GROUND LOOPS IN MOBILE INSTALLS

[freecell]

YB0EMJ - Ground System

 

[loosecannon]

well,

from reading that article, it sounds to me like what i need to do is:

1. run the positive wire from the amp and the radio to the battery terminal.

2. run the ground wire from the amp and the radio to the same place on the engine block.

3. connect the engine block to the vehicle chassis with a braided copper ground strap.

4. make sure the trunk, hood, doors, and exhaust system are all connected to the chassis of the vehicle with copper straps.


i have read before about the ground wire needing to be shorter than a quarter wavelength in base station setups to avoid an RF ground loop.

in my mobile, to get the ground wire to the engine block from where the amp and radio are, will put the length of the ground wires at around 8 feet or so.

will this cause problems for me?
i noticed that freecell mentioned that he asked his customers how long the wires from the radio to the battery were.

anyway, thats what i think i have surmised so far. LOL

thanks for the help so far,
LC

 

[unit_399]

LC -

re: your last post

#s 1, 2, 3, and 4 are correct. BUT first make sure you UNDO all of the things you did before... start from scratch so to speak.

Your antenna is good to go based on your previous posts.

The length of the DC power wires is important. You can help eliminate any rf and emi pickup problems by running the wires as a twisted pair.

Connect everything as recommended in Freecell's posts. You should have no problems...UNLESS your charging system isn't up to the task. Use a voltmeter to determine this

- 399

 

[loosecannon]

thanks 399,

the charging system shouldnt be a problem.
i installed a new 130 amp alternator, and a new battery just a few months ago.
this being a normal 4cyl passenger car, i should have enough amps to run a 4x2879.

ive heard of the twisted pair thing a long time ago.
its worth a try.

later,
LC

 

[W5LZ]

Still a lot of unnecessary wiring. Simply ground the engine block to the frame/chassis of the vehicle, then ground the radio/etc, to the chassis. No need for all that additional cabling. And for that 8 feet being a problem, it could be. Won't know till you try it.
As for running a dedicated cable to the battery's (+) terminal, sure why not. Unless you already have such a cable already, going to something else? If it's heavy enough to carry both 'loads', good. What about an interconnection between devices? You've already got them, a new cable won't make any difference, other than the current carrying capacity, and the possibility of another ground loop. If a ground loop isn't detrimentally affecting something, who cares if it's there or not? Don't make mountains out of them mole hills unless you have to.
- 'Doc

 

[steved]

dudmuck,

thanks for the reply.

i currently have the positive and negative cables from the amp running right to the battery.
the problem exists with the amp wired this way.

later,
LC

Ground the case??? I had an issue with a 3-pill, and it turned out the case not being grounded caused the issue, may be acting like an antenna instead of an RF shield??

I'm plagued by a unique problem with static...its there, I can touch the radio and it goes away?

 

[freecell]

"i currently have the positive and negative cables from the amp running right to the battery. the problem exists with the amp wired this way".

damn skippy it does. what is the approximate length of each of those two conductors?

 

[loosecannon]

freecell,

i would estimate that they are between 6-8 feet long each.
LC

 

[freecell]

for either a radio or an amplifier, at RF those lengths are (too damn long) excessive, especially for the B- line.