Then later, some rigs used PLLs. I can't remember if the Signal One
used one, but certainly in the seventies they came along. Same basic
idea as the premixer, but the PLL was the filter so the VCO directly
fed the receiver's first mixer.

Michael VE2BVW


Well the CX-7 didn't use a PLL, but the CX-11 did. It was however only for
generating a comb frequency to be used with premixing. The analog PTO's
still tuned 3.1 to 4.1 MHz.

The main problem with up conversion is the hit you take on oscillator phase
noise. These days, with the advent of the "H" mode mixer, oscillator phase
noise and birdies are THE limiting factor in receiver compromise.

W4ZCB