Electronics Notes Ham Radio Store: Dummy Loads

An SWR meter or standing wave ratio meter is an essential item for any amateur radio station. Although many rigs already have an SWR capability fitted internally, they can still provide a god vital indication of the standing wave ratio and the level of reflected power being experienced by the transceiver.

As modern semiconductor based transmitters do not like high levels of reflected power because the peaks in voltage or current that can be experienced can damage the power amplifiers. Accordingly the protection circuits fitted in most rigs reduce the maximum power under high SWR levels.

When selecting an SWR meter to buy there are several points that may be of interest:

• Frequency range:   SWR meters have frequency limitations. Check that any SWR meter being bought can cover the frequencies required.
• Power handling:   SWR meters also have power limitations. Ensure that any SWR meter being bought can handle the power being passed though it.
• Power measurement capability:   Some of the higher end SWR meters also have the capability to measure power levels. The lower end meters just provide a forward and reverse power ratio and are not intended or capable of giving direct or absolute power readouts. If a power measurement capability is considered a useful addition, then check that the one you want to buy can meet this requirement.
• Meter and box dimensions:   The dimensions of the SWR may be important. Smaller meters may not be as easy to see. They will also be lighter and they may tend to move more easily. Conversely smaller ones may fit the bill if they are needed to fit in a small space.

There are many different SWR meters that are available to buy. There is a good selection so it will be possible to choose one that fits the requirements well.