended taping 25-50 feet of fine wire to the case for use as an emergency antenna.

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