CAN THE LEGNTH OF THE COAX COUSE THE SWR TO BE HIGH

first of you have to set the SWR on the radio first . then some liniers require you to run low wattage and others high wattage . the SWR is what you have to control by keeping it low . You must take into consideration the length of the coax plus any jumpers you have . You say you have 18 ft of coax plus a 3 ft. jumper ,thats 21 ft..You should keep that jumper as short as possible ,like 12" . plus you should make sure the antenna is grounded good , like to a good spot under the vehicle . 102 " whips are supposed to be almost perfectly tuned for a good match .

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Generally, high SWR relates to an antenna problem. It could be as simple as the coax connector isn't tight enough. You could have damage to the coax cable, or the antenna may be damaged due to wind, or water in it. If you have access to an antenna analyzer, it will help you troubleshoot your antenna and coax, if not, start with a thorough visual inspection, looking for damage, cracking, or water infiltration.

Then there should be an internal unit problem in the swr detector line like a bad diode or a bad connection between it and the output coax connector.

Check the coax cable and connectors for damage / solder bridges and replace / repair as needed. Make sure the cable isn't getting pinched anywhere - use a thinner, low loss cable if needed to avoid pinching.

you have no power because your radio is not tuned to your antenna.You get a new radio and put junky coax and a decent antenna and you expect it to work right. Get 75 ft of rg-213 and you will see a change.

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!

All CB radios use a loaded antenna to match impedance of 52ohms from radio to the antenna.

Mobile and home antennas with a meter (swr) are adjustable for the lowest possible reading----1 to one or up to 2 to one readings indicate a useable antenna.

Readings are adjusted by adjusting the antenna for the lowest reading in the middle of the channels (19 or 20) and some radios have the meter for this built into the radio and some do not.

Running a radio at high swr (standing wave ratio) of over 2 to one reflects the transmit back at the radio and can damage the radio.

let me know if more specific questions

IF YOU CANT RECIEVE THAT IS A VERY GOOD SIGN THAT YOUR SWR MATCH IS OFF....I DONT KNOW IF YOU MATCHED UP YOUR RADIO WITH YOUR ANT.IF NOT YOU CAN BUY A CHEAP SWR METER @ RADIO SHACK...CHECK THAT YOUR COAX CABLE IS OK TRY TO REPLACE THE COAX......GOOD LUCK

have you checked the coax connectors? It's gotta be a bad connector,damaged coax or a defective antenna. Careful--don't test "too much" or you'll burnout the final amp!