How much of a performance hit is there running CB off of a fuse block?

pagrey said:
. . . Just use a 12V jumper battery or a friends car and jumper cables to power your CB if you suspect power noise. If your problem doesn't go away then power supply isn't your problem. . . .
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Or you can test by powering the CB with your own jeep battery with nothing else connected to the terminals, i.e., the circuit consists of only the battery, two wires and the CB. I suppose one can use a different battery to completely eliminate the possibility that RF interference is being generated by the jeep battery, but I am not aware of any widespread concern that automotive batteries themselves are the cause of RF interference.

I do check new CB's with nothing else hooked up to the battery terminals, but only to check to be sure that the radio powers on and the functions work before I go to the trouble of a full installation. Next time I'll listen for RF interference as well.

But riddle me this, how is powering the radio with nothing else connected to the power supply in order to check for power supply related RF interference really any different than powering it with everything hooked to the terminals, the ignition "off," and nothing turned on?
 
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Mr. Bills said:
But riddle me this, how is powering the radio with nothing else connected to the power supply in order to check for power supply related RF interference really any different than powering it with everything hooked to the terminals, the ignition "off," and nothing turned on?
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The noise is with the engine running, that's what makes the noise, the fuel pump and electronics. If you use your Jeep battery to only power the CB the engine don't run. Maybe I don't understand what you're getting at?

Edit: I assume most people don't have problems with the engine off, maybe I assume too much?
 
pagrey said:
The noise is with the engine running, that's what makes the noise, the fuel pump and electronics. If you use your Jeep battery to only power the CB the engine don't run. Maybe I don't understand what you're getting at?

Edit: I assume most people don't have problems with the engine off, maybe I assume too much?
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Nah, while it's running I get some general RF noise. As opposed to when it's off(the engine) there's virtually zero RF noise. All hell breaks loose when I turn on my blower fan for the climate control lol.
 
Yellow_Machine said:
Yes, would it be better to ground it elsewhere?
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Maybe, maybe not. This is where CB installs fall into the murky area between science and voodoo. One might think that connecting both the positive and negative wires directly to their respective battery terminals will necessarily result in the least RF interference, but sometimes a shorter ground wire terminating closer to the radio actually provides the best real world performance.

Its worth experimenting. Perhaps a positive or negative wire in close proximity to the blower motor is the issue and re-routing the wires and changing the ground point will help. Or not. Its CB after all.
 
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Yellow_Machine said:
Yes, would it be better to ground it elsewhere?
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Theoretically, it's best to ground it straight to the battery, as the battery acts as the voltage stabilizer of the system.

For high quality stereo systems, often times the amplifiers are grounded to the nearest bare metal and a small wire is run back to the battery negative terminal. Thus most current flows through the body of the vehicle, but the wire is there to help eliminate any noise from poor grounding through the body.

A stiffening capacitor near the radio would probably help absorb some of the noise, but solving any grounding issues would take priority.
 
Mr. Bills said:
Maybe, maybe not. This is where CB installs fall into the murky area between science and voodoo. One might think that connecting both the positive and negative wires directly to their respective battery terminals will necessarily result in the least RF interference, but sometimes a shorter ground wire terminating closer to the radio actually provides the best real world performance.

Its worth experimenting. Perhaps a positive or negative wire in close proximity to the blower motor is the issue and re-routing the wires and changing the ground point will help. Or not. Its CB after all.
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Have you guys thrown some ferrites on your power and ground leads for common mode noise?
 
Since my volume is also the on switch I ran my CB to the sPod. This way it comes on to the volume I want at the flip of the switch.

I’ve never had any issues with interference.
 
Jeepn_Texas said:
Have you guys thrown some ferrites on your power and ground leads for common mode noise?
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There's no need for that for a CB when the CB is powered directly to the battery or at least from the power input lug at the rear of the Power Distribution Center. The power is clean at either of those two points. Basic mobile 2-way Radio Installation 101 always says to power directly from or as close to the battery as possible.

This is my favored power connect point for my ham and CB radios in my TJ. That lug is at the rear of the PDC under a small snap-off plastic cover.

Power-Distribution-Center-Power-Lug.jpg
 
Jerry Bransford said:
There's no need for that for a CB when the CB is powered directly to the battery or at least from the power input lug at the rear of the Power Distribution Center. The power is clean at either of those two points. Basic mobile 2-way Radio Installation 101 always says to power directly from or as close to the battery as possible.

This is my favored power connect point for my ham and CB radios in my TJ. That lug is at the rear of the PDC under a small snap-off plastic cover.

View attachment 136427
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No, it's not... There is NO active filtering outside of the ECU. I did Military grade power systems for just about everything. What you can get is Common mode noise from the Alternator, Switching noise from Ignition and Fuel injection... the list is long... I will go out and do a scope check on my jeep...

1500RPM.jpg


hookup.jpg


idle.jpg


As you can see, it is not clean 14.1V, In the hook up picture you can see I am tapping from the power block to the ground on battery. That noise is nearly 200mv... that going into a CB power connection will be heard on the audio and the transmitted signal.
 
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Look up how batteries act as noise suppressors, they act just like a big filter capacitor. I grew up using Tektronix scopes, even built my own 5" scope from a kit many years ago... so you can use a scope to show pretty much anything you want it to. Like making small voltage variations look huge. I spent too many years in the industry to not know of what I speak.
 
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Jeepn_Texas said:
No, it's not... There is NO active filtering outside of the ECU. I did Military grade power systems for just about everything. What you can get is Common mode noise from the Alternator, Switching noise from Ignition and Fuel injection... the list is long... I will go out and do a scope check on my jeep...

View attachment 136538

View attachment 136539

View attachment 136540

As you can see, it is not clean 14.1V, In the hook up picture you can see I am tapping from the power block to the ground on battery. That noise is nearly 200mv... that going into a CB power connection will be heard on the audio and the transmitted signal.
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The heavy red /black wires going through the Ferrite then the 30Amp fuses on both +14V and GND IS my power for my ham radios. The other end is disconnected so the bead would not overly impact the scope readings.
On the other end there are more fuses and more beads. There is nearly NO noise where it enters my radios.
I often use a few caps as well to bleed off any non-common mode noise.

Car batteries are not like a big CAP, their internal resistance is too high to react to noise higher in frequency than about 30 hz what you saw on the scope went all the way up to 5 mhz. THAT noise would not even be nulled a little. If you loose even 1 diode of 6 in the 3 phase bridge rectifier in the Alternator, the noise would be HUGE.
On the following picture, What you see is the top 100mv of alternator's Half wave rectified "Clean Power" at the battery terminals. If it was a cap, they would not be there, would they?

Alternator.jpg
 
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Steel City 06 said:
You will need to add a grounding strap to the battery at the minimum if you're using a lot of current. In my Jeep, I used a 1 foot section of 2 AWG cable straight to the radiator support bolt.

It is the yellow wire in the below photos.
View attachment 114357

View attachment 114358

Amperage testing proved that the new strap is a far better ground than the stock one. Notice that 80% of the current is flowing through the new yellow wire, not the stock one. This not only improves the efficiency of the system, it also reduces noise due to grounding issues. For larger systems, it even reduces the fire hazard due to the stock strap becoming overloaded.
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OK, OK,... Got my ass handed to me on that one, missed the DC setting...
I haven't bought a new meter in a few years and the DC capable clamp meters were out of my price range.
 
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Jeepn_Texas said:
Oh that is interesting...
You have a clamp on Amp meter, Set to AC current, And it is reading... 28.72A of current...
The most I ever see on that circuit is < 2.8A .
At that point you are measuring just the non-overlapping AC peaks coming off of the alternator.
If your are getting that much current, you would need at least 1 phase of your alternator dumping it's raw AC on the battery. Over time, that will destroy the power filter caps in you ECU.
Then the erratic starting , misfire, then not running and or weird codes like crazy.
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The clamp meter is on the DC mode in those photos. On the screen there is either a ~ symbol or the solid line/dashed line symbol. One of the buttons toggles AC/DC.

Look immediately left of the numbers (up in reference to the first photograph orientation).

In addition, the engine is off in those photos.
 
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