Question about Cobra 29 LTD CB Radio

1 Answer

Cant recieve or output , I bought a new cable and antenna plus a swr meter.

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  • Cobra Master
  • 3,287 Answers

With an antenna connected, volume set to 1/4 from minimum, squelch / RF squelch fully counter-clockwise (or minimum) - do you hear anything from the speaker? If not - plug an earphone / external speaker into the external speaker jack on the rear - any sound? If not, do you see the S/RF meter needle moving (not resting on 0 or 1)? If not - find a channel with activity on as indicated by the S/RF meter first.

Try with another antenna connected if possible, or transmit with another CB radio on the same channel nearby - and try again.

If you aren't able to receive sound (not just static) - or indicated signals on the S/RF meter, the radio *MAY* need to be professionally serviced. Make sure you get an estimate for the work before authorizing - otherwise you may be spending more on a repair than the radio is worth. It is not uncommon to have to pay a diagnostic fee - that most shop will put toward the repair if allowed to do the work.

Good luck!

Posted on Sep 07, 2010

  • Steve Sep 07, 2010

    Let's get the receiver working on this before try to get the transmitter going. The SWR meter is much more useful on the transmit side - receiving (at this point - especially with another radio transmitting close by) isn't as critical for antenna adjustments. If the receiver isn't functioning - it's a waste of time trying to get the transmitter working correctly.

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1 Answer

My swr meter will not calibrate. I put it on fwd, Key the mike, put it on ref,and it pegs the needle. why?


Antenna may have a dead short or is open, there may be water in the cable, SWR is beyond the scale of the SWR meter.
Check all connections, make sure you have the radio and the antenna well grounded. if possible disconnect both ends of the coax cable and test cable with a ohm meter for a short or open.
Test the SWR meter on a known good antenna and cable if possible.

Oct 16, 2014 | Radio Communications

1 Answer

I have a galaxy dx48t it has no calibrate on the SWR meter, how do I check my SWR?


Best way to check your SWR is with a separate SWR meter installed between the radio and the antenna. Be sure to check the input and output sides of the meter. With the meter in-place, key up your radio and adjust your antenna for max output / minimum loss. This may require that you change the length of your antenna and repair any questionable connections. Also, be mindful of the fact that CB radios broadcast in AM. That means your antenna should be well grounded to your vehicle. AM radios rely on "ground plane" antennas, which means that your entire vehicle (with good grounding) becomes apart of the antenna system. Hope this helps.

Jul 09, 2014 | Radio Communications

1 Answer

1 mile range on cb


Check cables and connectors.

• check antenna SWR,

A good SWR ranges from 1.2 to 1.5.

• check power output.

Jul 27, 2012 | Connex Cx-366ce Night Runner 40ch Cb...

1 Answer

Why does my moonraker cb change channels by itself.


This can be caused by RF feedback. RF is radio frequency energy - the same energy that your transmitter puts out onto the coax cable & antenna.

RF feedback is similar to audio feedback in that some of the output re-enters the circuit in a place it doesn't belong or is designed. RF feedback is a direct result of a poorly matched antenna system as shown by an SWR meter. A standing wave ratio or "SWR" of 2.0:1 - 2:5.1 (read this as: two point zero to one and two point five to one) or greater is generally accepted as the worst SWR a transmitter can tolerate - but also requires lowering RF power (wattage) to continue transmitting.

Some common sources of high SWR are: 1) wrong cable type (usually a 50 ohm cable is used), 2) damaged cable, 3) untuned antenna, 4) damaged previously tuned antenna, etc. The SWR of an antenna system should be checked and adjusted as needed to assure maximum power transfer to the antenna. If the system has a high SWR, the antenna reflects some of the RF energy back on the coax - into the radio. The effects can be tingles / burns on the lips - if using a mic with a metal guard, noise, and erratic operation of some rig settings. This energy is unexpected and can cause all sorts of strange radio operations and is not an uncommon occurrence in a situation such as this.

You can correct this problem by purchasing or borrowing an SWR meter or bridge designed to work in the range of frequencies that your CB uses. Follow the directions included to lengthen or shorten antenna elements as needed. An ideal SWR is 1.1:1. Generally, any value of SWR less than 1.5:1 is considered very good. A check of SWR on the low, mid and highest frequencies will give you an idea as to how well the antenna works on the frequencies you use, and let you know which frequencies you should avoid.

Good luck!

Apr 21, 2012 | Radio Communications

1 Answer

C.b. is transmitting weak.


If it is low audio, it could be a problem with your mic or his speaker. If your signal is low, I suspect it is likely to be an issue with your antenna system.

The antenna systen consists of the feedline or coax cable and the antenna. The feedline should be inspected for evidence of damage from being pinched, cut or water entry over its entire length., Remove, replace or reposition to prevent the cable from becoming damaged in any way.

The antenna itself should ideally be located at the highest point on the vehicle. Further, it should be secured to firmly into the metal parts of vehicle - preferable to a large, flat surface. The surface should be grounded.

Matching the antenna system for lowest SWR to the transmitter is required. SWR is a ratio of "power out" of the transmitter to "power that is reflected back" from the antenna. Ideal theoretical ratio or "match" is 1:1 (or one to one). Real-life is more like 1.1:1 (one point one to one). Most transmitters are perfectly happy with a match (or mismatch as the case may be) of 1.5:1 and some even up to 2.0:1. More than this is asking for trouble. A mismatched antenna system can cause RFI and failure of the output final transistors.

Matching or lowering the SWR of a radio to an antenna system requires that an SWR meter be installed between the antenna coax or cable and the transmitter's antenna connection point. There are two types of meters - dual needle and single needle. The dual type is more expensive, but easier to work. The meter must be capable of working on the frequency it is to used on. This means if it is marked as a 400 - 512 Mhz or UHF type, it will probably not be accurate on 27 Mhz or HF.

Once the meter has been installed, transmit the highest frequency or channel and take readings. Do the same at the lowest and a middle frequencies and record findings. Physically adjust the length of the antenna whip up or down in the antenna base - by no more than 1/4" inch (for 27MHz CB frequencies) and check again. After a few tries in one direction, you should begin to see how shortening or lengthening the whip changes the SWR of the system. Once set correctly, the middle frequency will have the lowest SWR value while the lowest and highest frequencies will have pretty close to equal, but higher SWR values. It would look something like this: Ch1 = 1.6:1 Ch 20 = 1.2:1 Ch40= 1.6:1 Of course, if Ch1 = 1.7:1 and Ch 40 = 1.6:1 that would be fine, too. Once completed, the SWR meter can be removed from the antenna system.

A poorly matched antenna system can cause permanent damage to the transmitter, if not corrected.


Sep 21, 2009 | Cobra Radio Communications

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

1 Answer

Cb equipmebnt


Hi,

Connect the INput of the amp to the TX out of the radio. Connect the OUTput/Ant of the amp to the INput of the meter (SWR/Power). Connect the OUTput of the meter to the cable that leads to the antenna.

With this arrangement, you will be able to measure the SWR of the antenna and power output (of the amp) going to the antenna.

Hope this be of some help/idea. Pls post back how things turn out or should you need additional information.

Good luck and kind regards.

Dec 31, 2007 | Cobra 148 GTL 120-Channels Base CB Radio

2 Answers

SWR calibration waaay off the chart


You are using an inline swr meter to set your swr right, not looking at the meter on the radio? Here is the process to set swr on an antenna:

You must have an inline swr meter, which can be purchased online or from a truck stop. The ones at truck stops are cheap ones, but will do the trick for the most part.

You connect your antenna 18ft coax to the antenna plug of the swr meter, and a jumper coax (any length) to the transmitter plug of the swr meter and then to the radio.

Close all doors and make sure no one is messing around with the vehicle or antenna. You must be set up as you would normally be transmitting.

Now set your cb radio to channel 40 and your swr meter to fwd. Key up your microphone1.gif and at the same time turn the set knob on the swr meter until the needle is at the line that reads set. Unkey your mic and set the the swr meter to ref. Key up again and note what your reading is. Now leave the swr meter in ref and turn the cb to channel 1. Key up and take your reading. If the reading on ch 1 is higher than ch 40 you must raise the stinger on your antenna. If ch 1 is lower than 40, you lower your stinger. You are trying to get lower than a reading of 3 and as close to 1.5 as possible. If you lower your stinger as far into the antenna as it will go and you need it shorter, you cut the bottom of your stinger no more than 1/2" at a time, and recheck your swr reading after each cut.

Once you have gotten the best reading you can, connect your antenna directly back to the radio.

The setting of your swrs is to make your antenna as efficient as possible, by trying to get it as close as you can to a 50ohm impedance. THE ONLY PART OF YOUR SYSTEM THAT CAN CHANGE YOUR SWR IS YOUR ANTENNA, not your coax and not your radio. Your radio and coax can give you false readings, but only the antenna can actually change the swr.

On the swr meter, the fwd/ref switch stands for forward (power that is being transmitted out) and reflected (power that is reflected back into the radio.

Just for information sake, the swr cal switch on your radio is used to set the meter to reflect the swr that your antenna is set at. The meter on your radio is like a dummy light on your car. ONCE AGAIN, YOU CAN NOT SET YOUR SWR ON YOUR RADIO, only the antenna.

Dec 29, 2007 | Connex 3300 240-Channels Base CB Radio

3 Answers

Connex 3300hp radio


Hi,

Based on your post/description:

1. how do i set the swr
Normally SWR are calibrated on your operating channel (where you usually stand-by). This is to maximize transmit power and receive sensitivity. To set SWR, switch to channel of your choice, switch SWR control to CAL, key or press PTT, while pressing PTT rotate ADJ knob until max deflection of needle on meter, release mic, switch control to SWR, key/press PTT, needle reading/deflection is SWR for that channel.

I would suspect that your SWR will vary from your current 1.4. This is because you have too big excursion of channels (240 channels).

2.reading a 1.4
This reading is good enough and should do. However as earlier stated, you seem to have 240 channels which would mean that your radio + antenna moves in a wide bandwidth and since the antenna tuning is affected by frequency, your SWR will also be affected by channel.

Best if you can further lower it down.

3. some cb cant get me
This is because the standard CB radio is only 40 channels. The next would be a 80 channel and then 120 channels.

4. is it my radio
Yes, you have a wide coverage radio almost an extended 10 meter rig.

5. do i have to set my radio on high or low to set my swr
I will assume you are referring to power output, set it to HIGH when doing SWR calibration

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

Good luck and kind regards.

Nov 08, 2007 | Connex 3300 240-Channels Base CB Radio

3 Answers

Cb radio


When you asy that you have an swr meter, you are refering to an inline meter, not the one on the radio, correct? Have you set the SWR by the instructions of the inline meter (if that is what you have)? Have you made sure the antenna is mounted to the bracket with the white plastic washer in between the antenna and the top of the bracket? You have checked the antenna coax for a broken center conductor and for a center conductor shorted to shield with a multimeter? Check antenna bracket to ground with a multimeter?

Dean
Rollin CBs

Oct 31, 2007 | Cherokee CBS2100 40-Channels Base CB Radio

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