Digital vs Voice — Power Output Comparison
- 4 min reading time
Modes: FT8 · SSB · CW
One of the questions I get asked a lot is why FT8 works so well with low power compared to voice. The short answer is that FT8 doesn't need a strong signal — it needs a detectable one. Here's a breakdown of what that actually means in practical terms.
The Core Difference
FT8 can decode signals as low as -20 to -24 dB below the noise floor. Intelligible voice on SSB requires a signal roughly 10 to 15 dB above the noise floor. That's a swing of about 30 to 35 dB — which translates to a massive difference in the power required to make a contact at the same distance.
In real numbers: 5 watts on FT8 can do what might take over 100 watts on SSB under identical conditions. That's not a typo.
SNR Comparison by Mode
All three common HF modes handle noise differently:
- FT8 — reliable contacts down to -20 dB SNR (referenced to 2.5 kHz bandwidth)
- CW (Morse) — readable down to around -10 to -15 dB
- SSB Voice — needs +10 to +12 dB for intelligible speech, +30 dB for armchair copy
CW sits in the middle, which is why it's long been the go-to for weak signal and DX work. FT8 just took it to another level entirely.
What That Looks Like on the Air
Here's a practical way to think about it — if you're hearing a station at a given FT8 SNR, this is roughly what they'd sound like on voice:
| FT8 SNR | SSB Voice Equivalent |
|---|---|
| -20 dB | Not copyable — total silence |
| -10 dB | Barely audible |
| 0 dB | Marginal — intelligible with effort |
| +10 dB | Solid copy — clear voice |
The Duty Cycle Trade-Off
FT8 is easier on your signal path but harder on your radio hardware. During each 15-second transmission burst it runs at 100% duty cycle — full power, constant carrier, the whole time. SSB voice by comparison only peaks when you're actually speaking, averaging out to maybe 20-50% duty cycle.
For a 100-watt radio, most FT8 operators run 30-50 watts to keep things cool and avoid splatter on the waterfall. For portable rigs like the X6200, keeping it at 10-25 watts is smart for the same reason — and honestly you don't need more than that to work serious DX.
The Bottom Line for Portable Ops
This is why FT8 is such a game changer for POTA and QRP operation. Running 5 watts from a park with a simple vertical, you can work stations that a 100-watt SSB station would struggle to reach. The math works out to roughly:
- 10W FT8 ≈ 300W SSB for making a contact
- 100W FT8 ≈ 3,000W SSB
- 100W SSB ≈ 30mW FT8
That last one is the one that really puts it in perspective. FT8 doesn't replace voice — there's nothing like a good ragchew on SSB — but for chasing DX, working new grids, and getting contacts in the log from a park bench with a battery, nothing touches it.
Technical SNR specifications referenced from WSJT-X documentation and established amateur radio literature.
73 de W4GGJ