Question about Cobra 19 DX IV CB Radio

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Would a slightly damaged co phase coax affect radio transmitting capabilities

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Yes. Co-phasing is very touchy anyway. The co-phase unit needs to be matched and it needs to be in almost perfect condition.

Posted on Apr 27, 2010


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My cb keeps saying antenna warning

The swr is too high. You may have a coax damaged or a bad antenna. Do not operate the radio on transmit until this is resolved or it may damage the radio.

Dec 01, 2014 | Cobra 29lx Cb Radio W/clock 29 Lx Lcd

1 Answer

Will a bad antenna blow to transmit fu?nction. If so, how do you trouble shoot antenna

Yes, if your antenna presents a high SWR to the radio, the finals could be overloaded and damaged. the first thing you should do is make sure the coax is not damaged and shorting. Then check the antenna to make sure the connections are all good.

Oct 18, 2014 | Radio Communications

1 Answer

Repair northstar marine radio

It could be a self-protection circuit activating.

Radios that transmit require a matched antenna for the frequency of operation. A bad coax line from the radio to the antenna or a faulty antenna that would otherwise destroy the radio may trigger a protection circuit inside the radio to prevent damage. Check the coax, and have someone test your antenna with an SWR meter or directional coupler. Good luck

Aug 20, 2014 | Radio Communications

1 Answer

I have a cobra29 LTD Classic and the ant warning led lights each time I key the mike. I have the radio mounted in an overhead dash, the radio is grounded to the truck via the power plug. That ground goes...

A VSWR meter is your best bet. They are cheap for cb's . If the antenna is badly mismatched you will get an antenna warning lamp on. If the antenna has a tuning coil you will see usually continuity to ground from the whip. Use the vswr meter on the radio. Set to calibrate first, transmit on channel twenty while rotating the swr cal knob. set needle on orange triangle at top right of scale. Select VSWR mode and transmit. needle should move up slightly if antenna is tuned correctly. Try chaneel 1 and 40 with same procedure. You can tell if antenna is tuned more toward the high or low frequency by how high the needle is on the scale. The higher the reading the worse the match is. If there is always a high scale reading then try another antenna that you know works.Watch for flattened/damaged/water in between braid and jacket or corrosion on coax as this will change the coax impedance drastically

May 13, 2012 | Cobra Radio Communications

1 Answer

My swr are high with proper calibration

You may need to retune the antenna system if the coax has not been kinked or damaged. If you simply moved it over from the old rig, the antenna was tuned to that layout and the groundplane was the shell of the truck and chassis. The Cobra can tune it somewhat, but the best results are achieved with a baseline adjustment of the antenna. But check the coax for damage first, then check the connections to the antennas. If you are using a baseloaded whip, there is actually an inductor wound that attaches to chassis/coax ground, and it may be corroded. As may the center conductor terminal at the antenna.

If those sheck out okay Check to see if your SWR is higher on 40 than on 1, or if it is higher on 1 than on 40.

if it is higher on 40 than on one, shorten the antenna slightly, first and see how it looks.

If it is higher on 1 than on 40 try lengthen it slightly and see how it looks.

If you are running with dual whips, that complicates matters a little bit due to phasing.

I had set up a radio to be portable from vehicle to vehicle and found changing tuning length was always required when I moved it to a new vehicle. What made matters worse was I chose a cheap Walmart baseload and it had lousy quality coax.

Feb 20, 2012 | Cobra 29 LTD CB Radio

1 Answer

I have cobra cb that is connect to 2 whip antennas in the box of my pickup, and everytime i talk to someone they say im really fuzzy and cant understand me and i cant figure out the problem

First, determine if the sound is related to audio - or signal.

Have someone listen to your AM radio transmission nearby. With an un-modulated carrier, the signal should sound clear. If there is noise on the signal, try with a different mic. If no mic is available, key up the radio by shorting the PTT pins on the jack on the radio itself (this will remove the mic element from the circuit - effectively disabling any audio noise entering from the mic cable or element. If the noise disappears or is significantly reduced, the problem lies with the mic, cable or connections at the mic plug or the inside the hand help portion.

If there is no problem in the above test - then the trouble can be a result of the signal. Signal issues are more pronounced when there is more space between your transmitter and the other person's receiver. If they are close to each other, it will be difficult to hear problems. Things that can affect signal quality - and noise can be: 1) vehicle electrical systems. See if there is a noticeable difference with your signal compared when transmitting with the engine on and engine off. Fuel pumps can be a source of noise, as can ignition noise, alternator whine, etc. A "choke input" filter or a large value microfarad capacitor rated at more than 15 VDC installed between + and - wires can help mitigate these noise sources - but it is unlikely that either will eliminate it. 2) power wiring. Always get power directly from the battery. This is the cleanest source of power available in the truck. You can interrupt the 12+ line with a relay that is controlled by the accessory terminal if you want the radio to shut off when the ignition key is removed it you wish - but resist the urge to use the accessory terminal to power the radio directly. 3) Antenna issues. Dual antenna installations require 75 ohm coaxial cable (co-phase harness) to perform properly. These can be as simple as pinched coaxial cables to improperly tuned antennas. Damaged cables need to be replaced. High quality, low loss, 75 ohm coaxial cable is required for the demands placed on it in mobile situations. Tuning for the lowest SWR or VSWR is a necessity from effective power transfer from the radio and antenna coax to the radiator or antenna. A detailed description of how to can be found here. Be sure to keep in mind the last sentence in the article regarding co-phased antennas: Adjust BOTH antennas to keep them in balance.

Hopefully, one or more of these suggestions will help solve or reduce the problem you've got. Good luck!

Jun 21, 2011 | Cobra Radio Communications

1 Answer

Mini Magnum Radio not transmitting after Final Replaced

Not knowing what kind of equipment you have, its hard to say, but .10 watt? Sounds like the buffer or driver also got involved. Usually you get 1/4-1/2 watt to the driver on a stock radio. I would also check the bias resistors like you suggested. Also check for burnt foil around the final you replaced. Good just be a slightly damaged circuit. Let me know if this helps.

Feb 04, 2009 | Motorola OEM Compatible 6060937H02 Two-Way...

1 Answer

CB Squeal When Transmitting

I believe the coiled coax may indeed be the problem. To check, try a temporary rerouting of the cable which eliminates the coils. Dave g.

Dec 20, 2008 | Galaxy Radios DX-44V 40-Channels Base CB...

2 Answers

Galaxy DX959 CB radio reception and broadcast

You Need to check and set you SWR on the antenna system. You may also have a bad coax or the ant studs ( mounting hardward ) for the antennas may be bad. It definally sounds like an ant/coax problem Good Luck
NC Electronic
Mills, Wyoming

Dec 08, 2007 | Cobra 18 WX ST II 40-Channels Base CB...

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