This tester can switch a HF signal ON / OFF fast.
Controll it with a 1 Hz square signal, then look on your scope what happens with the audio from the reciever on test.
Adjust your HF signal generator to 0dBm, then the input signal will change from -120 dBm to 0dBm
Make sure to add a "wall" with a small hole arround each diode, this will give good HF isolation
If this tester is only to be used at HF, then just use 1N4148 diodes.