Short-Wave Converter

When the first sputnik was launched with its 1-watt trans­mitters, operating at approximately 20 mc and 40 mc (mega­cycles), most owners of short-wave receivers were able to tune to the lower frequency, and with moderately good antennas pick up the signals from the satellite, especially when it passed over at some minimum angle above the horizon. However, many ordinary short-wave receivers would not tune to 40 mc, and the need for converters or new receivers was apparent.

A popular solution to the matter was to construct a converter. This unit could be provided in a very stable form by using a crystal-controlled oscillator at a frequency, which when fed into its mixer — either as a fundamental or a harmonic — would provide a signal which could be tuned in by the main receiver. Good signal-to-noise ratios were obtained by using a cascode radio frequency amplifier ahead of the converter mixer. The output of the mixer can be established at some relatively low frequency, such as 3 to 4 mc, so that good stability will be realized in the main receiver.