[R-390] Re: [Milsurplus] Transplanting R-390 IF modules to R-390A

[kirklandb at sympatico.ca]

Use a filter with a Gaussian response (to 6 or 12 dB points) for 
minimum ringing, i.e. for CW.  If you design a narrow flat passband, linear phase filter, it will ring for quite a while. (due to the sharp cutoff corners).  I suspect that the tuned circuit IF lent themselves 
better to a Gaussian shape unless they were staggered tuned to get a flat passband.

For CW, a filter with non-linear phase is not that much of an issue. However go to digital or RTTY, the phase response of the filter
becomes more important.


bill, ve3jhu