Tonna Driven Elements – why they fail
The picture below
shows a 2m driven element that has been in use for a few years, you can see
that the plastic moulding has fractured in numerous places allowing water to
get in and corrode the connections.
Once the plastic moulding is stripped
away to reveal the method of construction it becomes clear why these things
fail. The Hairpin is connected to the Aluminium driven element tube by two
steel self tapping screws. A dissimilar corrosion point is created here
The N connector centre Pin is made of
Brass, it is riveted to the Aluminium Driven element creating another point
where dissimilar metal corrosion will take place.
The outer body of the N socket is
once again riveted to the Aluminium Dipole creating another point for corrosion
to take place.
The entire structure has no
mechanical rigidity on its own, and relies on the plastic moulding to ensure
the connections are not compromised. The idea falls apart as soon as the
plastic moulding starts to crack.