Larry,
I in part agree with your last post. The problem with my fisher maybe that its operating frequency is set at 13 KHz give or take a few tenths for being able to shift the frequency to avoid EM interference (this shift is in reality negligible to detecting performance other than potentially avoiding EM). I just don't think that's the best frequency for what I want to do, find old silver coins or old coins in general. I think it's great for relic hunting. As I mentioned I could find a BB at 8 inch depth, but I wont find something coinsize any deeper than that. Also, the Frequency may not be as good for the soil conditions where I live. I think the FBS allows having that low frequency in the selected range of frequencies the minelab FBS's run at. For relic hunting I don't know. I do know the guys who have minelabs up here are finding deep silver coins, some guys up here are in the 400's, 300's mid 100's for silver coins this year from parks that have been -Heavily Hunted- for years. I haven't had my minelab for very long, but I have had it long enough to tell the difference over my fisher.
Besides frequency, I think having conductivity and inductivity (FE) numbers, verses just conductivity makes a huge difference as well. My fisher, any target lower that 7 inches would sound like iron and the TID gave iron values. With the minelab, on the deep targets the sound will be high if its highly conductive, since the inductivity values are measured separately. Or put in other words, TID, which is far less reliable than sounds, remain relatively unchanged at depth for conductivity values. What depth will do will mess with the FE (inductivity values). But If I know the target is deep, and is registering right for conductivity, and it has that nice high tone, then I will dig even if the FE value is raised. On my fisher it would just sound blah- iron and give me an Iron TID. That may have something to do with the characteristics of soils here, but the minelab does solve the problem.
I do agree with Rebel's assessment that the f75's are incredibly light, which is good, they get 40+ hours on 4AA which is incredible (minelab if you don't use the rechargeables -- 16 hours off of 8 AA's). And I am inclined to agree that it is superior for relic hunting. I guess it just depends on what you want to detect for. I'd rather dig coins.