Dude said:
The biggest difference between the two is the F4 can be ground balanced and it does carry over to the Disc and A/M modes. A quick call to First Texas Instruments confirmed it does carry over to other modes contrary to a earlier posting.
When you called FT about the F4 ground balance did you talk with customer support or did you talk to one of the "Chief Desingner's" or one of the other lead engineers?
Seeing how Dave_J posted that information about the ground balance on the F4 then I would say unless you talked to someone more knowledgeable than him (up the latter) the ground balance on the F4 is fixed in discrimination mode!
The below is a copy & Paste from Dave_J profile (open for public view information) I'm going to say that's its not likely to place a call into FT and get redirected for general questions to somebody like Dave Johnson, you more than likely talked to someone down line from the engineering/designing department.
Dave Johnson said:
Chief Designer: Bounty Hunter, Teknetics, and Fisher brand metal detectors.
Located in El Paso, Texas.
Now that don't mean you have to believe the information in Dave's post but, short of writings on a tablet of stone from God I'm going to say that the F4 ground balance really is fixed in the discrimination mode! and that by no means is to say that the F4 isn't a great little detector.
Mark