Question about Cobra 29 LTD CB Radio
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Posted on Jan 02, 2017
SOURCE: CB transmission
Make sure the radio is grounded properly and that the SWR is around 1.2:1, 1.3:1 is good but try to get it to 1.2:1. Also take a power output reading while keying the mic. To do this with your power meter put it in-line with the CB and your antenna and key the mic you should get about 4 to 5 watts PEP. If this is the case your unit is putting out the proper power level, if not have the power amplifier checked by a qualified repair shop.
I hope this helps
Posted on May 14, 2008
Hi - You can download the manual from the link underlined in blue below:
75 WX ST
Other info here.
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Posted on Aug 31, 2008
Antenna light should be a warning indicator for high VSWR..... simple rule of thumb for CB antenna.... the lower the frequency "channel" the longer the antenna length, higher the frequency "channel" the shorter the antenna length. Your vehicle is a ground plane, where you mount the antenna will also affect its operation and tuning. A properly tuned antenna will have lower reflection on the midband channels and gradually rise as you near the upper and lower end of the band. Some base loaded antennas will be noticably narrow in bandwidth, if you have that problem then tune it for the channel you use most!
K40 has always been good for easy tuning and band coverage, center it on the vehicle top for good omni coverage!
PS... always make sure your connectors are secure, a loose shield will ruin your day when adjusting SWR!
Posted on Dec 22, 2008
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.
Posted on Apr 12, 2009
Its the antenna. it is not tuned correctly for the radio. First, stop transmitting. You can burn out the final transistor. If the antenna light is coming on, that means your SWR is too high,
first. Check to make sure that the antenna coax is securely attached and fastened tightly to both the radio and antenna.
Next inspect the coax. Make sure there is no damage to it. If there is a slice in it, it is kinked really bad, that could be the problem.
Now, if the coax looks good and is connected tightly, now its on to tuning the antenna. Your antenna is either too long or too short. Antenna's usually have a way to adjust this. Most common is where a metal whip sits in a collar. You loosen the collar, and you can move the whip up and down in it. That is how you adjust the length of your antenna. Fiberglas whips usually have an adjustment at the tip that you can adjust usually by screwing it in or out.
Now here is how to check your SWR.
Make sure you are in an open area like a parking lot as structures such as buildings and trees can cause reflection and give you a false reading. Always take an SWR reading with your doors and windows shut as not doing so can also cause a false reading.
Now that you are in an open area, turn on the radio and turn to channel 20. flip the switch located all the way to the left by the signal meter to CAL. Now turn the knob all the way to the right just before the channel selector marked SWR CAL all the way down to the left before you start. Now key the mic without talking into it and turn the SWR CAL knob up until the needle on the meter is all the way to the right to the mark for CAL. its a little upside down triangle with the letters CAL next to it. You want the needle to be on that triangle. Now while still holding the key in, flip the switch all the way to the left next to the signal meter up once to SWR.
The needle should swing back giving you your SWR reading. Ideally you want this reading to be as low as possible, but 1.5 and under is acceptable. If it is higher then 3 and in the RED stop transmitting. Try to do the steps quickly so you can un key as soon as possible to avoid damage to the final resistor if the SWR is higher then 3.
If the reading is 1.5 or under and the ant light is going on, it could be something else. I will go more into this at the end.
Now we have to figure out if the antenna is too long or too short. Here is how to do this.
Turn to channel 1 and repeat the steps to take an SWR reading. Make note of the reading.
Turn to channel 40 and repeat the steps again to take an SWR reading. Not that number.
If the SWR is higher on channel 40 then channel 1, then your antenna is too long and you need to adjust your antenna so it is lower.
If the SWR is higher on channel 1 then on channel 40, then the antenna is too short, and you need to adjust the antenna higher.
If the signal is over 3 on both channels, then there is something wrong with either your coax, antenna or both, and you should replace the coax, and if its still high, the antenna.
If your antenna is too long or too short, make adjustments to correct. Raise or lower the antenna a 1/4 inch at a time. each time taking a measurement to see if it is still to long or too short. You want to try to get the SWR the same on 1 as on 40. And channel 20 will have the lowest reading.
If your SWR reads low, under 1.5, or even a 2, the light should not come on. If you have had the radio worked on at a radio shop, or purchased it from some where that modifies the radio to put out more power before they sell it, then that can cause that light to go on falsely. Purchase an external SWR meter. You can get one off ebay, or from radioshack. Check the SWR with the meter, and if the SWR is still good, then you can do 1 of the following.
1. ignore the light because it is not right.
2. go in the radio and try to adjust VR6 so that the light doesn't go on. Not recommended if you don't know what you are doing.
3. take it to a cb shop and have them adjust VR6 for you.
I would leave it alone.
Most likely your antenna is not tuned properly.
Posted on Apr 29, 2009
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