08-04-2013, 04:12 PM
The plate shape in Alans first picture is very similar to the 4 gang HRO capacitor shape.
I will have to experiment, if it's a bit out on linearity I am not too bothered, what I am try to incorporate in my design is no obvious cramped up scale readings at one end of the scale rotation, the arrangement in question will only sweep 500 Khz (2 to 2.5 Mh) The HRO has the scale graph in Khz plotted against the rotational index of the dial at any given point, these plots have a slight sag (to be expected) on all the coilpack graphs but for all intents I would class it as linear or about as near as you can get, if I can get my set up as good as that then I will be happy, I might find a correct value variable SLF capacitor (150pf) or series pad an HRO variable capacitor which is approx. 225pf or modify a higher value SLF variable capacitor by rotor vane removal.
Lawrence.
I will have to experiment, if it's a bit out on linearity I am not too bothered, what I am try to incorporate in my design is no obvious cramped up scale readings at one end of the scale rotation, the arrangement in question will only sweep 500 Khz (2 to 2.5 Mh) The HRO has the scale graph in Khz plotted against the rotational index of the dial at any given point, these plots have a slight sag (to be expected) on all the coilpack graphs but for all intents I would class it as linear or about as near as you can get, if I can get my set up as good as that then I will be happy, I might find a correct value variable SLF capacitor (150pf) or series pad an HRO variable capacitor which is approx. 225pf or modify a higher value SLF variable capacitor by rotor vane removal.
Lawrence.
