VSWR

Troubleshooting RF systems can be difficult and having good diagnostics, both locally and over-the-air to remote sites, is critical in making an accurate determination of your system. One of the most important is VSWR or 'voltage standing wave ratio.' It is basically the measurement of the impedance match (or mismatch) between a radio and its antenna/feedline. Most radios won't actually give you the ratio, but the better manufacturers do provide a 'reverse power' reading. Reverse power is the amount of RF energy that is reflected back into the radio. The higher the reverse power, the more likely that something is wrong.

For example, say you've got a radio that is transmitting at 5 Watts and it has a reverse power of .2 Watts. That's actually pretty normal, since achieving a 1:1 ratio is quite hard to do. In that scenario, everything's okay. But, if you see that reverse power start to climb, to say .6 or higher, something is not right. You've got a bad radio, a loose connector, a squirrel's been gnawing on your feedline, something. Verify that it isn't the radio itself by putting on a different antenna, and see if it goes back down. After that, inspect the feedline, connectors and antenna for damage or water.