Radio data, delivered with unnecessary personality.
A compander is a noise-reduction system that compresses your audio on transmit and expands it on receive. The name is a portmanteau of "compressor" and "expander." When both radios in a conversation have compander enabled, the result is noticeably clearer audio with reduced background noise.
On the transmitting side, the compander compresses the audio's dynamic range - it makes quiet sounds louder and loud sounds quieter, squeezing everything into a narrower range. This compressed signal travels over the air. On the receiving side, the compander expands the audio back to its original dynamic range, restoring the natural loud-and-quiet variation. Because the background noise was compressed along with the speech, the expansion process pushes it back down below audible levels, making the voice stand out much more clearly.
A compander typically applies a 2:1 compression ratio on transmit - meaning a 20 dB variation in your voice gets squished to 10 dB over the air. On receive, the 1:2 expansion restores it. Noise that entered the signal during transmission gets expanded downward. In practical terms, this means the compander is most effective against noise that sits below your voice level. Noise that's as loud as your speech doesn't get pushed down much - the expansion affects everything proportionally.
Compander is usually a simple on/off toggle in your radio's menu, often labeled "Compander," "COMP," or "Compand." It can typically be set per channel. Enable it on both the transmitting and receiving radio:
The setting exists on most budget and mid-range handhelds, under slightly different names:
If you program via CHIRP, look for a "Compander" column in the channel list - it's easier to set consistently across all channels than using the radio's front panel.
The best way to evaluate compander is a quick A/B test with a partner on a simplex channel:
Don't rely on gut feel alone. The improvement is sometimes subtle and easy to miss without a direct comparison.
This is the most important thing to know about compander: both radios must have the same setting. If one radio has compander on and the other has it off, the audio will sound distorted, muffled, or "pumping" (volume surging up and down unnaturally). This is because one side is compressing or expanding audio that the other side isn't compensating for.
Important: Do not use compander on repeaters. You can't guarantee that every radio accessing the repeater has compander enabled, and the repeater itself won't compress or expand the audio. The result would be distorted audio for anyone whose compander setting doesn't match yours. Reserve compander for simplex (direct radio-to-radio) conversations where you control both ends.
People sometimes confuse compander with scrambler, or assume compander provides some privacy. It does not. Compander is not encryption and not a scrambler. It changes the dynamic range of your audio to reduce noise - the words you say are fully intelligible to any radio, compander or not, that's close enough to receive a usable signal. The only side effect is that mismatched compander sounds distorted, which might make you harder to understand on a radio without it - but that's a bug, not a privacy feature. If you want reduced eavesdropping, look into DTMF selective calling or digital modes. Compander is purely a noise reduction tool.
Compander improves audio quality at moderate range with good signal. At extreme range - where the signal is weak and the noise floor is high - compander can actually make things worse. The expansion stage amplifies everything equally, including the heavy noise on a marginal signal. You may find that disabling compander at the edge of your range gives you more intelligible (if noisier) audio than letting the expander push everything up together. If a contact sounds garbled rather than just hissy, try turning compander off before giving up on the contact entirely.
Compander is a simple feature that makes a real difference in audio quality - but only when both ends are configured the same way. When in doubt, leave it off.