Re: Raymarine AIS 500
I would have tried a direct attached antenna first.
The VHF antenna we installed for the AIS came with a ready made cable that was to short, so we had a extension cable made.
When we installed our AIS (Emtrak b-100) the configuration SW reported unsatisfactory SWR level.
Attached our emergency VHF antenna - problem solved.
We had no measuring equipment available - but suspected the cable that was custom made for us by our supplier.
Bought a over length ready made cable and problem apparently vanished.
6 months later I did some other work in the area where the cable from the AIS (VHF) was connected to the cable going to the antenna.
The plug on the cable attached to the antenna slid right off, it was not properly crimped..
We found that the ready made cable that was delivered with the antenna was the real problem, must have pushed it into place while testing the emergency antenna...