I use the Timewave 599 zx with the Omni IV + and find it enhances cw work
considerable. The greatest asset of the zx is not so much noise reduction but
rather the digital AGC. The shortcoming of the Omni's dsp noise reduction is
that one moment the signal is blasting and the next it is so faint as to be
almost lost. The zx nearly eliminates this problem but can introduce another;
distortion, if the gain on the Omni is too high. A little trial and error
setting of the RF/AF controls minimizes this though. I also find that setting
the RF gain on the Omni to about 3 o'clock really cuts down on the ambient
noise level. That last notch or two of RF gain is really noisy. For really
weak signal stuff, turn the AGC off and ride the AF gain. The zx AGC will
help lessen knob turning here.
With the zx and Omni noise reduction on, the zx AGC on, and the 500 hz
Omni filters plus the zx cw bandpass filters all in, signals seem to appear
from silence. This combination is by far the easiest listening, hour after
hour, I have ever experienced in 34 years of radios.