On 1/10/2013 2:01 PM, Ed Muns wrote:
> The KFLA-250 is nominally 370 Hz wide at the -6 dB points.
Which is why it makes little sense to put both the KFL3A-400 and
KFL3A-250 in the same K3<G>. Again, see the Elecraft filter plots:
http://www.elecraft.com/K3/K3_filter_plots.htm
370Hz is very close to the theoretical limit - one can debate whether
the 3rd, 5th or 7th harmonic of the 22.727 Hz "clock" are required to
adequately reproduce the edges of the keying waveshape - for minimum
ISI. The 400 Hz filter provides just a bit more ease of tuning at
minimal added risk of close in AGC effects and 400/200 is a better
combination that 500/250 on CW.
73,
... Joe, W4TV
On 1/10/2013 2:01 PM, Ed Muns wrote:
The KFLA-250 is nominally 370 Hz wide at the -6 dB points.
If SHIFT is needed to center the filter on the Mark/Space signals, then the
filter needs an offset in the CONFIG parameter. Despite the claim that the
8-pole filters have zero offset, I've found a number that do. This is
especially important on these narrow bandwidth filters.
Ed W0YK
Dave K6LL wrote:
I use the 250 Hz roofing filter and DSP BW 350 as my go-to
RTTY settings on the K3. It seems to work well for me. Use
the SHIFT control to make sure the mark and space are
centrally spaced in the spectrum display. The mark and space
should be just about the same amplitude as the center
amplitude, with the sidebands tailing off on both sides from there.
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