11-05-2021, 02:21 PM
I have noticed this same drop in sensitivity as one goes down in frequency of the AM BCB on several radios. I don't think it is restricted to the 20, or to particular tubes. It may be an interaction between the tuned RF circuit and the antenna, as I have noticed the need to adjust the antenna trimmer on my communications receivers between the low and high ends of the AM BCB range.. Have you tried using an antenna tuner between the antenna and the radio?
