Been reading various sources about FT8's claimed sensitivity threshold of -21dB in 2500Hz bandwidth. The Signal ID Wiki and other sources consistently quote this figure, but I'm seeing real-world variations in my shack. Most successful contacts seem to happen between -5dB to -24dB, with signals below -20dB often completely inaudible but still decodable.

Running an IC-7300 with SignaLink USB interface and wondering if my setup is limiting performance or if the -21dB spec represents ideal laboratory conditions. Anyone done actual SNR testing with calibrated signal generators? What's your real-world minimum decode threshold?

Also curious about the bandwidth reference - the 2500Hz reference seems to be based on SSB receiver IF filter width, but actual FT8 bandwidth is much narrower at around 50Hz. Makes the SNR comparison somewhat artificial.

The -21dB spec is legitimate but depends heavily on your receiver's dynamic range and AGC settings. On HF bands with lots of strong signals, dynamic range becomes more important than sensitivity. Try turning off preamp and using attenuator if you're seeing overload - counterintuitive but often improves weak signal decoding.

I consistently decode down to -22dB on 40m with my FT-991A and homebrew interface. Key is proper audio levels - keep that bar graph in the green zone. If it's hitting red, back off RF gain or add attenuation. Also make sure your PC clock is NTP synced to within 1 second.

Been testing this exact question with my HP signal generator. Real threshold varies by 2-3dB depending on band conditions and adjacent signal activity. The -21dB figure assumes clean lab conditions with no QRM. In practice, FT8 significantly outperforms PSK31 and RTTY for weak signal work, but don't expect miracles in high-noise urban environments.