I installed a second hand Raymarine
AIS250 receiver which worked fine from the AIS
perspective. Seemed to recieve OK but Xmit modulation was very much attenuated. SWF showed almost as much power with the AIS
as without and the SWR was about 2. A base station could hear the carrier but voice was very much attenuated.
This has really got me tricked. I would have thought the carrier would attentuate and the modulation with it but it seems the carrier gets through the AIS with little loss.