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Q: I have a marine SSB, and it has worked well for over 10 years. But lately, it has been act­ing strange on trans­mit, though it is fine on re­ceive. Specif­i­cally, the dis­play dims on each voice syl­la­ble, and some­times the ra­dio com­pletely cy­cles off. It is wired di­rectly to the bat­tery, which is brand new. I was told the SSB is old and that I should just get a new one. Strange. D. Effin­ger, Bay St. Louis, MS


Not so strange. It could hap­pen to any SSB ra­dio with its as­so­ci­ated ground con­nec­tion shared with other high-cur­rent equip­ment on board. High-cur­rent-draw­ing SSB ra­dios, per NMEA in­stal­la­tion stan­dards, are wired direct to branch cir­cuit pos­i­tive ter­mi­nals, and to a branch DC neg­a­tive buss. Read “neg­a­tive bat­tery,” not a ground buss. On some in­stal­la­tions I have seen, the red and black wires go direct to a lo­cal

bat­tery un­der the nav sta­tion floor­boards. After a few years, con­nec­tions on the neg­a­tive DC line can work loose so that a high-cur­rent an­chor wind­less, for ex­am­ple, may try and draw ex­tra cur­rent through the ship’s ground sys­tem, tied into the bat­tery neg­a­tive lead through the SSB ra­dio ground and neg­a­tive leads. This path, in turn, may be in se­ries with the ra­dio’s neg­a­tive black wire lead fuse, which can cause the fuse to pop on the ra­dio’s neg­a­tive lead. The ra­dio can still turn on, using its ground con­nec­tion all over the ves­sel to get back to bat­tery neg­a­tive. Also, no prob­lem on low-cur­rent re­ceive. How­ever, on trans­mit, you end up with a big drop in volt­age and poor out­put power. Not good. So cure the blown black fuse with a new 30 amp fuse. Also be sure to check why the an­chor wind­less, or bow thruster, or other piece of gear, has a loose low-re­sis­tance direct neg­a­tive DC con­nec­tion to the bat­tery neg­a­tive ter­mi­nal.


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