Better Check on that doubling the distance you did . The calculates shown earlier in this thread is very popular and the one I usually use. Most of the calculators I have seen and used ,anticipates the return footage. Some will say “ enter distance in feet one way” others will say list distance “round trip.”. In the old days printed tables sometimes were confusing about that so double check.
If it says “one way “ then put in 170ft and it is normally building in the round trip calculation (340 ft ) for you ( for the other wire returning) I always use two or three calculators to see if the all jive…I verify the answer…mistskes and glitches do happen……Hope that helps , until your more solid in knowledge you should verify anything you hear unless you are very confident about what you heard …. Verify- verify - verify…. It’s your money , not theirs.
Jim.
