No, the roofing filters aren't superfluous even with lower level
signals. If you set the bandwidths similarly as I do all of the time,
the rejection of the filter adds to the rejection from the DSP. I think
this should be pretty obvious.
Dave AB7E
On 3/31/2020 8:36 PM, Don Wilhelm wrote:
Hopefully that we will remember that the DSP filter skirts are steeper
than the crystal filter skirts, so judicious use of the HiCut and
LoCut will provide us with a better passband than narrow roofing filters.
What the roofing filters will do is keep the receiver from reducing
the hardware AGC for stations which are within the roofing filter
passband.
It takes adjacent signals in excess of S-9 +30 for the adjacent signal
to activate the hardware AGC (which protects the front end DAC from
overload). If the interfering station does not exceed that threshold,
then the DSP filters will take care of it, and the need for more
narrow roofing filters is superfluous.
73,
Don W3FPR
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