An SWR meter is an essential tool for installing a CB radio and antenna. It allows you to tune your antenna, which is adjusting the length of the antenna for optimum performance. This not only gives you the best range but it can also prevent damage to your radio.
The AUSWR from Accessories Unlimited is our most popular SWR meter. It includes a 3 foot coax jumper, for connecting the meter to your radio and antenna, as well as detailed instructions for tuning your CB antenna. You can find similar instructions in our guide for tuning a CB antenna. This basic SWR meter does its job well and accurate. It measures 3 7/8" W x 2 1/4" H x 2 1/8" D.
Covers 26-30 MHz range.
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How to tune the CB antenna using the external meter:
Very Important: Before starting the tuning process, be sure to properly store any excess coax in a figure 8, about one foot in length, and bound in the middle.
- Turn your CB off and disconnect the antenna coax cable from the back of your radio.
- Connect the end of your antenna coax to the SWR meter where it indicates "antenna" or "ANT". The connector inputs could be on the back and the labels on the front of the meter.
- Connect the short coax jumper cable coming from the transmitter position on the SWR meter to the back of the CB where you took off the coax cable in step 1.
- Close the hood and doors on your vehicle, and make sure there are no people or other large vehicles around the vehicle area.
- Turn on the CB.
- Set the CB to channel 40.
- Set the SWR meter to the FWD (forward) position.
- Key the microphone by depressing the talk button and turn knob until the SWR meter indicates the "set" position. Unkey the microphone by letting up on the talk button.
- Flip the SWR meter to the "REF" (reflect) position.
- Key the microphone and look at the SWR reading on the SWR meter for channel 40. Take note of that reading.
- Repeat steps 6 through 10, this time on channel 1.
Now that you have both SWR readings on channel 1 and 40, you will make adjustments (if needed) to your antenna system to optimize the system.
The goal is to achieve similar SWR readings on channel 1 and channel 40 that are within an acceptable SWR range.
See SWR Range Explanations below. The lower the reading, the better your CB radio will perform. The goal is to set the antenna to the lowest SWR readings possible, evenly across the 40 channels- for example, the reading on channel 1 and 40 at the same at 1.5. By having the SWR readings match on channel 1 and 40, your radio will perform well on any of the channels within the 40 channel bandwidth. If they do not match, adjusting the antenna is advised.
- IMPORTANT: If the meter reading is in the red zone, indicating HIGH SWR readings, DO NOT operate the CB. You could potentially damage your radio.
If the reading on channel 1 is higher than the reading on channel 40, your antenna system is too short and you need to lengthen your antenna system.
- For example: If the SWR meter reading on channel 1 is 2.6 and the reading on channel 40 is 1.3, your antenna is too short. Possible solutions include adding a spring or quick disconnect, raising the antenna, getting a longer coax (and just make sure to store any excess coax in a figure eight style, about a foot in length, and loosely bound in the center), or re-positioning the antenna.
Alternatively, if the reading on channel 40 is higher than channel 1, your antenna system is too long and you need to shorten your antenna system.
- For example: If the SWR meter reading on channel 1 is 1.2 and the reading on channel 40 is 2.3, you'll need to shorten the antenna to get better efficiency. You can do that by turning the tuning tip or the adjusting ring, or you can take the antenna mast out and trim it about 1/8 inch, and place it back firmly against the coil. Remember, it's easier to cut a little more off the antenna than to have to add some length (remember the barber who cut your hair too short?).
If any adjustments are needed, they should be made in small increments. Re-check after each adjustment. Be sure to have all components on the antenna when testing, including the tip/cap if there is one.
If you have already optimized your current antenna setup (similar readings on Channel 1 and 40) and you still want to improve your SWR readings, you can try a different antenna, a different mounting location, or, if you are setting up a dual antenna system, try utilizing only one of the antennas instead of both. Sometimes, you will get better performance from using one antenna instead of two.
SWR Range Explanations:
SWR 1.0-1.5: The ideal range! If your SWR is under 1.5, you're in great shape. If you're at 1.5 and really, really want to drop down to closer to 1 it's likely possible to do with additional tuning, different equipment or a different mounting location. But the drop from 1.5 to 1.0 won't make a substantial increase in performance. It's not nearly as noticeable as, say, going from 2.0 down to 1.5.
SWR 1.5 - 1.9: There's room for improvement, but SWR in this range should still provide adequate performance. Occasionally, due to installations or vehicle variables, it's impossible to get SWR lower than this. You should try to get it lower, but performance should still be acceptable in this range. If you've tuned the antenna, SWR in this range is likely an issue of a less-than-ideal mounting location for your vehicle and/or an antenna that isn't ideal for the mounting location. To troubleshoot, see this article on problematic CB antenna mounting locations.
SWR 2.0 - 2.4: While not good, this likely won't damage your radio with casual use. However, you should definitely try to improve it if you can. SWR in this range is usually caused by a poor antenna mounting location and/or a poor choice of equipment for your specific vehicle. To troubleshoot, you'll likely need to move the mounting location and/or use a more suitable antenna. It's by no means a good tuning job, but will function if you've exhausted all other troubleshooting possibilities.
SWR 2.5 - 2.9: Performance in this range will be noticeably decreased, and you might even damage your radio if you transmit frequently and for extended periods. We advise you not to operate your radio in this range. SWR in this range is usually caused by a poor mounting location and/or a poor choice of equipment for your specific vehicle. To troubleshoot, you'll likely need to move the mounting location and/or use a more suitable antenna.
SWR 3.0+: Performance will be severely affected, and you're likely to damage your radio with extended transmission use. You SHOULD NOT transmit with your CB at SWR levels above 3.0. If your SWR needle swings all the way to the right (off the charts) when getting your 3.0+ readings, you almost certainly have a major installation problem. This is almost always the result of a poor ground or incorrectly assembled stud, but on rare occasions can indicate a faulty coax, antenna, or incorrectly attached SWR meter.