Connect a microphone to the mixer with parametric equalization or digital audio workstation (DAW) software. If you would like the vintage AM radio announcer effect for live use, you will need to create this effect on the mixer. Using a DAW allows you to record your voice, then process the announcer effect afterward. In both cases, the approach is similar.
Equalize the vocal signal to create the basic effect. With a three-stage equalizer, remove about 12 decibels (dB) of signal at 130 hertz (Hz). Add about 12 dB at 900 Hz and cut about 8 dB at 3000 Hz (also described as 3 kHz). The hollow, nasal sound that creates the radio voice effect is in the 900 to 1000 Hz range. Experiment with additional boosts in this range and further cuts in the low frequencies until you get the desired vintage AM radio sound.
Setting up a compressor/limiter to limit the signal will add to the effect, as radio signals are heavily compressed to aid broadcasting and to make music clear in noisy environments like moving cars. Heavy compression and limiting can create audible artifacts that would be considered flawed in proper recordings, but which may be appropriate to your voice; so, experiment with extreme compression settings to obtain the desired effect.