Cobra 29lx RF stuck on channels 1-11.

[RookieRooster]

Hello, I just got my CB, it's a Cobra 29lx with a 3 foot Firestick 5/8. It has 16 feet of cable. I installed the radio on my aluminum F-350 so I can't get a magnetic mounted antenna. I happened to notice every time I transmit on channels 1-11, the RF Gain meter stays stuck to the right and the radio stops transmitting. It's a internal meter. Is my radio toasted, is it my antenna, what should I do?

 

[KB4MSZ]

Have you followed the SWR calibration instructions on pages 10-12 in the user manual? This meter does not self calibrate, you must calibrate it at each channel you wish to check. Do the checks as quickly as you can when working with an unknown match. The ideal would be to have the center of the CB band tuned to the lowest SWR (channel 19, 27.185 MHz) and the SWR should rise slightly on channels 1 and 40.

 

[FPR1981]

You are likely triggering the unit's built in safety measures, which will disable transmit capabilities when SWR levels are dangerous to the transmitter.

Because an antenna must be tuned over the entire band, you may have a passable SWR at the lower or higher end of the spectrum, respectively, but not the entire band.

Time to tune that antenna

 

[FPR1981]

To elaborate further on my previous post, when I build dipole antennas, it is common that during the tuning I encounter an SWR in the 1.7 to 1 (sucky, but safe at legal output levels) on channel 1, only to find the antenna near a 3:1 (lossy and eventually dangerous the transmitter) on channel 40.

The more I trim off, the better the upper end of the band looks.

I had a Hustler IC100-S mobile antenna that had an SWR of almost 3:1 on 1 and around 1.8 on 40. In that case I had to raise the mast within the spring, and even had to resort to adding stainless washers to artificially lengthen the antenna.

Eventually I got it passable, but not to my satisfaction. 1.7 on 1 and a nice 1.2 on 40. I gave the antenna away and it presented with the same numbers on my buddy's truck.

Bought another one of the same antenna and had great SWR figures right out of the box. I don't mean to to stray off topic, but just know that tuning matters, a lot.

 

[mmckenna]

Hello, I just got my CB, it's a Cobra 29lx with a 3 foot Firestick 5/8. It has 16 feet of cable. I installed the radio on my aluminum F-350 so I can't get a magnetic mounted antenna. I happened to notice every time I transmit on channels 1-11, the RF Gain meter stays stuck to the right and the radio stops transmitting. It's a internal meter. Is my radio toasted, is it my antenna, what should I do?

You'd need to go into some details about how and where the antenna is installed. Photos would be helpful. It's difficult to troubleshoot issues like this when we have no idea what your installation looks like.