I am able to copy easily SSB signals which do not move the S-meter.Those signals would have been barely intelligible on the 756. The measured sensitivityon 20m with Pre-amp 1 on, and 500 Hz bandwidth, is 0.1 µV for 10 dB S+N/N (using an HP8640B generator).
Overall, the Pro pulls the "weak ones" out of the noise noticeably betterthan the 756 (or any of its other predecessors in my shack) did. These are clearly due to the NB gatingon signal peaks, and are eliminated by switching the NB out. I observe significant artifacts under strong-signalconditions only when the noise blanker is enabled. The combination of the DSP-NR and noise blanker renders night-time 40m listeningmuch more pleasant and less fatiguing. The DSP-IFfiltering, including a tuneable notch filter, is all inside the AGC loop (unlike theIC-756). It makes an S9+20 undesired tone disappear off the S-meter. The manual pre-AGC IF notch filter (70 dB deep) isdynamite. Also, read George's "Notes on roofing filters" (below). George, W5YR's IF Filter Page dramatically illustrates this point.
The DSP IF filters have much steeper skirts than the analogue crystalfilters in the older rig, and are much more effective against adjacent-channel QRM than analogue filters. I find the Pro a big improvement over its predecessor, the 756.The Pro receiver seems much quieter than that of the 756 - probably due to a cleaner DDSLO implementation. In July 2000, I sold my IC-756, and bought a 756Pro from a local dealer. Adam, VA7OJ/AB4OJ's IC-756Pro User ReviewĪdam, VA7OJ/AB4OJ's IC-756Pro/Pro II User Review
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