FT8 versus SSB: which mode to reach for

FT8 works when nothing else does. SSB is a conversation. They are not competing for the same evening.

The short answer

FT8 decodes signals about 20 dB below what a human ear can pull out of noise, so it makes contacts on paths and at power levels where SSB produces nothing. SSB exchanges real information and teaches operating skill. Most stations run both, using FT8 when conditions are poor or the antenna is compromised and voice when the band is open.

FT8 decode floor: About -21 dB SNR
SSB usable floor: About 0 dB SNR
FT8 bandwidth: 50 Hz
SSB bandwidth: 2.4 to 2.8 kHz
FT8 contact length: About 1 minute
FT8 duty cycle: 100 percent

FT8 is the most consequential thing to happen to amateur radio in twenty years and the most argued about. It made small stations viable on bands that were closed to them, it filled the low bands during a solar minimum, and it drew a large share of activity away from voice. Whether that is good depends on what you think the hobby is for.

What is not in dispute is the technical difference. FT8 encodes a fixed 77 bit message into a 15 second transmission occupying 50 Hz, and its decoder recovers that message from signals about 21 dB below the noise in a 2.5 kHz reference bandwidth. SSB needs a signal roughly at or above the noise to be intelligible. That is a gap of around 20 dB, which is more than most amplifiers and most antenna upgrades combined.

The technical comparison

Mode comparison

What each mode does with the same transmitter

Factor	FT8	SSB voice
Decode threshold	About -21 dB SNR	About 0 dB SNR
Occupied bandwidth	50 Hz	2.4 to 2.8 kHz
Information exchanged	Callsign, grid, report	Anything you can say
Contact duration	About 1 minute	2 minutes to an hour
Duty cycle	100 percent while transmitting	20 to 50 percent
Skill required	Software setup	Operating technique
Works on a compromise antenna	Yes, well	Marginally
Works during poor conditions	Yes	Often not

The 20 dB gap in decode threshold is the whole story. Twenty decibels is a hundredfold power ratio, which is why 25 W of FT8 works paths that 1,500 W of SSB does not.

What each one is good for

FT8 is right when: Conditions are poor, your antenna is a compromise, your power is limited, you are chasing entities or grid squares, or you want the station doing something useful while you do something else. It is also the fastest way to find out whether a band is open, because the automatic reporting networks show live path data.
SSB is right when: The band is open and you want a conversation. It is where you meet people, where nets and emergency communication happen, and where operating skill actually develops. A rag chew on 40 metres is a different activity from clicking through a decode list, and most operators who do both would not give up either.
CW deserves a mention: It sits between the two: about 10 to 15 dB better than SSB on weak signals, a genuine conversation, and a skill that takes months to develop. Many operators who tried FT8 for the weak signal performance ended up learning CW instead, because it offers most of the sensitivity and all of the conversation.

What running FT8 demands of the station

A computer with an accurate clock. Slots are aligned to the wall clock and drift beyond about a second stops decoding entirely.
A sound and control interface, unless the radio has USB built in. A Digirig Mobile digital modes interface or Tigertronics SignaLink USB interfacenot on amazon covers a radio that does not.
Correct drive level, with the ALC meter barely moving. Any visible ALC action means the signal is being compressed, which splatters across the band.
Reduced power, because 100 percent duty for 13 seconds at a time is far harder on the finals than SSB. Thirty to fifty percent of rated output is normal.
A power supply rated for continuous duty rather than peak. See sizing a power supply.
A revised RF exposure evaluation. Digital duty is roughly four times harsher than SSB duty, and a station that passes on voice may not on FT8 at the same power.

Safety

RF exposure: you must evaluate your own station

The FCC requires every amateur station to perform a routine RF exposure evaluation and to keep the result. The categorical exemption that used to excuse amateurs by power level alone was removed, so there is no wattage below which you can simply assume you comply.

Radio frequency energy at close range is a real hazard, not a paperwork exercise. Transmitting at power into an antenna a few feet from a person, especially on the bands between 30 and 300 MHz where the exposure limit is at its strictest, can exceed the maximum permissible exposure for an uncontrolled environment.

Nothing on this page evaluates your station. The answer depends on your frequency, your power at the antenna, your antenna gain, your duty cycle and how close people actually get. Run the numbers for your own installation.

This is the specific case worth restating: FT8 transmits at essentially full duty for 13 of every 15 seconds. If your exposure evaluation was done at SSB duty factors, it does not cover your digital operating.

How to run an RF exposure evaluation

Running both well

A station that does both

One radio, one antenna, and an interface if the radio needs one.

Icom

Icom IC-7300

USB sound card and CAT control built in, plus a scope that shows band activity at a glance. No interface hardware needed.

Check price$1,255.74

Yaesu

Yaesu FT-891

The value 100 W radio, excellent on both modes, needing a small interface for digital.

Check price$769.95

Digirig

Digirig Mobile digital modes interface

A tiny combined audio and CAT interface for a radio without USB. The simplest digital add-on there is.

Check price$64.95

Not on Amazon

Tigertronics

Tigertronics SignaLink USB interface

An isolated interface with a physical level knob, which makes setting drive far easier than a menu dive.

Find comparable gear

Sold by Tigertronics, not Amazon. The link searches the category.

Not on Amazon

microHAM

microHAM USB III interface

A full station interface handling audio, keying and CAT with proper isolation throughout.

Find comparable gear

Sold by microHAM, not Amazon. The link searches the category.

Astron

Astron RS-35M-AP linear power supply

A linear supply with no switching noise, which matters more on digital where the noise floor decides what decodes.

Check price$551.00

JYR

JYR8010 8-band end fed half wave, 150 W

A multiband wire, which is all the antenna FT8 needs to work the world at 25 W.

Check price$89.99

Heil Sound

Heil Pro 7 headset microphone

For the voice half. A headset with a proper communications microphone is what makes SSB audio worth listening to.

Check price$457.75

Common questions

Questions people ask about this

Is FT8 really 20 dB better than SSB?

Roughly, on the decode threshold. FT8 recovers its message at about 21 dB below the noise in a 2.5 kHz reference bandwidth, while SSB voice needs a signal at or above that noise to be intelligible. Twenty decibels is a hundredfold power ratio, which is why 25 W of FT8 completes contacts that 1,500 W of SSB cannot on the same path.

Should I learn FT8 or CW for weak signal work?

FT8 is far more sensitive and takes an evening to set up. CW is about 10 to 15 dB better than SSB, takes months to learn, and gives you a genuine conversation at the end of it. If the goal is contacts on a difficult path, FT8. If the goal is a skill and a mode you will still enjoy in twenty years, CW. Plenty of operators do both.

Does FT8 damage my radio?

Running it at full output does, over time. FT8 transmits at essentially 100 percent duty cycle for 13 of every 15 seconds, which heats the finals continuously in a way SSB never does. Run 30 to 50 percent of rated output, give the radio airflow, and size the power supply on its continuous rating rather than its peak figure.

Why does everyone complain about FT8?

Because it exchanges almost no information and the software conducts the contact, so a mode that dominates band activity produces very little conversation. That is a fair criticism of it as an entire hobby and not a reason to avoid it. Using FT8 when conditions are poor and voice when they are good is what most active operators actually do.

Can I run FT8 with a compromise antenna?

Yes, and it is where the mode shines. An attic wire, a balcony vertical or a short loaded whip that produces almost nothing on SSB will complete FT8 contacts across oceans, because the mode tolerates a signal 20 dB weaker. For anybody stuck with a restricted antenna, FT8 is the single largest improvement available.

Keep going

Related on this site

Keeping your own cut lengths, SWR sweeps and exposure record? The Station Build & Antenna Planner is the paid version of these pages: 8 printable worksheets you fill in with your own numbers, plus the full PDF, $29.

Disclaimer Researched guidance for planning purposes, not professional engineering, electrical or legal advice. Antenna work, RF exposure, mast and tower work, grounding and battery handling all carry real risk that depends on your specific site and installation. Verify anything safety-critical against current FCC rules, the National Electrical Code and the manufacturer's own documentation, and hire a professional where the job calls for one. We research equipment from published specifications, regulatory documents and verified owner reviews rather than claiming hands-on testing we have not done.