RG11 connector

It was unexpectedly hard finding a way to connect RG11 cable (chosen because length of coaxial run is 23 meters) to the TRIA.

I found it hard to find suitable connectors in the local shops and I'm not sure what to ask for via mail-order.  For now, I've found a combination involving a BNC-connector that seems to work.  One concern is that it doesn't look very waterproof, at least the bayonet part: picture follows,



Comments/advice welcome! Thanks
Frank