On Sat, 29 Jan 2005 03:17:10 GMT, Larry W4CSC wrote:

"tkranz" wrote in
:

I have a 15 year old Raytheon set that has lived in Florida and
Bahamian waters all it's life. I often open it to grease the gears.

There is essentially NO corrosion of the kind you describe. I don't
think your problem is with the fresh water moisture. It sure sounds
like an electrolysis problem. Is your unit grounded per specs? Do
you have electrolysis problems in other parts of your boat?


There aren't any "gears". The new 2KW radomes have a flat piece of PC
board with a phased array of stripline antennas on them. It sits on a pin
where the RF enters from the waveguide. Around that is a pulley with a
rubber O-ring that's driven from a stepper motor pulsed by the PC board
inside the potmetal box. The motor is the same one used to pull the
printhead back and forth in a PC printer. The pulse rate sets the rotation
rate of the pc board antenna. No gears, it's cheap.

The water in the dome is fresh water. I've tasted it. It's condensate
from the air breathing in and out of the dome every day with no way of
escaping until the flat bottom of the dome is flooded enough to drain out
the tiny rubber tube grommeted into a hole in the flat bottom.

Too bad Raytheon isn't making good radars any more for small boats. Looks
like yours is much more sophisticated than ours.

You still need to find the problem. Every radar I have seen, Furuno or
Ratheon, has the drain tube in the bottom, so the interior is open to
the atmosphere, but protected from splash.



Rodney Myrvaagnes NYC J36 Gjo/a


"Biologists think they are chemists, chemists think they are phycisists,
physicists think they are gods, and God thinks He is a mathematician." Anon

Rodney Myrvaagnes wrote in
:


You still need to find the problem. Every radar I have seen, Furuno or
Ratheon, has the drain tube in the bottom, so the interior is open to
the atmosphere, but protected from splash.

Well, the problem must be with the design. There's been three DIFFERENT
radomes, the first two all got water in them. Raymarine said in "some
environments this happens". Sounds crazy. Charleston SC must be one of
them. I'm convince the same thing is happening inside the dome as a half
empty gas tank, which will just fill with water around here. Sucks in 100%
humid air at dusk, condenses all night, then the dense air blows back out
the drain hole when the sun shines on it until the sun set again when the
process repeats. A vented gas tank does the same thing, especially if its
sitting out in the sun with little gas in it.

The cure is to SEAL the dome. That's pretty hard to do with such thin
plastic and only 4 little screws holding the top to the bottom around the
seal, which only grips the bottom well. I'm for putting in a Muffin fan to
dry it out while its sitting at the dock. Hell, none of it's sealed,
anyways.....