RE circuit design (5) - VHF/UHF noise generator

EE 62 November 1986 RF CIRCUIT DESIGN VHF/UHF NOISE GENERATOR Noise is a phenomenon most constructors of RF (and AF) equipment have come to know as an undesirable, yet inherent, property of active devices. Therefore, it is paramount to lay out input stages for minimum noise production, we are told in most textbooks. Then why purposely generate noise when it is to be suppressed with all means available? It was already noted in various ar- ticles in this magazine that aligning an RF input stage for maximum am- plification is not usually the best way of achieving optimum performance if the receiver is to detect input signal levels only just above the noise threshold. Setting-up pro- cedures for receivers therefore com- monly finish with some instruction to align the RF input stage for lowest noise, not maximum amplification. But how does one go about doing that? The present design of a wideband noise generator is based on the prin- ciple of audible comparison be- tween receiver and g...