Tony asked me to add my Ranger VFO experience to his thread so here it is.
I too had drift problems with the VFO on 40M and above, but mine was not a slow drift. It was stable for the first 15 minutes or so, but then it would suddenly QSY down the band FAST - like somebody spun the dial. I suspected C20, the tubular ceramic 47pf N150 temperature compensating capacitor. I had read somewhere on the web that these caps can break down after being subject to extreme heat. Indeed, my VFO showed signs of past Chernobyl meltdowns, and the cap body had black and brown scorch/bake marks on it.
Of course getting an exact replacement for that cap is impossible. Surplus Sales is sold out, and DigiKey, Mouser, etc. don't carry modern equivalents. So I figured I'd try something close and see if it worked. I located some NOS 39pf N150 1000V disc ceramics and installed one. The 40 LO and 40 HI trimmers have plenty of range, and I was able to zero it in to proper dial calibration without trouble. So this tells me a replacement need not have the exact pf value, several pf higher or lower will work.
The original Ranger assembly manual calls for this cap to be installed 1/16" away from the oscillator inductor. As I understand it, C20 is intended to compensate downward as the 40 M side of the inductor heats up and expands. So it makes sense that this cap needs to be really close to the oscillator coil so it experiences the same temperature variations.
