Tuning CB

ncsutj

ncsutj

Well-Known Member
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Mar 20, 2005
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I have the Uniden Pro520XL radio and 2' wilson antenna in my TJ. When tuning using a SWR meter I turn it until the needle is on the "set" mark. When I swith to the "Ref" the needle jumps to the right on the scale. The readings are always in the red on the meter. From what I've read it looks like I have a short somewhere.

Any ideas what could be wrong?

Thanks in advance.

Casey
 
Here's some good trouble shooting info. If you need a hand let me know.

The following list shows the most probable causes of high SWR in order from the most common causes to the least common causes. If experiencing SWR problems, check each of the following conditions in the order shown until problem has been uncovered.

Shorted Stud Mount
Disconnect coaxial cable at antenna mount. Test continuity from mount to antenna coupling nut. There should NOT be any continuity. If shorted, reposition or replace insulators and retest.

Improper Type and Length of Coax
Single antenna installations require RG-58 type coax and dual antennas require the use of RG-59 type coax cables. We recommend 18 foot long coax leads from the radio to each antenna, especially on installations that are displaying high SWR problems.

Shorted Coaxial Cable
Disconnect coax at radio end. Test for continuity between center pin and threaded sleeve. There should NOT be any continuity. If shorted, repair and retest.

No Chassis Ground at Antenna Mount
Test for continuity between the antenna mount and the vehicle's common ground. There MUST be continuity. Repair and retest as required.

Open Coaxial Cable Center Lead
Disconnect coax at radio end. Test for continuity from center pin to antenna base. There MUST be continuity. If necessary, repair and retest.

Open Coaxial Cable Ground Shield
Disconnect coax at radio end. Test for continuity from the antenna mount to the coax connectors threaded sleeve at the radio end of the coax. There MUST be continuity. If necessary, repair and retest.

Improper Installation Location
Transmit antennas need free space around them if expected to perform properly. If more than 30% of the antennas overall length is parallel to the side of the vehicle and within twelve inches of that surface, SWR problems are probable, i.e. between truck cab and shell, corner of truck bed near cab, low mount position on motorhome, etc. Relocate the antenna to a position of performance (versus convenience or appearance) and retest.

Insufficient Ground Plane Available
Fiberglass, plastic and thin aluminum vehicle bodies lack the reflective characteristics needed for proper antenna performance. On some occasions, running a 12ga or heavier wire from the antenna mount to the vehicles chassis ground will be sufficient. Otherwise, a no-ground-plane antenna system may be required.

Low Quality Coax Cable
Delivering radio frequency to an antenna via poor quality coaxial cable is the equivalent of watering your lawn with a hose full of holes. The bitterness of low quality will linger long after the sweetness of low price is gone. Use high quality coax only.

Antenna Tuned Without Tip
If the antenna is tuned without the tip then put on after tuning is completed, the SWR will change when the tip is installed. All readings must be made with the antenna tip in place.

Defective SWR Meter
Some are made bad and others have been known to go bad. Try to confirm readings with a second meter.

Damaged Antenna
Aside from apparent damage that is visible from the antenna striking immovable solid objects, you can test for any internal damage by checking continuity from the antenna base to the tunable tip extender or end of wire. There MUST be continuity. If there is no continuity, the antenna must be repaired or replaced.

http://www.firestik.com/Tech_Docs/swr-trblshoot.htm
 
My antenna is mounted like the pic on the right. I'll take an actual pic tomorrow.

The ground for the radio is to a ground screw on the floorpan.
Do I need to ground to something better?
 

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Is the mount painted? You may need to sand the area where the fire ring makes ground contact. Is the mount grounded? Can you test continuity between where the radio is grounded, chassis ground and the antenna ground? I'd also recommend dielectric grease to keep the ground area from oxidizing. When your checking SWR are the doors shut and the cap on the antenna, yes it can make a huge SWR difference. Spring, coax length, was the cable pre-terminated? 2 foot antennas are a PIA to tune because they are so short, where is it mounted on the TJ?
We had a similar problem on ord.sgt.NC.26's CB in his TJ and it turned out his coax was bad.

I have fire ring's on two vehicles and they work great but I have heard of people having issues with them. Is this a new install or a change in equipment?
 
Which SWR meter are you using?


Matt
 
The antennae is mounted on the top of my tire carrier. Top of antenna sticks up about 6" above the top of the jeep. Surface is painted.

Doors where on and shut and top was on and cap on antenna when checking with see meter. Radio is new. I bought the antenna and cable from Brian. And using Brian's see meter.

Brian if you need your meter just let know.
 
Sand the area on the mount where the fire ring ground makes contact with the mount and that should fix your problem.
 
I would also verify that the mount is making a solid connection to ground. If it's a bumper mounted, swing away tire carrier, you may want to run a separate ground strap. From the Firestik site:
"If it is a swing-a-way tire carrier we suggest that a dedicated ground wire from a known good chassis ground point to the antenna mount is used. Swing-a-ways with nylon bushings insulate the carrier from chassis ground and those with brass bushings go through periods of high resistance or total lack of grounding on rough terrain."

^From the following link. Has some good recommendations for jeep installations. http://www.firestik.com/Tech_Docs/jeeps.htm

Keep the meter as long as you need it. If for some reason you can't get the antenna to work right, I'd be happy to buy it back from you. It was in a useable range when installed on my jeep. Let me know if you need any help troubleshooting it.
 
autozone carries braided ground straps that come in handy for grounding stuff if you need them - in the painless / replacement oddball parts section

technically the spare tire mount should have a decent ground to the gate, and the gate to the body/chassis, but .. well.. you know how that goes

if you have an ohm meter it's pretty easy peazy to track that stuff down
 
Probably you do not have the antenna mounted in the best location. Move it to another location and check the SWR. You probably need to raise the antenna so that more than 1/2 of it is above the Jeep. I have had similar issues with mounting mine on my tire carries on the YJ. If I move it to one side or the other I can solve the SWR problem. I have raised it well above the Jeep and still have tolerable SWR but high in my opinion. Sometimes grounding can be the problem and sometimes it can solve the problem. I have tried several antenna types, some with ground wires and some without, and still have SWR issues mounting on the tire carrier. If you are running a amplifier it can affect your SWR readings.
 
What kind of coax do you have? I recommend the 18' K40 or one that is equal in outside diameter. If it's the thin black one, it's junk and that will be your problem. Also, is the antennae fiberglass? They are notorious for breaking at the base and not telling you. I recommend a Wilson 2000 Trucker or 5000 Trucker. Steel mast and coil wound base.
 
I checked the continuity on the antenna and the end of the coax at the radio. Had several issues so I decided to use a piece of stainless I had to make a different mount. Continuity is good now at both ends.

The SWR reading is still over 3. I used it this weekend and got good reception from it. Didn't try to transmit anything from it though.

The antennae is a 2' Wilson fiberglass.

What should I look at next? Coax?

Here is a pic of the mount.
 

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ncsutj said:
I checked the continuity on the antenna and the end of the coax at the radio. Had several issues so I decided to use a piece of stainless I had to make a different mount. Continuity is good now at both ends.
The SWR reading is still over 3. I used it this weekend and got good reception from it. Didn't try to transmit anything from it though.
The antennae is a 2' Wilson fiberglass.
What should I look at next? Coax?
Here is a pic of the mount.
Click to expand...
That coax looks suspect. Replace it with a heavier density one like the K40.
 
yeah that Kink near what looks like the hi-lift pinched it could be your issue

those 2' antennas can be a real bear to tune in, but out of the box with a good coax and mount it should still be in the 2-2.5 range untuned

the hi-lift running parallel to the stick will cause some issues but shouldn't be pushing you to 3. It may end up being easier to tune if you remove the hi-lift real quick and check it
 
The Hi-lift is very likely going to act as a parasitic element to the antenna and you probably won't get it to tune with it there.
If you remove the hi-lift tune and replace then the tuning is going to be off again because of the parasitic interaction.
I hate to say it, but you need to permanently move one or the other.

Matt
 
The high lift can be an issue but I have mine mounted on the the same carrier and and was able to tune my 2ft FirestickII with the high lift in place, of course it is different equipment and every set up is different.

Is your excess coax wound up in a loop? If yes you need to change it to a bow tie.

I have a 4ft Firestick II you can use to test with. It may help you rule out the rest of the set up.

You also really need a spring to keep any fiberglass antenna alive.
 
cj777 said:
Keep the meter as long as you need it. If for some reason you can't get the antenna to work right, I'd be happy to buy it back from you. It was in a useable range when installed on my jeep. Let me know if you need any help troubleshooting it.
Click to expand...

Brian I appreciate the offer of buying it back. I think it will work just need to get the bugs worked out.

Brian or Len I may take you up on the offer to help troubleshoot one day.
 
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