Where Do You Ground Your Comms?

Where Do You Ground Your Comm Radio?

  • Back to Battery

    Votes: 12 66.7%

  • Nearest Location on Tub

    Votes: 6 33.3%

  • Other ...

    Votes: 0 0.0%
  • Total voters
    18
SSTJ

SSTJ

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Stop me if this exists, but I don't see a thread dedicated to this question. I've read conflicting information here and elsewhere, and would like to understand whether my Ham and CB radios should be grounded to the battery or to the nearest paint-free spot on the tub.

p.s. I have my CB and Ham grounded back to the battery. With an upcoming re-wiring job, I'd like to ground them to the tub instead, as long as someone on here can make me feel ok about it.

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Update: Best answer so far is here.

Update 2: Chrysler released a TSB about this in 1999: "INSTALLATION OF RADIO TRANSMITTING EQUIPMENT—Special design considerations are incorporated into this vehicle's electronic system to provide immunity to radio frequency signals. Mobile two-way radio and telephone equipment must be installed properly by trained personnel. The following must be observed during installation. The positive power connection should be made directly to the battery and fused as close to the battery as possible. The negative power connection should be made to body sheet metal adjacent to the negative battery connection. This connection should not be fused. Antennas for two-way radios should be mounted on the roof or the rear area of the vehicle. Care should be used in mounting antennas with magnet bases. Magnets may affect the accuracy or operation of the compass on vehicles so equipped. The antenna cable should be as short as practical and routed away from the vehicle wiring when possible. Use only fully shielded coaxial cable."

Update 3: A related post can be found here on ham.net.
 
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It really doesn't matter. Don't use the frame. There is allot of nonsense regarding this. If you test two different points and notice a difference please post the results. Most people change ten things and then say they fixed it with the one thing they thought was the problem ignoring the other nine they changed.
 
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pagrey said:
It really doesn't matter. Don't use the frame. There is allot of nonsense regarding this. If you test two different points and notice a difference please post the results. Most people change ten things and then say they fixed it with the one thing they thought was the problem ignoring the other nine they changed.
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I'm going to be re-wiring some things soon. If there is no difference then I'll opt for a nearby spot on the tub, just to avoid running that many wires back to the battery. But I figure there must be some reason that so many say to run it back to the battery?

Edit: For instance, doesn't running all the way to the battery put you at risk of having too long a ground wire? Sites like this one say to keep your grounds no longer than 18".
 
my reasoning going directly to the battery was years ago, when I installed a CB in my CJ, I had a lot of noise interference, I can't remember where or how it was conveyed to me but if I were to wire CB directly to the battery, the noise would go away. It did. I have wired them up that way ever since...
 
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I had my CB wired directly to the battery with an inline fuse for the least amount of electrical interference. Never an issue over the years. My gmrs is powered similarly, albeit to a power distribution box which is powered directly from the battery.
 
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Direct from battery for power, nearest good spot on the tub for ground. No sense in having an antenna on the ground side. As @pagrey notes, don't use the frame - UNLESS you have a good ground strap on same - and I'd still not use it, but the tub instead.
 
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mvigo said:
my reasoning going directly to the battery was years ago, when I installed a CB in my CJ, I had a lot of noise interference, I can't remember where or how it was conveyed to me but if I were to wire CB directly to the battery, the noise would go away. It did. I have wired them up that way ever since...
Click to expand...

Yea, I hear you. I just don't get it though: wiring all the way back to the battery increases the length of your ground wire, and likely runs it past the sources of interference, like alternator or distributor. So I'm glad it worked for you; I'd just like to understand why.
 
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pagrey said:
It really doesn't matter. Don't use the frame. There is allot of nonsense regarding this. If you test two different points and notice a difference please post the results. Most people change ten things and then say they fixed it with the one thing they thought was the problem ignoring the other nine they changed.
Click to expand...

Ok, understood. I think I'm just interested in understanding why it's often taught that we should ground the radios back to the battery, whereas we don't do that with any other accessories (like my subwoofer amp). I did it because I was told to, but I'd rather not if I don't have to.

Here's a question for you: if my antennas use the tub of the Jeep as their ground-plane/counterpoise, then can my RF transmissions cause interference back to the radio, if the radio itself is grounded to the tub?
 
SSTJ said:
I'm just interested in understanding why it's often taught that we should ground the radios back to the battery, whereas we don't do that with any other accessories I did it because I was told to, but I'd rather not if I don't have to.
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The radio manufacturer wants you to get the best results with their product.
They instruct you to power/ground directly from the battery.
Why toss out their R/D ?
Is your R/D is so much more advanced than theirs?
 
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Head Lice said:
The radio manufacturer wants you to get the best results with their product.
They instruct you to power/ground directly from the battery.
Why toss out their R/D ?
Is your R/D is so much more advanced than theirs?
Click to expand...

Thanks. It wasn't actually the manufacturer who instructed me, but rather someone from my local radio club. So I actually didn't know what the manufacturers recommend, and that's a good point.

p.s. I'd also just like to understand why.
 
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Not to hijack but how do you guys go from inside the cabin to the battery? Do I need to drill behind the dash or is there a hole after removing the dash that I will find to go through firewall?
 
Crutchfield says a lot of things, but offers no real explanation for keeping a ground wire short. One of the problems with grounding to the body or frame is creating a ground loop. Another is like the article said, your antenna and electrical grounds sharing a path. I mounted a CB with a kicker and ran a wire from Bat+ to the radio and ground to the body. The first time I keyed up it killed the engine. Released the PTT and it ran again. The ignition module didn't like the radio. An old school solution is to run 3 wires. Pod and Neg both ran to the battery, and a 3rd wire run from the battery to the radio but only connected to one, not both. It acts as a drain to keep interference away from the radio. If you have or are worried about interference you should also run a flat braid from body to frame and/or engine.
 
Deputy Dodge said:
Crutchfield says a lot of things, but offers no real explanation for keeping a ground wire short. One of the problems with grounding to the body or frame is creating a ground loop. Another is like the article said, your antenna and electrical grounds sharing a path. I mounted a CB with a kicker and ran a wire from Bat+ to the radio and ground to the body. The first time I keyed up it killed the engine. Released the PTT and it ran again. The ignition module didn't like the radio. An old school solution is to run 3 wires. Pod and Neg both ran to the battery, and a 3rd wire run from the battery to the radio but only connected to one, not both. It acts as a drain to keep interference away from the radio. If you have or are worried about interference you should also run a flat braid from body to frame and/or engine.
Click to expand...

Interesting, thanks.

As for that flat braid, TJs do come with one from the body to the engine. And of course a thick ground cable from the body to the negative terminal.
 
Deputy Dodge said:
Crutchfield says a lot of things, but offers no real explanation for keeping a ground wire short. One of the problems with grounding to the body or frame is creating a ground loop.
Click to expand...
No. A ground loop is caused by multiple ground paths with varying impedances for a given load. Short grounds are ALWAYS better - they're lower impedance and less likely to pickup stray RF.

With that said, grounding is 1/4th science, 3/4ths black magic.
 
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Zorba said:
No. A ground loop is caused by multiple ground paths with varying impedances for a given load. Short grounds are ALWAYS better - they're lower impedance and less likely to pickup stray RF.

With that said, grounding is 1/4th science, 3/4ths black magic.
Click to expand...

But Zorba, what do you think about the argument that it doesn't make sense to use the tub as the ground path for the radio itself, since the tub is also acting as the counterpoise for your antenna?
 
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