Question about Radio Communications

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No transmit on usb.only recive but all works on am and lsb.1stGen.pres.whst

Has no transmit on upper side band only recieve but will transmit on am and lower sideband just fine.thanks

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  • Contributor
  • 24 Answers

The transmitter section of the radio needs to be aligned you need to look for a cb shop its nothing you can fix on your own

Posted on Apr 27, 2014

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Posted on Jan 02, 2017

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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

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

  • 1 Answer

SOURCE: magnum 257 it will not transmit on lsb or usb it will on am and f

With SSB you have to put audio on the carrier you cant just key the microphone and expect it to output a signal unless you talk into the microphone at the same time this is how SSB works.
So if you talk and the meter starts to move then its ok, if you talk or whistle and nothing moves then the circuit on the SSB side of the unit is faulty.

Posted on Feb 07, 2009

  • 5 Answers

SOURCE: magnum s 9 sideband fault

sounds like tuning, have you been through the alignment procedure? take a look at cbtricks.com for the info

Posted on Jun 25, 2009

  • 1 Answer

SOURCE: Superstar 3900 with no USB or LSB on receive.

hi, my superstar 3900 is dead, no receive audio, tx light goes red when i key the mike, but swr meter not moving?

Posted on Jul 07, 2009

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1 Answer

Uniden washington cb


Is it off on both upper and lower sideband? how about AM? Did someone mod it so that the clarifier works on transmit too? Hope not.
If it is off on LSB adjust CT2 next to C104 and for upper side band CT1 next to C105. You will be tweeking on a capacitor in series with a crystal. caution as it could stop it from transmitting (oscillating) if it isn't set right. best if you use a frequency counter to see if the stage is working right on frequency. Here is a diagram hope you know how to read one. If you dont and you attempt to tweek on this and that, you have a great chance that you could foul it up to the point it wont work at all or sound really bad. The main thing is to narrow it down where the problem is: Is it just LSB or USB or both? If both do not tweek on C1 or C2. I would say it is the 11Mhz crystal area. meaning the problem could be a bad varactor diode, even a resistor or capacitor failure in that portion couldmake it off frequency as the varactor is voltage controlled. By varying the voltage to it, the capacitance changes and therefore changing frequency.
If both uper and lower sideband are off then I suppose AM is off too. the reason you are not being heard as well. Adjust CT3 to bring it back on frequency. You got it CT3 if upper and lower and AM is off or if only lower is off CT1, if only upper is off CT2.
Good luck. I am not responsible for your actions. I am only giving my opinion and logic on this. here is the diagram, dont hurt yourself.....
http://www.cbtricks.com/radios/uniden/washington_mb8719/graphics/uniden_washington_mb8719_sch.pdf

Dec 23, 2013 | Radio Communications

1 Answer

Ihave a gargeled recive sound


Check the position of the mode selector switch. You may be receiving a SSB (single side band) transmission that is not on the exact same frequency as you or, your radio is in AM or FM mode. You will need to select either USB or LSB (upper or lower side band) and vary the clarifier knob until the sound becomes intelligible. If the sound does not become clear, try the other side band and repeat varying the clarifier knob.

Conversely, if you are in USB or LSB mode and there is a transmission on AM or FM, it will have the same garbled sound. Try changing the mode to AM and the FM. If it does not become clear, it is likely a SSB transmission and you are not on the exact same frequency of the transmission you are hearing. Vary the clarifier knob until it becomes clear - or change to the other side band if needed and try the clairfier again.

The short story is that you must be in the same mode and on the same exact frequency. When in AM or FM, this is less of a problem as these are much more wide banded signals than SSB signals.

The 2990 is really a 50 watt 10 meter amateur radio - but is geared to CBer's as it is easily modified to work in the CB frequency range and the so called "free band" between USA's CB (11 meters) and worldwide amateur 10 meter bands. Be careful transmitting this radio on CB frequencies as it violates FCC rules for power output there - and transmitting in the 28MHz - 29.7MHz requires a valid amateur radio license. Fifty watts on ham frequencies is tiny compared to the 1500 watts permitted. Why not get your ham license (here's how) and leave the "Chicken Band" (and all it entails) behind. You won't miss it!

I hope this helps and good luck!

Apr 12, 2012 | Cobra Radio Communications

1 Answer

Looking to find the frequenecies of the upper and lower channels



  • Hi I can help.
  • For the Grant 40 channel CB there are 40 frequencies I will list below.
  • When you refer to the upper and lower channels for this raidio you must mean USB (Upper Side Band) and LSB (lower side band).
  • This is called single side band modulation which is to say the the carrier is removed from the upper or lower sideband depending on which your pick and the signal goes farther on less power.
  • So the upper and lower side bands are the same frequency just upper side band or lower sideband.
  1. 26.965 MHz 21. 27.215 MHz
  2. 26.975 MHz 22. 27.225 MHz
  3. 26.985 MHz 23. 27.255 MHz
  4. 27.005 MHz 24. 27.235 MHz
  5. 27.015 MHz 25. 27.245 MHz
  6. 27.025 MHz 26. 27.265 MHz
  7. 27.035 MHz 27. 27.275 MHz
  8. 27.055 MHz 28. 27.285 MHz
  9. 27.065 MHz 29. 27.295 MHz
  10. 27.075 MHz 30. 27.305 MHz
  11. 27.085 MHz 31. 27.315 MHz
  12. 27.105 MHz 32. 27.325 MHz
  13. 27.115 MHz 33. 27.335 MHz
  14. 27.125 MHz 34. 27.345 MHz
  15. 27.135 MHz 35. 27.355 MHz
  16. 27.155 MHz 36. 27.365 MHz
  17. 27.165 MHz 37. 27.375 MHz
  18. 27.175 MHz 38. 27.385 MHz
  19. 27.185 MHz 39. 27.395 MHz
  20. 27.205 MHz 40. 27.405 MHz.
  • If you have any comment please feel free to leave them here.
  • Hope this helps and thank you for using FixYa.

Regards, Tony

Aug 29, 2011 | Uniden GRANTLT 40-Channels Base CB Radio

1 Answer

Cannot select USB or SSB.Displays LSB or LISB? Very poor reception


On the Satellit 750 you have a button marked SSB. If you have selected a shortwave band then you can press the SSB button. Pressing the button repeatedly will toggle between LSB and USB.

You will need to know the exact frequency and the broadcast time, and the side band. Turn the radio on. Select a frequency which you know carries SSB signal and wait. Those that broadcast on SSB are not radio stations, maybe ham radio operators.

You can also select a short wave band, press the SSB button once or twice to select the side band and launch the automatic tuning system. It will scan the meter band and stop for a few second when it receives a strong enough signal. If you are able to perceive a clear signal on LSB or USB then you found a broadcaster. Some radios just have SSB and you cannot choose the side.
Personally, when I buy a radio I always insist on SSB but I have never been lucky tuning in an SSB signal. I keep trying once in while.

Jun 23, 2011 | Grundig Satellit 800 AM/FM/SW Radio

1 Answer

Galaxy 99 has same frequency 27.185 on am also on upper side and lower side band how come?? thank you


The frequency doesn't change when you change to USB or LSB. Basically the AM frequency takes up a certain amount of space, known as bandwidth, so it could fill in for example use 50 hertz above and below 27.185 giving 100 hertz bandwidth. When you use sidebands the am bandwidth is split in two so the upper side band would use the 50 hertz above 27.185 and the lower side band would use the 50 hertz below. The idea is that twice as many operators can operate without interference.

Sep 17, 2010 | Galaxy Radios DX-99V 40-Channels Base CB...

1 Answer

Wat ar FM,AM,USB,LSB.CW. On a CB radio


FM - Freq. Modulation

AM - Audio Modulation

USB - Upper Side Band

LSB- Lower Side Band

CW- Morris Code

Nov 27, 2009 | Ranger Communications RCI-6900F-25 CB...

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

2 Answers

Uniden president grant stops transmitting wait 1 or2 minutes and it will transmit for a little bit then does it again never lose my recieve thank you for your intrest


i cant afford 20 dollars to fix that radio your add said free i am laid off the old grant will have to waite i am not a teck have no idea what is wrong thank you for your time sorry to bother you ihave a good ole cobra29 that i talk on now grandadmac50@ yahoo.comm

Jan 30, 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

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