Normally, most people use spectrum analyzers

Specific methods:

Use a spectrum analyzer to connect to the antenna, set the frequency of the spectrum analyzer to the approximate range, and then press the switch, so that the spectrum analyzer will be able to test the signal, and then read out the frequency of the spectrum analyzer can be read

The oscilloscope needs to be detached from the remote control, and the probe is connected to both ends of the transmitter antenna to test the waveform of the transmitter signal and then read out the frequency. If you want to use an oscilloscope, you need to detach the remote control and connect the probes to the two ends of the transmitter antenna to test the waveform of the transmitter signal and then read out the frequency.