Oops! - I missed one point in your email. Yes, the above board mounting
of the KSB2 reduces ultimate rejection due to its longer ground return
paths. But as you noted, with 80 dB of ultimate rejection, following it
with the KDSP2 kills any residual blow by.
A number of the $3K and above DSP rigs on the market today take a
similar approach to the K2. They use a simple moderate rejection crystal
filter followed by the brick wall DSP to gain ultimate filter rejection.
The crystal filter does the heavy lifting to keep off frequency signals
from pumping the AGC and the DSP cleans up any weak residual blow by
that gets past the crystal filter.
73, Eric
Larry Phipps wrote:
You may have just sold me on a KDSP2 down the road Eric. I just ran some
tests on my "new used" K2 (#568), and to cut to the chase... I measured
ultimate rejection out 5 kHz as 80dB with the KSB2 OP1 filter in, better
than you indicated. But with FL2, which is set for 1.8 kHz, I measured
115dB. Is this a result of the KSB2 being outboard?
Larry N8LP
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