Radiotelegraph Keying Transients

An investigation into the nature of transients occurring when keying takes place shows that objectionable features of these transients may be reduced by suitable precautions. In the usual form of low-pass plate-supply filter, high C or low L are essential preventives of transients, and poor voltage regulation sometimes reduces their harmful effects. The transient is a damped sinusoid causing an initial drop in plate voltage when the key is closed. Two-section filters produce a double-frequency transient, the low-frequency component being the more important. Theoretical deductions are confirmed by oscillographic measurements on both rectifier and generator plate supplies.