CB SWR-What are you getting? CB guru needed! - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 18 Old 12-24-2009, 04:55 PM Thread Starter
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CB SWR-What are you getting? CB guru needed!

I just picked up a SWR from Radio Shack in order to check/improve my CB. I can't seem to get better than 2.5-3 with everything double checked.

I started by grounding my antenna base (TF tail gate mount) to the roll bar-this improved it from 7ish to 3ish, then adjusted the Firestik, etc. Nothing I do improves the signal. When I initailly checked, I was around 7 on the SWR meter. When I unscrewed-lengthend-the antenna and grounded the mount the rating improved. I had to unscrew the tip of the antenna just about to the end. I can't get it any longer without it falling off.

Midland 1001Z-wired to the battery
Firestik 5'
TF tail gate mount-grounded
just enough coax-not bunched up

Any ideas? I did a bunch of searching and found guys getting much closer to 1 with smaller antennas. WTF am i doing wrong? Also, what are you guys getting for range? What antenna are you using?

I can talk about a mile away on the road, but I started checking everything after seeing Sandspurs range.

BIG RED JEEP


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Last edited by H8T2W8T; 12-24-2009 at 04:59 PM.
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post #2 of 18 Old 12-24-2009, 06:02 PM
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here is a good site to debug issues with your swr:
http://www.firestik.com/Tech_Docs/swr-trblshoot.htm
hth
and
MC HNY
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post #3 of 18 Old 12-24-2009, 06:18 PM
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Mine was a little over 1, The CB shop tried several antenna's till they got the best one.
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post #4 of 18 Old 12-24-2009, 08:40 PM
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1.5

2015 JKU Sport Virgin
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post #5 of 18 Old 12-24-2009, 08:43 PM
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I'm read no higher than 1.5. Down as low as 1.3 on the channel I use most.

Antenna has a grounding strap running to the body. Having the antenna mount grounded isn't doing near as much as grounding the antenna.

As for range, I haven't really tested it but I'm sure I get a couple miles easy on the highway. On the trail, I have no problem talking to anybody in my group and even can talk when we split up doing trail maint. over some distance. I run a Cobra 75. On many of the fullsize units, you can mod them to get much greater range though.

Last edited by oz97tj; 12-24-2009 at 08:45 PM.
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post #6 of 18 Old 12-24-2009, 09:08 PM Thread Starter
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Quote:
Originally Posted by oz97tj View Post
I'm read no higher than 1.5. Down as low as 1.3 on the channel I use most.

Antenna has a grounding strap running to the body. Having the antenna mount grounded isn't doing near as much as grounding the antenna.

As for range, I haven't really tested it but I'm sure I get a couple miles easy on the highway. On the trail, I have no problem talking to anybody in my group and even can talk when we split up doing trail maint. over some distance. I run a Cobra 75. On many of the fullsize units, you can mod them to get much greater range though.
You don't happen to have a picture of your ground from the antenna. My rating went from 7ish down to 2-3ish when I grounded the mount itself. Can't seem to fine tune past that.

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post #7 of 18 Old 12-24-2009, 10:05 PM
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Pitch the Firestick and pick up Wilson that has the matching wire at he bottom. It makes it a whole lot easier, I couldn't get better then 2 with my set up and now I'm pretty flat 1 to 1.2.

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This is exactly why we need to practice proper gun control.

If he was aiming down the sights correctly and had plenty of practice rounds under his belt, there would only be one side of this story.
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post #8 of 18 Old 12-25-2009, 01:02 PM Thread Starter
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I just ran out and picked up a Wilson 3'. After hooking it up I'm done in the 1.8-2.0 across the board. Time to go fine tune it. I can't believe how much difference that made. What's the deal with Firestik? I thought they were good to go.

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post #9 of 18 Old 12-25-2009, 01:15 PM
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I have a Wilson with the pigtail for the ground as well. I actually just purchased a Wilson Flex to replace it so it has some more give, but it also has the pigtail.

I've run Firesticks before and was able to tune them, but every install is different so I don't really have an answer for you. I have seen where guys actually solder a wire to Firesticks for grounding purposes.

I should also mention, I don't believe the lenth will make a difference in tuning, as they all have the same amount of wire in them. The shorter ones are just coiled a little tighter. I don't know how you have it mounted, but be sure your antenna sticks above the roof at least a little. My first install had mine below the roof line on the tire carrier so it wouldn't snag branches and I wouldn't get much range in front of me. I moved the mount higher up so it sticks about 6 inches above the roof line and it's much better. The tuning was the same with both, just used a different bolt from tire carrier.

Last edited by oz97tj; 12-25-2009 at 01:17 PM.
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post #10 of 18 Old 12-27-2009, 01:45 PM
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Here is the mount i use for my ant. looks similar to the Quadratec ecept this one is self grounding. you get new bolts and all with this system.

http://tmrce.stores.yahoo.net/jeep-w...amp-cable.html

Here is the antenna i use as well. no problems with any of it. i have it hooked to a Original side pin mic Cobra 29 with a few mods to it.

http://tmrce.stores.yahoo.net/lr--59...-cb-anten.html

Jersey
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post #11 of 18 Old 12-27-2009, 03:55 PM
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The problem may be your "just enough" coax. What length coax are you using? The Firestick site is an excellent source for installation issues.

I have the JK Cool Tech cb antenna kit and run SWR less than 1 across the 40 channel band. You should be able to tune your antenna to an SWR of less than 2. I bet the problem lies in your coax.

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post #12 of 18 Old 12-27-2009, 07:36 PM
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The problem may be your "just enough" coax. What length coax are you using? The Firestick site is an excellent source for installation issues.

I have the JK Cool Tech cb antenna kit and run SWR less than 1 across the 40 channel band. You should be able to tune your antenna to an SWR of less than 2. I bet the problem lies in your coax.
Coax should be run as short as possible. If changing the coax length changes your SWR, then you have another problem.

The debate on coax length is classed like a steering stabilizer fixes death wobble. Some people will say it works but if you really check out their system it's not running efficiently.

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Originally Posted by Jscwerve View Post
This is exactly why we need to practice proper gun control.

If he was aiming down the sights correctly and had plenty of practice rounds under his belt, there would only be one side of this story.
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post #13 of 18 Old 12-27-2009, 08:00 PM
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If you are running a no ground plane system, the length of the coax is very important based on everything I have read. I also understood the length of coax for a ground plane system was also important. None of my installations by CB shops had the coax run as short as possible. They were all around 18 foot lengths and multiples thereof. Extra coax was folded and stored, not coiled or clipped. Those systems all had SWRs around 1 across the channels. My motorhome has the cable hidden from view and access. I have no idea of its length. It is a no ground plane system. I have not been able to get the swr below 3 in the higher channels so I just stay on 19 and lower.

From the Firestick web site and Firestick Antenna Company Technical Support group, copyright 1996:

"About the length: This is a testy subject with many engineering types. They have argued with us on many occasions regarding this matter. They say that if your system is set-up properly that the length of the coax is irrelevant. We agree! However, mobile installations have so many variables that a perfect set-up is the exception, not the rule. One guy has a pick-up and another has a fiberglass motorhome. One wants the antenna on the bumper, another on the hood and a third on the roof. Few people want to drill holes in their vehicle so quality grounds are always a consideration. Because of the imperfect world, we almost always recommend 18' (5.5m) when our products are used. We do so with good reason too! At 18' the voltage curve has dropped back to the zero voltage point where the cable meets the antenna which reduces the reactance within the cable itself (a null cable if you would). It has been our experience that if the antenna location makes it somewhat out of sync with its surroundings, cable lengths that are not multiples of our 18' suggestion adds to the problem. To that, our complaining experts say, "Then the antenna should be moved!" to which we say, "You tell the guy with the $30,000 vehicle that he must drill a hole in his roof so he can use a 9' cable". We solve problems in the best way we can given the boundaries that the customer establishes.

On that note, when you have 18' of coax going to a radio that is only 8' away, what should you do with the other 10'? We recommend that you serpentine it like a skein of yarn so that it is 10-14" long and tie it in the center with a wire tie then tuck it away. Do not roll it up in a tight circle as this can cause it to act like an RF choke, which often times will cause system problems."

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post #14 of 18 Old 12-28-2009, 10:40 AM
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Quote:
Originally Posted by JKDoc View Post
If you are running a no ground plane system, the length of the coax is very important based on everything I have read. I also understood the length of coax for a ground plane system was also important. None of my installations by CB shops had the coax run as short as possible. They were all around 18 foot lengths and multiples thereof. Extra coax was folded and stored, not coiled or clipped. Those systems all had SWRs around 1 across the channels. My motorhome has the cable hidden from view and access. I have no idea of its length. It is a no ground plane system. I have not been able to get the swr below 3 in the higher channels so I just stay on 19 and lower.

From the Firestick web site and Firestick Antenna Company Technical Support group, copyright 1996:

"About the length: This is a testy subject with many engineering types. They have argued with us on many occasions regarding this matter. They say that if your system is set-up properly that the length of the coax is irrelevant. We agree! However, mobile installations have so many variables that a perfect set-up is the exception, not the rule. One guy has a pick-up and another has a fiberglass motorhome. One wants the antenna on the bumper, another on the hood and a third on the roof. Few people want to drill holes in their vehicle so quality grounds are always a consideration. Because of the imperfect world, we almost always recommend 18' (5.5m) when our products are used. We do so with good reason too! At 18' the voltage curve has dropped back to the zero voltage point where the cable meets the antenna which reduces the reactance within the cable itself (a null cable if you would). It has been our experience that if the antenna location makes it somewhat out of sync with its surroundings, cable lengths that are not multiples of our 18' suggestion adds to the problem. To that, our complaining experts say, "Then the antenna should be moved!" to which we say, "You tell the guy with the $30,000 vehicle that he must drill a hole in his roof so he can use a 9' cable". We solve problems in the best way we can given the boundaries that the customer establishes.

On that note, when you have 18' of coax going to a radio that is only 8' away, what should you do with the other 10'? We recommend that you serpentine it like a skein of yarn so that it is 10-14" long and tie it in the center with a wire tie then tuck it away. Do not roll it up in a tight circle as this can cause it to act like an RF choke, which often times will cause system problems."

I understand I fall into that "many engineering types" group. I don't sell one size fits all CB's. I install custom communications/navigation equipment in aircraft. Like I said before you will find people who sware it works, but if you look deeper there system isn't running up to par, it may be fine for them but it could be better.

NGP Antennas use the coax as a part of the ground plane. It's a whole different animal then what we're talking about here.

Most SWR problems on the Jeep come from ground issues and antenna length. In my Case I could have used an extension a raised my antenna another 8" to pull the SWR down but the Wilson does that for me electrically.

Coax is designed to allow RF to travel from point A to point B. Except as stated above, it should not be a part of the transmission system. Your radio will last a lot longer if you have it right.

Obama, The greatest gun salesman since the invention of firearms.
Quote:
Originally Posted by Jscwerve View Post
This is exactly why we need to practice proper gun control.

If he was aiming down the sights correctly and had plenty of practice rounds under his belt, there would only be one side of this story.
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post #15 of 18 Old 12-29-2009, 07:20 PM
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I've done electronics all my life - use to make mobile/base illegal CB amplifiers back in the 70s during the heyday of CB (have the required high voltage scars) and crazy enough to be installer for large antennas 100+ foot towers ( I believe they still make Moonraker antennas), later went legit with amateur radio... besides the usual home brew rigs helped with a 1KW mobile install - the arcs we could draw off the antenna were really something - RF tubes were great stuff - wish RF electronics surplus was still widely available and cheap.

With grounded antennas on a Jeep, I think seeing SWR ratio's 2 to 3 and above indicates a serious problem.

First thing I would do is check the coax isn't shorted (registering anything on an Ohm meter) - especially if I cut the cable and put on my own connector - it is easy to get a small strand of shield that you can barely see shorting the connector. Also take a reading along the length to make sure there is good contact (i.e. very low ohm reading).

Stay away from groundless antennas - too quirky and no reason to do that on a metal Jeep - leave those for fiberglass boats. Have to have a good ground to the chassis, sandpaper paint away for any bolt/washer/nut. Don't get those "cut to tune" antennas - easy too snip too much and then it is a throw away.

I have a tunable slug antenna from Radio Shack - SWR 1.0 to 1.1 across the CB band (tune on a center channel or if you use only one channel pick that one to tune the SWR on). I cut the coax to length with my own soldered connectors.

I agree with the coax length not being very relevant for grounded antennas - just don't round coil up extra length.

Oh - one last thing, make sure you understand how to set up your SWR meter - read the instructions!

I use the CB on the Jeep for communication in groups. CB does not transmit very far mounted on a Jeep - better to get an amateur license (which is not difficult these days) if you want a radio for emergencies in the outback.

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post #16 of 18 Old 12-31-2009, 12:04 PM
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Little bit of a hijack but what is the difference between a 100 watt and say a 2000 watt antenna?
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post #17 of 18 Old 12-31-2009, 12:50 PM
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Little bit of a hijack but what is the difference between a 100 watt and say a 2000 watt antenna?
Unless your running an amp, nothing. All the rating is saying is that the Antenna can handle said wattage. CB's are regulated to 4 watts. It's just another sales tactic. Some people believe that the higher the watt the more durable the antenna, but that isn't true in most cases.

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Quote:
Originally Posted by Jscwerve View Post
This is exactly why we need to practice proper gun control.

If he was aiming down the sights correctly and had plenty of practice rounds under his belt, there would only be one side of this story.
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post #18 of 18 Old 01-01-2010, 11:00 PM
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Originally Posted by Broncojohn View Post
Unless your running an amp, nothing. All the rating is saying is that the Antenna can handle said wattage. CB's are regulated to 4 watts. It's just another sales tactic. Some people believe that the higher the watt the more durable the antenna, but that isn't true in most cases.
Gotcha, thanks.
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