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Old 09-25-2012, 06:06 PM   #1
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Checking ground

I just installed my cb mount and when checking my ground with multimeter, I get a 1. I mounted it to my spare tire and ran a ground wire.
I'm new at using this and I'm thinking zero is perfect. Is 1 considered good enough?

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Old 09-25-2012, 07:11 PM   #2
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If you are using the continuity test in a multi meter no.

1-continuity
0-open (no connection)

You just want a fairly heavy gauge low resistance ground connected to the chassis.

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Old 09-25-2012, 07:11 PM   #3
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Depends. What does your meter read when open? (Set to ohms, turn on, then hold the leads out in the air, what does the screen say? If 1, that is no good at all.)

Lol, mutual post. Most meters use 1 for open, some use OP or other signals, I find it crazily odd that you have exactly 1 ohm resistance.
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Old 09-25-2012, 07:40 PM   #4
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Originally Posted by BlueRidgeYJ View Post
Depends. What does your meter read when open? (Set to ohms, turn on, then hold the leads out in the air, what does the screen say? If 1, that is no good at all.)

Lol, mutual post. Most meters use 1 for open, some use OP or other signals, I find it crazily odd that you have exactly 1 ohm resistance.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sorry to toss out information that is hard to understand. I'm using my brother in laws FLUKE 111 Multimeter.
I set it to the "tone" setting and the screen says "OL" without touching the probes. When I touch them together I get a "0" and a tone. I noticed that when I tried to get a connection and it wasnt' good, I would get a higher number.

I just noticed that there is an upside down horse shoe. Is that the ohms? When I touch the probes I get a .2 Haven't tried it on my ground wire yet. I'll run down and try it now.


It is 1.6 on the upside down horse shoe.
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Old 09-25-2012, 07:52 PM   #5
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Yes, the symbol for ohm looks like an inverted horseshoe. Iirc, 111s are autoranging, so just put it on that. That is resistance test, and FYI NEVER test a live circuit for ohms. You will become the lightbulb.

1.6 seems a bit high, are you contacting paint or bare metal for both the mount to vehicle and probe testing location? Mine, with a direct bumper mount, is .2, and thats in the probes/cheap meter i used/testing locale.
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Old 09-25-2012, 07:56 PM   #6
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Yes, the symbol for ohm looks like an inverted horseshoe. Iirc, 111s are autoranging, so just put it on that. That is resistance test, and FYI NEVER test a live circuit for ohms. You will become the lightbulb.

1.6 seems a bit high, are you contacting paint or bare metal for both the mount to vehicle and probe testing location? Mine, with a direct bumper mount, is .2, and thats in the probes/cheap meter i used/testing locale.
~~~~~~~~~~~~~~~~~~~
I ground away some powder coating and drove a screw through the metal for my ground. From there I ran it to the body of the jeep inside the door.
When I checked the bolt for the spare tire was a .2 and the screw from the ground was a 1.6

Looks like I'll need to work on this. I was hoping that 1.6 would be a decent ground. DRAT!
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Old 09-25-2012, 08:13 PM   #7
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Its all up to the swr test, as long as youre under 2 youre OK, but that is probably too high to acheive that on a Jeep.

So you tested one bolt holding the cable and he other bolt holding the cable and it was 1.6? Ya usein a rubber hose???
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Old 09-25-2012, 08:43 PM   #8
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Its all up to the swr test, as long as youre under 2 youre OK, but that is probably too high to acheive that on a Jeep.

So you tested one bolt holding the cable and he other bolt holding the cable and it was 1.6? Ya usein a rubber hose???
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Not sure what the rubber hose question is.

I ran a ground wire from the tub inside the rear fender area to the bracket that holds the cb mount. I used the Multimeter to check the ohms placing one lead on the muffler and one on the screw holding the ground wire to the bracket and I got a 1.2 (just rechecked). When I moved the probe over to the bolt that holds the bracket to the jeep I got a .2 (muffler to bracket)
I need to find a better ground at the other end of my ground wire. I realize that tailgate grounds are not consistant.
I suppose it wouldn't kill me to grind some powder coating away from the head of the bolt while I'm there.

Can't check my swr's yet. I had to order the antenna and it won't be here for a few days. Just wanted to get this part nailed down while I'm waiting.
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Old 09-25-2012, 08:48 PM   #9
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Gotcha. Yea, the mounting spot on the tailgate seems to be the snafoo if youre .2 muffler to tub, 1.2 muffler to bracket.

If youre worried about letting the metal equalizer in, put some dielectric grease, just a tab, on the exposed metal.
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Old 09-26-2012, 04:59 PM   #10
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Update on ground issues

Quote:
Originally Posted by BlueRidgeYJ View Post
Gotcha. Yea, the mounting spot on the tailgate seems to be the snafoo if youre .2 muffler to tub, 1.2 muffler to bracket.

If youre worried about letting the metal equalizer in, put some dielectric grease, just a tab, on the exposed metal.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

OK, my antenna arrived and now I'm going to finally see how this works. NOT!

I am having a weird problem with my ground. I changed the ground cable and I am getting .2 at the tub and at the mounting plate. You would think that I would be happy.
I have tried and I keep getting very high swr readings. Still way up in the red. So when I check my ground with the cb on, the ground reading is 2.4 When I turn the radio off my ground is .2 AND my swr readings suck.

I'm pulling my hair out, and I'm not sure what to do next. The radio came from my motor home, and I got just below 2 on the swr with a window antenna. So I know the radio is good. Not sure where my problem is.
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Old 09-26-2012, 05:07 PM   #11
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What type of antenna are you using and what is yk urban sir at ch1and at ch 40? Most likely need to adjust the antenna
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Old 09-26-2012, 05:33 PM   #12
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Sounds like you are experiencing a voltage drop. Try switching your meter to DC volts, and connecting the black probe to the battery ground, red probe to the antenna's grounding point. Turn the CB on and see what you get. If it's higher than a half-volt, you have a poor grounding point. You can try a grounding strap from the antenna's mount to the actual chassis of the Jeep to see if your situation is improved, or play around with new mounting locations.
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Old 09-26-2012, 05:35 PM   #13
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What type of antenna are you using and what is yk urban sir at ch1and at ch 40? Most likely need to adjust the antenna
It is a 3' Firiestik Firefly. I just spent a little more time adjusting it and the best that I can get is around 3 on the swr.

I'm stumped. I thought that it was going to be a ground issue, but I have that straightened out.

Just a thought... is it a big deal to be away from houses? I'm sitting in my driveway.
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Old 09-26-2012, 05:36 PM   #14
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Sounds like you are experiencing a voltage drop. Try switching your meter to DC volts, and connecting the black probe to the battery ground, red probe to the antenna's grounding point. Turn the CB on and see what you get. If it's higher than a half-volt, you have a poor grounding point. You can try a grounding strap from the antenna's mount to the actual chassis of the Jeep to see if your situation is improved, or play around with new mounting locations.
Thanks.
I'll give that a try tomorrow. I'm pooped and I need to walk away from it right now.
You think that the ground needs to be better? I'll see if I can improve on it tomorrow.
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Old 09-26-2012, 05:55 PM   #15
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If the ground does need to be better, that voltage drop test is the best way to figure it out. In a perfect world, the connection should read 0 volts between it and the battery ground, but as long as you are under a half-volt, your ground *should* be fine.
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Old 09-26-2012, 07:32 PM   #16
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It does sound like a voltage drop from the symtoms, which would mean an incomplete ground, which a voltage drop test would check.

BUT:

You didnt get an acurate reading of ohms. You tested a live circuit, and effected the path of ground by testing the ground connections with it on. Were it a positive circuit, the fuse in your cousins 111 wouldve blown, and hed be mad. Theyre 20$ea. All good, and I dont mean to pick on ya, rather to teach you what that meter does and how to do it

Is the antenna insulated from the mount with a nylon washer?
Adjusting your antenna while swr is over 3 is pointless, there is another problem.

And yes, be away from buildings, power lines, antennas, etc when testing, with the jeep in the condition that the radio will be used, like doors closed or off or what have you. It will all effect swr, but not as much as what youre seeing.
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Old 09-27-2012, 11:08 AM   #17
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Also, have you done a continuity test from the radio hookup side? Coax could have a short.
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Old 09-27-2012, 07:47 PM   #18
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Here is the latest:

I found a great ground. The hold down hook in the back of the jeep. I added that to the system. Meaning, I ran a jumper from that ground to the other ground and I get between 0 and .1 It jumps back and forth. I was pleased that my antenna now has a super ground.
Problem is, it jumps to around "10" when I turn the key on. Not really sure what you guys are talking about with the "voltage drop". I'll spend some time tomorrow trying to figure that out.
In the mean time, should I take the first 'tub ground' out of the loop? If I run the ground from the tie down hook to the antenna bracket would I be better off?
Now I'm not sure if the first ground that I used at the tub is causing the problems.

I almost got the antenna tuned down to a 2 on the swr, but the adjusting screw at the top of the antenna was almost all the way out. That told me that things weren't good.
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Old 09-27-2012, 07:51 PM   #19
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Something else to add to the mix.

I don't have the cb mounted. It is sitting on the drivers seat while I try to get the antenna tuned. My plan is to use a hose clamp and secure it to the bottom of the drivers seat.
It sill be snug and out of the way. I figure that I can set the channel before hitting the trail. If I really need to change the channel, it only takes a second to stop. Or I can keep a mirror in the glove box. This isn't something that I'll be using that often, so under the seat should be perfect.

I just wasn't sure if it picks up a ground through the mounting bracket.
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Old 09-27-2012, 08:47 PM   #20
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The meter you are using is a digital multi meter, meaning it displays readings of multiple funtions (tests) as a digital readout.

One of these tests is a continuity test, and is is a test of the resistance of a circuit, measured in Ohms, after some guy that was really smart a long time ago. Ohms are represented by a symbol that looks like a horseshoe upside down. The meter does this test by sending a small pulse of electricity out of one probe and measuring how much makes it to the other side. The best example of a ohm test is testing a lightbulb to see if the fillament is blown. Due to how it reads this test, you MUST isolate the circuit or componant being tested to get an accurate reading and avoid damaging your meter or the circuit. If you test a circuit that is energized, you are altering the available path of current. For example, if you tested a circuit containing an oven for continuity while baking cookies, you would glow real bright for a few seconds; the electricity would go through your wires and meter instead of going through the load (oven) because the path would be easier, that is it would be the path of least resistance.

So how do you know a circuit is properly conducting electricty in the desired current? A voltage drop test. A voltage drop test looks at the voltage at one probe, then the voltage at the other probe, and displays the difference. So with our oven test, we would be just fine, as the circuit tester keeps the probes isolated.

Voltage is indicated by a V, an equal sign with one line broken means direct current, one line like ~ means alternating. All (well, most) vehicles use 12V direct current systems.

Testing the Ohms while the radio is on provides an alternate path to ground for the current, and is not an acurate reading. A voltage drop test must be done to determine how "good" your ground is. Put the meter on the direct current voltage symbol, put one lead on the neg battery and the other on the radio mount bracket, the reading should be .5 or less (as ebovan said).

You may have to reset the probes in the meter depending on the testing capabilities of the meter. I dont remember wih a 111, but it will have the test symbol next to where the red probe goes, black goes to comm.

Hope that helps
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Old 09-27-2012, 09:04 PM   #21
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You said radio, but antenna makes more sense.
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Old 09-27-2012, 09:18 PM   #22
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Oh, my bad, antenna mount bracket, not radio bracket. Sorry.

You want to see if the ground current at the antenna mount is the same as the ground current at the battery, the ground currents final destination. That would mean your antenna bracket ground is electrically one with the battery, but that's a lab result, so less than .5 is good real world.
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Old 09-28-2012, 02:27 PM   #23
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If the ground does need to be better, that voltage drop test is the best way to figure it out. In a perfect world, the connection should read 0 volts between it and the battery ground, but as long as you are under a half-volt, your ground *should* be fine.
Just did the voltage drop test, and I went from 0 to .001 and I still can't get a good SWR reading.

I'm going to start a new post with my problems because I've polluted this one.

Thanks for all of your help.
Dave

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