Technical Topics

摘要

The use of two gang-tuned LC resonant circuits in a low-noise VHF oscillator for a synthesised HF receiver was first described by Colin Horrabin, G3SBI, in 'TT' (July 1994) including details of a prototype stripline design, and a similar approach was used by John Thorpe for the AOR AR7030 receiver. This form of low-noise oscillator was revisited in 'TT' April 2002, pp62-65 which stressed the importance of reducing close-in phase noise in high-performance receivers, particularly those with synthesisers. In subsequent issues, Mike Hall, G3USC, and John Crabtree, KCOGGH, questioned the theoretical basis for the lower noise achieved by the double-tank approach, although both stressed the importance of reducing oscillator noise in order to minimise reciprocal mixing.