Flux gate vs JL Speaker

[Russ Calasant]

I have a Raytheon flux gate mounted pretty close to the only place I can install a pretty hefty 8” speaker. I assume it will interfere however it is the only place and moving the flux gate is no easy chore. My question is how will the magnetic field affect the compass? Is the result an incorrect heading on the AP? Is that all? Because I only use the AP on long cruises in a straight line to stay on the course the boat is headed. The actual compass heading is irrelevant to me. Can anyone enlighten me? Thanks!

 

[ttmott]

I have a Raytheon flux gate mounted pretty close to the only place I can install a pretty hefty 8” speaker. I assume it will interfere however it is the only place and moving the flux gate is no easy chore. My question is how will the magnetic field affect the compass? Is the result an incorrect heading on the AP? Is that all? Because I only use the AP on long cruises in a straight line to stay on the course the boat is headed. The actual compass heading is irrelevant to me. Can anyone enlighten me? Thanks!

Russ - yes a speaker will have a very adverse affect on the fluxgate compass instrument that would be impossible to calibrate out. On the other hand if the interference was steady state the autopilot calibration (driving your boat in circles) will zero out that interference. Large speakers have a significant magnetic influence distance and obviously that influence varies greatly. In relocating the fluxgate, it's best if possible to install at or below the water line to limit pendulum's swing.

 

[Russ Calasant]

Russ - yes a speaker will have a very adverse affect on the fluxgate compass instrument that would be impossible to calibrate out. On the other hand if the interference was steady state the autopilot calibration (driving your boat in circles) will zero out that interference. Large speakers have a significant magnetic influence distance and obviously that influence varies greatly. In relocating the fluxgate, it's best if possible to install at or below the water line to limit pendulum's swing.

Thank you. So would I be ok to leave as is and just re-calibrate the auto pilot? Or would I be better off moving it? To move it I will have to cut and splice in an extension. I tested it as is and it threw the heading out 180 degrees. The compass is located in the starboard locker facing forward. If I extend it I can relocate to the lazarrette on the starboard side, facing forward.

 

[CSR_Admin]

You'll need to move it. It will never work right being near a speaker.

 

[techmitch]

You'll need to move it. It will never work right being near a speaker.

I couldn't agree more.

 

[ttmott]

Thank you. So would I be ok to leave as is and just re-calibrate the auto pilot? Or would I be better off moving it? To move it I will have to cut and splice in an extension. I tested it as is and it threw the heading out 180 degrees. The compass is located in the starboard locker facing forward. If I extend it I can relocate to the lazarrette on the starboard side, facing forward.

No - you won't be able to calibrate the autopilot and the speaker will cause major issues. I probably should have been a bit more clear.

 

[Russ Calasant]

Understood - thank you both. I have conceded to the fact that I will need to move it.