06-12-2016, 10:56 PM
Looks good!
The trouble with single-stage modulated oscillators is that there's a tendency to get some FM. The envelope can look lovely on a 'scope, you can have trapezium figures with super straight sides, but if there's FM going on too, when it hits the receiver's passband you get slope detection, which combined with the intentional AM, gives weird tuning and distortion effects. Your circuit with a crystal should, hopefully, reduce this at the expense of being stuck with whatever frequency the crystal is.
The idea of an audio preamp with another Russian rod valve is really the only way to go, who'd want to drive it with a tr*ns*st*r? A third valve, configured as a detector, could demodulate the RF and allow a bit of negative feedback to reduce distortion.
I'll watch with interest!
The trouble with single-stage modulated oscillators is that there's a tendency to get some FM. The envelope can look lovely on a 'scope, you can have trapezium figures with super straight sides, but if there's FM going on too, when it hits the receiver's passband you get slope detection, which combined with the intentional AM, gives weird tuning and distortion effects. Your circuit with a crystal should, hopefully, reduce this at the expense of being stuck with whatever frequency the crystal is.
The idea of an audio preamp with another Russian rod valve is really the only way to go, who'd want to drive it with a tr*ns*st*r? A third valve, configured as a detector, could demodulate the RF and allow a bit of negative feedback to reduce distortion.
I'll watch with interest!
