aluminum boat as antenna

petreaux1

Cadet
Joined
Sep 15, 2012
Messages
7
Since my boat is aluminum can I run antenna wire from back of am/fm receiver directly to hull and thus make it a big floating antenna? I don't want a traditional vertical antenna because it gets in the way. Anybody ever try it?
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
Re: aluminum boat as antenna

Never tried and I wouldn't. All you'll do is ground your antenna.
 

matt167

Captain
Joined
Sep 27, 2012
Messages
3,630
Re: aluminum boat as antenna

Yea, it will work and it will work well BUT. It could also introduce voltage to the aluminum which will cause electrolysis and actually corrode it
 

SolingSailor

Petty Officer 2nd Class
Joined
Dec 24, 2009
Messages
197
Re: aluminum boat as antenna

You just gotta try it. Could be good, maybe not. No harm to try.
I'm a former commercial radio engineer, and I think it's not supposed to work, but I also think no one can predict your results.
Don't forget to try a wire hanger. Could be better.
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
Re: aluminum boat as antenna

Yea, it will work and it will work well BUT. It could also introduce voltage to the aluminum which will cause electrolysis and actually corrode it

Are you sure? The motor is electrical ground and through the mounting bolts, the hull is electrical ground as well. Put a meter between the battery ground and the hull and it will show a short. A grounded antenna won't work.
 

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: aluminum boat as antenna

Are you sure? The motor is electrical ground and through the mounting bolts, the hull is electrical ground as well. Put a meter between the battery ground and the hull and it will show a short. A grounded antenna won't work.

Could that be the reason auto antennas have rubber/plastic washers isolating the antenna from the metal body?
 
Last edited:

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
Re: aluminum boat as antenna

Could that be the reason auto antennas have rubber/plastic washers isolating the antenna from the metal body?

Mainly to seal the hole. The mounting part of the antenna is grounded to the coax shield of the antenna lead. But the aerial/mast portion is isolated from ground or it wouldn't work.
 

matt167

Captain
Joined
Sep 27, 2012
Messages
3,630
Re: aluminum boat as antenna

Aluminum hulls should not be wired so that the hull acts as a ground or rather, current introduced as a ground.. Antennae may not have enough voltage on it to start electrolysis BUT, I wouldn't want to be the person to try it out.. Yes auto antenne's are isolated, but an old hotrod trick is to mount them inside the frame rail and they will be hidden and work reasonably well.. As to running the wire direct, after thinking about it. I agree, it won't work like that, still, I don't know as I would add an antennae where it could touch aluminum hull, not because it wouldn't work, but just in the case of introduced voltage. Electrolysis is not a good thing unless your cleaning up a rusty old part.,, AM/FM is not LOS so it does not matter if you tuck the antennae where it cannot be seen altho aluminum makes a pretty good isolator from AM/FM signals as experience from not being able to get good reception in a tin building 7 miles from the station's radio tower
 

smokeonthewater

Fleet Admiral
Joined
Dec 3, 2009
Messages
9,838
Re: aluminum boat as antenna

for GOOD reception on the water (generally low surrounded by land mass of higher elevation) an aerial is GOOD to have but if you really want to avoid one there are several options... one is to lay an antennae down under a deck or gunwale ..... another is a fold down aerial that is only put up when signal is weak and another would be a wire "taped" around the outside of the hull under a vinyl stripe...

an antennae is supposed to have a specific resistance between the radio and ground IE 75 ohms etc... a dead short won't work
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Re: aluminum boat as antenna

For omni directional reception and transmission, a simple dipole cut to a certain frequency aka length is the required antenna. The antenna pattern resembles a doughnut lying on it's side. Rather than have the whole wave length of antenna, especially at frequencies like CB, aka 27ish MHz, The antenna is usually cut to 1/2 wavelength and the water or boat in your case becomes a reflector and gives you the performance of the long antenna without the inconvenience of the long length. Once you get up to VHF (couple hundred MHz) the antenna gets a lot smaller and it can be half or full wavelength. Course whatever length, the feed impedance of the antenna must match the transmitter/receiver and interconnect cable if you expect any kind of performance and no damage to your equipment.

So in answer to your question: NO!

Mark
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: aluminum boat as antenna

In my fiberglass boats, a 3' single piece of insulated wire tossed under the dashboard gave good FM reception. An aluminum boat with closed bow may act as a RF shield, reducing the effectiveness of that method. Try it. If reception is not good, find a place where the wire is hidden, but open to the sky. Tape it to the bottom of a wooden seat, for example.
 

agallant80

Commander
Joined
Oct 25, 2010
Messages
2,328
Re: aluminum boat as antenna

I would think you would hear a wine from the motor running if you do that.
 

haulnazz15

Captain
Joined
Mar 9, 2009
Messages
3,720
Re: aluminum boat as antenna

Just mount a stubby antenna out of the way or under the console somewhere. Your other option is to get an antenna with a swivel base so that you can point the mast up if better reception is needed, and lay it down along the gunnel/console when not needed. Should stay out of the way as long as you aren't mounting some 3'+ whip.
 
Top