Topband: Bead balun waterproofing

[wyc]

I'm considering a bead-based common mode choke for a 160m vertical.  (I've
got surplus 75 ohm CATV hardline that I thought I'd bury to keep it safe
from the mower, and beads seem like an easy common mode choke approach.)

I get why waterproofing would be needed with split-beads - to keep water
out of the gaps.  But if the beads aren't split, but are solid donuts, it
seems like rain intrusion (or dirt, for that matter) between the coax and
the ferrite wouldn't be much of a problem.

(I'm running only 100w, so I don't expect much thermal excitement.)

Am I missing something?

tnx,

/Bill, K2PO