SWR Adjustment

Common CB Questions Continued


Continuing from our previous post about CB Radio Commonly asked questions we get to daddy of them all !!!!
How do I adjust my SWR and whats it all about?

Put the hammer down here we go!!!

SWR (standing wave ratio) is a term every CB'er should know. SWR shows you how well your coax, antenna mount, ground plane and antenna match the output capability of your CB radio. It is a ratio of maximum voltage or current to minimum voltage or current. Generally speaking, the lower the ratio the better. Defective or inferior components, bad installations and antennas not tuned to the specific location on the vehicle increases the SWR. You should strive to achieve a ratio below 2:1 on all channels. An SWR Meter is required. You should never key up your radio if your SWR is 3.0 or above.

Tools needed to check SWR

1. SWR Meter there are many types to choose from some CB Radio have the SWR meter built in. For Simple adjustment we would suggest a simple and easy to use meter like the PDC1 or PDC7 from Valor. SWR meters are available with many different features we will not go into now.

2. Jumper Coax Cable you will connect this from the SWR Meter to the CB Radio's antenna jack. Normally about 3'.

3. Depending on the antenna you are using read the instruction on how to tune your particular antenna. Some require you to cut or lengthen the antenna other will have an adjustment you can make on the antenna.

Let's Check that SWR

1. Connect your SWR meter between the CB output and antenna input. Your meter should have some type of indication like TX or ANT. Using your jumper cable connect your SWR TX to the CB Radio's Antenna jack. Then connect the CB Antenna cable to the ANT or other on your SWR Meter.

2. Any SWR meter you have should have a FWD & REF/SWR switch. The meter will also have a knob or control that reads Set/Adjust check the instructions that came with your Meter for details in operation.

3. With the radio on Ch. 1 switch the SWR meter to the FWD position, key the cb microphone.
The radio should be transmitting
Using the SET/Adjust knob on the SWR Meter rotate until the meter needle points/lines up to the Set or CAL position, this depends on the type of meter you are using.
Once lined up flip the FWD/REF to REF or SWR position. You are now reading the SWR value on ch. 1, make a note of the reading 1.5, 2, 3, didn't move etc.. release mic button to end transmission.

4. Now tune the radio to Ch. 19 and repeat the above steps. make a note of your readings

5. Now tune the radio to Ch. 40 and repeat the above steps. make a note of your readings

Understanding the measurements your just took.

If SWR on channels 1, 19 & 40 is below 2.0, your radio can be safely operated on any channel you are good to go take the meter out and connect your antenna back to the radio, your ready to talk!!!

If SWR on all channels is above 2.0 but not in the "red zone" (normally over 3.0) can be caused by coax cable length, bad antenna ground plane, or your antenna mount is ungrounded.

If SWR is in the "red zone" (normally over 3.0) on all channels, you probably have an electrical short in your coax, or your mounting stud was installed incorrectly and is shorted. You will need to find and correct the problem before operating your CB Radio, this can cause damage to the radio.

If the SWR on channel 40 is greater than that on channel 1, your antenna is to long shortening the antenna should correct this situation. Refer to your antenna's tuning instructions on the proper way to achieve this.

If SWR on channel 1 is greater than that on channel 40, your antenna is to short increasing the length of the antenna should correct this situation. Refer to your antenna's tuning instructions on the proper way to achieve this.

Of course we could go into even more details but this should be enough to get your SWR checked and adjusted.

More helpful tips and product information coming stay tuned and visit us online at www.buyreliant.com