(Caution: Rant Ahead)
It's designed that way. The WR20/RS87 is a sophisticated network-dependent system which, IMHO, is a very dangerous way to design a VHF
intended for use on small boats.
Despite all the hype in Simrad's advertising, I think it's just plain courting disaster to design a VHF radio
which is dependent on network operation -- 0183, 2000, SimRad
, or whatever.
This is not a step forward. Yeah, it's cute. Imagine...a handheld device which can integrate with all the other (Simrad) electronics
on board. And a wireless remote
which can do the same. Neat, huh? Definitely. But sensible for use on a small boat? I don't think so. It's a big step backwards in terms of reliability
, and since IMHO the VHF transceiver is one of the most important safety
devices on a boat ANYTHING which compromises its basic functionality is undesirable.
A standalone VHF with its own wired in microphone and connected directly to good quality coax and a well-situated VHF antenna
has been the standard for many years. It's incredibly reliable, even under adverse conditions. Why do ANYTHING to compromise that reliability
(including, e.g., installing a "splitter" so you can hook up an AIS
Sometimes it's important to strongly resist the siren call to "integrate everything".
That said, sorry for your problems Akio. In your stead, I'd rip it out straight away and stop fooling with it.