I've had this model omni directional antenna on my boat for the past 3 years
and had marginal reception. Often suspecting that the unit might have
moisture inside. Possibility no fault of the design since I had it mounted
upside down under my radar arch. (no room over the radar)

When I installed it initially, upside down, I sealed all the screw holes and
around the coax cable connector.

Yesterday I took it down because I couldn't get any reception and the fuse
in the control unit kept blowing. As soon as I had it off the mount, I could
hear water inside.

My next though was how to open the case to drain the water. There were the
screws on the bottom but no apparent seam between the bottom and top shells.
So I carefully drilled a couple holes around the top and bottom and drained
about a half cup of water out. I now suspected that the circuit board inside
and components must be wet, so I enlarged one of the holes into a slot and
held my heat gun, set on low, up to this hole and began the drying process.
In about 5 minutes I notice that the tight seam between the top and bottom
were opening slightly. As it turns out the seam was only snapped together. I
removed the four screws and coax connector nut and pried the unit apart.

On initial inspection I found several areas of corrosion on the circuit
board. It was obvious that there had been no attempt to "marine seal" this
circuit board or the connection to the antennal elements.

Fortunately I was able to clean the corrosion with a stiff brush and
penetrating oil, followed by a hot soapy water scrub and rinse. (I didn't
have any PC board spray on board and will go back later and coat everything
before it corrodes again.)

I realize my unconventional installation lead to the problem since the rain
water must have entered though the "snap" seal around the edge. I really
think it should have been sealed with a sealant. I will do that when I'm
finished with my work inside.

After re-assembly and replacing the fuse for the second time, I found I had
better reception on almost all the local channels. (channel #5 seemed to be
the exception. However by morning it was working fine. Must have been a bit
of moisture under some surface mounted component.)

Sorry, this was so long, but if anyone else is having problems with their
SeaWitch, I think this procedure would be useful..


--
My experience and opinion, FWIW

--
Steve
s/v Good Intentions