Question about Cobra 148 GTL 120-Channels Base CB Radio

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My cobra 148 work well on am but not on lsb

I clipped r131 and my radio is not transmitting on lsb its ok on am help me

Posted by nutchie629 on

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jim smith

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Clipping the limiter should not have prevented tx on sideband are u sure u didn't do something more accidently. r 131 is the correct limiter for the 148. just out of curiosity what year 148 is it?

Posted on Oct 29, 2012

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Anonymous

  • 1139 Answers

SOURCE: cobra 148 gtl new model

Hello bluzfan, Do you remember the old 40 channel CBs? they used basic A3A transmission (dual sideband single carrier)remember how you got crosstalk sometimes, if your power was too high? Then they went to 80 channel CBs (using a single side band as Lower Side Band (lsb) and the other as the upper side band (usb))? more crosstalk but they invented anl (automatic noise limiter)circuitry to compensate. Now you have the 120 channel CB which uses a form of side band multiplexing (20QAM) to generate 3 times more channel density 40 X 3 = 120. Here is my problem; Cobra should not have done this because you will have massive crosstalk and unaudible sounds because of the increase in channels but not an increase in initial (physical)bandwidth. I hate to tell you this but the only cure for the is to use it in 40 channel or 80 channel mode forget the 120 channel mode, or get a radio with better channel separation.

Posted on Oct 07, 2007

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Anonymous

SOURCE: cobra 148 gtl

Open the radio up and find the L22 Can/Pot. It's the one with the wire soldered on top. With both fine and coarse Claifier/Voice Locks in the 12 O'Clock positions, confirm, then listen for someone that is on the correct frequency and turn this pot (small ferrite core inside) with a small plastic preferred screwdriver, until they sound clear. Do this for USB as well except, the Can/Pot is L59. Don't adjust the VR5 (transmit) unless you need to.

Posted on Dec 01, 2007

Anonymous

SOURCE: cobra 148 gtl

First take a jumper wire and connect it to the DC Ground of the input of the radio then touch it to the TX pin on the radio if it does keyes up then its in the mic or mic cord on the end of the mic plug or where it goes into the mic cable goes up inside the mic. If the radio don't key up at all then check the main voltage regulator chip one pin will have 8 volts transmit and another pin will have 8volts recieve. If you get no switching DC voltage on the regulator then its bad and needs replacing there is also a known bad capacitor in the radio thats only 10 volts change it to 25 volts at the same capacitance.

Posted on Jan 08, 2008

Mechanic688

Mechanic688

  • 204 Answers

SOURCE: No am power

Radio dude, What you have is a blown am regulator. The sideband side does not use the mentioned transistor. They use a few different numbers here for the am regulator. One of them is a 2sc1419. On the Uniden Grant they put the transistor on the rear right above the antenna jack. On the 148 they put the transistor back in the right rear of the radio as your looking inside on the speaker side. Fixing it includes unsoldering the transistor and purchasing a replacement and resoldering it back in. This transistor is bolted to the side rail in the rear. I usually use a ECG152 as a replacement. It's not unusual to blow this one if the radio has been tuned. Let me know if your comfortable swapping it out. Otherwise it needs to go to a shop with a decent tech that won't take you to the cleaners. Let me know,, Mechanic

Posted on Feb 21, 2008

Anonymous

  • 36 Answers

SOURCE: have a new cobra 148 gtl took out of box no transmit or recieve

make sure that your [swr] hadn't changed or went higher than a 1.5, anything higher will interfere with your tranmitting an recieving. other than that with out being there to see an hear your radio this would be the first place to start.

Posted on May 05, 2009

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1 Answer

I have an cobra 148 gtl no transmit


If theres no carrier its either the finals or driver. If theres no audio its the white wire in the plug that screws into the radio..its either broke or most likely come unsoldered. It keys but no audio.

Mar 05, 2015 | Cobra Radio Communications

2 Answers

Cobra 148 gtl d has problem transmiting with covers off. trying to tune radio up. was thinking I need to ground the chasis


I would say a bad or cold solder joint on board somewhere. Bad quality control. Might flex radio chassis slightly while keying? A tooth pick and hours of probing around switching area on board and the pa section till problem found.

Oct 25, 2012 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Cobra 148 gtl-st wont transmit but receives great


Check first your microphone

• check if TX is engaging when PTT is pushed.


• check for continuity ( mic and cable )



If you have not done these steps,

try it first, or borrow other compatible mic for Cobra 148GTL

from your friends on air.

Jul 28, 2012 | Cobra 148 GTL 120-Channels Base CB Radio

3 Answers

Schematics for a cobra 148 NW


Most units do NOT allow modulation adjustment as any more than 90-100% modulation causes adjacent channel signal "Splatter" therefore is subject to restrictions, hence generally that is locked. Also there really is no reason to have more than 100% modulation..as well ... why? I would suggest a voice/speech "Compressor" would be more suited.

Jan 31, 2010 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

I dont really have a problem


THE ACTUAL FREQUENCY IS THE SAME THE ONLY FREQUENCY THAT CHANGES IN THE RADIO IS THE CRYSTAL OSCOLATOR. IT SHIFTS FREQUENCY UP OR DOWN IN THE SIDE BAND MODES. SO YOU WILL TRANSMIT
AT 27.285 ON CHANNEL 19 OR 27.335 CH 35 AND SO ON.

Mar 11, 2009 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Cobra 148 gtl new model


Hello bluzfan, Do you remember the old 40 channel CBs? they used basic A3A transmission (dual sideband single carrier)remember how you got crosstalk sometimes, if your power was too high? Then they went to 80 channel CBs (using a single side band as Lower Side Band (lsb) and the other as the upper side band (usb))? more crosstalk but they invented anl (automatic noise limiter)circuitry to compensate. Now you have the 120 channel CB which uses a form of side band multiplexing (20QAM) to generate 3 times more channel density 40 X 3 = 120. Here is my problem; Cobra should not have done this because you will have massive crosstalk and unaudible sounds because of the increase in channels but not an increase in initial (physical)bandwidth. I hate to tell you this but the only cure for the is to use it in 40 channel or 80 channel mode forget the 120 channel mode, or get a radio with better channel separation.

Oct 07, 2007 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Cobra 148 gtl


Open the radio up and find the L22 Can/Pot. It's the one with the wire soldered on top. With both fine and coarse Claifier/Voice Locks in the 12 O'Clock positions, confirm, then listen for someone that is on the correct frequency and turn this pot (small ferrite core inside) with a small plastic preferred screwdriver, until they sound clear. Do this for USB as well except, the Can/Pot is L59. Don't adjust the VR5 (transmit) unless you need to.

Oct 06, 2007 | Cobra 148 GTL 120-Channels Base CB Radio

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