Whatever Next

摘要

Early commercially-built VHF handheld transceivers forthe amateur market were FM single-banders. Next came the dual-bander, then the dual or tri-bander with wideband receive and detectors for AM and wide FM. Unfortunately, on these transceivers, AM is all too often received through the narrow FM filter. Even a filter for 12.5kHz FM channel spacing is a little too wide for AM broadcasts, because medium-wave AM stations are spaced at smaller intervals (9kHz in Europe, 10kHz in the USA). On short wave the position is even worse, the standard spacing for AM broadcasts there being 5kHz.