Part of our Start Here guide.
New hams learn to press PTT and talk long before anyone explains what is actually happening inside the radio in that moment. It is worth understanding, it makes troubleshooting far more intuitive later.
Your Voice Becomes an Electrical Signal
The microphone converts sound pressure into a varying electrical voltage. That raw audio signal gets processed, filtered for the useful voice frequency range, sometimes compressed to boost average loudness, before it goes anywhere near the actual radio frequency stages.
Modulation Puts Your Voice on a Carrier
Your radio puts your audio onto a radio frequency signal by modulating it, varying either its amplitude (AM, and SSB, which keeps one sideband and drops the carrier) or its frequency (FM) in step with your voice. Most modern radios do this at a lower intermediate frequency first, then mix the result up to your operating frequency. This is the fundamental trick that lets a radio signal actually carry information.
Amplification and Filtering
The modulated signal at this point is tiny, milliwatts. Power amplifier stages boost it up to your radio’s rated output, while filters strip out unwanted harmonics and spurious emissions generated in the amplification process, keeping your transmission clean and legal rather than splattering energy across unintended frequencies.
Out Through the Antenna
The finished signal travels down your feedline to the antenna, where it converts from electrical energy in a wire into an actual radio wave radiating into space. All of this, mic to modulation to amplification to radiated wave, happens in a fraction of a second every single time you press PTT.
How This Helps You Troubleshoot
- No one hears you but the radio shows power output: start at the microphone, its cable, and the mic gain setting.
- Reports of distorted audio: too much mic gain or compression is overdriving the modulator. On SSB, watch the ALC meter.
- Low power or the radio cuts back: high SWR, so check the feedline and antenna.
- RF getting into other gear or your audio: common-mode current on the feedline, which a choke usually fixes.