The Morse code signals sent by a transmitter long used for on-the-air radio vintage radio events at W2AN, the amateur radio station of the Antique Wireless Association, Holcomb, New York, have a distinctive bongy, "bell-like," blown-Coke-bottle sound that many long-time radio amateurs find tuggingly nostalgic. That's the sound of primary keying—Morse code formed by making and breaking the alternating-current (ac) mains connection to the plate (or plate and screen) power supply of a vacuum-tube-based transmitter. As it was commonly implemented, primary keying is potentially hazardous and may involve some sacrifice of transmitted-signal purity to achieve acceptably rapid keying waveshape rise and fall times. This page describes two approaches to obtaining the primary-keying sound: a vacuum-tube cathode keyer and real primary keying—real primary keying done at a heater-class ac voltage rather than at 120 V, that is. In both cases, the aim is to recreate the beautifully soft sound of primary keying without interrupting dangerous voltages and without adding ac hum to the transmitted signal—at keying speeds suitable for each New Year's Eve's ARRL Straight Key Night.

To be continued...