SSB BROWN OUT

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

GORDON WEST REPLIES

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.