You said: "In addition, when the DSP IF filters are set to about the same width
as the roofing filters, the two filters "cascade" -- the rejection of adjacent
signals is the sum of the rejection of the two filters. "
There is no requirement that the widths be about the same. They could be widely
different. If one passes an interfering signal with no attenuation and the
other has 100 dB rejection then the sum is 0 + 100 = 100. Either could be first
in the lineup.
If the K3 second mixer was stronger, hardware AGC might not be necessary and the
only need for a "roofing" filter would be to eliminate the image. A single
10-12 kHz filter would suffice and DSP would be the final filter. Sounds like a
K4HD doesn't it?
On 4/1/2020 10:23 AM, Jim Brown wrote:
On 4/1/2020 7:17 AM, Wes wrote:
Until you get down to the noise floor isn't it always the sum (in dB) of the
rejection?
Isn't that what I said? Perhaps I said it badly.
73, Jim
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