A 0.5 dB noise figure front end amplifier with NO other losses would produce -149.5 dB MDS. That is the absolute maximum MDS sensitivity obtainable with 250 Hz BW and 0.5dB total input noise figure.
I meant OFF and not ON for the internal preamp. I don't use internal preamp ON. The issue is most internal preamps are not designed for 160m, they need to cover up to 50 MHz Even the ICOM Norton prea