See the video: https://www.bilibili.com/video/BV1Y541147Sv
It can be seen that when I am in the analog audio app, in nfm mode, I can click the RSSI button, and the sound emitted at this time will change to a tone calculated according to the signal strength. This tone is in line with the radio direction finding movement of. Just install a directional antenna at the antenna port to do radio direction finding in this way.
The Fox Hunting code itself is actually hidden in the nfm demodulation, I just added the commented out code back. What I really add is the RSSI numerical display function.
Because sometimes the sound recognition is not accurate enough, I added an RSSI value display function myself. In the upper right corner, it will only appear when the value fox hunting function is switched in nfm mode. If it is only the normal demodulation mode of nfm, the upper right The corner of this position is displayed by ctcss.
In addition, as you can see, now the sound is sent directly from the portapack, not from the earphones, because I added the speaker amplifier function in the previous tutorial.