16-06-2015, 07:39 PM
That stuff is still relevant today in many respects.
I built a regen and the only valve I had to hand for the regen detector was one with a top cap connection for the control grid, initially there was stray hum pick up issues due to the high impedance of the grid leak circuit, I eliminated the hum by using a screened lead but the sensitivity was reduced, this was due to the self capacitance of the screened lead, I checked the self capacitance of other bit's of screened lead I had and chose the one with the lowest value and that cured that.
The capacitance of the screened lead together with the valves input capacitance was initially the problem, it forming a potential divider together with the capacitor in the grid leak circuit and the tuning capacitor.
Lawrence.
I built a regen and the only valve I had to hand for the regen detector was one with a top cap connection for the control grid, initially there was stray hum pick up issues due to the high impedance of the grid leak circuit, I eliminated the hum by using a screened lead but the sensitivity was reduced, this was due to the self capacitance of the screened lead, I checked the self capacitance of other bit's of screened lead I had and chose the one with the lowest value and that cured that.
The capacitance of the screened lead together with the valves input capacitance was initially the problem, it forming a potential divider together with the capacitor in the grid leak circuit and the tuning capacitor.
Lawrence.
