SSB, explained
Guide · updated July 2026
Single sideband is the voice mode that owns the HF bands and weak-signal VHF/UHF — the one you’ll hear working DX, running nets and chasing a 6 m opening. Here’s what it actually is, when to pick LSB or USB, how wide it is, and how to run it so you sound good.
What SSB actually is
Start with plain AM. An AM signal is a carrier in the middle with two mirror-image sidebands stacked on either side. Here’s the catch: the carrier holds no information at all, and the two sidebands are identical copies of your voice. So an AM transmitter pours most of its power into a carrier that says nothing, and takes up twice the bandwidth it needs.
SSB fixes both. It throws away the carrier and one of the two sidebands, transmitting a single sideband that carries the whole voice. Two big wins fall out of that:
- Efficiency. Nearly all your power now goes into the intelligence instead of a dead carrier — far more “talk power” per watt, which is why 100 W of SSB reaches so much further than 100 W of AM.
- Narrowness. One sideband is about half the width — roughly 2.5 kHz versus ~6 kHz — so more stations fit and weak ones are easier to dig out.
That combination is exactly what you want when signals are weak and bands are crowded — so SSB became the standard voice mode on HF and on weak-signal VHF/UHF. FM, which is wider and needs a strong signal to sound good, rules the opposite world: strong, local repeater contacts.
LSB or USB?
An SSB signal keeps either the upper or the lower sideband — and both stations have to agree which, or you won’t understand each other.
| Band(s) | Sideband |
|---|---|
| 160 / 80 / 40 m | LSB |
| 60 m | USB (channelized) |
| 20 / 17 / 15 / 12 / 10 m | USB |
| 6 m / 2 m / 70 cm and up (SSB) | USB |
| Digital (FT8, RTTY…) | USB |
The rule of thumb: LSB below 10 MHz, USB above — and USB on everything VHF/UHF. It’s convention, not law: a leftover from early rigs built around a 9 MHz filter, where LSB-below and USB-above happened to be cheapest to make. Tune in on the wrong sideband and a perfectly good station turns into an underwater, “Donald Duck” mumble — just flip to the other sideband and it snaps clear.
How wide it is — and why that matters
A voice SSB signal runs about 2.4–2.8 kHz wide, and most radios let you set it anywhere from roughly 1.8 to 3.0 kHz. That number is a trade-off you make on every contact:
- Narrower — more signals fit on a busy band, and a weak one is easier to pull out of the noise. The cost is slightly thinner audio.
- Wider — fuller, more natural voice, but you take up more room and invite splatter from (and into) your neighbors.
It cuts both ways: your receive filter matters as much as your transmit width. In a pileup or heavy QRM, crank the RX bandwidth down and a wall of noise becomes a readable signal. For scale, here’s where SSB sits among the common modes:
| Mode | Typical bandwidth |
|---|---|
| CW (Morse) | ~100–500 Hz |
| SSB (voice) | ~2.4–2.8 kHz |
| AM | ~6 kHz |
| FM (narrowband) | ~10–16 kHz |
Tuning it — and sounding good
- Tune carefully. SSB is fussy: a few hundred hertz off and voices go squeaky-high or booming-low. Nudge the dial until the audio sounds natural, and use RIT / clarifier to fine-tune the other station without dragging your own transmit frequency along.
- Don’t overdrive. Watch your ALC and set mic gain and speech processing so you’re loud but clean. Cranking them past the limit doesn’t make you louder — it makes you splatter across the folks either side of you.
- Listen first. SSB isn’t channelized — you can land anywhere. Listen, ask whether the frequency’s in use, then call. Answer a CQ, or send your own; join a net; work a contest.
- The “Donald Duck” fix. If everyone sounds like a cartoon, you’re either on the wrong sideband or off frequency. Flip the sideband first, then fine-tune.
Where you’ll use it
- HF. The main voice mode of the phone bands — DX, ragchews and contests, from 80 m up to 10 m.
- Weak-signal VHF/UHF. On 6 m, 2 m and 70 cm, SSB (USB) reaches distances FM can’t — the calling frequencies are 50.125, 144.200 and 432.100 MHz.
- As the bones of digital. Most digital modes (FT8, RTTY and friends) are just audio tones fed into an SSB transmitter running USB — learn SSB and you’re most of the way to those, too.
New Technician? You already have SSB on 10 m (28.3–28.5 MHz) and across all of VHF/UHF — a great place to make your first sideband contact. See what to do with a Technician license.
Ready to key up on sideband?
Bring your first SSB contact — or your “why do I sound like Donald Duck” — to #ham-radio.