Thanks Ron!

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

and
if (interruptTime - lastInterruptTime > 10) { ... instead of 5

Changing from calling DIAL on a LOW to calling DIAL on a FALLING edge made the largest change.
Increasing interupt debouce was just added insurance ;)

--
, Ron WB9YZU