Deltatango
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Got an old 9v battery RF oscillator from my early days (40+ years ago) which "covered up to 30MHz" at the time I became aware 24MHz was its max, because it would go into some very low frequency oscillation and then start to go into reverse during the final gang rotation.
It is an Armstrong based oscillator, and I heard then some HAM operators were trying to see why, though never found out any result.
I have tried many normal things like transistor change, bias resistor variation and capacitor changes to no avail, then tried upping its sniffer winding from 2 to 4 turns but it remains steadfast on about 24+ MHz (which is double the minimum range on that position) so are we fighting this in some way. I enclose a circuit which helps but note 100k bias resistor is now a 6k8 original in this unit as well as 0.01's are 0.05uf. Thinking about lowering the sniffer winding to 1 turn, also its layout is spread about with a old style wafer switch of 34mm, I expected inter-coupling issues and tried screening so am a bit puzzled.
Any insights into this would be welcome............
David
It is an Armstrong based oscillator, and I heard then some HAM operators were trying to see why, though never found out any result.
I have tried many normal things like transistor change, bias resistor variation and capacitor changes to no avail, then tried upping its sniffer winding from 2 to 4 turns but it remains steadfast on about 24+ MHz (which is double the minimum range on that position) so are we fighting this in some way. I enclose a circuit which helps but note 100k bias resistor is now a 6k8 original in this unit as well as 0.01's are 0.05uf. Thinking about lowering the sniffer winding to 1 turn, also its layout is spread about with a old style wafer switch of 34mm, I expected inter-coupling issues and tried screening so am a bit puzzled.
Any insights into this would be welcome............
David