I will add to the conversation with a direct story relating to radio grounds, in this case it was a sail boat... At one time I spent much of my life Surveying boats, another survey friend asked me to look at his sailboat as he could not keep zinc's on the boat they would last about a month.. An arriving throwing a silver anode over the side (in salt water) showed about 1.75 volts between the water and his ground. So that is why the zinc's were plating off of the boat.
All grounds on the boat lead to a grounding plate at the foot of the mast (42 foot). As I was disconnecting each ground wire on the grounding plate, suddenly the ground went away, and Lee said "the VHF radio went dead", it was on as he was listening to the weather. So what had happened.. This was a case where the radio was wired directly to the battery, with fuses in both the positive and negative leads. The fuse in the negative lead was indeed blown (unknown reason). The ground path to the radio was up the coax shield to the masthead antenna, this antenna was DC grounded flowed then down the mast to the ground plate. This connection raised the ground potential in reference to all other grounds 1.75 volts.. and was the cause of all of the problems. Properly grounding the radio ground to the ground plate permanently resolved the issue.. This was a case of small currents (radio in receive), however should a starter have been involved as Tom (W8JI) explains the currents would have been great and could easily have caused a fire. My point is where ground connections are made can have consequences.. Regards.. Fred On 9/12/16 9:34 AM, Don Wilhelm wrote: > Brian, > > There is a lot of controversy over fuses in the ground lead. > The reason for them dates way back to days when the battery to engine > ground strap would commonly corrode or break. IMHO, that was more > common in automotive designs of the 1940s through 1980s vehicles when > it was a piece of uninsulated braid. I believe that connection is > much more reliable in modern vehicles and better protected from > exposure to the elements. > > The reasoning behind putting a fuse in the negative lead is that it > will protect the radio from having current from the starter current be > routed over the radio's ground wire paths should the battery to engine > ground strap be faulty. > > BUT, there are other paths to ground that can go through the radio > even if the fuse in the negative lead goes open - consider that the > antenna coax shield is also connected to the vehicle body and provides > yet another ground path. > > IMHO, fusing the ground lead is not necessary in modern vehicle > installations. In fact I recall W8JI insisting that the radio ground > be obtained from the chassis of the vehicle instead of routing the > ground wire all the way to the battery. That solution eliminates the > problem path. > > 73, > Don W3FPR > > > > On 9/12/2016 9:03 AM, brian wrote: >> Don, >> >> Perhaps you can clear up an issue. >> The link below does not include fuses in the ground side. >> I thought there were some very good reasons to do so. >> >> 73 de Brian/K3KO >> >> On 9/12/2016 12:50 PM, Don Wilhelm wrote: >>> Wayne, >>> >>> Take a look at >>> http://www.elecraft.com/manual/Rev-B1-1.6-KX3-Mobile-Owners.pdf. >>> >>> 73, >>> Don W3FPR >>> >>> On 9/12/2016 8:24 AM, Wayne Michael wrote: >>>> I have a 2012 Kia Sedona minivan. >>>> I currently have a FTM-400 mounted using a seat mount. >>>> Any ideas what mounts might be available to put a KX3 in the van along >>>> with the FTM-400? >>>> Anyone have experience with the KX3 mobile in a car? Worth the >>>> effort? >>>> Thanks, >>>> >>> >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:Elecraft@mailman.qth.net >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to als...@comcast.net >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to donw...@embarqmail.com >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to f...@fmeco.com > -- Fred Moore email: f...@fmeco.com f...@safes.com phone: 321-217-8699 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
