[Boatanchors] Linear Tuning in VFOs...

[Gary Peterson]

“A general coverage type will almost always be bunched up at the high end of a dial. There are/were also capacitors designed and cut generally not all that great, and mostly in the 1920s-30s-40s -  to simulate equal tuning regardless of which end of the band.”

My recollection is that there were three shapes of capacitor plates.  One has a linear relationship between capacitance and angular rotation, causing frequencies to be bunched up at the high end of the dial.  Another has a linear relationship between wavelength and angular rotation.  The third has a linear relationship between frequency and angular rotation.  Calculating the last two plate shapes must have challenged someone’s command of calculus.

I have seen PTOs (permeability or inductively tuned oscillators) in which the pitch of the coil winding changed along the length of the tube containing the moving ferrite slug,

Gary
KzeroCX