More fun with SWR

[scottjk]

I have been through the searches and various threads, and am coming here as a last try before I knuckle under and head over to the local Pilot or TA for someone better and smarter than me to figure this out.

2005 TJ Unlimited

I cannot get my SWR below 3.0-3.3. I am running a 3' Firestick with a hood channel mount (driver's side forward) and a Cobra 29 LTD Classic.

I have run 10 gauge grounding wire directly from the antenna mount to one of the vehicles' grounds (center firewall, same place the hood grounding strap goes to).

I have verified continuity of the ground, I have verified continuity of the antenna mount and parts, I have verified continuity of the coax (18' Fireflex - came with the antenna - 50 ohm).

I am running a ground plane set-up.

I am trying to mount the CB center of the dash right above the vents on top of the dash.

I do have a roof rack which is why I'm not mounting the antenna off the rear bumper or tail lights.

Sooo...I think I'm where I need to be, but no appreciable change on SWR. So I'm getting down to...

1. The Cobra CB's built in SWR meter is off or wrong.
2. The brand new, Firestik recommended, 18' coax is bad.
3. My Jeep doesn't have enough steel in it to act as a ground plane.
4. I suck and am stupid.

Hoping that #4 isn't the answer, but knowing that it probably is anyway...any thoughts?

thanks...

[nwoods]

I am having similar issues. My SWR is pegged off the meter, no matter what tuning I do. More frustrating, is that it worked perfectly the day after I installed it (did a full day's trail run), and now it doesn't.

[dadasjp]

Head here and see if any of this info helps:

http://www.firestik.com/Meas-SWR.htm

I've often found that SWR problems come from a short at the base of the antenna and/or the coax cable point of connection to the antenna base, there's a helpful chart on this page. Good luck.

[ECV Jeep]

I might go so far as to suggest a seperate SWR meter. You can pick on up at any decent truck stop and the occasional radio shack for $25. I have found that the SWR meter in my Cobra does a very poor job of tuning my system.

[Old Fart]

Gotta suggest what ECV (Brian?) siad - I've never found an "in-unit" SWR meter that matched a "real" one.

Have you verified that you do NOT have continuity between the center conductor and the braid on the coax with both the antenna and the radio disconnected?

Is the SWR showing the same at CH 1 as CH40?

[USMC 0369]

scott, check your PM's.

[Double G]

Check to see if you actually are "grounding" the coax, depending on the type of antenna mount you have if you overtighten it it will "ground" and you will have high readings.

You can test it with a seperate battery and a test light, mine was reading high also, sure enough, it was grounding in the adapter.

[SAR Jeeper]

Frys Electronics sells an SWR meter for like $10.

You didn't say, but did you adjust the tip of the Firestick?

Just curious, what type of coax? The one I originally got was the regular connect on the radio side, and a donut style connection on the antenna side. I didn't know, but that donut has to be mounted a certain way. If you have the donut connector, flip it over, and try again.

Continuity doesn't necessarily work when it comes to RF. You can show no continuity, but still leak RF over. When you go to Fry's to get a SWR Meter get a length of coax (usually 18' with CB's) just to rule out the cable.

[Mtbikbob]

Gotta feel your frustration, just went through it as well. Checking continuity with the swr meter hooked up is not correct (as I found) because the meter will register continuity to ground. I also could not get a reading less than 3.0. So I experimented by raising the 4' firestick by way of springs. Springs Fry sells that thread right into the antenna base. I ended up with 6, 4 inch tall springs and now have a reading of 1.5.
Good luck,
BobO

[scottjk]

Answers

Thanks for all fo the quick input...

dadasjp - The Firestik site is great for me because I don't know what I'm doing. There are some posts that doubt some of the accuracy of their information, but I think antenna theory is a lot like the short arm vs. long arm debate. Anyway - out of the articles I've seen, I had not seen the one you sent, so I'm going through it now...thanks..

ECV and Old Fart - I'm kind of with you about a new SWR meter and will start shopping. I have tried to narrow down the number of variables and I'm down to either a bad meter, or I need to start moving the antenna around. Channel 1 and 40 started about 0.2 apart (1 - 3.1 and 40 3.3). After increasing the size of my antenna mount grounding wire (14 gauge to 10 gauge) they are now just about even at 3.0 on the nose. Interestingly, when I try to calibrate at 19 and 40, there is not enough play in the calibration dial for me to get the needle to the proper spot. The literature tells me it is a power issue to the radio - not enough juice to push the needle to the calibration mark. True? I have thought about powering the radio directly to the battery - but would radio power have that much of an effect on the SWR? And if that is a stupid question...yep, I just asked it.

double g and sar jeeper - I have the 18' Fireflex that Firestik sells (RG-58 for single antennas). It does have the donut on the end and I double checked to ensure that the insulated side was up. Continuity on the antenna mount remains proper as does grounding. I double checked coax continuity itself. The coax is not shorted (no continuity between center wire and braid/jack). Also, proper continuity the length of the cable. Even went so far as to check continuity of the braid all the way to the vehicle ground - good.

mtbikbob - I have the same thought - first, it just makes sense to put it on a spring. After I got everything delivered I kicked myself for not doing it, so I'll go ahead and order one.

At this point I think I've eliminated the major variables. If the new SWR meter confirms that I am still up at the 3.0 range, and my spring extension doesn't work, I guess it is time to begin moving the antenna around the vehicle to find a sweet spot.

Thanks for the help today - will keep this thread updated and hopefully will have an answer to post in the coming days.

[Mtbikbob]

Yes please do update when you overcome your dilemma. Also I did just that, as you suggest. With an alligator clip to the antenna and the receiver part, I moved the antenna around and up and down till I found the 'sweet spot'. Thats how I finally found my problem of being to short and added the springs. Mine is mounted rear passenger side of the jeep.

[Mtbikbob]

And.....just as I thought I had it all licked, raised up, reading a good solid 1.5, for no reason the needle shoots off the scale. After a good amount of carrying on with choice words, I proceed in the work of discovery. Final result, the new antenna would have a bad wire where it wound around and connected to is own base, under the plastic wrap.
Replaced antenna. This CB stuff is killing me. Or at least expanding my vocabulary.

[Materdaddy]

And.....just as I thought I had it all licked, raised up, reading a good solid 1.5, for no reason the needle shoots off the scale. After a good amount of carrying on with choice words, I proceed in the work of discovery. Final result, the new antenna would have a bad wire where it wound around and connected to is own base, under the plastic wrap.
Replaced antenna. This CB stuff is killing me. Or at least expanding my vocabulary.

Bob,

Sorry I wasn't more help with your CB woes!

Were you really expanding your vocabulary, or just exercising your collection of four letter words?

[nwoods]

My issues is that my CB squeals whenever I transmit, much to the annoyance of those on the trail with me. During lunch today I went to The Solder Joint in Orange to have the CB radio looked at. Of course, it worked perfectly while I was there. Transmit and receive both worked great, no background noise, no squeal. We tested it with the truck on and off, with the radio on and off, quiet and loud, in and out of the truck, iPod connected/disconnected...etc… No issues, it worked fine.

Thinking about it now, the only thing different was that I did not test it with the Lowrence GPS unit turned on, and it typically is when we go off roading. I will check that later.

My SWR is still pegged way off the meter though. The Solder Joint guys think it's just too much powder coat on the rear rack/bumper that my antenna is mounted to. It may not be getting a decent ground. They reccommended sanding off the paint to bare metal at the point where the coax mounts to the anntenna fitting, and then doing the same where the bumper mounts to the frame.

[Mtbikbob]

Bob,

Sorry I wasn't more help with your CB woes!

Were you really expanding your vocabulary, or just exercising your collection of four letter words?

Expanding. Its more meaningful to find four letter words that fit this new type of technical frustration I was feeling.
No worries, I knew in time I would figure it out and keep on learning how it all works. And I still am. Just wish my learning curve was faster. Thats what amazes me about you, you find the whole, complete answers to your quieries faster than anyone I have ever met.
I think I learned in this thread that the coax must be 18' long within the jeep to help create a bigger ground. I need to do that yet and then try resetting the height of the antenna again.
I'm just an impatient kinda guy.
I know if I was really jammed up, I could bring it to your place and you'd have it up and running in no time. And I thank you for your support.
BobO