07-03-2020, 05:42 PM
Radioroslyn, I have been hitting the calculators. I still have not figured out which side of the am band for the osc. to create the spec'd 260KHZ if. Almost seems like it is a mistake.
From what I currently see I need .26 mh to het to 260, right now I am at .23 which I plugged in the calcs and was at around 230 KHZ or so, thus I IF'd it at that with the signal generator, and it dialed right in. I am comparing the sound of this unit to many other old vintage radios I have had, and at times it amazes me, but it is sensitive to every adjustment. The original OSC. wire measures most like 32AWG by my mic, .02 off. The way it is coupled back to the det coil may have something to with it, series. It tracks well, 1100 am on the spot, 600 hits high around 620.
'Now unfortunately I’ve never acquired an inductance meter, so I cant help there on that osc coil. The coil is original. I did ohm it out a while ago and it is 6.8 ohms total (5.2 ohms and 1.6 ohms where its tapped with a 50K.) So I’m assuming the coil is OK.' - Instailled I get around 7-8 ohms top primary .23 mh and 1.8 feedback .03 mh (milli henry) on the osc. coil. Seems like if my RF coil winding is off, it still would be passing the correct frequencies to hit the osc, I can zero beat correctly to a station. I can say this though, hearing the original with the bad coil, I am close but not there yet. Could the the 'power detector' causing distortions, might look into some tweaks there, maybe a diode or cap combination to solve it. Grid leak to try. 1500 into the grid, 1 meg to ground see what happens.
From what I currently see I need .26 mh to het to 260, right now I am at .23 which I plugged in the calcs and was at around 230 KHZ or so, thus I IF'd it at that with the signal generator, and it dialed right in. I am comparing the sound of this unit to many other old vintage radios I have had, and at times it amazes me, but it is sensitive to every adjustment. The original OSC. wire measures most like 32AWG by my mic, .02 off. The way it is coupled back to the det coil may have something to with it, series. It tracks well, 1100 am on the spot, 600 hits high around 620.
'Now unfortunately I’ve never acquired an inductance meter, so I cant help there on that osc coil. The coil is original. I did ohm it out a while ago and it is 6.8 ohms total (5.2 ohms and 1.6 ohms where its tapped with a 50K.) So I’m assuming the coil is OK.' - Instailled I get around 7-8 ohms top primary .23 mh and 1.8 feedback .03 mh (milli henry) on the osc. coil. Seems like if my RF coil winding is off, it still would be passing the correct frequencies to hit the osc, I can zero beat correctly to a station. I can say this though, hearing the original with the bad coil, I am close but not there yet. Could the the 'power detector' causing distortions, might look into some tweaks there, maybe a diode or cap combination to solve it. Grid leak to try. 1500 into the grid, 1 meg to ground see what happens.
