Interesting observations during last weekend's contest when Kp rose from quiet (1.0) on Saturday morning to active (4.67) by Sunday afternoon. The storm's impact on high-band propagation was quite noticeable, but I found FT8 was still pulling through contacts on 17m when SSB was completely dead.

FT8 is more effective in weak-signal conditions, decoding signals as low as -21 dB, compared to -17 dB for FT4. During the disturbance, that extra sensitivity really showed. Anyone else notice similar performance differences between the modes during rough conditions?

Absolutely! FT8 offers operators the ability to communicate despite unfavorable conditions such as those seen during low solar activity, high RF noise, or with low transmitter power. During that same period I was seeing FT8 decodes on 15m while FT4 wasn't getting through at all. The extra 4dB sensitivity matters when propagation gets sketchy.

FT4 transmissions last 7.5 seconds compared to FT8's 15-second transmissions, allowing more contacts in less time, but you're right that FT8 wins on weak signals. Choose FT4 when faster contacts are needed and signals are strong enough to support shorter transmission cycles. During that disturbance, FT8 was definitely the better choice.

This is exactly why I keep both modes configured in WSJT-X. Operators typically choose FT8 for maximum decoding performance and FT4 for speed when signal conditions are strong enough. When conditions start deteriorating, I switch from FT4 back to FT8. Nice to have options depending on what the bands are doing!