SSB Audio Settings: Mic Gain, Compression and a Clean Signal

On crowded bands, the quality of your voice signal often matters more than the number of watts behind it. The right SSB audio settings can make a modest station easy to copy through noise and interference, while the wrong ones can make a powerful station sound distorted and splatter across neighbouring frequencies. This guide walks through the controls that shape a single-sideband transmission: microphone gain, ALC, speech compression, equalisation and monitoring. It also covers microphone technique and a simple test routine that you can repeat whenever you change equipment.

The advice here is general. Every radio has its own menus and meters, so use your manual for specifics, and treat the principles below as the framework.

Why SSB Audio Is Different

Single-sideband modulation is a refinement of amplitude modulation. As the overview of single-sideband modulation explains, it uses transmitter power and bandwidth more efficiently by sending only one sideband and suppressing the carrier. The result is a signal that occupies roughly half the bandwidth of AM, and puts all its power into the information.

That efficiency has a consequence. With no carrier, an SSB transmitter produces power only when you speak, and the strength of the signal at the other end depends on the level of your modulation. Quiet speech means weak output. Loud peaks mean strong output, but only up to the limits of the transmitter. The goal of setting up SSB audio is therefore to maximise the average level of your speech without exceeding those limits and without making the voice unnatural.

In amateur practice, the convention is to use lower sideband (LSB) below 10 MHz and upper sideband (USB) at 10 MHz and above. The common example is voice on 40 meters in LSB and on 20 meters in USB, with a published exception for the channelised 60 meter band, where USB is used. Using the wrong sideband makes your signal unintelligible to everyone, so check the setting before you adjust anything else.

The Audio Chain at a Glance

Your voice passes through several stages before it becomes RF. Each stage has controls that can help or hurt.

The first rule of the chain is to set the levels in order, from the microphone toward the antenna, and to change one control at a time. Adjusting several at once makes it impossible to know which change helped.

Microphone Choice and Technique

Before touching a menu, look at the microphone itself. The most expensive processing cannot fix a poor pickup. A few principles apply to nearly every setup:

• Distance matters. Keep a consistent distance, usually a few centimetres, from a close-talking microphone. Moving away and toward the microphone changes the level and the amount of bass boost.
• Avoid plosives. Speak slightly across the microphone instead of directly into it, or use a foam cover. Blasts of air on “p” and “b” sounds cause thumps that waste modulation.
• Reduce room noise. A quiet room, away from computer fans and the shack’s power supplies, keeps background noise out of the signal. A compressor will amplify background noise along with speech.
• Use a headset for contest work. A headset microphone holds a constant distance. Our guide to contest headsets and footswitches covers the choices.

If your radio has a choice of microphone input impedance or bias settings, match them to the microphone type. A dynamic microphone and an electret need different settings, and a mismatch can make the audio thin and quiet.

Mic Gain and the ALC Meter

Microphone gain sets how hard your voice drives the transmitter. If it is too low, your average level is low and your signal is weaker than it needs to be. If it is too high, the speech peaks exceed the level the transmitter can handle cleanly, causing distortion and out-of-band energy.

Most radios have an ALC meter, which shows the action of the automatic level control. ALC reduces gain when the drive is too high, so that the final stages are not overdriven. A small amount of ALC action on speech peaks is normal on many transceivers, but heavy ALC action indicates that the drive is too high. The manufacturer’s manual gives the recommended range, and it varies between models, so follow it rather than a rule from another radio.

1. Put the radio into SSB with the correct sideband, with any compressor turned off at first.
2. Set the drive or power control to the level you will use, usually below the maximum.
3. Speak into the microphone at your normal level and distance, saying something like a normal call.
4. Adjust mic gain so that the ALC meter moves on the loudest peaks but stays within the range the manual recommends.
5. Do not use extra mic gain to raise output power. Use the power control for that.

The most important point is the last one. ALC is a safety mechanism, not a power control. If you push the drive to get more output, the ALC will clamp the signal and distort it. Set the power with the power control, and the audio level with the mic gain.

Speech Compression: The Biggest Gain and the Biggest Risk

Dynamic range compression is an audio operation that reduces the volume of loud sounds or amplifies quiet sounds, so the difference between loud and quiet is smaller. As the overview of dynamic range compression notes, it is used in amateur single-sideband voice communication to make a station more readable to a distant station, or to make it stand out against others, which is especially useful in DXing. Because an SSB signal’s strength depends on the level of modulation, a compressor increases the average level of the modulation and so increases the effective signal strength. Most modern amateur SSB transceivers have a speech compressor built in.

A compressor has a few key settings:

• Threshold. The level above which compression starts. A lower threshold means more compression.
• Ratio. How strongly levels above the threshold are reduced. A ratio of 4:1, for example, means that a signal 4 dB over the threshold comes out 1 dB over.
• Attack and release. How quickly the compressor reacts and recovers.

On a typical transceiver these are reduced to a single compression level control. The principle is the same: more compression raises the average level of speech and reduces the peaks.

The danger is overuse. Too much compression makes your voice sound strained, raises background noise and room echo, and can reduce intelligibility, particularly in the presence of interference. Use the minimum that gives you a worthwhile increase in readability. If a station asks you to turn it down, they are probably telling you that you have gone too far.

A sensible approach

1. Start with the compressor off and a clean, undistorted signal.
2. Switch it on at the lowest setting and listen on the monitor.
3. Increase it a step at a time while you watch the ALC and listen to the tone.
4. Stop when the voice starts to sound squeezed or when the noise comes up.
5. Ask for a report from a friendly local station, and adjust.

Equalisation: Shape the Tone Carefully

Many modern transceivers have a transmit equaliser, and some stations use an external audio processor. The aim is to improve intelligibility by shaping the frequency response. A voice that is too bass-heavy sounds boomy and wastes power on low frequencies that carry little information. A voice that is too bright is fatiguing and can sound harsh through a noisy band.

A typical SSB filter passes roughly 2.7 kHz of audio, which is why extreme high and low frequencies are wasted. Equalisation works best when it gently trims the lowest frequencies and adds a little presence in the mid-range, where speech information lives. Avoid dramatic boosts. Small changes are usually enough, and large ones usually mean the microphone is wrong for the job.

When you change the equaliser, change one band at a time, record yourself and compare. Your ears on the monitor are not the same as the receiver at the other end, so get a second opinion.

Monitoring and Testing

You cannot judge your own signal by what you hear in the room. These steps give an honest picture:

• Use the radio’s monitor function. It lets you hear the processed audio in your headphones.
• Record a test transmission into a dummy load, or use the radio’s voice recorder if it has one, then play it back.
• Ask for reports. Contact a nearby station or use a local net, and ask for an honest report on audio quality, not just signal strength.
• Use a second receiver or an SDR. Listening to your own transmission on another receiver, with a dummy load or low power, shows how the signal sounds and how wide it is.

When you have settings that work, write them down. If you change microphones or sit at a different desk, you will need them again. Our guide to making your first HF contact is a good companion for a beginner who is still finding a comfortable operating style.

Bandwidth, Splatter and Good Neighbours

Overdriving a transmitter does more than distort your voice. Overmodulation produces spurious emissions and a distorted signal, which spreads across neighbouring frequencies as splatter. On a crowded band that is unkind to everyone near you, and it is one of the most common causes of on-air complaints.

Common causes include excess mic gain, too much compression combined with high drive, and driving a linear amplifier too hard. If you use an amplifier, set the drive according to the amplifier’s requirements, and keep the exciter’s ALC quiet. Our article on what to know before adding an HF linear amplifier covers the drive requirements, and our IARU band plan explainer shows how bandwidth fits into the band plan.

Special Situations

Pileups and DX

In a pileup, a punchy, clean signal helps the DX station copy your call. Modest compression and a slightly lifted mid-range are common choices, with a short, crisp call. Calling more loudly does not help if the audio is distorted. See our guide to working a pileup for technique.

Ragchewing

For a relaxed conversation, a natural tone with little compression is more pleasant. Aim for clarity, not loudness.

Data modes through the same radio

If you switch between SSB and digital modes, remember that the audio settings for each are separate. A mic gain that suits voice is wrong for a sound card interface. Check the settings after every change of mode.

Common Mistakes

• Using the wrong sideband. LSB below 10 MHz and USB above is the convention, with exceptions such as the 60 meter channels.
• Too much mic gain. Flat-topped, distorted audio and heavy ALC action.
• Using ALC to set power. It protects the transmitter, it does not control it.
• Deep compression with a noisy room. The compressor lifts background noise.
• Heavy equaliser boosts. They create a harsh or boomy sound and can cause distortion.
• Never asking for a report. You are the last person to hear your own problems.

The Bottom Line

Good SSB audio is not about loudness. It is about a clean, consistent signal with a healthy average level. Choose a microphone that suits your voice, hold a steady distance, set mic gain so that the ALC meter stays within the manufacturer’s guidance and use compression sparingly to raise the average level. Shape the tone gently, test with a monitor and a second receiver, and ask for reports. The reward is a signal that is easy to copy on a crowded band, and a reputation as an operator who sounds good and keeps clear of the neighbours.

Frequently Asked Questions

How do I set mic gain on SSB?

Set the sideband and power first, then speak at your normal level and adjust the mic gain so the ALC meter moves on the loudest peaks but stays within the range recommended in your radio’s manual. Do not use mic gain to raise power.

Should I use the speech compressor?

Often yes, in moderation. Compression raises the average level of your modulation and so the effective signal strength, which helps in DX and contest work. Too much makes the voice sound strained and raises background noise.

What does the ALC meter tell me?

It shows how much the automatic level control is reducing the gain to protect the final stages. Heavy ALC action means the drive is too high, and the signal may be distorted.

Which sideband should I use for SSB voice?

By convention, lower sideband below 10 MHz and upper sideband at 10 MHz and above. A known exception is the 60 meter channels, where upper sideband is used.

Why do people say my audio sounds splattery?

Overdriving the transmitter, with too much mic gain, compression or amplifier drive, produces distortion that spreads to neighbouring frequencies. Reduce the drive until the ALC is quiet and the audio is clean.

Do I need an external audio processor?

Not usually. Most modern transceivers have a built-in compressor and equaliser. An external processor is a refinement, not a requirement, and a good microphone and technique matter more.