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Audio-based automatic regeneration control - The RadioBoard Forums
I've been discussing with cool386 recently about his audio-based automatic regeneration control method at https://www.cool386.com/regenrx/regenrx.html (old and dead link: http://members.iinet.net.au/~cool386/arc/arc.html) . He was kind enough to post a YouTube video of his receiver in operation: https://youtu.be/o12X9JP_lcE?t=72 In particular, watch the part of the video starting at 72 seconds. There, you can see that in the absence of any signal, the cool386 scheme allows the detector to briefly enter the squegging condition with an AF quench frequency, which then generates a blip of high-volume AF. This AF then is coupled to a fast-attack, slow-decay AGC circuit such that the blip of audio very quickly throttles down the regeneration quite far, then allows the regeneration voltage to recover only very slowly (over several seconds). As the regeneration voltage is recovering, if no signal is found, the cycle repeats. However if a signal is tuned in, then as the regeneration voltage is recovering, the signal's audio will be detected when the regeneration voltage recovers to around critical threshold, and then the detected audio serves to continuously throttle back the regeneration voltage to below critical. The appeal of the cool386 scheme is that it uses only the detected AF to automatically control regeneration, not detected RF. And large amounts of stable AF gain are easier to obtain than large amounts of broadband RF gain (compare/contrast with viewtopic.php?p=80838#p80838). With careful circuit design (which is now underway ), I'm thinking the cool386 scheme could be implemented with one transistor as the regenerative detector, and one IC as the audio amp.