Posted by
Don Wilhelm-4 on
Sep 18, 2007; 9:35pm
URL: http://elecraft.85.s1.nabble.com/K3-2-7-k-Filter-vs-2-8-k-tp453169p453175.html
Mike,
Not necessarily. As long as the signals within the passband of the
roofing filter are not strong enough to overload the DSP, that is
sufficient. In other words, the ultimate rejection of the roofing
filter is not critical. If the roofing filter is able to knock down the
unwanted signal to a level the DSP can handle, then the DSP will not
overload and the DSP itself will provide great ultimate rejection.
These are roofing filters and not final filters. If they were final
filters, then the ultimate rejection would become important.
There is an article on roofing filters in Oct QST that may help to explain.
73,
Don W3FPR
Corboy-Poteet wrote:
> I have a question. The standard IMD test is a two tone test. In a
> contest type situation with multiple strong signals in close
> proximity, wouldn't greater ultimate rejection by the crystal roofing
> filter be a significant advantage?
>
>
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