Hey JohnGC,

I'm glad you are messing with this and observing it. It's not really the string guage, although that can have some effect.

Try your same experiment and try every note up the neck one fret at a time, see how the tuning is against the tuner. I'm no expert on why this is, but I always encounter out of tune fretted notes, especially when low on the neck.

I have found that there are sort of "nodes" where notes go in and out of intonation. For instance, open string will be intonated perfectly, then it will go sharp at the first fret until the 5th or 7th or so, where it corrects itself. Then back out again to varying degrees until the 12th where it is dead-on with the tuner again. This particular oddity has something to do with natural string tension, I believe.

It's pretty common as a recording trick to tune certain fretted notes on areas of the neck to avoid these oddities. We've done this many times when filming songs.

There have been some pretty interesting inventions over the years to try to solve intonation "problems" inherent in electric guitar. (Depending on if you consider them problems.) Check out some of this stuff to get deeper into it and maybe get even more confused:

Buzz Feiten Tuning System:[br]https://www.youtube.com/watch?v=j2Yfee69bTk

True Temperament:[br]https://www.youtube.com/watch?v=D8EjCTb88oA

-Carl.