Touch antenna and swr goes up, please help

[stsmith7]

I have a question about my recent cb radio install. I will try to be as specific as possible. Here are the specs: Cobra 29 LTD BT with 18ft. of firestik coax running to the front passenger stake hole in a toyota tundra access cab. there it meets the mount from firestik along w/ a firestik spring and firestik 5ft. tuneable tip antenna. Everything is brand new and was installed by my dad and I. Sitting in my driveway the swr stays around 1.5 on ch 1 and 40. The problems start when I start to drive. When moving I can key the mic and the antenna warning light lights up red . The swr also spikes to 2.5-3. This is across all channels and always when moving. This can also be repeated in the driveway by pulling down the antenna(like your going fast). The light will come on if you touch the antenna while holding down the mic. Also the excess coax is loosely coiled in the back seat. Thinking about taking it to a shop in Raleigh,NC or surrounding areas but don't really have any more money to spend . I hope it is something I can fix myself. Any help would be great as I am stumped on how to fix this. Also, I posted in the chat area buy figured a proper first post was in order.
thanks,
SEth

[715minigrass]

Your mount might be ggrounding out. Bad insulator I guess.

['Doc]

From what you've described, things sound normal. Any antenna that changes it's 'shape' or position will also change it's 'tune'. Everything around that antenna will affect SWR to some extent. One way of 'curing' that SWR change is to not let the antenna 'bend over' when moving. Stiffer spring, or no spring? Is there anything specific to do? I have no idea, I'm not familiar with your vehicle and antenna set up. I'm sure things could be done a little 'better', but can't tell you how to do that.
Good luck.
- 'Doc


(A change from about 1.5:1 to 3:1 is a bit much.)

[North Texas Mudduck]

take a few pictures and post them up and give us a closer looksee

[231]

I agree with Doc. It sounds pretty normal to me as well...especially when you touch the antenna while transmitting. You have effectively shorted out the antenna when you touch it, so no surprise there.

The Firestik is a VERY heavy antenna which is one of the reasons I'm not a fan of them. But that aside, I'd also agree with Doc on removing the spring completely. Friend of mine had a 4' on his Jeep with a HD spring, and it would go over more than 45º when driving at highway speeds. You have a 5' which is going to flex even more...no matter what spring you use. If you plan on wheelin' your rig, invest in a smaller lighter antenna for wheelin' that will give with the foliage hits and just swap it on before you hit the trail. Once the antenna is tuned up, you shouldn't need to mess with it again unless something changes.

On my Jeep(s) I have quick disconnects so I can quickly swap to whatever I want. Maybe that would be an option for you too? Just a couple of additional thoughts.

Best of luck and let us know how it goes.

[stsmith7]

[Please login or register to view this link]
Here is the pic, the extra wire was added to rule out losing ground.

Thanks for the replies, I may just remove the spring and only use it when offroad only. Will the antenna be okay being that stiff and heavy w/o a spring? A Quick disconnect is an option I have not yet explored. I know the antenna is heavy and definitely bends back more than 45deg at speed. I only got a spring because I do go offroad some and the firestik guy said its $10 insurance. He also said that the antenna system should not be that sensitive as to trigger a light at speed. He said guys drive all day with antennas bent way back and don't have swr change. Maybe this doesn't apply in my case but thought I should mention.

Conclusion: I'm going to remove spring, drive around, and see if the light stops.

['Doc]

Did that 'firestick guy' also say that needed to be tuned? They all do you know, or at the very least they need to be checked to make sure the SWR is reasonable. That light is sort of like an 'idiot light', it only tells you when something is 'bad'. Lot's of room between 'good' and 'bad'.
[At the risk of being really 'unfair' about it, it sounds like your 'firestick guy' isn't as knowledgeable as he should be in giving advice.]
Adding that spring makes your antenna longer by the length of that spring. Unless you compensate for that, the antenna just isn't going to be close to the right length, it'll be too long, which is not good.
How well with that antenna do without the spring? Beats me, just how much of a beating will it be subject to? Fiberglass just isn't going to take a lot of beating around, at least not as much as steel will, which just stands to reason.
Good luck, I hope it works out for you.
- 'Doc


(Big ugly and strong almost always works better than short pretty and weak. Sort of. At least with antennas.)

[stsmith7]

Update--- I removed the spring and it definitely helped but the ant warning light still comes on on the higher channels like 29-40.
I know I need to really take some time and properly tune the antenna.The cobra has the built in srw meter but I read somewhere
that built in meters are not that accurate. That true? If so I plan to buy a swr meter. Any recommendations?
Hopefully removal of the spring and a proper tuning job will remedy my problem.

[SUBWAY]

You are correct, the meters built into radios are usually not very accurate. In other words don't trust it or you may lose a radio. They are ok as a reference after you have used a seperate meter to adjust swr. In my opinion one of the better meters is Dosy. The bad part with this meter is the price, the are 90 +. I usually use a workman meter that costed me 35 dollars. It has a larger meter with swr and power and 95 % of the time I leave it hooked right to my radio to monitor the stats. There are cheaper meters but once again you get what you pay for and I'd rather not make a habit of replacing radios because of a meter that didn't give an accurate reading.

['Doc]

Are the built-in SWR meters always bad? No, not always, but how do you know until you check it? If you can borrow a meter, that would be one option. Otherwise, buy one.
From what you've described, the SWR being lower on the lower channels and higher on the higher channels, it sounds like your antenna is just a bit too long. The idea is to shorten it till the lowest SWR is sort of in the middle, around channel 19 or 20. The high and low channels about the same values.
There are a couple of ways to do that shortening, just depends on which antenna you have. if it has a screw type thingy on top, adjust the screw further down into the antenna. If not, then pull the cap off of the top end, there should be a loose wire in the center of that fiberglass 'tube'. Shortening that wire a little bit at a time ought'a work just fine. Stuff that wire back into the antenna and replace th cap to do the checking. Repeat as necessary, but don't go too far! It'll probably take a while.
Good luck.
- 'Doc

[909WiSCoNSiN]

a external meter would give you a more accurate reading.

[sideways]

I had a quad mag mount that came with one of the coax ends in your pic..I never got an antenna to tune with that end,so I went with a standard pl/so set-up and it worked fine. Just some food for thought, maybe swap a piece of coax with ends and see if the prob. goes away just to test it? Good luck

[stsmith7]

Just ordered a workman swr meter from amazon. Will definitely do some better tuning when it gets here.

---Sideways you're saying get rid of the black ring and try a standard connection with the coaxial soldered? like the first pic in this link?
[Please login or register to view this link] Continuity
think I know what you're talking about but wanted to clarify.

But I am not going to do anything until the meter comes.

[stsmith7]

edit---you have to scroll down to testing continuity to see the pics.

[sideways]

First, I would also wait until you have the meter. And yes that is what I was suggesting (I had no luck with the type end you have). On my vech I have the first and second types of mounts (two locations). I prefer the middle (lug) mount method. I have a base loaded K40 as an alternate which is the pl/so mount.

[stsmith7]

got the swr meter in and did some proper tuning yesterday. sitting still I'm getting like 1.3, 1.4 and driving it goes up some to 1.5 or 1.6. both the internal meter and the workman external meter show about the same thing. Maybe off by .2 max. Problem is the warning light still comes on when I key the mike!!! The swr has never gone above 2 when keying the mike and yet the light comes on. Is the antenna warning light in the cobra 29 ltd bt just really sensitive? can I just ignore it? this is what dad and I are thinking since both meters show 1.4-1.5 when the mike is keyed.

[country29]

yes the ant. light can be turned down by a shop or some on here maybe able to tell u which screw to turn, but it is sensitive if they didnt adj. it properly at the factory.

[rbodenbender]

just a small note on tuning your SWRs.....i have always tuned my radios to the band i talk on, and in this case, it is in 26.805 meg area. i do not have much variance between where i talk and where people normally tune (ch 20). so take your talking frequencies in to consideration when you are tuning your setup.

[9898]

vr6 this will solve your light.

[stsmith7]

thanks for the replies. I usually stay on the low channels so I might tune to like 11 or 12 instead of 20. Which way do you turn vr6 toadjust the light? I thought vr6 was what people turned to get more power/modulation? radio is all stock, so how hard is it to get to and adjust?

[TheCBDoctor]

Hi stsmith7

I would say you have broken antenna. Many of the wire wound antennas will break at the stud. The wire wrapped around the fiberglass is making a physical connection when sitting still but is no longer brazed to the 3/8" stud. Try and pull back the antenna and let it go back and forth while keying the radio, if the meter moves in rhythm with the antenna then replace the antenna.

I suggest a Francis antenna. The wire is embedded inside the fiberglass. The problem with the bounding cement has been cured years ago.

Good luck,

[9898]

vr6 clockwise and vr4 is the modulation and L14 is your dead key power.

[Xcis]

Stsmith7, you stated in your original post that the excess coax was loosely coiled in the back seat of your vehicle. It would be to your advantage to coil the excess coax as a figure "8" that is approximately 1 foot long. You could use duct tape, electrical tape or something else of your choice to hold its shape.

[Hawk1]

I had your same problem. The solution is to relocate the antenna and I'll tell you why. With the shielding fo the coax, ie: location of the mount with coax routing through vehicle, without the need for extra shielding which is provided by the current coax coating, will result in backfeed response and interference with your dash electrical system. Move the antenna as far away as possible away from the electronics of the dash. Then route the coax as much as possible, uncoiled the furthest distance from any dash exposure, coil only in long figure eight loop's. This will help eliminate the final coax hookup to your unit. The interference will also diminish as the unit is placed in an area 2 ft. away from the dash. When transmitting, you are "amp" powering your "mic". which can increase the amount of interferance. I hope's this work's for you as it did for me and am now metering my antenna at 0.5 at 1,20 and 40 with no problem.

[stsmith7]

Yeah since my last post I remounted the antenna on my toolbox and retuned everything. Since
then everything has been good.