30-01-2014, 08:20 PM
If you fitted a log pot instead of an anti log pot as a screen grid regeneration control then it would be very critical to adjust to just below oscillation (max signal)
You can get a reasonable aproximattion to anti log from a linear pot by including a taper resistor, in the case of a screen grid regen the resistor would go between the HT side of the pot and the pots slider, a typical value would be around 8.2kk for a linear pot value of say 50k.
Also note that you can't do an angular advance versus resistance plot with an ohm meter and expect an anti log plot... It has to remembered that it is a voltage divider therefore to get the correct plot it has to be connected to a voltage source across it's two ends and then angular versus voltage can then be read off the slider.
Using an ohm meter from any end to the slider to plot angular versus resistance will always give a linear plot because the resistors are linear....
I've used this method in a regen I built and although it's not a true anti log it's much better than linear and most certainly better than log.
Lawrence.
You can get a reasonable aproximattion to anti log from a linear pot by including a taper resistor, in the case of a screen grid regen the resistor would go between the HT side of the pot and the pots slider, a typical value would be around 8.2kk for a linear pot value of say 50k.
Also note that you can't do an angular advance versus resistance plot with an ohm meter and expect an anti log plot... It has to remembered that it is a voltage divider therefore to get the correct plot it has to be connected to a voltage source across it's two ends and then angular versus voltage can then be read off the slider.
Using an ohm meter from any end to the slider to plot angular versus resistance will always give a linear plot because the resistors are linear....
I've used this method in a regen I built and although it's not a true anti log it's much better than linear and most certainly better than log.
Lawrence.
