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  Speaker Interference with VHF Marine Band Radio Antenna

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Author Topic:   Speaker Interference with VHF Marine Band Radio Antenna
siyc126 posted 04-21-2011 02:09 PM ET (US)   Profile for siyc126   Send Email to siyc126  
I'm considering installing 6-inch Fusion-brand speakers in the covers to the port and starboard of the center console [of a Boston Whaler OUTRAGE 18]. As I have read in my searches I'll stiffen this up with some starboard as a backing plate inside the cover. My concern however is with potential interference from the speaker magnet and the VHF cable running behind the same starboard cover to my vhf antenna mounted on the gunnel? Anyone with any thoughts or experience here?
jimh posted 04-22-2011 08:37 AM ET (US)     Profile for jimh  Send Email to jimh     
The magnetic field from a loudspeaker will not affect the radio frequency signals inside a coaxial transmission line.
jimh posted 04-22-2011 09:15 AM ET (US)     Profile for jimh  Send Email to jimh     
There is probably more likely to be interference to the dynamic permanent-magnet speakers from the magnetic field surrounding the coaxial transmission line when the VHF Marine Band radio is transmitting than there is in the other direction, that is, the magnetic field of the speakers interfering the the radio frequencies inside the transmission line. Generally the transmission line currents are equal between the center conductor and the inner surface of the outer coaxial shield, and not much of a magnetic field is created. However, if antenna current flows down the outer surface of the outer shield, it could create some magnetic field around the transmission line, and this field might affect a dynamic loudspeaker. I would anticipate that his effect would be very small, but, I would consider it when routing the radio transmission line. I would not bundle together the radio transmission line and the power leads for the loudspeakers. Keep them separated as much as possible.
siyc126 posted 04-23-2011 07:44 AM ET (US)     Profile for siyc126  Send Email to siyc126     
Jim,
Thank you very much for your reply. I'll keep the wires and cable as far apart as possible given that they have to run through the same under deck conduit. Again Thank you!!
Eric

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