Icom AT141 Exposed Location?

[Singleprop]

I'm about to determine the location of my AT 141 tuner - the manual says that the tuner is weather resistant, so I am considering to place the tuner on a stanchion on the railing.

Does any one have problems with an exposed tuner, are there any precautions that should be taken, with regard to an exposed location?

[colemj]

Our Icom AT130 and SGC230 couplers have sat on top of our bimini for 14yrs now with no problems at all. We have a fiberglass box sitting over them that keeps direct sun and overhead rain off them, but the boxes simply sit on top of them with an open bottom so the couplers are still exposed to lots of weather. You could do similar, or use a canvas cover instead.

Mark

[funk-an-bord.de]

The recomendation of Sailor (Thrane & Thrane) is to place the tuner as near to the water grounding surface.
then you have to consider the cable between the hot point of the tuner and the connection to the backstay / glas fibre also as part of the antenna length.
So you have to isolate it, but there are _not_ 10.000 Volts.
When you place the tuner as high outside the reach of a human contact,
then the wire from the grounding point of the tuner down to the water grounding surface - e.g. that might be 3 meter, will produce a electromagenical field that works in contra to the field of the antenna.
So look for a place in the aft cabin close to the grounding point.
Greetings, Wilhelm

[Singleprop]

Thanks.

I should have mentioned that this is a steel boat. Does that change the Funk-an Bord recommendation about the grounding point?

[colemj]

Yes. We use our large aluminum bimini hardtop (also connected to the lifelines) as the sole counterpoise with no connection to seawater. Works very well. 1" copper foil connection to the counterpoise right below the coupler and 12" GTO connection to the whip antenna located right above the coupler. You will be using your entire boat as the counterpoise (connected to seawater), so will work even better.

You didn't mention what you are using as an antenna, but I assume its feedpoint is near your intended mounting point.

Mark

[Singleprop]

it will be a rope-antenna. There will be about 2 meters of braided wire (as recommended on the rope-antenna website) between the tuner and the rope antenna.

[gordwedman]

Personally I would not do that because a wave hitting the box could force water into it. The gasket might also deteriorate over time as well. Mine is in the stern lazarette.

[funk-an-bord.de]

You may download the manual including 6 pages of SSB grounding recomendations of Thrane&Thrane.

""Keep in mind that the vertical antenna always starts at its electrical ground-plane, whether or not you physically put the antenna there. First determine the antenna’s electrical ground-plane. This is where the Antenna Tuning Unit must be mounted. Always think in terms of taking the Antenna Tuning Unit to the ground, rather than taking the ground to the Antenna Tuning Unit.""
Greetings, Wilhelm

[colemj]

On a steel boat, the boat itself will be the counterpoise. Having the coupler on deck puts it immediately above the counterpoise, putting it below deck puts it in the middle of the counterpoise and requires the antenna to run through 3-8' of counterpoise before finding electrically free space.

These couplers are waterproof and intended for exposed locations. It is very easy to improve even that by covering them with a simple plastic box or canvas. We have two of them exposed for 14yrs with no problems.

Mark

[fairbank56]

Wonder why they have a designated "water drain screw" on them

Eric

[colemj]

Perhaps you should read the manual for that answer, Eric?

From the Icom AT141 manual: "The antenna tuner can be conveniently installed both on the deck or in the cabin".

Also: "The AT-141 is housed in a durable, completely weather resistant case. You don’t have to worry a lot about rain, splash, and so on."

They also show 19 illustrations in the manual of mounting the coupler on a ship and on land. In all 19 illustrations, the coupler is shown mounted free outside of any structure.

While older versions of the manual mention a water drain screw and instructs you to remove it after installation regardless of where it is installed (and instructs that installing it outdoors is perfectly OK), the most current manual makes no mention of this drain screw at all. Perhaps it no longer exists in the newest models?

14 yrs on the top of our bimini with no water intrusion. We have the AT130 and SGC230, though.

[fairbank56]

I was just joking . Iv'e installed and serviced lots of these tuners. Iv'e come across a few which were mounted horizontally that were full of water and completely rusted/gunked up inside. I would suggest mounting them with the cable entry end lower than the rest of the unit.

Eric