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Passive AGC just like the AM radio AGC. The signal is rectified and fed back to the tuner RF amp and a portion of the IF amplifier section. The strength of the signal directly determines the AGC strength with no amplification. Most, if not all, early TVs used this type of AGC.
Active AGC is amplified AGC. The rectified AGC voltage is amplified by prior to being sent back. Examples include keyed AGC, etc. This type of AGC was used in the 1960s and later.
I have had no overloading trouble hooking a VCR or one of the Radio Shack receivers to sets built after about 1960.
I have had issues hooking cable directly to some of these sets due to very poor tuner selectivity. The channels next to the desired chanels bleed through. This is the issue with the Portacolors. Even back in the 1960s, we lived next to a strong station on channel 10(ABC) and a weak one on channel 9(CBS). We had trouble viewing channel 9 due to the bleedtrough from channel 10 on the GE(one the worst TV manufacturers in the 1960s in my opinon) that we had. My grandfathers Emerson and the RCA roundie that we later got did not have this issue.
To date, in hooking cable directly to a TV, I have had the best luck with the RCAs with the Nuvistor front end.
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