+++++++++++++++++++++ Reply-To: "Bob Lewis (AA4PB)" From: "Bob Lewis (AA4PB)" To: Subject: Re: [Elecraft] K2 mobile power fusing Date: Mon, 22 Jul 2002 15:51:14 -0400 > so what happens if the fuse in the negative lead blows ? Yes, the rig will still be grounded via other paths (coax shield, case mounting, etc) and you might not even realize it has blown. The reason for having a negative lead fuse is still valid however. If you take the negative lead back to the battery and if the vehicle's grounding wire between the engine block and the battery negative were to open, all the vehicle's current including the starter current would attempt to flow through your coax, mount, radio, and ground lead. In order to protect the radio system from an open or high resistance battery ground lead, a fuse is used in the negative radio lead. It should be sized the same as the fuse in the positive lead. ++++++++++++++++++ From: "Charles Bland" Organization: Entropy Reduction, Inc To: Date: Mon, 22 Jul 2002 13:48:35 -0700 Subject: Re: [Elecraft] K2 mobile power fusing Reply-To: BlandRanch at BlandRanch.net This is why you don't want to connect your ground lead at the battery. Ground it at the chassis ground point used by the rest of the vehicle. That way, if the chassis-to-battery connection fails, your K2 is not part of the new path. I also do not fuse my ground line.........that's a different discussion. Chuck +++++++++++++++++ Reply-To: "Bob Lewis (AA4PB)" From: "Bob Lewis (AA4PB)" To: Subject: Re: [Elecraft] K2 mobile power fusing Date: Mon, 22 Jul 2002 20:31:43 -0400 On my Mazda PU the main vehicle grounding stud is very close to the battery and has a smaller wire going to the battery negative terminal along with the large wire going to the engine block (all original factory stuff). I figure that if the wire to the block opened, the higher resistance of the smaller wire *might* permit some current to flow via the radio ground when attempting to start the engine. For that reason, I still include a fuse in the negative lead. I didn't want to get a ground from elsewhere on the chassis because you never know how quiet or reliable the ground path will be (experience shows me that some of the other grounding points can have a good deal of alternator whine present). I can't think of any disadvantage to using a fuse in the negative lead since it would only blow if there is a problem with the vehicle's grounding system. Some of the newer rigs by the way, take the negative lead straight in to the PC board (the Alinco DR-135 is an example). If you develop a grounding problem it would be quite possible to "smoke" the PC board runs inside the radio. +++++++++++++++++++