[OZAPRS] set up ford territory

[Justin Albury]

This the same reason all fuel injection computers in cars have only 1 earth cable to the -ve and then everything is cables from a -ve tag/bolt.

Good advice is often given freely but not acted upon ........ not such a bad thing as it provides plenty of work for others ;-)

Justin - VK2HJA

-----Original Message-----
From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On Behalf Of Bob VK6KW
Sent: Monday, 28 May 2012 1:58 AM
To: 'Australian APRS Users'
Subject: Re: [OZAPRS] set up ford territory

Sorry Pete,
Bad move if it is #1 battery.
Figure this... radio connected as you described + & - direct to batt, both fused :- During use/over time Batt -ve strap to body gets loose or resistance increases or is disconnected for some reason...
One cold morning you crank the engine... what does it draw 200A? 400A? 600A for diesel?  All those amps gotta get back to the -ve terminal somehow...
You have provided lovely low R path from antenna mount ground to body via coax braid to radio, possibly even radio grounded to body as well, and direct to the -ve batt term. 50A fuse carries a lovely lot of current and creates much fun when the insulation melts off those two cables especially where they are bundled to the loom here and there.

I saw it once in a farm ute with a bushfire radio installed (not mine) it took months before problems stopped - we should have simply replaced the whole loom outright!
There are other scenarios that can lead to similar results.

Lesson: #1 the batt -ve terminal should have only ONE connection, the earth strap to the body. This also makes quick isolation possible and safe in an emergency.
#2 all other "earths" go to the body to a SEPARATE point as close as you like to the first but not on it. Any loop created will be very small.
#3 Do not fuse the ground wire unless the item warranty depends on it and then use the same value fuse as the supply.
#4 Do exactly the same with connections to the AUX batt i.e. (solitary
ground) unless it is totally isolated from the vehicles electrical system.
#5 If you have a noise problem it is far more effective to remove or suppress it at source than taking risks to minimise pick-up loops.

Happy and safe mobiling,
73,
Bob 

Bob Lockley VK6KW mob +61(0)407 442 650
President, West Australian VHF Group Inc.
Net Control, Australian 14.116 Traveller's Net.
WIA member 132586
RAOTC 1172
NZART member 104063 Branch #99


-----Original Message-----
From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On Behalf Of Peter Bye
Sent: Sunday, 27 May 2012 2:38 PM
To: ozaprs at aprs.net.au
Subject: Re: [OZAPRS] set up ford territory

Re the below, why not??  I have done several mobile installs, most my own, but also for others.  I always connect both +ve and -ve direct to the battery, with a fuse on both.
I also use rig runners for power distribution.

Cheers
de
Pete VK2MPJ

On 27/05/12 14:32, Michael Carey wrote:
> ...
>
> Make sure you don't connect the negative wire to the battery... always 
> connect to an earth point on the body, close to where the negative 
> battery wire is connected...
>
> ...
>
> Michael.
> VK5ZEA
>
>

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