I've been comparing FT4 sensitivity specs showing it's 3.5 dB less sensitive than FT8 but offers twice the QSO rate with my actual on-air results. While FT4 has performance boosts, FT8's narrower bandwidth provides better decoding in extreme weak signal situations and longer duration helps average out fading issues. Anyone doing systematic A/B testing between the modes at various signal levels? I'm particularly interested in how FT4 performs with signals 10 dB weaker than required for RTTY versus FT8's advertised -21dB threshold.

I've been running both modes side-by-side for months. FT4 is twice as fast with 7.5 second transmissions versus FT8's 15 seconds, but you really notice the sensitivity difference on 40m during high noise periods. FT8 consistently decodes stations that don't even show up in FT4's waterfall.

From a technical standpoint, FT4's four-tone CPFSK at 23.4 baud with 90 Hz bandwidth trades some sensitivity for speed. The math works out - you're processing more information faster but need stronger signals. Perfect for contest scenarios where band conditions support it.

New to digital modes here - should I start with FT8 or jump to FT4? My setup is pretty basic (IC-7300, wire antenna, 100W). Sounds like even compromised antennas can work well with these weak signal modes, which is great for HOA-restricted operators.