22-08-2017, 07:46 AM
Hi.
Using a TL431 to provide reaction back through the frame aerial was no good. The gain in one of these devices is around 55dB from what I can gather, even using a neat layout it is really unstable, it does work but the least little change like moving the headphones and it takes off. What it does do is work beautifully as a frequency shifter, place your transistor radio close to the frame, tune it low down the band and then tune in the station required on the frame aerial, works just fine.
I'm going to change direction slightly. Previously I tried one of the Russian rod pentodes, the one with dual grids strapped together via my little RF transformer in a reflex circuit, it worked but it didn't get to the point of oscillating, I'm going to try it off the main winding and see if it will be a bit more lively using a tap on the main winding. The input impedance is very high with these valves so loading should not be an issue.
Using a TL431 to provide reaction back through the frame aerial was no good. The gain in one of these devices is around 55dB from what I can gather, even using a neat layout it is really unstable, it does work but the least little change like moving the headphones and it takes off. What it does do is work beautifully as a frequency shifter, place your transistor radio close to the frame, tune it low down the band and then tune in the station required on the frame aerial, works just fine.
I'm going to change direction slightly. Previously I tried one of the Russian rod pentodes, the one with dual grids strapped together via my little RF transformer in a reflex circuit, it worked but it didn't get to the point of oscillating, I'm going to try it off the main winding and see if it will be a bit more lively using a tap on the main winding. The input impedance is very high with these valves so loading should not be an issue.
