[R-390] IF sweep alignment

[2002tii]

Tim wrote:

>there's been a trend in the past half century in filter specsmanship 
>to optimize the shape factor at the expense of increased ringing. 
>The fact that the ham radio magazine reviews publish the shape 
>factor, but do not say anything about ringing, has led to this 
>unfortunate situation. CW-oriented homebrewers have been singing the 
>praises of constant group delay filters for a long time now but few 
>of the ham manufacturers have listened (but note that many of the 
>military radios have had constant group delay filters for digital 
>modes for decades now.)

Some of the radios available to hams and SWLs at least have two 
filter modes in their DSP routines ("sharp" and "loose," or similar 
designations).  The JRC NRD-545 and Ten-Tec RX340 both do, and they 
both sound much better in their "relaxed" modes.  The Drake R-8 
series uses the traditional analog approach of well-designed LC 
filters at a low final IF frequency.

Best regards,

Don