06-02-2019, 10:45 PM
I isolated the grounds on the 2 compensating capacitors using nylon washers and a little heat shrink over the threads on the screw. I re-aligned the radio and spent some more time tweaking the tuning cap bendable plates to try and maximize sensitivity and tracking across the band. Tracking is now almost perfect all the way across the band. Sensitivity is maximized on most of the band. I loose a little on the low end but the only station I listen to down there at 590 is fairly strong. 650, WSM Nashville (playing blue grass tonight), comes in wonderfully (with some fading), as does zoomer radio 740. The AVC works great, reducing the effects of the fading. And, no more blaring stations!
Interesting comparison: I have an AM frequency generator/audio modulator that puts out a very weak signal. It can be picked up only a couple of feet away from the output conductor. It's purpose is to drive an RF amp, which I don't have so i wrap the "antenna" around the antenna post of the radio. it is capable of clean modulation from 20 to 15K Hz. I have the 570 sitting right next to my model 96, feeding both radios with the signal. The difference in audio quality is dramatic. Granted, the 96 has a push pull output and a larger speaker, but it also produces a much cleaner top end, producing a more balanced sound. The 570 seems muted in comparison. ( I removed the added cap labeled "see text" in Ron's drawing.) I was reading an article that was saying that the old TRF radios could produce a better sound than the typical, non HiFi superhet. The superhet certainly has far better selectivity, but the TRF holds its own in the tone quality department. At least the 96 does. I may play with the 570 and broaden out the IF curves to see what it does to the sound at the sacrifice of selectivity. It kind of sounds like fun!
Ron, keep plugging away as much as you can. I'd like to know your results of this "experiment".
Rob
Interesting comparison: I have an AM frequency generator/audio modulator that puts out a very weak signal. It can be picked up only a couple of feet away from the output conductor. It's purpose is to drive an RF amp, which I don't have so i wrap the "antenna" around the antenna post of the radio. it is capable of clean modulation from 20 to 15K Hz. I have the 570 sitting right next to my model 96, feeding both radios with the signal. The difference in audio quality is dramatic. Granted, the 96 has a push pull output and a larger speaker, but it also produces a much cleaner top end, producing a more balanced sound. The 570 seems muted in comparison. ( I removed the added cap labeled "see text" in Ron's drawing.) I was reading an article that was saying that the old TRF radios could produce a better sound than the typical, non HiFi superhet. The superhet certainly has far better selectivity, but the TRF holds its own in the tone quality department. At least the 96 does. I may play with the 570 and broaden out the IF curves to see what it does to the sound at the sacrifice of selectivity. It kind of sounds like fun!
Ron, keep plugging away as much as you can. I'd like to know your results of this "experiment".
Rob
