What is SWR (And Why Should You Care)?

SWR stands for Standing Wave Ratio. You may also hear it called VSWR, but don’t worry - they mean the same thing.

In simple terms, SWR tells you how well your radio and antenna system are working together:

• Your radio wants to send out power when transmitting.
• Your antenna system (connectors, coax, mount, antenna, and vehicle or ground plane) needs to accept that power and radiate it.
• SWR measures how much power actually makes it out versus how much gets reflected back.
• A perfect match would be 1.0:1 SWR if all power goes out.
• For HF/VHF (below 30 MHz), anything under  2.0:1 is considered good
• At 2.0:1, the signal loss is tiny - about ½ dB - which you’ll never notice on the air.
• Once you’re already under 2.0:1, chasing tiny improvements usually isn’t worth the effort unless the antenna is easy to adjust.
• Multi-band antennas (an example being those that transmit on totally different VHF and UHF frequencies) are a compromise and try their best to use antenna whip lengths and internal components to be usable on both bands.  These models are unlikely to get an SWR better then 1.5:1 even in an ideal mounting location.

SWR is About the Entire System, Not Just the Antenna

An SWR meter can’t tell where the problem is - it only reports the result. High SWR could be caused by:

• Bad or poorly installed coax
• Faulty connectors
• A bad or incorrectly mounted antenna
• Poor grounding (especially on mobile installations)
• Antenna placement that blocks proper radiation (ie corner of a vehicle, trunk, mirror mounting)

For mobile antennas that depend on a ground plane, good vehicle grounding is critical for ground-dependent antennas as is antenna location.

Antennas are Tuned to One Main Frequency

Most antennas resonate best at one primary frequency.

Example (on the Amateur Radio 2-meter band):

• Band range: 144 - 148 MHz
• Centre frequency: 146 MHz

When tuned correctly:

• SWR is lowest at the centre frequency
• SWR rises equally as you move higher or lower in frequency
• A flatter curve means wider bandwidth, but a high gain antenna may have a narrower bandwidth

You’ll often hear people say:

“The SWR should dip at the centre frequency.”   That’s exactly what you’re looking for!

What You’ll Need

• A basic understanding of what not to do (don’t transmit into high SWR on high power settings).
• A properly installed antenna system (mount, coax, antenna).

• • Check for shorts and opens first.
  • Some antennas are DC grounded - this can look like a short and still be normal.
• A working transceiver.
• An SWR meter capable of covering the frequencies you're wanting to test.
• A short coax jumper with PL-259 connectors on both ends (or a cable that matches your SWR meter and antenna socket on your transceiver.

How to Hook Up the SWR Meter

1. Disconnect your coax antenna cable running from your antenna to the antenna socket on your transceiver.
2. Connect that coax to the SWR meter socket labelled "Antenna" or "ANT".
3. Then use a short jumper:

• One end to the radio
• The other end to the SWR meter jack labelled "Transmitter" or "TX"

Your SWR meter is now in line with the radio and antenna.

Before You Measure

• Check coax cable and antenna base shorts or opens - prior to fitting the antenna.
• Park in an open area.
• Close all vehicle doors and hatches.
• Fully assemble the antenna and mount it where you plan to use it.
• Use AM or FM mode, not sideband, when checking SWR.
• Be sure to switch your transceiver to transmit on low power

Measuring SWR (Standard Meter)

Note: (Cross-needle and digital meters do this automatically and need no calibration.)

Step 1: Lowest Frequency (144 MHz)

• Set the SWR meter switch to FWD (or Forward).
• Key the microphone.
• Adjust the meter knob until the needle lines up with the SET mark.
• Flip the switch to REF (or SWR).
• Read and record the SWR.
• Release the microphone.

Step 2: Centre Frequency (146 MHz)

Repeat the same process:

• FWD → Set
• REF → Read SWR
• Record the value

Don’t worry if the needle barely moves here - that’s normal with a good system.

Step 3: Highest Frequency (148 MHz)

• Repeat again and record the SWR.

⚠️ Important Warning:  If the needle slams hard to the right (“pegs”), stop transmitting immediately.   You likely have a short in the coax, connectors, or antenna mount.

How to Read Your Results

SWR above 2.5:1 (in the red zone): Serious Problem. Likely a short or incorrect installation. 

❗ Do not use the radio until fixed 

SWR above 2.0:1 Everywhere (but not extreme): You need to check:

•  Poor coax
•  Bad grounding
•  Ungrounded mount

SWR under 2.0:1: On all three frequencies:  Good News → Safe to operate.

Is Your Antenna Too Long or Too Short?

⚠️ Before cutting any antenna parts refer to the documentation that came with the antenna.  Not all antennas are tuneable and if attempted,  irreversible damage may occur which could immediately void your warranty. 

Antenna is Too Long

• SWR is higher at 148 MHz than at 144 MHz
• No dip in the middle
• Fix: Carefully shorten the antenna in small steps, checking SWR each time

Antenna is Too Short

• SWR is higher at 144 MHz than at 148 MHz
• Fix: Increase the physical or electrical length

⚠️ Short antennas at high frequencies (VHF and UHF) are very sensitive - make tiny adjustments.
⚠️ Dual Band Antennas for VHF/UHF models should NOT be adjusted.

Why Vehicle Antenna Location Matters

For mobile installations:

• The antenna radiates
• The vehicle reflects

Change the antenna location (bumper vs roof), and SWR will change. The centre of the roof usually works best, but convenience sometimes wins - and that’s okay as long as the antenna is properly tuned.

Final Tips (Very Important!)

• High SWR can damage your radio.
• Don’t rely on the radio’s protection circuits.
• Always check SWR on a new installation.
• Recheck monthly to catch problems early.
• If you’re unsure, ask a HAM Radio Operator - or a knowledgeable antenna installer for help.

A Tuned Antenna System Gives You:

✅ Better performance
✅ Longer radio life
✅ Less frustration on the air
✅Take a little time to do it right - it’s worth it.