if you read through the 11 pages in the pinned post top of page, "alternative ferret finder" you'll see the pictures, write up etc of the loca8tor I was doing a review on, I use it alongside the mk3 as it finds above ground to 400ft, collars still need modifying a bit, myself and richie came up with the idea of placing it along the collar, inside a piece of "heat shrink" tubing,
getting used to putting the collars on at the correct tightness, while at home can only be a good thing, if a ferret wants the collar off, it will happen weather its above or below ground, and then adjustments (ext