SWR കൂടിയാൽ റേഡിയോ കേടാകുമോ? SWR (standing wave ratio) tells you how well your antenna system matches your radio. Here is a quick cheatsheet.
Why power comes back
Your radio sends power along the cable to the antenna. If the antenna does not match the radio and cable, part of that power is reflected back. SWR is the number that measures this. 1 : 1 is a perfect match.
How much power is reflected
| SWR | Power reflected | Rough verdict |
|---|---|---|
| 1 : 1 | 0% | Perfect match |
| 1.5 : 1 | about 4% | Very good |
| 2 : 1 | about 11% | Usually acceptable |
| 3 : 1 | about 25% | Worth fixing |
The percentages come from the standard reflection formula. Labels such as “good” or “poor” vary a little between sources, so treat them as a guide.
What to do
- Know what it meansSWR measures how much power is reflected back from the antenna system.
- Check the numberUp to about 1.5 : 1 is very good. Around 2 : 1 is usually acceptable.
- Radio protectionAbove about 3 : 1, many modern radios reduce power or shut off to protect themselves.
- A tuner is not a cureA tuner makes the radio see a better match, but the mismatch between the tuner and the antenna remains.
- Measure with a meterUse an SWR meter and test at low power first.
- Find the faultIf SWR is high, check the antenna, the cable and the connectors.
Transmit only if you hold a valid licence, and only on the frequencies and power levels your licence allows. Follow your radio manual for tuning power.
Made for the Captain.Ramkumar reel series. Radios differ in how they protect themselves, so check your own manual.
Want your own ham radio licence?
Our book is available in English and Malayalam. The Licence Complete bundle adds a 16-lesson video course, a year of Scout Pro and two one-to-one sessions, in a single payment.
See the bundleRead the free guide
