If you want to just measure SWR, then you don’t need to measure RF power meter, then you can use a cheap meter and get adequate results. SWR only is only a relative measurement comparing power going out and power coming back. Given this is does not matter if the frequency response of the RF detectors in the meter are good or bad. Only the forward and reflected sensors need to be equal. If they are equally bad it will work, if they are equally good it will work. The main thing is that they are equal and this is usually the case. This type of meter will work fine for SWR only measurements.
Measuring RF Power
If you want to measure RF Power at 88 – 108 and SWR, then you cannot use cheap meters. If you need power sensors that have a flat and uniform response over the frequency range you are measuring. Cheap meters are available with the RF power function, but they will not indicate the correct power. You need to use something like this.
Aareff RF Power
All our 100W transmitters and higher in power have a built in meter. On the front panel there’s a forward and reflected switch which allows you to measure the power actually going out to the antenna and if any is being reflected. You don’t need to use an external meter, but you can if you want. If there’s reflected power of between 10 and 15% of the full power, then there’s probably a problem with the connectors, or maybe the screen or ground on the coax where it enters the connector. It’s also possible the antenna has gone off tune a little due to the weather taking it’s toll. With our transmitters if the reflected power is between 15 and 25%, it usually means the cable or antenna somewhere in the line is completely open circuit, basically the signal disconnected somewhere or the exact opposite the signal is being shorted completely to ground.
By Paul Hollings