Question about Cobra 25 LTD 40-Channels Base CB Radio
It's a 2001 model. In 2005/06 was when it started acting strange. It's been so long ago and i'm trying to remember what really happened. I believe there was a time that it shut down on it's own and I had to turn it off/on a few times for it to power up. I actually remember there being other times I had to mess with the off/on switch for it to power up. Eventually it didn't power up period. I tested it the other day with my volt meter and there is power leading to the switch but that was the only place I tested. I just wanted to see if power was actually getting through. When I first purchased the radio, I was using a cigarette lighter plug (not the cheap kind either) and I believe I had installed correctly.
Spray some contact cleaner into the switch portion and cycle it a few times and see if that clears it up. I had a similar unit with a similar issue and it was jsut a matter of patience and carefully directed contact cleaner that brought it back to life.
Also check the solder tracks to make sure the solder or the track has not broken as well.
Posted on Feb 25, 2012
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Posted on Jan 02, 2017
SOURCE: cobra 29 LTD cb radio
Strange problem indeed, this is why I don't like Cobra radios, they're no good. But try adjusting the receive gain on the radio, if that doesn't work, you might need to check the antenna, check if it is connected properly, or if the antenna actually works. Honestly though, if you want a solid performance radio, go Galaxy or Uniden, no Cobra. I worked with radios for years, and Cobra has failed to meet my expectations for a good radio, they may have a lot of features, but they have no reliability.
Anyway, I hope this helps somewhat.
Posted on Jul 01, 2008
SOURCE: cobra 29 ltd modulation problen
You need to check the modulation on a modulation meter. Just because the meter doesn't peg, doesn't mean the modulation isn't working. Usally a meter pegging, means the swr's are too high or the meter is misadjusted. If in fact the modulation is low, their is a pot inside the radio (VR4) that will add gain to the modulation circuit. This setting is legally supose to be set by a qualified technician.
Ed Meshechek ( Radio Man )
PO Box 1696
414 6th St.
Posted on Dec 03, 2008
SOURCE: swr meter not moving.
If the radio is working don't worry about the meter unless you absolutely want it. These little meters are not very accurate or reliable. Get an external SWR meter to check the antenna.
Posted on Apr 23, 2009
Wow. That's not at all a solution to what this guy is asking. And why all the caps??
The one point jm77437 has that is correct is that you do not set the radio, you set the antenna. The rest is blah blah.
Here is how you tune your antenna for you radio. First off it depends on what kind of antenna you have. most fiberglass antennas have a tunable tip to adjust the height of the antenna. Metal whips either have a collar at the base that the whip will either slide up or down in to adjust the height. The other type of metal whip's you have to physically clip to shorten the antenna, you must be careful with this type because once its clipped, that's it. You cannot add what you cut off.
I am going to give this example using a metal whip with an adjustable collar.
First after your radio is hooked up in the vehicle, drive to an open lot. Buildings and other structures can cause extra reflection. turn to channel 1. Flip the meter to CAL. Key the mic without talking. Now turn the CAL knob up until the needle reaches the little upside down triangle all the way to the right marked CAL. Now you have just celebrated your radio for your setup to measure you SWR. Now while still holding the key, flip the meter switch to SWR. The needle will move, and where it stops is your SWR reading. The lower the better. Anything under 1.5 is considered really good. But still, the lower the better.
Make note of what your SWR was on ch 1.
Now flip to channel 40. Repeat the SWR process. You must recalabrate each time you take a reading.
Now like jm77437 said. If your SWR reading is higher on 40 then 1, then your antenna is too long, and you must make it shorter. Loosen the collar and lower the antenna in the collar 1/4 inch at a time. check the swr each time you adjust the antenna.
If your SWR reading is higher on channel 1, then your antenna is too short. You must make your antenna longer. Do this by loossening the collar and pulling the antenna upward in the collar 1/4 inch at a time, again checking the swr each time you adjust the antenna.
What you want to achieve is having the same SWR reading on channel 1 and 40. then you have the best match you are going to get with that antenna.
If your swr is under 1.5 on all channels, you don't need to fuss unless you are a perfectionist. then by all means go ahead.
If your reading is higher then 3, or your ant light comes on, something is really wrong. Make sure your antenna is connected all the way, and the coax is not damaged.
Its important to have an appropriate SWR because if you do not, you are reflecting too much signal back into the radio, and eventually you will burn out your final transistor, and your radio will be toast.
Some tips: make sure you check the swr with the doors and windows shut. Make sure you are in an open lot. Remember to calabrate ecah time you take a reading. If you have had your radio peaked by a radio shop, and they have lowered your dead key, or have done a swing modification, then the meter in your radio will not work when taking an SWR reading and you will have to use an external meter.
Posted on Apr 24, 2009
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