Question about CB Radios

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New radio does not receive or transmit

The radio also does not let me check the swr with the built in meter. I wondered if something went wrong with the antennas so I reinstalled an old cheapo radio that I had in the garage and it seems to work fine, but I don't think the problem is with the radio. This new radio is an exchange for an identical radio that I could only get to work for a while then it would not receive or transmit either, even though the swr meter was reading between 1 1/2 &2 on channels 1,19,&40. I called cobra tech support several times and they just had basic suggestions. Any help would be appreciated. I drive otr and really need a good radio this time of year. THANKS!

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  • AnyMHz.com
    AnyMHz.com May 11, 2010

    what kind of radio is it? and double check your antenna mounts make sure its install correctly. but if this is second radio prob.. let us know what model it is. Or visit the radio shop in temple, tx www.radiotx.com.... they can help too.

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Buy an old 148m the new ones are junk

Posted on Dec 06, 2008

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How do I adjust my swr on cOnex 3300


SWR is adjusted at the antenna. I am not sure how familiar you are with SWR so forgive me if I repeat something you already know.
The first thing you need is a way to measure SWR, an SWR meter. Theses can be found on ebay or elsewhere. The SWR meter attaches to the radio with a short coax cable of about 2 feet or less. The other connector on the SWR meter goes to the antenna coax. Once hooked up you should see a switch that reads forward and reverse or abbreviations of such. Place it in forward position. Now there should be a knob adjustment that you can turn. You key the radio, meaning press the mic button to transmit. While holding the button and transmitting adjust the knob on the SWR meter until it reads exactly full scale. After you have done that flip the switch to reverse while transmitting and read the value shown. At the low end it should read 1,2,3,4 etc. If you are lucky it should be between 1 and 2. If so say it is 1.5 then you can say your SWR is 1.5:1 which is ok. If you had a 2.0:1 Swr you would be losing only 11% of your power, giving you 89% still going out the antenna. 3.0:1 would be a 25% loss and so on. Really not that big of a deal. But some radios need better than that or they will reduce their power slightly or not at all if its too far off meaning something is terribly wrong with the coax or antenna. If its less than 2.0:1 I would just leave it alone. But if you find in reverse that the meter goes way over to the right, then you need to find the problem. a shorted or open coax or same with antenna. If you are ok with swr but just want to play and dial it in better than all you do is raise and lower the antenna ever so slightly by loosing the set screw at the base of the antenna. Make sure you mark the old spot in case you need to return it back to that position. Now on other antennas there will be an adjustment at the very top of the antenna that can be turned. Like a carbon ferrite type of screw inside the antenna. This is of course for a short antenna. If you are using a 1/4 wave whip which is the best to use in my opinion kit is around 102 inches long. gives you more range and better receive. If you drive a truck then that is out of the question. But somthing that is overlooked is the fact when you take the meter out after you are done checking the SWR. Your SWR will change and wont be what you just had with the meter in line. So leave meter inline or do this: Most meters have a field strength option. What you do is attach a small wire antenna to the SWR box where there is a small screw hole for it to attach. If you dont have an antenna make one out of a bout a 10 inch stiff copper wire. In this test you will not be hooked up to the cb radio with your SWR meter. Hook you cb back up just to the antenna coax to your antenna. Key the mic again to transmit, tape it into place to hold it there. Now put the swr meter on forward or field strength if if has a selection for that. Now walk away from your antenna about 10 feet so with the adjustment turned up all the way for full meter deflection on the swr meter you should see it get stronger as you get closer to the antenna or weaker as you move away from it. You are actually seeing the power coming from the antenna. You can now set you meter on something away from your antenna where you can see the meter but dont have to hold it. Note the reading. Go back to the cb and stop it from transmitting. You can now make adjustments to your antenna then transmit again and look at the meter. Did it go up or down? Ideally you want maximum meter deflection for maximum power. I f you hook up the swr meter again with cables and it shows something other than 1:1 doesn't matter because like I said once you take the meter out or put it in the swr changes. you are changing the length of the coax. What matters is maximum power right? That's what most people try to achieve by adjusting swr. But like I said on that too, really you wont be able to tell the difference on the receiving end of somebody elses CB when you are talking. To be real you would have to 4 times your power in order for the s meter to go up one s unit on your buddys receiver while you are transmitting. So don't get lost in in all the CB hype of other peoples theory of how important swr is. Your radio is looking for about 50 Ohms of value to work as it should. a 2.0:1 swr would say that it is seeing either 25 Ohms or 100 Ohms. The coax cable should be rated at 50 Ohms meaning if there is 50 Ohms t the other end the coax will be 50 Ohms if you were to measure it at any point on the line. But if there is anything different, then these rf waves travel from your radio to the antenna where if not 50 Ohms will not consume or output all the power at the antenna and the result is waves not going out will come back toward your radio, hence the reverse setting where you are seeing this happen. This can be so involved and yes just because there might be 50 Ohms at the antenna doesn't mean the antenna is resonating at the right frequency. This is why the field strength is important too. The value where the coax meets the antenna ideally should be 50 Ohms but it can be anything because of the design and length of the antenna. So you see you can be moving the antenna in and out to make it 50 Ohms but at the same time you are changing the frequency it wants to emit the best too which could be different. So to say the swr can be off a little if you get more power coming out of the antenna. Sorry for such length but hoping it makes more sense for you.

Jul 17, 2016 | CB Radios

1 Answer

How do you calibrate a uniden pc68xl which has a built in swr meter but no calibration button?


That is not a built in SWR meter. The meter on that unit only measures S which is signal strength and relative transmit power.

Sep 04, 2013 | Uniden Bearcat Pro PC68XL CB Radio

1 Answer

I have a Cobra CB Radio and was wondering if I have it on SRF or SWR or CAL


S/RF/SWR/CAL SWITCH. When in the S/RF position, the meter swings
proportionally to the strength of the received signal. When transmitting,
the meter indicates relative RF output power.
When in the "CAL" position, the SWR meter can be calibrated by adjust-
ing the "SWR CAL" control to the "CAL" mark on the meter face.
When in the "SWR" position, the standing wave ratio is measured.

You will want to operate on S/RF position.

Jul 14, 2011 | Cobra 29 LTD CB Radio

1 Answer

I just need to know how to use it for conversations and what every turn dial means.


you need to hook this up to an antenna. If you are putting it in a car, you need a mobile antenna, if in a house, you need a base antenna. The antenna needs to be tuned for best SWR or you will damage the radio.

Starting from the left of the radio.

Knob 1. Volume/ squelch. The little knob does the volume of what you hear. Big knob squelches out static noise.
knob 2. Dynamike. This is the volume of your voice transmitted. Its how loud people hear you.
Knob 3. RF gain. This is the receive sensitivity. The higher you turn this, the further you can hear. There is almost no reason for you to have this anywhere but full.
knob 4. Delta Tune. This knob should be in the center. If you encounter some one transmitting off frequency, you can move your receive up and down frequency so you can tune that person in. It does not effect your transmit frequency.
Knob 5. CAL. This is to calibrate the meter for taking an SWR reading off the antenna.

Switches starting form the left.

Switch 1. Meter switch. S/RF - will show on the meter, Your signal going out when transmitting, and the signal coming in while receiving. SWR - will show on the meter, your SWR on that channel after you have calibrated the meter. CAL - This is used to calibrate the meter in conjunction with the CAL knob.

Switch 2. ANL - Automatic noise limiter. - This gets rid of electrical interference noise from the vehicle, or other interference sources. ANL/NB - This is the same as ANL, but with NB "noise blanker" This function blanks louder noises that may make it hard to hear people. It's kind of like an automatic squelch, but not nearly as effective as the actual squelch. Also, NB will lessen your receive in that, really low signals will be blanked out.

Switch 3. CB - the radio is in CB mode. This is the normal operation mode of the radio. You can transmit and receive as normal. PA "Public Address" - If you hook a PA speaker to the PA jack in the back, you can mount the speaker on the out side of the vehicle, and talk over it (Its loud). Also, anything you receive over the radio when not holding the mic key, will come over the PA speaker. This is useful when you are not in the vehicle, and need to hear when some one comes on the radio.

Switch 4. BRT and DIM - this is the brightness of the meter light and channel display. BRT stands for bright.

Switch 5. Normal and CH 9, When the switch is in the normal position, everything is normal, but when you flip it up to CH 9 it instantly puts you one channel 9 with out having to turn the dial. CH 9 is the international emergency channel. So it lets you go to Channel 9 quick. when you put it back to normal it will put you on the channel you were on.

Meter explanation. - You have 3 horizontal lines on the meter. the top line is your SWR (only when in SWR mode on the switch. The next one down is you Signal going out. And the bottom one is your signal coming in, in DB's. ***Also noted that part of the SWR line has a CAL )calibration mark. When you have the switch in CAL, and key the mic, you turn the CAL knob up until the needle is at CAL triangle, and then put the radio on SWR and key it. where the needle falls, on the top line is your SWR. If it is in the red your antenna is not tuned, and you can damage your radio.


HERE IS HOW TO TUNE YOUR ANTENN:



It is important to tune your CB radio antenna to the proper length. The length must exactly match the wavelength of the frequency you transmit on. Or be really really close.

All Cb antenna's have a way to adjust the length of the antenna. If it's a mag mount, the metal whip can be slid in and out of a metal collar. Usually a set screw. If its a fiberglass whip, the way to tune it is on top. It either has a small metal rod with a set screw to adjust the length, or it threads in and out to adjust length.

Either type you have it will need to be adjusted for proper length. Here is how to tune the antenna to lowest SWR.

Some radios have a built in SWR meter. Some do not. If yours doesn't have an SWR meter, then you have to use an external SWR meter. Radio shack carries one, and you can find them cheap on ebay.

If you have a built in SWR meter or external, the procedure is the same:

1. Turn the radio to CH 20.(This is the center of the band.)
2. Switch the meter switch to CAL. (CAL stand for calibrate.
3. Key the radio. (Important. Do not talk while keying the radio.)
4. turn the CAL knob up until the meter hits the CAL mark.
5. Now while still keying the radio flip the meter switch to SWR.

Where the meter falls after that point is you SWR reading. If its above 3, that is real bad. 2 is not gonna kill your radio but its not the greatest. 1.5 and under is a good place to be, but the lower the better.

If your SWR is high, Here is how to find out if your antenna is too long or too short.

1. Turn to CH 1
2. Repeat SWR procedure. You must calibrate every time you do it.
3. Remember the SWR reading.
4. Turn to CH 40.
5. Again repeat SWR procedure.
6. Compare the reading between CH 1 and CH 40.

Now if the SWR is higher on channel 1 then channel 40 your antenna is too short. You must make it longer.

If the SWR is longer on channel 40 then on channel 1, then the antenna is too long, you need to make it shorter.

Make height adjustments about an eight inch at a time, and take reading each time.

once the SWR is significantly lower and the reading on channel 1 and 40 are about the same, you a about matched. At this point turn the radio to the center of the band, channel 20 and take an SWR reading.

You should now have a low SWR reading, 1.5 or under. If you are 1.5 or under, you are good to go.

If you cannot get the SWR to an appropriate level, there may be an antenna problem.

Nov 12, 2010 | Cobra 29 LTD CB Radio

2 Answers

Radio will "receive" but not "transmit". Radio, antennas, and wiring are all less than two years old. Should I try a new mike?


Firts you have to check for carrier.For this you need an swr meter.2) Check continuity between the pl259 tip and antenna.3) Check for modulation (voice) if all of the above are OK. 4) Check if your display changes to transmit when you press the mike. IF all fails,then try another mike.

Jan 27, 2010 | Cobra 29 LTD CB Radio

1 Answer

TO SETUP MY SWR, SHOULD I USE THE METER IN THE RADIO OR AN EXTERNAL SWR METER . THE SET IS THE NEW 29LTD BT. ALSO AT TIMES THE ANT LITE COMES ON WHEN TRANSMITTING. IS THIS NORMAL?


Always use an external meter to set SWR. If the ant. warning light comes on it indicates a problem with the SWR. Check it with external meter.

Oct 19, 2009 | Cobra 29 LTD CB Radio

1 Answer

I have a cobra 25 ltd and when i key the mic the gauge of the db barley goes up. is something wrong ? also the gauge says its measuring tx power what does that actually mean/ do


TX means transmit. There are 3 settings for the meter. The top one is to measure your TX/RX that's transmit and receive. CAL is to calibrate the meter to check your SWR.

Reasons your needle may not be moving much when you key while on TX/RX. The dynamic is probably all the way down. That is your mic gain. If you turn that up when you talk the needle will swing more. If the radio is stock and not modded, you can turn this all the way up and leave it.

Also there could be something wrong with the mic. If people can hear you then its not the mic.

If people can hear you fine when you transmit, it may just be a bad meter. Not a big problem, you will just need an external meter to make sure you swr is not high.this is important because if it is over 1.5 you run the risk of blowing the final transistor.

Oct 11, 2009 | Cobra 29 LTD CB Radio

1 Answer

Matching c b antenna with c b radio


here is some information that will help you test SWR with an inline watt meter. To get proper results you need to use an inline watt meter. Here is a really good site you can go to for help www.cbradiotalk.com

Equipment needed: SWR meter, short jumper coax 3 foot.
midland.jpgProcedure: The SWR meter needs to be placed in line between the antenna and the CB. Connect the antenna (normally connected to the back of the CB ) to the connector marked "Antenna" or "Ant" on your SWR Meter. Connect one end of the short jumper coax to the "transmit" or "Xmit" on the SWR meter. Connect the other end of your jumper coax to the CB.
Assuming you have a standard SWR meter the switches should read as follows: REF or SWR, FWD, and there should be a slide switch marked "set" or "Adjust". If different consult your meter's owners manual.
With the radio on the lowest channel (1 on CB) and the SWR meters switch in the Forward (FWD) position, depress the transmit switch (key up) located on the microphone. While holding the unit in this transmit mode, adjust the meter needle to the set position using the Set or Adjust knob on the meter. As soon as the needle is in alignment with the corresponding mark on the meter face, flip the switch to the Reference (REF) position. The meter is now showing your SWR on channel one. Note the value and quickly release the microphone switch. Record this reading.
Repeat the previous step on channels 19 and 40.
How to read your results: If SWR on channels 1, 19 & 40 is below 2.0, your radio can be operated safely.
If SWR on all channels is above 2.0 but not in the "red zone" (normally over 3.0), you may be experiencing coaxial cable reaction (bad quality, wrong length, etc.), insufficient ground plane, or have an ungrounded antenna mount.
If SWR is in the "red zone" on all channels, you probably have an electrical short in your coax connectors, or your mounting stud was installed incorrectly and is shorted. Do not operate your radio until the problem is found, serious damage can occur to your radio.
If SWR on the lowest channel is higher than it is on the highest channel, your antenna system appears to be electrically short. Your antenna length may need to be increased.
If the SWR on channel 40 is greater than that on channel 1, your antenna is considered to be "LONG" and reduction of physical height and/or conductor length will correct this situation.


Aug 01, 2008 | Cobra 29 WX NW ST 40-Channels Base CB...

1 Answer

John Q president cb


Hi,

If by calibration, you are referring to the check if your antenna is tuned, below information may be of help.
S/RF/SWR/CAL SWITCH. When in the S/RF position, the meter swings
proportionally to the strength of the received signal. When transmitting,
the meter indicates relative RF output power.
When in the "CAL" position, the SWR meter can be calibrated by adjusting
the "SWR CAL" control to the "CAL" mark on the meter face.
When in the "SWR" position, the standing wave ratio is measured.

SWR METER. Measures standing wave ratio of the antenna system.
Used to properly adjust the length of the antenna and to monitor the
quality of the coaxial cable and all RF electrical connections. If there is any
degradation whatsoever in any of the foregoing, due to humidity, salt
spray, vibration or corrosion, the SWR meter reading will rise, thereby
indicating that a problem exists.
To calibrate, switch to the "CAL" position, transmit by pressing the mike
switch, and adjust the SWR control to the "CAL" mark on the meter; then
switch to "SWR" position for the SWR measurement.

If however you are referring to the internal calibration or tuning of the transmit and receive sections, you would need several instruments/equipment such as RF generator (0-30Mhz with 1Khx modulation), Spectrum Analyzer, Modulation Scope, Dummy Loaded Wattmeter, Frequency Meter and some others. These of course are not readily available to the average user.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.

Jun 12, 2008 | Cobra 29 LTD CB Radio

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