Most ham repeaters these days use sub-audible tones such as PL (Private Line) or digital tones to minimize interference from distant repeaters. And, public services using two way radio also use sub-audible tones. Well, if you use HDSDR software to run your dongle, you can identify the tone being used, just make sure you have the audio spectrum option to display the audio spectrum and waterfall, zoom out until you get to the Hertz level (tones are in Hertz) and look for the peak. In the example below a repeater in use shows a PL tone of around 131 Hertz, a common PL tone.
This can help if you need info on a repeater's PL tone. Also interesting to see the different tones used by other business and government users.
This can help if you need info on a repeater's PL tone. Also interesting to see the different tones used by other business and government users.
