1. Setting the SWR. Insert the antenna whip 3/4" into the antenna adjustment mast at the top of the coil. Using a good external SWR meter, calibrate on channel 20. Switch back to SWR and record the readings on three channels; 1, 20, and 40. If the lowest SWR reading occurs on channel 1, the antenna whip is to long and must be shortened. Loosen the mast set screws and lower the whip 1/4'' into the mast. Tighten mast set screw's and again read SWR. Repeat until lowest SWR is obtained. If the whip is fully lowered into mast and the SWR is still high, remove the whip from mast. Using a hacksaw, grinder, or bolt cutters, cut 1/4'' from the bottom part of the whip. Re-insert the whip into the mast and test again for SWR. Repeat the above procedure until the SWR is below a 1.5 on channel 27.205 witch is Channel 20. If the lowest SWR reading occurs on channel 40, the antenna whip is to short and must be raised. Loosen the mast set screws and raise the whip 1/4'', re-tighten set screws and test SWR again. Repeat the above procedure until the SWR is below 1.5 of all channels.
2. The whip is raised to the top, but the SWR is still lower on CH 40. This generally occurs on vehicles with very small ground plains, such as the compact cars, cars with hatch-backs, etc. It indicates the need for a longer whip than the standard one supplied.
3.If the SWR on a trunk lid mount is 3.0:1 on all channels. When a reading of 3.0:1 is present on all channels, this indicates a lack of ground for the antenna. For example, some of the vehicles today insulate their trunk lid from the actual chassis or frame, ground of the body. This is done by inserting plastic washers on the trunk hinges, and/or sandwiching a layer of styrofoam type material between the two piece trunk lid. To eliminate this situation, a jumper wire must be installed from the actual bottom lip of the trunk lid to metal on the body of the car. To accomplish this, loosen one of the hinge bolts on the trunk-lid side and install a braided strap. Re-tighten the bolt. Loosen the bolt on the other side of the hinge (trunk-body side). Install the other end of the braided strap to this bolt and re-tighten. Be sure to leave a long enough loop to prevent pulling apart when the trunk lid is fully open. As added ground insurance, you may wish to add a jumper from the set screw on the trunk lip mount to the hinge bolt on the trunk-lid.
4. If the SWR is good until power is applied: The antenna is not the problem. In this case, it is the amplifier. You have already established that the antenna is properly tuned and in good working order with low SWR, except when power is applied. Assume a ham operator is on 10 meters using a solid state amplifier. With the radio only, the SWR is 1.1:1; and when the amplifier is turned on, the SWR jumps to 2.0:1. The amplifier is not only transmitting at 28 MHz, but is also transmitting on a second frequency of 56MHz. This is known as a ''second harmonic'' (2X the fundamental frequency of 28 MHz, transmitting at 56 MHz). The SWR meter is reading both the reflected signal of the normal frequency and the rejected second harmonic. The antenna will not accept energy transmitted at 56 MHz, and returns it back to the radio, which shows up on the meter as high SWR because the meter can not tell the difference between 28 MHz and 56 MHz. In fact, as much as 30% of the power is at 56 MHz. This is generally due to an amplifier that is not adequately filtered. Adding a Low-pass filter at the amplifier output is the only solution. For best results, connect the low pass filter directly to the amplifier using a barrel connector.
5. How low can the SWR be brought down to? Ideally it is nice to get the SWR to 1.1:1, but practically a 1.5:1 works just as well. Some installations will not even allow you to achieve a 1.1:1 SWR because of the grounding of the vehicle, the amount of metal available as a ground plane, and other circumstances. However, the loss with a 1.5:1 (using 18' of coax) is actually less than 1/2 of 1% of your output power, which on a normal 5 watt radio means a loss of .025 watts of power. This means that instead of transmitting 5 watts, you are actually transmitting only 4.975 watts. This is not even noticeable at a receiving station. Therefore, spending the extra time to get below 1.5:1 is purely a matter of choice, especially if you have a high performance antenna. But, what actually happens if your SWR is 2.0:1 instead of 1.5:1 or less? Most CB radios today have protection circuits that starts to shut down (by lowering the output power) when the SWR reaches above 2.0:1. This reduces the output power of the final transistor amplifiers. So generally, anything between 1.5:1 and 2.0:1 is acceptable and useable for good, solid, reliable communications. Readings of 3.0:1 or higher indicates a problem may exist in the system. Check for complete grounding of the system.
Most popele ask what's the distance that they can talk on there new CB radio ?, "There’s good news and bad news. The good news is, sometimes you can talk to someone down the street, or halfway around the world. The bad news is, you may not always be able to talk to someone down the street, or halfway around the world. That is the nature of communications on the CB Radio's. The frequencies that CB radios operate on are affected by terrain, ambient weather conditions, the forever changing height of the ionosphere, sun spot cycles with their radio frequency (RF) interfering magnetic waves, and the quality and design of the equipment. On any given day (or hour of the day) you might find that the person you spoke with can no longer be contacted. And, while you are trying to talk to that person who is two or three miles away, somebody that lives a thousand miles or more away comes in as if they were in the other room. Since it is humanly impossible to change the things in nature that affect all radio wave transmissions, especially those in the CB band, knowledgeable people with honest intentions will not promise the CB user a specific distance that they can consistently communicate over. Of course, dishonest people are apt to tell you anything when trying to separate you from your hard-earned money.
If ask to make an honest statement regarding the distance that one may expect from a legally operated CB, the statement across the industry must read as follows. CB operators can expect a fairly consistent operational range of three to five miles in an area of limited obstructions. Prolonged periods of relatively consistent performance between two or more sites in the five to twenty-mile range is a very common occurrence. Consistent operation between locations beyond twenty miles will most often be sporadic. During the course of any given day, for a period that will vary in duration, could occur at any given hour and be in any possible direction, communicating over hundreds, thousands or even tens of thousands of miles with no more than 4 watts is a very probable possibility. There are many things that a CB operator can do to maximize performance under any set of conditions.
· Adjust the SWR as lo as you can
· Use high quality coaxial cable even 213
· Use a good loaded antennas
· Use 5/8 wave antennas
· Select a longer antenna
· Mount antenna higher
· Use antenna(s) with proven history of performance
· Clean coax and power connections
· Make sure other station has quality components
· Use power microphone on stock radios
· Have radio peaked by qualified technician
CB is meant to be a fun, useful, inexpensive, and unlicensed means of communications for you! a Citizen of the USA. Cost is minimal and airtime is free. If you are aware of the limitations that go along with the frequency, you can expect your CB to perform exactly as it was intended, so long as you do the most that you can do with the pieces you can control. Have fun! CB’ing!
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