What is SWR and why is it SO important?
- The term “SWR” means standing wave ratio. An “SWR” meter is used to measure how well the transmit power signal emitted from a transceiver (radio) is traveling through the antenna system into the atmosphere.
- Checking and setting the antenna SWR is critical to overall performance of transceiver (radio).
During installation of a Business Band, CB, Ham or Marine radio antenna, the SWR must be checked to ensure that the transmit power coming from the radio is traveling through the antenna system correctly. See our article on How to Tune a CB Antenna.
A poor reading on the “SWR” meter will provide you with your SWR readings which can indicate that there is a problem with installation of your radio or antenna system. When the “SWR” test is performed, the meter will indicate if your antenna is working properly and provide a reading so the antenna can be adjusted for optimum performance. Poor readings can indicate if there is a poor or bad (radio/antenna) ground, improperly set antenna, poor antenna location or coax obstruction or short.
If you get a SWR test reading on the “SWR” meter in the red, this indicates that there is a significant problem with the antenna system or a bad radio ground that requires correcting or adjusting prior to using the radio.
DO NOT OPERATE THE RADIO UNTIL A GOOD “SWR” READING CAN BE ACHIEVED.
Some radios include a built-in meter while other compact radios do not. If you do not have one built-in to your radio, you will need to get one so that you can tune your antenna for your application. Most CB radio “SWR” meters (26-27 MHz) are fairly inexpensive, like the AUSWR, however, meters that check other radio frequencies can be expensive.
Checking and setting the “SWR” on all radio applications is the most important step in obtaining the best performance possible.
When testing and adjusting the antenna, make sure to check “SWR” on the lowest channel and the highest channel. By adjusting and setting the “SWR” on the entire bandwidth (high and low channels), it will ensure optimum performance on all of your radio channels. The radio will receive and transmit well with a good “SWR” reading of 2.5 or less across all channels. The lower the “SWR” reading the better your radio will perform.
Check SWR on AM only, not on SSB. Your other readings will be ok if you have good SWR readings on AM.
SWR Reading 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.
We have a troubleshooting section for HIGH SWR- check it out!
NOTE: If your SWR reading is below 1, you have a problem. You might have a bad SWR meter, something wrong with your antenna or antenna connection, or possibly have a damaged or defective radio.
If the SWR 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.
Alternatively, if the SWR reading on channel 40 is higher than channel 1, your antenna system is too long and you need to shorten your antenna system.
Please see our article for additional important information: How to Tune a CB Antenna
IMPORTANT NOTE: Radio damage will only occur when you're TRANSMITTING from an antenna with high SWR readings. Leaving the radio on to receive signals poses no risk to your radio.
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.