Question about Cobra 148 GTL 120-Channels Base CB Radio
I clipped r131 and my radio is not transmitting on lsb its ok on am help me
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
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
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
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
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
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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