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Discussion Starter · #1 ·
I made a custom antenna mount last year for my cb on the spare tire carrier (08 JKU) when I had my trektop NX softtop on. Unfortunately it was not out far enough from the hard top and kept hitting my wiper on the hard top so I removed my antenna. I never got around to making a new mount so I didn't use it for a few months. Since I got my trektop back on, I re-installed my antenna. I re-tuned it (school parking lot) and am at < 1.3 for channels 1,19 and 40. I am using firestick 3' on spring mountain. I have a cobra 75 and using RG-58 coax (18') i picked up from fry's. The weather radio channels 1 & 2 work well with static on the others.

I'm in the Atlanta area and I can't pick up any CB traffic on any channel. I find it hard to believe no one is using a CB on the highways especially with all the truckers around.

I'm wondering if this is an issue with either the coax or a limitation of the cobra 75.

Is it worth it to swap out the RG-58 with RG-8 or LMR400? Should I consider getting a different CB? Is 3' too short of an antenna?

I went with the cobra 75 because it was small and compact and I can lock it up in my best top under seat lock box when not in use.
 

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Is the RF control turned all the way up and sqelch all the way down?

RG-58 is fine with the length being used in the Jeep, not enough loss to worry about.

Keep listening on 19.
 

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A lot depends on where you live, in my experience CB traffic is very limited these days. Keep listening on 19, I'd also check 12. Maybe someone here is nearby so you can get a radio check.

You might also want to try asking for a radio check on 19. There may be someone listening.
 

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Yep, that RG58 is fine, no worries at all on that. I'd recheck the SWR & if it's still as low as it was, chalk up the lack of CB traffic on the fact CB isn't all that popular any more. I can drive on the highways/freeways and not hear any CB traffic for long periods of time. Not even many truckers still use it.
 

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Discussion Starter · #5 ·
I knew something was wrong, last fall/winter traffic was consistent. Atlanta is big city along a major cargo routes.

One of the ends on the cable was not fully secured. I think it was being jolted around by these less than smooth highways around here.

I'm still around 1.2/1.3 on channels 1 & 40. Is there anything else that can be done to drop it even lower? I'm wanting to maximize my output. I think I've tweaks the antenna as much as I can.
 

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1. If it stayed near the same with or without the cable terminated properly, I wouldn't trust your SWR readings.

2. Car CB antennas require a good ground. Using the spare tire carrier as the ground may not be sufficient. A ground strap from the carrier to the main body may help. Further a strap from the body to the frame would be even better.

Do all that and retune the antenna using a good SWR meter.
 

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Discussion Starter · #7 ·
1. If it stayed near the same with or without the cable terminated properly, I wouldn't trust your SWR readings.

2. Car CB antennas require a good ground. Using the spare tire carrier as the ground may not be sufficient. A ground strap from the carrier to the main body may help. Further a strap from the body to the frame would be even better.

Do all that and retune the antenna using a good SWR meter.

1. The cable end was a little wobbly. I think jolts (ie pot holes, rough patches of road) were causing the connection to not be consistent.

I could get channel 1 or channel 40 near 0, but the best I can get across every channel was 1.2-1.3. While Good, I just want to tweak to be better.

2. The control box for the Cobra 75 is grounded (per instructions) and is mounted under my glove box. The coax is ran under the passenger side carpet to the rear of the jeep where i run it into the swing gate (same path as 3rd brake light) and out the grommet behind the spare tire (fairly common install path from my research). The mount is made of galvanized sheet metal.

Are you suggesting I ground the mount to the door/frame?
 

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Yes, the antenna is a 1/4 wave radiator. It works best with a 1/4 wave ground plane.

1/4 wave is about 102" at CB frequencies. The Firestik achieves its 102" electrical length by helical winding wire around a fiberglass core.

The more ground you get under the antenna, the better it performs.

Ideally the antenna should be in the center of a metal roof on a large car.

Impractical (impossible) on a Wrangler with a soft top or a fiberglass hard top.

The next best thing is to use the body and frame as the ground.
 

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Discussion Starter · #9 ·
A screw type ground from the mount plate be sufficient? Screw the ground wire using small ring connector to the mount plate then connect the other end to the door/frame be sufficient?

I don't think I've seen anyone ground their mount before in all of the pictures/descriptions I've seen.
 

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Not saying that what you have won't work.

You said that you wanted maximum performance. That is what I based my response on.

!. Ground from mount to tailgate.
2. Ground from tailgate to tub.
3. Ground from tub to frame.

Grounds should be braided wire. Ring terminals are ok. Star washers and paint removal under the terminals. Periodic checking for corrosion.

The better the ground, the better the performance. Will it be noticeable? Maybe not.

The above advice is based on 50+ years of mobile radio experience.
 

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Discussion Starter · #11 ·
I do appreciate the help. Yes, I do want maximum performance - without going to amp (illegal) route.

I think I would benefit from a good quality coax cable to start with.

I'll start by grounding the mount to the door and go from there.

thanks!
 

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This is a quote from a web site about coax cable losses: "A difference of 3 db or less between two antennas, two types of coax, or two station configurations is usually not sufficient to justify the higher costs of the more expensive, lower loss, coaxial cable unless you are a perfectionist with lots of money."

RG-58 = 0.5dB at 30MHz per 20'
RG-8x = 0.4dB
RG-8 = 0.2dB
LMR-400 = 0.1dB
 

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Discussion Starter · #13 ·
This is a quote from a web site about coax cable losses: "A difference of 3 db or less between two antennas, two types of coax, or two station configurations is usually not sufficient to justify the higher costs of the more expensive, lower loss, coaxial cable unless you are a perfectionist with lots of money."

RG-58 = 0.5dB at 30MHz per 20'
RG-8x = 0.4dB
RG-8 = 0.2dB
LMR-400 = 0.1dB
I maybe a perfectionist at times, but I don't have lots of money. :lmao:. But my cable sort-of failed already once. I was actually considering getting LMR-400. Do I spend $10 for another cheapie or $30 for good quality? Really not that expensive for 18-20 foot cable.

thanks again!
 

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Your SWR is very likely as good as it's going to get, and make no mistake in believing it is anything but very good. And the SWR is not going to improve with any of the cables listed by Jeffs92yj. There's a fine line between being a perfectionist and a perfectionist seeking something that is very likely unachievable when talking about a CB antenna mounted on a Jeep.

Don't waste your $$$ on even RG-8x, let alone LMR-400, it won't make a difference you'll be able to detect. I've been at this stuff since the 60's and have a little experience in it... military, commercial, and ham radio. Be happy with your 1.2 to 1.3 SWR, really.
 

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Discussion Starter · #15 ·
My cable needs to be replaced, that's a fact. Could be that I damaged it installing it (yanking on connector to pull through, etc), could be from installing/un-installing my antenna a few times and twisting it.

my point is that for me, a $30 quality cable makes more sense than spending another $10 for a cheapie that could very well break again.

I just epoxied the connector on last night, it was intended to be a temp fix anyway.

I agree it might not get better than what I have which is good, but I'd like to try to get it better if I can in a cheap way. To me spending $30 on quality cable and using wire/terminals I already have at home to do the ground is cheap enough for the effort.

If I get it better, others can benefit. If I don't, they know what not to try :) Either way it's a win / win / win situation for all here.

Appreciate the feedback from those more experienced at this than I am. that's what makes forums like this great!

Thanks
 

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RG58 is not a "cheapy" cable, it is only a type of cable that like any other cable can be made with high quality or not so high quality... we even used RG58 cable extensively in the military for some radio needs and it works extremely well. Just stay away from cheap cables like Radio Shack sells... foam insulation around the center conductor = bad, polyurethane insulation = good. Belden is a good brand of RG cable if you can find it.

I use larger diameter cables when it makes sense, like my RG-213 (like RG-8) for my HF ham radio that has a long cable run outside, but for a 4 watt CB with under a 20' cable run there would be zero significant benefit to even go with RG-8x. And again, you could go to even RG-8 and it would not change or help the SWR in the least.

But I have a feeling that I am shouting into the wind here. :)
 

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Discussion Starter · #17 ·
RG58 is not a "cheapy" cable, it is only a type of cable that like any other cable can be made with high quality or not so high quality... we even used RG58 cable extensively in the military for some radio needs and it works extremely well. Just stay away from cheap cables like Radio Shack sells... foam insulation around the center conductor = bad, polyurethane insulation = good. Belden is a good brand of RG cable if you can find it.

I use larger diameter cables when it makes sense, like my RG-213 (like RG-8) for my HF ham radio that has a long cable run outside, but for a 4 watt CB with under a 20' cable run there would be zero significant benefit to even go with RG-8x. And again, you could go to even RG-8 and it would not change or help the SWR in the least.

But I have a feeling that I am shouting into the wind here. :)
Cheapie being the quality of construction, only a few months of being installed (used maybe 4-5 times) and the end is falling off. that's what I mean. I picked it up at Fry's so it's probably comparable to radio shack cable quality.

Shouting at the wind isn't so bad, just depends what you ate for breakfast and the direction of the wind :)

thanks
 

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I doubt the quality of the cable has anything to do with the connector coming off after only a few months of use.
 

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I doubt the quality of the cable has anything to do with the connector coming off after only a few months of use.
+1

The type of coax cable (rg-58 vs. LMR-400) has nothing to do with the quality of assembly of the connectors.

You can do a crappy job of putting the connectors on LMR-400 just as easily as putting them on RG-58.
 

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Discussion Starter · #20 ·
Added ground wire from custom mounting bracket to existing hole inside swing gate. After re-tuning, SWR dropped on all channels to around 1.2.

Didn't grind paint off inside door yet, need to pick up some more grinding wheels for my dremel.

step in the right direction using existing materials.
 
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