[turretslug]

Some of the outboard SSB demodulators made for legacy military/professional receivers were extraordinary devices, large, expensive and sometimes rivalling the host receiver complexity and featuring sophisticated IF and AF filtering and ALC, tracking AFC and so on. It was one thing to be a keen amateur or SWL and carefully juggle RF gain, AF gain, main tuning and BFO with an envelope-detector receiver to make SSB reasonably intelligible for a few minutes at a time, another for an "oppo" to be able to depend on immediately being able to tune and read a faint and ephemeral SSB signal that might be of life-or-death nature under trying conditions, then be confident that after hours of no activity, the next reception would be instantly on-the-nose with nothing missed. Hence "couldn't they just have used a 6BE6?"-type objections from someone seeing an electronics-stuffed 19" rack! There was more to it than that....