VHF radio/compass ?

[yankeecause]

Ok, so I just bought a new Icom M504. The instructions tell me to keep it 3 feet away from my compass. Well, my electronics box is a lot closer than that, and that's where the old radio is at. Is this something I should worry about? What do you guys think? I guess I could move it to the box under the hardtop but I'm kind of used to it where it's at now. Thanks Joe.
sorry, maybe I should of posted this in the electronics forum.

 

[richie rich]

Its not ideal, but you can mount it on your bottom box, but I suggest getting your compass re-calibrated after the installation.....it should be fine then.

 

[freddy063]

yep I would mount in on the hardtop. I got my SSB and other radios up top away from the compass. Even the mic when you bring it down to talk can effect your compass, try it move your mic around your compass and watch the needle. I left a wrench next to it oneday, Just glad it wasn't foggy that day and i needed the compass.

 

[richie rich]

what do you do if you have a center console and no hardtop box? GPS, VHF, FM Radio etc all get mounted on a small console within a few inches of each other.....upstairs is preferrrable, but if you can't, recalibrating your compass after any installation like that is a good practice.

 

[capt chris]

You have to do what you have to do. Make sure you twist the wires from the radio around each other. That will negate some of the deviation. After you install it you should compensate your compass. Go to www.ritchienavigation.com and look at the methods of compensating your compass. Be sure to use a non magnetic screwdriver when you do it. There should have been one provided by Ritchie with your owner's manual on the compass. I have the ICOM 504 radio as well in my 225's electronics box directly in front and slightly above my compass. Good luck with it.

 

[seasick]

Hold the radio near where you want to put it and see if the compass moves.
Power the radio on and see if the compass moves. Finally, key the mike and see if the compass moves.
If it doesn't move in all those cases, you are good to go.

Twisting the wires will not lessen any magnetic filed. It could make it worse in theory.
The more common source of magnetic interference is magnets either in a radio's speaker or in a mike that has a speaker. Modern radios generally use shielded speaker magnets.

 

[capt chris]

Hold the radio near where you want to put it and see if the compass moves.
Power the radio on and see if the compass moves. Finally, key the mike and see if the compass moves.
If it doesn't move in all those cases, you are good to go.

Twisting the wires will not lessen any magnetic filed. It could make it worse in theory.
The more common source of magnetic interference is magnets either in a radio's speaker or in a mike that has a speaker. Modern radios generally use shielded speaker magnets.

Seasick,
I agree with your response except for your comment about twisting the wires. Let me refer you to Chapman Piloting and Seamanship 64th Edition, page 444, column one, paragraph two;
"The two wires of a circuit can be twisted together to avoid the creation of a magnetic field. Make sure that the wiring for the compass light is twisted. Wiring beneath the compass and instrument panel should be in twisted pairs, one pair for the two wires to each instrument of switch. The grouping of pairs is not important."

 

[seasick]

Hold the radio near where you want to put it and see if the compass moves.
Power the radio on and see if the compass moves. Finally, key the mike and see if the compass moves.
If it doesn't move in all those cases, you are good to go.

Twisting the wires will not lessen any magnetic filed. It could make it worse in theory.
The more common source of magnetic interference is magnets either in a radio's speaker or in a mike that has a speaker. Modern radios generally use shielded speaker magnets.

Seasick,
I agree with your response except for your comment about twisting the wires. Let me refer you to Chapman Piloting and Seamanship 64th Edition, page 444, column one, paragraph two;
"The two wires of a circuit can be twisted together to avoid the creation of a magnetic field. Make sure that the wiring for the compass light is twisted. Wiring beneath the compass and instrument panel should be in twisted pairs, one pair for the two wires to each instrument of switch. The grouping of pairs is not important."

I love this stuff. There are several factors that contribute to the magnetic field. The major factor is current. Yes the direction of the flux field in the supply wire is opposite to the flux lines in the return (ground) wire. If the two wires are run straight and next to each other, a dipole magnetic field is created. If the wires are evenly and tightly twisted, the magnetic orientation outsides of the dipoles are opposite each other and tend to cancel. To get all the lines of magnetism to cancel, there would need to be infinite turns, anything less and the magnetic dipoles are not parallel to each other and only a partial cancellation takes place. Is the field less than two straight wires? Yes but the length of the wires has to be longer because of the twists. Longer wire means greater resistance. Greater resistance means higher current for a given load ( the radio). Higher current means higher flux density. Am I full of crap?? Could be, but I like to argue the technical stuff

Twist the wires, it may help but if the compass moves as mention in my first post, you still have an issue.

Now Capt Chris, tell me you had that reference to Chapman's memorized.....

 

[capt chris]

Not at all. Just remembered reading it and knew where to look it up.