What an audio processor does
An audio processor changes the microphone signal before it reaches the modulator in your transmitter. The aim is a signal that is easier to understand, especially in noise or weak-signal conditions. In the transmitter chain, it sits after the microphone and before the modulator (see the diagram of a radio transmitter).
Processing cannot make a poor microphone or a bad room sound good, and too much of it usually makes things worse. Start with a clean source: a suitable microphone, placed correctly, in a quiet space.
Main types of processing
Equalization
An equalizer boosts or cuts parts of the audio spectrum. For SSB, which carries a limited audio bandwidth, many operators trim very low frequencies and slightly emphasize the midrange where speech clarity lies. Settings depend on your voice and microphone, so adjust gradually and check with a signal report or a recording.
Compression
A compressor reduces the difference between loud and quiet parts of speech. This raises the average level without raising the peaks, which can increase the average power in your voice and make you easier to copy. The risk is a harsh, “pumping” sound and increased background noise.
Noise gate
A gate mutes the audio when you are not speaking, reducing room noise. If set too aggressively it clips the start and end of words.
Limiting
Limiters set a ceiling on peaks to help prevent overdriving the transmitter.
Built-in versus external processors
Many modern transceivers include a speech processor and a transmit equalizer. Some also have a menu setting for microphone gain and compression level. External units, ranging from small boxes to desktop mixers and software-based processors, offer more control, but they add cables and settings that must be correctly matched to the radio’s microphone input.
Basic setup
- Set the transmitter to a dummy load or a clear frequency for tests if possible.
- Start with the processor off and adjust microphone gain until the ALC meter shows modest, not constant, activity (follow your radio’s manual).
- Enable compression at a low setting and adjust gradually.
- Record yourself or ask for a signal report from a local friend.
- Revisit settings for different microphones or bands.
Avoiding overprocessing and splatter
Overdriving the audio chain or the transmitter can cause distortion and wide signals, sometimes called splatter, that interferes with nearby stations. If your ALC meter is pinned or reports say you sound distorted, reduce the gain. Staying within the proper bandwidth is part of operating responsibly.
Other ways to improve audio
- Place the microphone a consistent distance from your mouth.
- Use a headset for repeatable positioning.
- Reduce room echo with soft furnishings.
- Avoid RF feedback by using good grounding and choke techniques (see reducing interference).
Choosing equipment
Think about what you need: if you operate a lot of weak-signal SSB, a processor may help; for casual FM use, it is usually unnecessary as FM radios include their own limiting. Read your radio’s manual before buying anything. The amount of power your amplifier delivers also matters; see ham radio formulas for decibel calculations that help you compare gains.
Frequently asked questions
What is the best sound processor?
There is no single best option. It depends on your radio, microphone and voice, so try the built-in processor first.
Does a speech processor increase output power?
It raises the average power by compressing peaks, but not the peak power limit.
Do I need an external processor for FM?
Generally not; FM transceivers already limit the audio.