I agree, the sender or transponder thingy up the mast is the same sort as some of the new style weather stations. One wonders if they perform when heeled over? I like the logging functions on the instrument though.
I was thinking of getting one until I pulled the Navman head unit apart and replaced the ribbon cable joining the board and display. Now as good as new again.
I have a speed SLT110 head unit that I bought online when the Navman failed. It is connected to my Navman through hull sender unit, even the temperature part worked.
I also have a VAH35 & PY30. So I can vouch for the quality of the product.