This is my first Arduino project, and though I was wondering why so many Arduino based radios used IO lines instead of the I2C Bus(it seemed to me they were going through a lot of effort), now I know why!
I haven't gotten to hacking libraries yet.
However, after making the HW changes that Dave suggested (which involved removing the pullups from the encoder/moving them to code), and changing 2 parameters in the code, all seems well. I've been tuning all over the dial with no pops, clicks, or PLL drop outs.
The 2 lines of code I changed were:
attachInterrupt(digitalPinToInterrupt(PinA), Dial, FALLING) ... instead of LOW
, Ron WB9YZU