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Old 03-15-2013, 05:45 PM   #1
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Can't Get SWR below 2

Okay, I have a Uniden PC68LTW with a 20 ft coax (all my radioshack had), and a 3 ft firestik. I also have a radioshack heavy duty spring on the antenna. I have checked everything: Polarity, etc. What should I do?

Channel 1=2.0
channel 19= 1.6
channel 40=2.1

Thanks,
-Chase

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Old 03-15-2013, 08:37 PM   #2
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Get a vehicle with a better groundplane?

Jeeps are a beast, and I imagine you have a rear mount antenna. Based of your post, I bet raising the mount or relocating to the cowl or front bumper will show better results.

I had a tailgate mounted whip that was about 2.2 on the extremes, they dropped to 1.6 or so on the front bumper and range/clarity drastically improved.

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Old 03-15-2013, 09:10 PM   #3
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Well, I can't get another vehicle (Don't need one) and I don't want to move the antenna. I have done that 2 times already. What else can I do?
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Old 03-15-2013, 09:15 PM   #4
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Well, I can't get another vehicle (Don't need one) and I don't want to move the antenna. I have done that 2 times already. What else can I do?
Where is it mounted, what kind of mount, what tests have you done and what are the results?
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Old 03-15-2013, 09:31 PM   #5
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It is mounted on the Driver side light. (Was on the passenger side) Mounted with a CB Mount from RadioShack. I have tested everything. No shorts, no damages on cable or antenna. Basically everything in everyother post on here. I even bought a spring to raise it up. I can get about 1.5 on 1 but thats the lowest.
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Old 03-15-2013, 09:44 PM   #6
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Generally speaking, once the high and low end match, the antenna is as tuned as can be... meaning height adjustments of the whip become moot.

Swr is not dc ground. In fact, it is very different from it.

Clap. Seriously, go ahead. You used both hands, right? That's a dipole (two-pole) antenna. Your Jeep has a monopole antenna, so put 1 arm behind your back. Now clap. You used the computer desk, wall, computer, your face... something else, right? Your antenna is one hand clapping, and needs a metal desk to clap with. No 2nd hand (or desk) means bad radiation of sound. That is groundplane, in a nut shell. Antenna height adjusts resonance frequency, and is not quite the same, but must also be matched.
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Old 03-15-2013, 09:50 PM   #7
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So I should get a longer antenna? I have read that the 4' works better on the jeep than the 3', but many have said the 3' has gotten a 1:1.
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Old 03-16-2013, 08:37 AM   #8
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So I should get a longer antenna? I have read that the 4' works better on the jeep than the 3', but many have said the 3' has gotten a 1:1.
The higher the antenna, the better. So yes a 4' should perform a bit better (I now run a 4' and like it), but if it has no groundplane availability it will still be reflecting power back to the radio (high swr).

Imo, moving it up front would do more than installing a taller whip. We gotta get those hands clapping, right?

Many say many things; I don't think rear mount jeeps can reach 1:1 effeciency. I think 1:3 back there is phenomenal, and youre close. Anything under 2 is OK from an equipment perspective, so do you want it better, are you concerned with system damage, or are you not satisfied with broadcast strength? If you like the mount location, leave it. You are more than fine for trail rides and should have a couple miles of broadcast distance, depending on terrain. If you need the broadcast distance extended, I would mount in the best place possible, which is not the taillight. Cowl, front bumper, and 3rd brake light are all better options from an RF perspective, with the first 2 being far and away better locations.

If ya really want it to get out, you need to track down an antenna analyzer (mfj 269) to find the actual resonance sweet spot of your system. Typically this is overkill for 11M CB, so we use SWR testing to get close enough. Or you can move to a longer range platform, like Ham or gmrs bands.

CBs in Jeeps have to compromise something. Location, distance, swr... something.

Got a hardtop? You can add a groundplane to the underside of it with copper tape and a bonding strap or 2.
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Old 03-16-2013, 11:21 AM   #9
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I do a lot of antenna problem solving for Jeepers that cures their SWR problems. 99% of those Jeeps have their antennas mounted at the rear, and typically up near the rear tail lights, where I never have any problems getting their SWRs down to levels like 1.1:1 or 1.2:1 which are very good ratios. Many of those installations are 2' Firesticks which I happen to run myself, the rest of them are 3' or 4' antennas of various types. So a good SWR can be obtained with even a 2' antenna if the basics of proper mounting are taken care of.

Typically, a very high SWR is caused by the antenna mount not having been assembled properly. A lower but still bad SWR is very commonly caused by the mount not having an adequate RF ground connection to the tub.

And there is plenty of "groundplane" on a Wrangler, simply providing the mount with an adequate RF ground connection to the Jeep via the tub is all that is needed. And with that adequate RF ground connection, which is more demanding than a simple DC ground connection, is usually enough to get a good solid low SWR.

Quite often the difference between a 2:1 SWR and a 1.1:1 or 1.2:1 SWR is nothing more than a little grinding to remove the paint and powdercoating so the antenna mount has a good bare metal connection to the Jeep. That is required to provide a good RF ground which is essential to a good low SWR and good antenna performance.
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Old 03-16-2013, 01:25 PM   #10
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I'd try it without that spring.
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Old 03-16-2013, 02:12 PM   #11
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I'd try it without that spring.
X2, I meant to mention that too but forgot. Springs add both physical and electrical length to an antenna which can make the difference in getting a good or bad SWR.
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Old 03-16-2013, 09:58 PM   #12
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Hmmm.
Today I went and bought a 10ft coax. It made a huge difference. I can now get about a 1.5 across all channels. I will try making a better ground (taking some paint off) The mount is from raido shack and is assembled how the instructions say. I also made sure that there is no continuity between the parts that don't need it.
What do ya'll think will help now?
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Old 03-16-2013, 11:26 PM   #13
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While someone started this thread im running around 7 i have no idea what the problem is hopefully I'm measuring that right i know nothing about cbs this is my first time but i have the same one as you. I have a 3ft firestick firefly mounted to the factory spare tire carrier. I even tried running a ground wire from the mount to the frame it didnt help any. Any suggestions something has to be wrong?
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Old 03-17-2013, 11:05 AM   #14
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Whoa! 7 isn't even on my meter. Sounds like your antenna mount isn't properly grounded. That would be the first thing I would check. I know you said you have, but your cable could be messed up or you don't have the mounting stud put together properly. Other than that it could be the antenna which rarely happens.
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Old 03-17-2013, 02:20 PM   #15
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That was my bad its a little past 3 I was running on 4 hours of sleep when installing and looked at the wrong part of the gauge. I'm sure it probably its a ground issue the antenna is put together right I'm just not sure what to do to fix it I could swear I have it grounded as well as possible paint is ground off each surface. Got a 14 gauge ground wire running from the mount self tapped to the frame
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Old 03-17-2013, 07:57 PM   #16
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You may try buying another coaxial cable.
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Old 03-17-2013, 10:32 PM   #17
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This is how I have mine mounted I have the ground wire self tapped to the rear frame cross member. I'm at a loss I got one of the coax with a removable end so I could get it through the tailgate hole I wonder if that could be my problem. Its harder to test when I have one around me to see if its actually receiving and transmitting
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Old 03-17-2013, 10:57 PM   #18
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It all depends on the setup. If your antenna is on the same side of the vehicle as the radio, that is normally a bad thing. Rule of thumb is antenna on the opposite side than radio. Also i have found that an 18 ft coax is best. And dont just wad all the extra coax. Roll it up into 3 ft lengths. I have a galaxy dx939 with a 4ft francis antenna and getting 7-10 miles range
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Old 03-17-2013, 11:04 PM   #19
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The cb is mounted to the center of the dash the antenna is in the factory tire carrier. I have an 18 ft cable under the carpet.
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Old 03-17-2013, 11:11 PM   #20
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I would go with a longer antenna then. Wilson 5000 is an awesome deal. Generally around $40. I am a trucker so i dont spare any expense on a good cb setup. My cb is under the driver seat with an ext speaker mounted on the roll bar above my head and i fabbed a bracket for my antenna thats bolted to the frame on the back pass side. It works great. You can always take your jeep to a local truckstop to see if they have a cb shop. It may cost $5-10 to have them check it out but depends on how much you would use the cb
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Old 03-17-2013, 11:26 PM   #21
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I got the 3ft firestick from recomendation of the guy at Walcott cb maybe I should run to the truck stop. I have a feeling its something stupid.
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Old 03-17-2013, 11:37 PM   #22
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Im pretty sure firesticks need tuned to your cb. If you havent had that done, thats probable it. Shouldnt take more than a couple min to set that.
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Old 03-17-2013, 11:44 PM   #23
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According
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Old 03-17-2013, 11:47 PM   #24
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Stupid phone according to the antenna package its tuned based off swr but I'm not even in a reasonable ball park I'm at probably 3.5 to 4
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Old 03-17-2013, 11:57 PM   #25
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Pull the red or black cap off the top of the antenna. If there is a metal rod, it would need to be manually tuned. Imo it sounds like your slack coax is just bunched up instead of streched out and ur antenna needs tuned. Simple fix if thats the case
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Old 03-18-2013, 12:16 AM   #26
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I'll give that a shot. It can't be to bunched up most of its neatly ran inside the tub. The tip is tunable guess I'm not sure it must need screwed out?
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Old 03-18-2013, 12:28 AM   #27
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I would just take it to the local truckstop or somewhere that has a cb shop. It wouldnt cost much to have it looked at and fixed. It sounds like a simple issue.
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Old 03-18-2013, 07:44 AM   #28
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Okay,
They tune the antennas at the factory to make sure they work....basically. No matter what you have to check your SWR. If it is fine, no tuning. If it really sucks, you must tune it. Try getting a shorter Cable. I had an SWR of 1.6-2.1 with a 20ft, then went to a 10ft and it went way down to a 1.2 across the band.
So in conclusion:
They tune the antenna Yes, but it isn't tuned for you. You have to tune it. If that doesn't work GET ANOTHER COAX! Sounds like yours is bad. Try a shorter one if you can.
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Old 03-18-2013, 09:11 AM   #29
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It all depends on the setup. If your antenna is on the same side of the vehicle as the radio, that is normally a bad thing. Rule of thumb is antenna on the opposite side than radio. Also i have found that an 18 ft coax is best. And dont just wad all the extra coax. Roll it up into 3 ft lengths. I have a galaxy dx939 with a 4ft francis antenna and getting 7-10 miles range
I can't let this one go.
It does not matter what side of the vehicle your radio is mounted. I have no idea where you heard that one.

Also 18' is not best. Best length is the one that reaches from radio to antenna with a little slack.
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Old 03-18-2013, 11:24 AM   #30
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I can't let this one go.
It does not matter what side of the vehicle your radio is mounted. I have no idea where you heard that one.

Also 18' is not best. Best length is the one that reaches from radio to antenna with a little slack.
X2, the type of antennas our CBs use could care less what the coax cable length is. Coax cable has nothing to do with getting a good or bad SWR on the types of antennas we use for our CBs. And I dunno where anyone would pick up a rumor that it matters what side an antenna or CB is mounted on but that's one of the more ridiculous ones I've heard.

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