A Regenerative Receiver with AGC for 80 and 40 Meters

Here`s a dual-band Regen that came from some encouraging emails from Jerry (K9UT) and another gentleman named Harvey, who built my original AGC-80, and its experimental `Regenerodyne` successor, the AGC-80/30. Jerry and I have corresponded on several occasions, and he tells me that he enjoys both receivers and that they work surprisingly well for

such simple circuits. A few other Hams have written to express their satisfaction with the AGC-80 as well. Many thanks to those of you who gave me helpful feedback. Jerry asked me when I was going to design an AGC-controlled Regen for 40 meters. I pointed out that I had already posted two other 40 meter receivers at my webpage, but neither has AGC. So Jerry`s request led to this project, the AGC-80/40. This is a successor to the original AGC-80, a Colpitts-based Regenerative receiver with audio-derived AGC [Automatic Gain Control] to prevent strong signals from "pulling" or "blocking" the detector. Like its predecessor, it is `varactor`-tuned [actually I use rectifier diodes as varactors] and has no bulky, expensive variable capacitors. Actually, the AGC-80 did have a pcb-mounted trimmer cap that calibrated the front panel, setting the band limits. This new receiver does away even with that trimmer cap. Bandswitching is accomplished by a double-pole, double throw toggle switch that switches capacitance values in the "front end" where the signal comes in from the antenna, and simultaneously switches coils (wound on small toroid cores) in the Regen Detector stage, for 80 and 40 meter operation. The receiver also uses passive filtering with switched capacitance values to kill the extreme highs with a 2500 Hz lowpass filter for voice transmissions, or an 800 Hz peaked lowpass filter for receiving CW transmissions. I probably...

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