Question about Cobra 29 LTD CB Radio
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Posted on Jan 02, 2017
SOURCE: CB transmission
Make sure the radio is grounded properly and that the SWR is around 1.2:1, 1.3:1 is good but try to get it to 1.2:1. Also take a power output reading while keying the mic. To do this with your power meter put it in-line with the CB and your antenna and key the mic you should get about 4 to 5 watts PEP. If this is the case your unit is putting out the proper power level, if not have the power amplifier checked by a qualified repair shop.
I hope this helps
Posted on May 14, 2008
Try making sure the RF gain is up all the way. Make sure all connections are good and tight, use the best antenna you can get. I love the 102 inch steele whip myself, just depends on what vehicle it would be on. conditions here the last few months have been pretty good for 10 meter ham and other ham bands, pretty bad for cb because so much skip/
Posted on Jul 29, 2009
make sure the RF gain is all the way up, and the dynamic is all the way up or most of the way up.
When you say the antenna is good, have you checked the SWR's and or have tuned the antenna to be the correct length for the radio? If this has not been done ever, your radio could be a brick.
Also, make sure the PA/CB switch is on CB. if its on PA(public address) it will not receive or transmit because it is on PA mode, which if you have one hooked up, a PA speaker, then you can talk to people through it out side your car.
Also, make sure the S/RF SWR CAL switch, its the first one on the left, is all the way up on S/RF. this is your signal/ receive setting for the meter. When you hold the key, does this needle swing forward? As well does the RX/TX light turn red? If it does, then the radio is transmitting.
There is another light on the radio under the TX/RX light. It is the Antenna warning light. If this light comes on when you transmit, or has come on all the time during transmit, and now it doesn't then the radio is a brick. That is a warning light. It means that the antenna is not matched, or has not been tuned to the radio. If this has not been done ever, you have killed the radio.
Here is why. When you transmit, you are sending off a radio wave. This radio wave, at 27mhz, is about 36 feet long. In order for the wave to radiate off the antenna, the length of the antenna has to match the length of the radio wave. Now it does not have to be a full 36 feet. It can be an exact multiple of 36 feet. In other words it can be 1/4( one quarter) or 5/8(five eights) of a wave in length. 1/4 of a wave is 108 inches, or 9 feet long. Your antenna is still probably does not seem 9 feet long, but there is usually a loading coil that is not exposed making up the rest of the length of antenna, so that it matches the length of the radio waves electrically. If you were to stretch the coil out with the antenna whip, it would be 9 feet long.
When the antenna does not match the wave length, part of the RF energy does not leave the antenna, and goes back down the feed line(coax) and hits the transmit transistor. Prolonged reflection to the transmit transistor, otherwise known as the final will blow it out. As well depending on how bad the length was off, the more off, the more reflect energy, the more RF energy you are blasting back into the radio, and this causes more things then just the transmit to blow out. Some time the receive goes along with it when it finally goes.
So if the RF gain is up all the way, which by the way is basically how much receive you have, and there really is no reason to have it down at all, and the CB/PA switch is on CB and the needle does not swing forward when its on the S/RF setting, chances are that the radio is now no good.
It is fixable, but if there are no CB shops near you then you will have to send it out. And Cobra will not cover this under warranty because its stated in their warranty that they do not cover damage due to high SWR.
Posted on Apr 06, 2010
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