Over the past few months we have answered a lot of questions about whether the WatchMate 850 Transponder can be mounted below deck without the need for the external GPS antenna.
The answer is, it depends!.... It depends on what it is being mounted under.
If you have anything metallic above the WatchMate you are unlikely to pick up a strong GPS signal using its internal antenna but if your boat has a fiberglass or wooden cabin you are likely to pick up sufficient GPS signal for the unit to work. The key is to ensure your GPS antenna, internal or external, has an unobstructed view of the sky. In some cases we have heard of metallic sail booms interfering with GPS signals so it’s worth putting a little thought and testing into this issue before drilling holes and running cables.
To be safe our recommendation is to use the external antenna if you are mounting a WatchMate 850 Transponder below deck to ensure you get an optimal signal as the external GPS antenna will amplify GPS signal.
As an example of GPS mounting, when Mike and Gay stopped in to Auckland on their south pacific travels in their yacht Expeditus (A 36.5ft (11.1m) cutter rigged yacht) they decided they would make their life a little easier and install a WatchMate 850 Transponder.
Although Mike found he could get a reasonable GPS signal when the WatchMate was installed below deck without the external GPS antenna he took the advice of Will at Nav Station and also installed an external antenna. As you can see from the images below this could be nicely tucked away up under his wooden cabin top without needing to drill any external holes. With the VHF/AIS Antenna Splitter also installed nicely behind the fuse board the WatchMate is now neatly flush mounted in a visible location. For extra volume from the WatchMate alarms Mike also installed an external alarm to make it that much easier to hear from up on deck.
You might also find our Installation Questions on our FAQ page useful.