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CB Radio Antenna Adjustment

Author: Quadna71

Here's a step-by-step method of adjusting the antenna to give you the best signal. It worked like a champ for me - I reached out almost 20 miles while on the interstates this past week. I don't take any claim in writing it - just yanked it off of the net and used it. Maybe this will help someone in getting ready for your next weekend trip.

Your CB/Ham Field-Strength SWR Meter helps you tune your CB or amateur radio system for the best performance.

CB and amateur radio systems work best when the antenna system's impedance matches the transmitter's output impedance as closely as possible. The meter's standing wave ratio (SWR) function helps you trim your antenna to the precise length you need for the maximum transmitted power.

The meter's field strength function helps you position your antenna for the best coverage and determine the effectiveness of changes you make to your antenna, antenna cable, and transmitter.


Measuring SWR shows you how much of your radio's transmit power is reflected from the antenna back into the antenna cable, generating heat and wasting power. With this information, you can adjust the length of your antenna or antenna cable so your antenna and radio combination can produce the maximum power they are capable of producing.


To connect this meter to your CB or amateur radio and your antenna, you need coaxial cable (50 ohm such as rg-8x) with a PL-259 connector on both ends . The cable must reach from the back of the meter to your radio's antenna jack.

Follow these steps to connect the meter to your radio and antenna.

1. Turn off your radio. Then disconnect the antenna from the radio and plug it into ANTENNA on the back of the meter.

2. Plug the coaxial cable into the radio's antenna jack and into TRANSMITTER on the back of the meter.


1. Set CALIBRATION switch on the front of the meter to FWD.

2. Turn on your radio. Then select a channel or frequency on your transmitter and hold down its transmit key. Do not speak into the microphone. Notes: An SWR reading will be different for different frequencies (channels). If you transmit on one channel more often then any other, select that channel. If you transmit on several channels, choose a frequency in the middle of the range of channels you use. (For example, if you transmit on all 40 CB channels, choose Channel 20, because it is midway between Channel 1 and Channel 40.) If you use a CB that has sideboard modes (SSB), do not select any of these modes. (Use only AM for SWR measurements). If you have an amateur radio, select the continuous wave (CW) or tuning mode to check the SWR.

3. While you hold down the transmit key, rotate the meter's knob until the needle points to CAL.

4. Release the transmit key, then set CALIBRATION switch to REF.

5. Press the transmit key again, then read the SWR by noting the needle's position on the upper SWR scale. A meter reading of 1 on the upper scale is ideal. The figure shown between the upper and lower scales on the meter (% REF POWER) indicates the percentage of power that is wasted through reflection of the signal from the antenna back into the antenna cable. For example, an SWR reading of 1.5 also means that 4% of your signal power is lost. However, 96% of the radio power is more than enough for almost all applications.

6. Repeat Steps 1-5 for each channel or frequency you want to get an SWR reading for.


An ideal SWR reading is 1.0, but this reading is usually possible only under laboratory conditions or with a dummy load. Actual antenna installations have higher readings. The information below will help you interpret the readings you get.

SWR / Efficiency / Interpretation

1.0 to 1.3 Excellent The antenna cable and the antenna length match the transmitter's output requirements almost perfectly. (Most desireable for power applications)

1.3 to 1.8 Very Good - The antenna, the cable, and the transmitter operate very efficiently.

1.8 to 2.2 Acceptable - The antenna, the cable, and the transmitter operate with some loss. If possible, adjust your antenna or antenna mounting system to improve.

Above 3.0 Inefficient - Adjust your antenna or antenna mounting system to improve efficiency


There are several ways to improve the SWR of your radio/antenna combination. Try these first.

Be sure you are using the type of cable recommended for your equipment. If the manufacturer recommends a 50-ohm cable, do not substitute another type that has a different impedance.

Confirm that you mounted your antenna according to the manufacturer's instructions. The angle and the base arrangement can affect the SWR reading.

Adjust the length of your antenna according to the instructions provided by the manufacturer. A change of as little as 1/8 inch can make a measurable difference.

I hope this helps somebody and if you have any questions, let me know!

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