Hi Cecil,
All the IC-756Pro-series radios have 2 roofing filters - the first at 64.455
MHz, and the second at 455 kHz (actually a two-section filter with the NB
noise gate between the sections.) In the Pro and Pro2, the 64.455 MHz filter
is discrete; in the Pro3, it is the same MCF as used in the 7800.
http://www.nsarc.ca/hf/756p3_p2.pdf
By definition, a roofing filter is required in a superhet. The purpose of
the roofing filter is twofold: to suppress images generated by the mixer,
and to reduce the statistical probability that strong out-of-band signals
will ride down the IF and overload downstream stages.
Cheers for now, 73,
Adam VA7OJ/AB4OJ
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