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[aprssig] 12V wiring ideas

Steve Noskowicz noskosteve at yahoo.com
Sat Oct 29 21:38:23 UTC 2011


David,
This thread is long and probably still growing and this isn't going to help either...
 
There are many good suggestions, but here are a few comments on Mobile power.
 
  The ground line at the battery should be fused, but at the next higher fuse rating.  The purpose of this fuse is in the event of a battery starter/ground-return fault whereupon some of the ENGINE cranking current flows through your radio ground wire, through the radio and then through the coax shield *if* it is grounded at the antenna.
  Therefore it should only be done for an individual radio because the coax can't handle the 60 amps required to blow a fuse as suggested in this thread.  Of course, *if* the antenna coax is NOT grounded @ the antenna, as in a mag mount, this "isn't necessary", but if you later change the antenna to a grounded version, you have to remember to go back and fuse the ground line, so doing it up front is better.
 
So if the radio fuse is 15A then the ground is 20A.
 
  Then there is the issue of wire shorts before the radio, say as it goes through the fire-wall.  In this case, a larger fuse would/could be better, but the specifics of this 'whatever' short may not provide high enough current to quickly blow a really large fuse and prevent hi temps even if it s a #10, 8 or larger wire.  With its reasoning, you fuse the wires at the battery and fuse the radio at the radio.  
 
  This seems to suggest using the largest wires you can, but the smallest fuses you can.
 
  It probably *is* silly to fuse the ground line in the boom-Boom audio application since there is no antenna coax to help the starter ground cable...(;-)
 
  Connecting the ground wire to the chassis/block near (not on) the Battery ground cable to avoid the 'cranking problem' gets around much of this leaving only potential starting transients with a poor battery ground, which is least likely.  
 
  For the ground-fault/current/coax reason, for multiple radios it is best to run separate wires from the battery - inconvenient, but "better" technically - or go the frame ground method.  Do whatcha' gotta.
 
  Working in the cellular field, we used AMP connectors that actually interface with the PowerPoles, but we used the next size up that are rated for a similar current (45) as the smaller Anderson units.  The first time I saw the ratings for the common (ham) Anderson connectors I couldn't believe it and still don't trust them at 40 amps.
 
  SO...  I use the larger size on  #10 wires from the battery then simply make a wire wye adapter between the larger size to the smaller "ham" Anderson size and use the "Ham" Anderson units for each radio to be ARES compatible.   It's really nice to have all radios with the same power connector in the car.
 
  With the larger size connector, it is easy to get two or three wires in one contact to make a wire WYE adapter from the large to 1, 2, or 3 "standard" Anderson connectors.
 
  I only solder the wires - and it does take some skill not to contaminate the contacts, or over solder the usually stranded wire.  Crimping is fine when done correctly, but it does require the correct, and expensive, crimper.  If not, it causes resistance and therefore heat and some Anderson Power poles have melted, probably for this reason.  A non standard crimper can deform the crimp and essentially destroy it.  I have even seen a crimper suggested that deforms the contact and then it has to be re-formed in another part of the crimper to get it to fit in the housing...YIKES!
 
  I recommend first dressing the connectors so there is *NO* stress on them - this is how they were designed to be used.  Then, they should require no mechanical assistance. However, if you want take extra care, put a TieWrap around the WHOLE connector pair - around both backs, between the two wires.  Putting anything through the "hole" stresses the slip-in joint holding the two together--I know the roll-pin is the recommended way, but it does put stress on the slip-joint and folks report they can even fall out.  I've considered putting a 4-40 screw, washers & nut in the hole, but haven't done it.  This would also facilitate mounting pairs on some type of a panel.
 
  All that said, if you take the radio out each night, cycling these connectors many times, screw terminals, such as the black barrier strips or the milky dual set-screw blocks, are a better choice.  These slide together connectors are pretty much a connect-and-leave-alone connector.
 
  Finally, if you want a really spiffy looking setup, go to a hi-fi, high power, Boom-Boom mobile audio shop.  They have some really cool looking fuse holders and connection systems that look pretty good to me as far as low resistance goes.  Screw clamping the wires.  They look like there is gold plating and the clear plastic housings yield maximum "spif", not to mention the clear insulation on the wires.
-- 
73, Steve, K9DCI
 
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