Question about Cobra 19 DX IV CB Radio

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My radio off frequency

Well just yesterday i was at the shippers,and the security moniter channel said that she could not understand what i was saying that i was breaking up rwally bad,so i started to try and correct it by turning my squelch and rf gain knobs,i tried it again and she said it was a little better,at that time i was still holding my mic button not realizing that i had just turned the channel knob by accident,and when i released the mic it was still on channel 3,then as i was leaving i went back to ch.19 and did the same thing again turning the ch.knob while holding the mic button,so then i asked for a radio check and the guy came back saying my radio was off frequency very bad,so how do i resolve this problem? My radio is a cobra dx 19. Thanks

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Re: my radio off frequency

To do it right, you'll need a watt meter, a frequency counter that reads atleast 4 digits to the right of the decimal point and a dummy load.
Connect the antenna connector from the back of the radio to the watt meter, to the freq. counter, to the dummy load. Connect the power leads to a decent power supply or atleast a charged 12 volt battery. (All of this applies only if you are in the U.S.A. or Canada!!!) Turn the radio on and tune to channel 1. Key up and ideally it will read a steady 26.9650MHz. It can read 26.9645 to 26.9655 and still be within FCC regs. Tune to ch. 20 and key up. It should read from 27.2045 to 27.2055. Tune to ch. 40. 27.4045 to 27.4055.
Several important things to take notice of. First, (If you are in North America), This is an AM only radio and there will be no external transmit frequency adjustments. The last 2, (3rd and 4th), digits on the freq. counter should be the same across the whole 40 channels. The 4th digit shouldn't vary by more than 1 number either way. If it reads 26.9649 on ch. 1, it should read 27.4049 on channel 40. If the frequency varies by more than .0001MHz and your power is unusually low on the order of 1 1/2 to 2 watts using a good 3 amp or better power supply, suspect your RF final and / or driver transistors. If the silicon chip in either of these transistors is cracked, it can still work but at reduced power while throwing out a wide range of harmonic frequencies draining power from your CB channels and that will bring the FCC, (in the U.S.), knocking on your door in short order.
If the freq. counter reads 26.9675 or 26.9625 or any combination of the last 2 digits like .9622, 9672 ect, on ch. 1 and reads the SAME last 2 digits up through the band to ch. 40, (27.4025, 27.4075 ect), then you can suspect the only crystal in the radio. Sometimes there is a small plastic variable capacitor next to the crystal. It looks like it has a SHINEY metal straight or philips screw in it's center. It can be red, blue, green, black or most any color, about 1/4 the size of a #2 pencil eraser. It will be right next to a small oblong shaped metal can anywhere from 1/16" to 1/2" tall. USING A PLASTIC SCREWDRIVER, key up on ch. 20 and adjust this part to bring the frequency to 27.2050 or as close as you can get to it. When you get there, start at ch.1 and key up, 26.9650, 2=26.9750, 3=26.9850, 4=27.0050. THIS IS NOT A MISTAKE!!! There is a 1 frequency skip between channels 3&4, 7&8, 11&12, 15&16 and 19&20. Channels 23, 24, & 25 will read 23=27.2550, 24=27.2350, 27.2450 then things straighten out with ch. 26=27.2650 ---40=27.4050. When there were only 23 U.S. channels, the skips between chs. 22 & 23 were referred to as 22 a & 22b. These were at one time business band channels that, with the proper license, could run up to 30 watts. All 23 ch. radios had 22a but was shorted out inside and it's space was sometimes used as a quiet spot for the PA speaker. The other 5 skips below this are still used today as radio control freqs for less expensive R/C toys. So much for CB history. ONE OTHER VERY IMPORTANT POINT!!! Make no other screw driver adjustments inside this radio!!! You can mess up your receiver, squelch, RF gain, transmit frequency, or reduce power output The bottom line here is the last 4 digits should follow the pattern laid out above. If you can't get the frequency tuned in, replace the crystal with the identical frequency as the one in the radio. Usually 10.240 MHz. Don't get any fancy ideas about changing freqs to the illegals in these radios. Changing this crystal a little bit up or down will change the freqs. but there will be no rhyme or reason to the new freqs you get. That 10.240 crystal not only controls the CB channels, it also controls channel spacing too. If you get ch. 20 to change to say 27.605, ch. 1 won't be 27.415 and 40 won't be 27.805. It's not worth the effort in the cheaper radios. It takes moving up to the Cobra 148 SSB or it's Uniden clones or the exports before you'll ever get it right.
I've rattled on long enough.
Good luck,
Jeff Mc.

Posted on Feb 03, 2011

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Re: my radio off frequency

You can't just trust what another truck driver tells ya. If you think it is off frequency, I would run it by a cb shop and ask them to check all the channels to see. Any cb shop should have a frequency counter that they can check it by.


Posted on Jan 26, 2008

Re: my radio off frequency

Is this set AM and the recievers FM? if so there will be no way round the 'problem' BOB

Posted on Apr 19, 2007

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I\'m assuming you\'re talking about converting an old 23-channel CB to a 40-channel radio.

You didn\'t specify what kind of CB you have so it\'s impossible to say for sure, but it\'s highly unlikely that this can be done cost effectively.

Most 23-channel radios used a set of 14 (6 base + 4 transmit + 4 receive) crystals whose frequencies were added together to result in the specific CB channel you were wishing to use.

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Tabla de frecuencias

CB Radio Channels (FCC)[32] Channel Frequency Channel Frequency Channel Frequency Channel Frequency 1 26.965 MHz 11 27.085 MHz 21 27.215 MHz 31 27.315 MHz 2 26.975 MHz 12 27.105 MHz 22 27.225 MHz 32 27.325 MHz 3 26.985 MHz 13 27.115 MHz 23 27.255 MHz 33 27.335 MHz 4 27.005 MHz 14 27.125 MHz 24 27.235 MHz 34 27.345 MHz 5 27.015 MHz 15 27.135 MHz 25 27.245 MHz 35 27.355 MHz 6 27.025 MHz 16 27.155 MHz 26 27.265 MHz 36 27.365 MHz 7 27.035 MHz 17 27.165 MHz 27 27.275 MHz 37 27.375 MHz 8 27.055 MHz 18 27.175 MHz 28 27.285 MHz 38 27.385 MHz 9 27.065 MHz 19 27.185 MHz 29 27.295 MHz 39 27.395 MHz 10 27.075 MHz 20 27.205 MHz 30 27.305 MHz 40 27.405 MHz

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  • 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.

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