Can anyone recommend an external GPS, i.e one of the dumb ones that sit on
the rail at the back with no display.

I have a seiwa chartplotter with internal gps, but it does not have an
option for an external aerial.

This plotter is fitted inside a steel hull, so reception is poor. I need
an nmea solution, an thought that the dumb external gps solution may be
best.

what do u think?

tia
garry