Have a cobra 148 gtl cb/ssb. It is brand new. I hvae it hooked up and have tuned the antenna using the swr meter on the cb. I habe channel 1 and channel 40 metting at about 1.6 swr. I have what appears to be good distance reception but little output.

you are not matching it correctly. get hold of a friend that knows how to match it and see if he will help you.

Several questions. 1) do you have it connected to antenna with good coax?2) did you check your match on the radio with an SWR meter? What kind of match do you have,is it below 3.0? If it is that high get down to around 1.5 - 2.0 and others should be able to hear you.

Could be TR41 or TR42. I would try TR41 first.

If this radio has been peaked and tuned already, and it is not in need of a full alignment, then it's most likely the antenna.

Your antenna is everything. You need a good antenna, and it needs to be tuned to the lowest SWR.



It is important to tune your CB radio antenna to the proper length. The length must exactly match the wavelength of the frequency you transmit on. Or be really really close.

All Cb antenna's have a way to adjust the length of the antenna. If it's a mag mount, the metal whip can be slid in and out of a metal collar. Usually a set screw. If its a fiberglass whip, the way to tune it is on top. It either has a small metal rod with a set screw to adjust the length, or it threads in and out to adjust length.

Either type you have it will need to be adjusted for proper length. Here is how to tune the antenna to lowest SWR.

Some radios have a built in SWR meter. Some do not. If yours doesn't have an SWR meter, then you have to use an external SWR meter. Radio shack carries one, and you can find them cheap on ebay.

If you have a built in SWR meter or external, the procedure is the same:

1. Turn the radio to CH 20.(This is the center of the band.)
2. Switch the meter switch to CAL. (CAL stand for calibrate.
3. Key the radio. (Important. Do not talk while keying the radio.)
4. turn the CAL knob up until the meter hits the CAL mark.
5. Now while still keying the radio flip the meter switch to SWR.

Where the meter falls after that point is you SWR reading. If its above 3, that is real bad. 2 is not gonna kill your radio but its not the greatest. 1.5 and under is a good place to be, but the lower the better.

If your SWR is high, Here is how to find out if your antenna is too long or too short.

1. Turn to CH 1
2. Repeat SWR procedure. You must calibrate every time you do it.
3. Remember the SWR reading.
4. Turn to CH 40.
5. Again repeat SWR procedure.
6. Compare the reading between CH 1 and CH 40.

Now if the SWR is higher on channel 1 then channel 40 your antenna is too short. You must make it longer.

If the SWR is longer on channel 40 then on channel 1, then the antenna is too long, you need to make it shorter.

Make height adjustments about an eight inch at a time, and take reading each time.

once the SWR is significantly lower and the reading on channel 1 and 40 are about the same, you a about matched. At this point turn the radio to the center of the band, channel 20 and take an SWR reading.

You should now have a low SWR reading, 1.5 or under. If you are 1.5 or under, you are good to go.

If you cannot get the SWR to an appropriate level, there may be an antenna problem.

Center the antenna on the vehicle, then check the SWR on channel 1 and channel 40.
with the switch in CAL position, key radio and use the swr/cal knob to set the meter so the needle is just touching the end of the red area on the right-hand side of the meter.
Once calibrated, unkey and switch the switch to SWR and key up again. The lower the reading, the better. If the SWR is Higher on 40, the antenna needs to be shorter.. if its higher on 1, then the antenna needs to be longer.

if it dont transmit period on AM, then there's an internal glitch :)

try adjusting the L36,L38 to the highest reading on the external meter and then adjust VR10 TO 4 watts. If this doesn't cure the problem, you have a weak final transistor. Good Luck

make sure that the rf gain is turned up all the way.Check diodes D-12&D-13.

Your problem is a faulty changeover relay on the circuit board. It is a small black device , and may have the brand name MRATA
etched on it (the switchover contact points are stuck together)
WORTH A TRY GOOD LUCK
[email protected]

Hi,

Connect the INput of the amp to the TX out of the radio. Connect the OUTput/Ant of the amp to the INput of the meter (SWR/Power). Connect the OUTput of the meter to the cable that leads to the antenna.

With this arrangement, you will be able to measure the SWR of the antenna and power output (of the amp) going to the antenna.

Hope this be of some help/idea. Pls post back how things turn out or should you need additional information.

Good luck and kind regards.

Hello k007,

It sounds like you may have damaged the RF power amplifier stage of the CB. Since you were adjusting the antenna characteristics. Did you have a SWR (Standing Wave Ratio) meter connected while you were tuning the unit? If you did you might have noticed the needle go past the 1.2 mark when you were adjusting the antenna or the unit itself. In any event I think that the RF power Amp is shot.

Thank you,
Shuttle83