I have a Uniden PC76XLW, which I have read is pretty much the same as the Cobra 29, that's why I posted here. I have it hooked up in my pickup truck. The antenna is a wilson 5' fiberglass, mounted on a plastic tool box, as far back on it from the cab as possible. I have a ground wire running from the negative shield of the coax where it connects to the antenna to the chassis of my truck. I have checked for continuity, and get good continuity from the positive lead on the PL-259 connecter at the radio to the tip of the antenna. There is no short along the coax or any connecters, and there is also good continuity from the negative lead on the PL-259 to the chassis. I think this is how it's supposed to be hooked up. I cannot get any transmission or reception on the radio, although I can hear faint static. When I try to tune the antenna to the radio with its built in SWR meter, the needle doesn't move no matter if I adjust the tip up or down. It reads well over 3. I'm guessing because there is no short in the antenna system or anything and I can't adjust any SWR that it's something internal.
When I got the radio, it had a blown protection diode, which I replaced. I was using a friend's magnet mount antenna which would get the SWR almost to 2, just to try it out. Now with a new antenna, it worked briefly while I was testing it very quickly, with high SWR (I hadn't had a chance to ground the antenna yet. Did that mess it up maybe), but then once I hooked up the ground, it hasn't worked.
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Is showing a bad swr which will only happen when transmitting. Get a swr meter and patch lead and tune your antenna for the lowest swr on channel 20 or middle frequency of your rigs frequency coverage. Easy fixed.
If your readings are below 0.5 with a dipole that is a excellent swr reading, most fall in the area of 2.0 or higher, you will not harm your RF output transistor, if you are getting antenna warnings see if you can recalibrate it.
Sounds to me like you need to check the connectors and connections on that coax. A cobra29 and a 102" whip is a simple enough set up and should not produce that high of SWR unless the coax or the connectors on the coax are pretty messed up. Also i recommend putting an SWR meter in line.
The meters on them Cobras can be accurate sometimes but I trust an inline meter much more.
follow these steps to adjust the standing wave ratio(SWR). 1. Turn on the CB. 2. Set S/RF/SWR/CAL to CAL. 3. Key the Mic and rotate SWR CAL so the meter points to CAL. 4. Unkey Mic. 5. Set S/RF/SWR/CAL to SWR. 6. Key Mic again and note the actual measurement on the SWR scale. Refer to the following table to interpret the reading.
1:1 - 1.5 Great 1.5 - 2:1 OK 2:1 - 3:1 Not So Good Higher than 3.1:1 Terrible
If the antenna is not the right length, then you will get signal reflecting back into the radio. this is bad and it can damage a radio.
The 29 has a built in SWR meter.
The lower the SWR the better.
Here is how to check the swr.
Turn to ch 20. Put the sf swr cap switch to CAL. Key the radio. With the radio keyed, turn the cal knob up until the meter is all the way to the right on the cal mark. with the radio still keyed, flip the switch to SWR. Where ever the needle falls is your swr reading. The top line is SWR. If it is above 3 this is really bad, and your antenna is no tuned and you are hurting your radio. You need to adjust the antenna length.
Turn to ch 1 and take an SWR reading the way I explained. Then do the same on ch 40. IF the SWR is lower on ch 1 then 40, your antenna is too short, make it longer. The antenna has a way of adjusting it. Usually the whip slides up or down in a colar.
If the swr is higher on ch 40 then 1, it is too long, and you need to make it shorter.
Keep making adjustments until the reading on 1 and 40 get lower, and are about the same.
Then check ch 20 again. It should be low, 1.5 or under. Then you are good to go.
you will find people hear you a lot better, way better then ever.
You insert an SWR meter in the antenna line, usually one end goes into the Antenna OUT socket, and the Antenna plugs into the SWR meter, you then tune you antenna coupler, inductor, & final PA, in the final stage, until you achieve a 1:1 SWR reading, this is however quite hard to achieve, so simply tune for the closest 1:1 SWR that you can achieve.
what type of aerial are you using? is the aerial near any metalwork ie fencing/metal sheeting etc if so move it away as you could be getting reflected power back into the aerial causing high swr, also 2.0 swr isnt too bad could be better but the swr meters built into cbs are not that acurate, I would use a dedicated in line swr meter (even a loan of one) and compare the readings, I take it all your electrical conections to the aerial are good? let me know and i will try and help, Thanks.
I hope this will help you on setting your swr put the radio on channel 1 check your swr. now go to channel 40 check the swr. If the swr is lower on 1 than it is on 40 the antenna must be shortened buy 1/4 inch.until you reach your desired swr.if the swr is lower on 40 than it is on 1 the antenna must be lenthened by 1/4 inch until desired swr.
I believe it to be feedback but be aware of your Standing wave ratio because using a linear amp radiates signal to the point that it could cause that light to come on. There is a problem if the radiated signal is feeding back into the amp a a higher level that it can withstand over time.