The am carrier seems unstable and when I transmit on upper or lower sideband there is a warble or like an under water sound coming out of the tranamit audio
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Galaxy Radios Master
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Re:
You will be better off taking this to a tech considering it is a ham radio also. he can set the freq and put it on a distortion meter also to find out the problem.
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Each channel is a AM carrier frequency which is the center frequency of the channel. Each AM frequency has two sidebands, a lower sideband which is the below the center frequency (AM) and a upper sideband which is above the center frequency.
See the following for some explanation of sidebands: https://en.wikipedia.org/wiki/Sideband
Hope this helps and 73
Jim
This Galaxy was built as a CB to run on AM (11 Meter). The majority of people on the CB run AM stations. Sideband (upper and lower) is where the carrier is removed and the wave being transmitted on is cut in half. You can do this just fine but mainly if you want to talk to someone and you both know your going to be on Sideband for a little privacy. 38 LSB is a great channel to catch some DX side band on world wide. But yea, AM is the best to find people to chat with.
If you have any comments please feel free to leave them here.
Well, AM is Amplitude Modulation and Sideband suppresses the carrier and uses only the top half (upper sideband) or lower half (lower sideband) of the wave.
Whether using AM, USB or LSB you are on the same frequency although if someone is on USB and you are on LSB you will not be able to understand what the other person is saying because you are using different parts of the wave. So 27.185 (channel 19) on AM, USB or LSB is still 27.185.
If you have further questions please let me know.
If you have any comments please feel free to leave them here.
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.
26.965 MHz21.27.215 MHz
26.975 MHz22.27.225 MHz
26.985 MHz23.27.255 MHz
27.005 MHz24.27.235 MHz
27.015 MHz25.27.245 MHz
27.025 MHz26.27.265 MHz
27.035 MHz27.27.275 MHz
27.055 MHz28.27.285 MHz
27.065 MHz29.27.295 MHz
27.075 MHz30.27.305 MHz
27.085 MHz31.27.315 MHz
27.105 MHz32.27.325 MHz
27.115 MHz33.27.335 MHz
27.125 MHz34.27.345 MHz
27.135 MHz35.27.355 MHz
27.155 MHz36.27.365 MHz
27.165 MHz37.27.375 MHz
27.175 MHz38.27.385 MHz
27.185 MHz39.27.395 MHz
27.205 MHz 40. 27.405 MHz.
If you have any comment please feel free to leave them here.
check tr 51 (Q 51) the sb754 on the back side mounting of the radio.. the center pin (collector) of this modulator ic should not be 13 volts. my bet is that it is.. this test is done in am mode.. not sideband. depending on you carrier setiing it should be between 3 -8 volts any higher in am mode and my bet is that its bad... much more common than the finals in this radio. good luck Rick
im not sure carriers are measured in pounds, but SSB is a supressed carrier mode, in SSB only one sideband is transmitted and the carrier is inserted at the other end in the receiver. In AM mode the carried and both sidebands are transmitted. with regular am there is a carried and when modulation (your voice) is added a signal appears both above and below the carrier frequency at a distance relative to the frequency of your voice. so if you have a carrier at 1000 khz and modulated it with a tone of 100 hertz the signal will contain frequencies of 900,1000, and 1100 hertz, then its changed to SSB by supressing the carrier (1000) and one sideband (1100) if you are on lower sideband and (900) if you one upper sideband, and transmits the remaining frequency.
Is the squelch off? Is there even a crackle from the speaker? Does it appear to go into transmit?
If you have a friend can listen in while you try transmitting, get him to let you know if voice can be heard, or a carrier appears (on AM). If TX OK, try sideband, if OK, look for faulty speaker/ socket/ wiring. If no audio on TX, suspect the audio amp is bad.
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.
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