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I understand that a 'Rubber Duck' antenna is not adjustable. My SWR reading is relatively high in my car. If I am unable to lengthen or shorten the antenna are there any other ways where I may be able to lower the SWR?

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Hi, my name is John. Welcome to FixYa. There are ways to adjust it. You have to remove the cover, let me know when you have done this. Thanks for choosing FixYa. ..John

Posted on Nov 20, 2010

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I can't get my swr to go down on my general lee cb radio


what kind of antenna do you have? Does it have antenna adjustment screws on it or is it a fiberglass antenna? If it is an adjustable antenna you have to raise the whip or lower it depending on what you have for a reading . Use an external SWR meter,don't go by the one on the radio,that's just for quick reference .Get the match down to at least 1.5 - 2 and you are good but now, if its a fiberglass antenna ,some have an adjustment screw others don't. If it doesn't have a screw on the tip and you have to shorten the antenna you will have to trim off some of the tip but if you have to lengthen it you may want to add a spring at the bottom connection to your mount.

Aug 11, 2015 | Radio Communications

1 Answer

Cobra 19 ultra iii


Do you or a friend have a SWR/Power Meter? If the Standing Wave Ratio of the antenna and feedline is to high you will not get the power from the radio to the antenna. You want you SWR to be 1.3 to get a good signal from your antenna. Most antenna have a set screw that is loosened and tightened after either lengthening or shortening the antenna stub.

Apr 09, 2014 | Radio Communications

1 Answer

How to set standing wave


The SWR is set by the antenna. It depends on the type of antenna you have as to the correct procedure. If the antenna has a stainless steel whip then a set screw is loosened so that the whip can be adjusted up and down. Most Fiberglass antennas have to be trimmed. Some of the fiberglass antennas have tuning adjustments under the rubber cap on the end. Check you SWR on channel 1 and on channel 40. If it is higher on 40 than it is on channel 1 then your antenna is too long and needs to be shortened. If your SWR is higher on 1 and lower on 40 then the antenna is too short. There are many articles on the web concerning SWR. I urge you to read up because having the SWR set on your rig will ensure many years of good operation and performance.

Mar 10, 2013 | Cobra Radio Communications

1 Answer

Why does my moonraker cb change channels by itself.


This can be caused by RF feedback. RF is radio frequency energy - the same energy that your transmitter puts out onto the coax cable & antenna.

RF feedback is similar to audio feedback in that some of the output re-enters the circuit in a place it doesn't belong or is designed. RF feedback is a direct result of a poorly matched antenna system as shown by an SWR meter. A standing wave ratio or "SWR" of 2.0:1 - 2:5.1 (read this as: two point zero to one and two point five to one) or greater is generally accepted as the worst SWR a transmitter can tolerate - but also requires lowering RF power (wattage) to continue transmitting.

Some common sources of high SWR are: 1) wrong cable type (usually a 50 ohm cable is used), 2) damaged cable, 3) untuned antenna, 4) damaged previously tuned antenna, etc. The SWR of an antenna system should be checked and adjusted as needed to assure maximum power transfer to the antenna. If the system has a high SWR, the antenna reflects some of the RF energy back on the coax - into the radio. The effects can be tingles / burns on the lips - if using a mic with a metal guard, noise, and erratic operation of some rig settings. This energy is unexpected and can cause all sorts of strange radio operations and is not an uncommon occurrence in a situation such as this.

You can correct this problem by purchasing or borrowing an SWR meter or bridge designed to work in the range of frequencies that your CB uses. Follow the directions included to lengthen or shorten antenna elements as needed. An ideal SWR is 1.1:1. Generally, any value of SWR less than 1.5:1 is considered very good. A check of SWR on the low, mid and highest frequencies will give you an idea as to how well the antenna works on the frequencies you use, and let you know which frequencies you should avoid.

Good luck!

Apr 21, 2012 | Radio Communications

1 Answer

I have a cobra 29 wx nw st withwilson little wil entenna. I am having issues with a no swr reading on channel one even if I turn my swr cal all the way up. My 40 cal reads on the swr at .5 no matter how...


first of all you are going about it wrong. To set your SWR you check it on channels 1 , 19 , and 40. If you reading is higher on 1 than on 40 you have to shorten your antenna . if its higher on 40 than on 1 then you have to lengthen it. before you do any adjustments to it ,loosen the set screws and let the antenna fall to the bottom then bring it up 1/4 " and tighten the screws. You should also use an external SWR meter not the one on the radio. Thats good for making checks every once and a while. With the meter you key the mic and have the needle go to set then put it on for and key the mic to obtain you reading . Anything under a two is good .

Dec 16, 2010 | Cobra 29 WX NW ST 40-Channels Base CB...

2 Answers

Can you adjust a 'rubber duck' antenna? I have a rubber duck antenna on my car and the SWR reading is relatively high. How do I adjust this antenna to bring the SWR reading lower, as there are no obvious...


Sorry, but each rubber duckie is cut to a specific frequency, with the actual antenna windings sealed inside the rubber/plastic outer shell. Because of this construction, there is no adjustment feature.

Nov 11, 2010 | Cobra 19 DX IV CB Radio

1 Answer

Every time I press my MIC to speak into it the red lights on the RX/T and ANT light come on alerting me of a problem. How can I fix this.


RX/TX light should change to red, however the ANT light is a bad light. This means that your antenna is not adjusted properly. Do not key the radio or talk on it for any other reason then to check the SWR and tune the antenna. If you have the manual that came with your cobra 29, there is a section that explains how to check the SWR. And the manual for the antenna, it will explain how to adjust it.

If not, here is how to do it.........

How to check the SWR on a Cobra 29

Step 1. Find out what your current SWR is on the center of the band.

  1. Turn the radio to channel 20.
  2. Set the S/RF SWR CAL switch to CAL.
  3. Turn the CAL knob all the way counter clockwise.
  4. Key the radio. Do not talk into the mic.
  5. While holding the mic key, turn the CAL knob to the right until the needle reaches the CAL mark on the top right of the meter.
  6. Now flip the S/RF SWR CAL switch to SWR while still holding the key on the mic.
The needle should fall. Where ever the needle is while holding the key is your SWR reading on channel 20. It should be as low as possible. If its a reading of 2, then its not gonna kill the radio but is border line. Any higher and its bad. Using the radio like this will damage the final output transistor. If its less then 2 this is better. You want it to be less then 1.5 or better.

The ANT light may come on with an SWR of 2. running the radio with an SWR of 2 shouldn't hurt the radio, but I don't like to mess around. Get it as low as possible.

How to adjust the antenna for SWR

The length of your antenna will change your SWR. SWR is basically how much RF energy is not leaving the antenna and getting reflected back into the radio. That's why it hurts the radio when its high. An antenna has to be the right length, matching the length of the radio waves in order for it to radiate all of the RF energy out of the antenna.

Most antennas have a way of lengthening or shortening the antenna. If its a mag mount antenna with a metal whip, there is probably a set screw that when loosened, will allow you to raise or lower the whip. If its a fiberglass antenna, under the rubber cap at the top is how you raise or lower the antenna.

Figuring out if your antenna is too long, or too short

Here is how to know weather or not you have to lengthen or shorten your antenna.

  1. Take an SWR reading as explained in the first step on channel 1. Write down the SWR for reference.
  2. Take another SWR reading on channel 40. Again write it down for reference.
Now if the SWR is higher on channel 1 then on channel 40, its too short. You need to make it longer.

If the SWR is higher on channel 40 then channel 1, then the antenna is too long. You need to shorten it.


Make small adjust ments about an 1/8th to a 1/4th inch at a time. each time checking the difference between channel 1 and 40.

You will know when you are a good match when there is little to no difference between channel 1 and 40's SWR. Once you are satisfied that the difference between 1 and 40 is about the same, and much lower, then turn the radio back to channel 20 and take an SWR reading.

You will now find that the SWR on channel 20 is really low. Most likely under 1.5 or better, Almost nothing on the meter.


Here is a Meter Key, so you know what you are looking at.
2d03348.jpg

Oct 11, 2010 | Cobra 29 LTD CB Radio

1 Answer

I can hear people fine,but my volume to them is very low. i have checked the swr. when i key up the needle goes to 3


On some radio's that are bone stock with a stock mic you have to speak directly into the mic and not mumble;as for your swr if it's high on channel 1 and low on channel 40 you need to shorten your antenna if it's low on 1 and high on 40 you need to lengthen your antenna.Good Luck. Dan

Nov 30, 2009 | Radio Communications

2 Answers

I installed a browning br-51 cb antenna on my cb radio.


You need to shorten the antenna,adjust the whip all the way down and see what you have and then cut off 1/4" at a time remember this low on 1 high on 40 it needs to be lengthened high on 1 low on 40 it needs to be shortened . I hope this helps and good luck.

Apr 11, 2009 | Cobra Radio Communications

3 Answers

Cobra 29 ltd classic antenna calibration ??


You should not calibrate the antenna before you install it on the car!! the antenna needs to be calibrated on the vehicle that it is going to be on. Type of vehicle, different mounts, and many other variables can change the amount of reflection you will get.

j0hn9999 did a much better job but left some info out.

Take your SWR readings on channel 1, then on channel 40.... NOW, if your SWR is higher on ch 40 then ch 1, then your antenna is too long and it needs to be shortened. Refer to the antenna instructions on how to shorten the antenna.

If your SWR is higher on ch 1 then on ch 40 then your antenna is too short. You must lengthen the antenna. Again refer to your antenna instructions on how to lengthen your antenna.

You must calibrate each time you take a reading.

Make sure your doors and windows are shut when taking a reading

Make sure you are in an open lot when taking a reading as buildings, trees and other structures can cause reflection and give you an inaccurate reading.

If you adjust the length of your antenna on another vehicle and then put it on yours, the SWR will be off. It will need to be tuned again.

An external meter is better then the one in the radio, but will need to be hooked up in the vehicle you have the antenna on.

If you are not running any kind of power, or do not have a swing kit installed, and the radio is stock, the meter in the radio is more then enough to get a correct SWR reading.

Sep 27, 2008 | Cobra 29 LTD CB Radio

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