FT8 was designed for several applications. First, for double-hop E-skip
on 6M, where openings are often brief and not very strong. Second, for
weak signal conditions, and conditions on any band where the path is
noise-limited. This is generally true of ALL of the WSJT modes -- legal
limit is often used on VHF for moon-bounce, meteor scatter, and tropo
communications. Note that WEAK SIGNAL does NOT mean QRP.
FT8 has signal to noise immunity that I would estimate as 6-10 dB better
than excellent CW operators on both ends of the QSO. When used on the
HF bands, fairly low TX power is generally enough. But when used on 6M
and 160M, it's common to run whatever power is needed to make the QSO. I
run my KPA500 at 500W on 6M, and I'm running a borrowed KPA1500 at 1.4 kW.
I don't generally use FT8 on the HF bands, although I did to work KH1
last month. My experience on 6M has been that even though I'm running
high power, my signal report, which is based on signal to noise at the
other end, is usually 6-10 dB worse than the report that I send.
Yesterday, for example, I failed to finish three 6M QSOs because the
other station, who was reading -14 dB, couldn't copy me! Sadly, it has
become increasingly common for us to have very high noise levels,
resulting from switch-mode power supplies, solar power systems,
variable-speed motor controllers, leaking from CATV systems, defective
components on power lines, and a host of other sources.
73, Jim K9YC
I thought FT8 was a low power mode. Am I wrong? I am not referring to Fox
Hound mode.
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