Ham Radio Microphone Guide: Dynamic, Condenser and Headset Compared

The microphone is the first link in the chain that carries your voice to the other station, and no amount of expensive amplification or clever processing can fully repair what a poor one has spoiled. Yet it is often the cheapest part of the station, and many operators use whatever came in the box with the radio. A deliberate choice of ham radio microphone can make a clear difference in how readable you are in a pileup, how pleasant your voice sounds on a long ragchew and how much of the background noise from your shack goes out on the air. This guide compares the main types, explains the practical differences between desk microphones and headsets, covers the wiring and bias details that cause confusion and gives a checklist for choosing one.

What SSB Audio Needs

Voice on the amateur bands is usually sent as single sideband with a narrow bandwidth, typically around 2.4 to 3 kilohertz. The radio’s filters remove everything below a few hundred hertz and above about 2.7 kilohertz or so. A microphone that gives a wide, flat response from 20 hertz to 20 kilohertz, as a studio device does, therefore spends most of its quality on frequencies that the radio will cut off, and it may pick up low-frequency rumble and high-frequency hiss that cause trouble. For this application the aim is a clear, intelligible mid-range with a slight lift around the frequencies that carry the consonants, and little energy outside the passband.

That is the reason why many hams find that cheap communications microphones work well, and why some expensive studio microphones disappoint on the air without equalisation. The question to ask is not whether the microphone is good in absolute terms, but whether its response matches the narrow channel and the environment in which you use it. Our guide to SSB audio settings explains how to adjust the gain, the compression and the equaliser once you have a microphone that suits you.

The Main Types

The Wikipedia article on microphones lists the most common types as the dynamic microphone, which uses a coil of wire suspended in a magnetic field, and the condenser microphone, which uses the vibrating diaphragm as a capacitor plate. Condenser microphones need a power source, provided either as phantom power from the equipment or by a small battery. Most amateur microphones fall into one of three groups.

For general use, a dynamic microphone with a cardioid pattern is the safest choice. The cardioid pattern is most sensitive in front and least sensitive at the back, so it reduces noise from the radio, the fan and the room. Electret capsules in headsets and hand microphones are often chosen for their small size and good output, and their behaviour depends on how well the radio supplies the bias voltage, as explained below.

Desk, Hand and Headset

The way the microphone is held matters as much as its capsule. A desk microphone on a stand lets you use both hands for the logging program and the controls, but it is sensitive to distance and to the direction in which you speak. A hand microphone is convenient for mobile and portable use and tends to be consistent in distance because you hold it. A headset, with a boom microphone close to the mouth, keeps the distance constant and cuts out much of the room noise. That is why it is the usual choice for contesters, as discussed in our guide to the contest headset and footswitch. For long periods, a headset also reduces fatigue, since you do not have to hold your head at a fixed position.

With any microphone, distance and angle make a large difference. A distance of a few centimetres gives a strong, full sound, but too close and the bass is exaggerated and plosives such as p and b cause bursts. Speaking slightly across the capsule instead of directly into it, or using a foam windscreen, helps. If you notice that your signal sounds boomy to others, the first thing to try is to move a little further from the microphone and to reduce the gain.

Connectors, Wiring and Bias

Here the practical problems begin. Radios use different connectors for the microphone, some with a plug of the round kind with several pins, some with a modular plug resembling a telephone one, some with a small jack in the case of handhelds. The pin assignments differ between makes and sometimes between models of the same maker. A microphone that works on one radio may be silent or noisy on another, even if the plugs fit. Always check the manual for the pin-out, and do not assume that two plugs of the same shape are wired the same way.

Many radios supply a small DC voltage on the microphone line, called bias, which powers electret capsules. A dynamic microphone does not need it and may be disturbed by it, so some radios have a menu setting to switch it off. If you connect a studio condenser microphone that needs phantom power, you will need a separate interface or a preamplifier that supplies the power and gives a suitable output level, and you must be careful that the output does not overload the input of the radio. A level that is too high causes distortion, and a level that is too low makes the radio use too much gain, which raises the noise. The impedance should also be compatible: many radios expect a low-impedance microphone, in the range of a few hundred to a few thousand ohms.

Another point is the push-to-talk line. A hand microphone has a switch that connects the push-to-talk pin to ground. If you use a headset or a desk microphone with a footswitch, the footswitch takes over this function. Keep the PTT wiring short, and put a ferrite on the cable if you have RF problems, as our article on common-mode chokes explains.

RF in the Microphone

A microphone cable is a long piece of wire near a transmitter, and it can pick up RF. The symptoms are distorted or buzzing audio, a signal that changes when you touch the cable, or an SWR that shifts when you move the microphone. The cure is the same as for other RFI problems: use a shielded cable, ground the shield correctly, put ferrite beads or a choke on the cable close to the radio and keep the cable away from the antenna feed line. A microphone that picks up RF will often not be a bad microphone, only a bad installation, and the problem may disappear when the antenna is moved or the power is reduced. If you also have hum, check for ground loops, the subject of our article on digital interfaces and ground loops.

Pop Filters, Windscreens and Placement

Small accessories make a noticeable difference. A foam windscreen or a pop filter reduces the bursts of air from plosive sounds and also protects the capsule from moisture and dust. Place the microphone so that the airstream does not hit the diaphragm directly: a position slightly off to the side, or a boom that sits at the corner of the mouth, is usually better than one in front of the lips. On a desk stand, a shock mount or a small piece of foam under the base reduces the thumps from the table, which is surprisingly noticeable when you tap a key or the mouse. If your room has hard walls, a few soft items, such as a curtain or a rug, reduce the echo that a sensitive microphone picks up.

Think also about the position of the microphone in relation to noise sources. A computer fan, a power supply with a cooling fan and an amplifier blower are all common sources of noise that a cardioid microphone rejects only partly. Pointing the null of the pattern, the rear of a cardioid, toward the noise source is a simple trick. A headset has the advantage that the capsule stays close to the mouth and far from these sources, with the result that the ratio between the voice and the noise is better than with any desk microphone at a normal distance.

Care and Maintenance

Microphones last for years if they are treated well. Keep them away from moisture, store the capsule with the windscreen on and do not drop it on a hard surface. Cables are the usual point of failure: bending near the connector causes intermittent contact that sounds like crackles when you move. Inspect the cable and the plug from time to time, and replace the plug rather than live with a flaky contact. If a headset has foam pads or windscreens that have become dirty or brittle, replace them. These small steps maintain the quality of your audio without any further expense and avoid failures in the middle of a contest or a net.

How to Choose

• Start with the environment. A noisy shack with fans and a computer calls for a dynamic cardioid microphone or a headset. A quiet room allows a condenser.
• Check compatibility. Look at the connector, the pin-out, the bias and the impedance of your radio before you buy.
• Listen to a recording. Record yourself and play it back, or ask a local friend for a report. A report from the air, comparing two microphones in the same conditions, is worth more than any specification.
• Consider the use. Mobile and portable operators prefer a robust hand microphone, contesters a headset, and ragchewers a desk microphone with a stand.
• Allow for adjustment. A microphone with an equaliser in the radio or a small adjustable preamplifier lets you tune the sound to the voice and the band.

Testing and Tuning Your Choice

Once the microphone is connected, test it into a dummy load or on a quiet frequency with a friend. Set the gain so that the ALC meter moves only slightly on voice peaks, and check that the radio’s compression, if used, does not exaggerate the background noise. Switch between a flat setting and the radio’s own equaliser to find a sound that is bright enough to cut through noise without becoming harsh. Remember that what sounds best at home may not be best on the band: a narrow, mid-range emphasis is usually more readable in a pileup than a rich, full sound. Our guides to choosing the sideband and setting up a voice keyer follow the same principle of testing before the contest, not during it.

The Bottom Line

A good ham radio microphone is one that suits the narrow SSB channel, the radio and the room, not necessarily the most expensive one. Dynamic cardioid types are rugged and reject noise, electret microphones and headsets are compact and clear but need bias, and studio condensers sound detailed but need phantom power and a quiet room. Check the connector, pin-out, bias and impedance of your radio, keep a constant distance from the capsule, deal with RF on the cable and test with real reports before you decide. A modest investment in the microphone and in the time to adjust it is among the cheapest ways to be heard better.

Frequently Asked Questions

Which microphone type is best for ham radio?

A dynamic cardioid microphone or a headset is a safe choice for most stations because it rejects room noise. Condensers can sound better in quiet rooms.

Do I need a studio microphone for SSB?

No. SSB passes only a narrow band of audio, so a wide-range studio microphone does not bring much benefit and may need equalisation.

What is bias voltage on a microphone input?

A small DC voltage supplied by the radio to power electret capsules. Dynamic microphones do not need it, and some radios allow you to switch it off.

Why does my microphone work on one radio but not on another?

Connectors and pin assignments differ between makes and models, as do bias and impedance. Always check the pin-out in the manual.

How far should I be from the microphone?

Typically a few centimetres. Closer exaggerates the bass and causes pops, and further reduces the level and increases room noise.

How do I stop RF getting into my microphone?

Use shielded cable, add ferrite chokes near the radio, keep the cable away from the feed line and antenna, and check the grounding of the shack.