How to Lower SWR on a Vertical Antenna?


Written by

Rafeal Hart


Fact-checked by

Norris Howe

how to lower swr on vertical antennas

Whether you’re an avid ham radio operator, a CB radio enthusiast, or an off-road adventurer relying on your two-way radio, you must get your SWR low for optimum performance. If your SWR radio is not calibrated to a lower SWR, you run the risk of ruining the quality of your radio.

Having a high SWR will result in weak outgoing signals, making it harder for others to hear you. Moreover, if your radio operates too high for an extended period, it can overheat and potentially cause damage to your radio.

Read this article and discover the ways how to lower SWR on a Vertical Antenna.

What is SWR and How is It Measured?

The standing wave ratio or SWR measures the ratio between the magnitudes of standing radio waves. If the ratio of the highest point of a standing wave and its lowest point is higher than 1.5, then you have a high SWR. So, if you measure it to be around 2.5 to 2.9, then your signal has some issues.

An ideal SWR range is generally considered to be under 1.5. This means that the highest point of standing wave voltage is only 1.5 times higher than its lowest point. However, the closer SWR gets to 1:1 or 1.0, the better the radio performance becomes.

What Happens When SWR is High?


What exactly happens if you’re operating on a high SWR?

A high SWR means your radio operates at extreme voltages and currents. When the SWR meter is 2.5 and above, this is considered very high, although the radio can still function.

However, when you’re operating at an SWR of 3.0 and up, performance will be severely bad. This can cause transmission issues or damage your radio.

1. High SWR on Signal Quality

When you are operating at a High SWR, you will notice that the signal received is weak. This is because the power reflected from the antenna system is not efficiently transferred back into the transmitter.

2. High SWR on Transmitters

Prolonged utilization of radio on High SWR will result in transmitter damage. It can be caused by overheating because excessive power is reflected. This will decrease the radio’s performance and transmission range which can eventually break the transmitters.

Why Does My Meter Say High SWR on All Channels?

1. Incorrect SWR Meter Attachment

The most common reason why your reader indicates a high SWR is because your SWR meter and antenna are not properly connected.

  • To fix high SWR, double-check your attachment because the reader may display a high SWR despite the radio being at a low SWR.

2. No Proper Grounding


High SWR can also happen if your vehicle has a “no ground plane” antenna. The vehicle’s metal body is usually used as a ground plane. However, if your car lacks that, you will likely receive a high SWR reading.

  • You can purchase an NGP antenna with a built-in ground system instead.

Steps to Lower SWR on a Vertical Antenna

Adjusting SWR can be done by following the steps below:

Step 1: Verify Antenna Installation

Make sure that your vertical antenna is properly attached and that you have proper grounding. Also, check for any loose connections or damaged components.

When you are sure there are no damages to your antenna, you should proceed to the next step.

Step 2: Determine SWR Reading Using an SWR Meter

  • For this step, correctly attach your SWR meter between your transceiver and antenna. You have to disconnect the cable from the back of your radio and reconnect it to the SWR meter. Also, connect your antenna cable to the SWR meter labeled “ANT.”


  • Set SWR meter to “FWD.” You can then choose which channel you want to check.
  • Then, turn the knob of the SWR reader until the meter needle is at the farthest left or near “SET”


  • Press the microphone button down and hold it. While holding down the microphone key, flip the switch to “REF.” The needle will show the SWR reading of your radio.If your reading is more than 2.5, then you have to lower your SWR level.

Step 3: Adjust the Height of Your Antenna


If a channel in your radio has a high SWR reading, you can try to tune your antenna to get it lower. You can shorten or lengthen antennas. Try moving it gradually until the reading comes lower to a desirable ratio.

Step 4: Improve Your Ground Plane

Grounding is a big factor that causes your radio to have high SWR readings. Grounded mounts should be connected to the metal part of your vehicle without any plastic or nylon, as they can potentially decrease grounding.

Step 5: Use an Antenna Tuner

If nothing above works, you might need to use an antenna tuner. This device can help match your antenna to your radio and reduce the SWR. However, antenna tuners only compensate for mismatch issues but cannot fix them.


Addressing high SWR can be done once you have a clear understanding of how radios and antennas work together. You can always follow step by step to on how to lower SWR on vertical antenna, including adjusting the antenna height, checking proper grounding, and utilizing antenna tuners.

By understanding the basics of SWR readings, you can start troubleshooting on your own.

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