Who has AGC... Fun Facts
Well I was wrong about Zenith having the first AGC. It was RCA that sued Zenith over a similar AGC design (now ancient history). I had to read my old papers again.
This is fun fact from the Antique Radio forum circa 1970: “RCA's Radiola 64 (below, 1929) is credited for being the first radio with AGC. Since the tubes in it were triode 27s, they were difficult to control with a simple rectified carrier, as later circuits had. This set, as well as others in those early days, had to have a DC amplifier to provide the voltage swing to bias the RF and IF stages from normal bias to near cutoff. This circuitry was tricky, but it worked. RCA also had a tuning meter on these sets, supposedly another first. In a couple of years, variable-mu tubes (35/51) came along and made AGC a lot easier. And it got better after that. Now in general, superheterodynes had AGC, but there were some exceptions. In about 1931, Western Electric made their 10A AM high fidelity tuner. It's monstrous, but it was a TRF with AGC and a tuning meter”. The Antique Radio guys would eat us alive for not knowing the distinction between AGC and AVC.