Fwd: Re: [Elecraft] K2 CW Filter Characteristics

[Bill Tippett]

Thanks guys (including W5YR off-list)!

         I believe my questions must have been confusing.  I realize that
CW FL1-4 are programmable for both bandwidth and center frequency.
I was wondering why the programmed bandwidth was off by nearly
2:1 (350 Hz actual vs 700 Hz programmed) in ARRL's Test Report.

         I'm also curious about the following from the manual (p.109):

"The shape factor and passband ripple content are optimized at around 300 Hz."

W5YR sent me several plots that appear to be Spectragrams,
but George's plots appear to be dynamic range limited (probably
due to ADC DR in his soundcard) and appear to include other
effects such as NB, AF, etc.  Has anyone (Wayne?) measured
the crystal filter only (not through AF, NB, DSP, etc)?  Here
is an example of what I'm looking for:

http://www.qth.com/inrad/graphs/759.gif

I don't need plots but am curious to know approximate shape
factors of FL1-4 (X7-11) for typical values such as Earl uses
(i.e. 100, 400, 700, 1000 Hz bandwidths)?  I assume filter
characteristics do not change for different CW offsets, since
that only affects the center frequency (correct?.

Although FL1-4 are "5-poles", if I understand the manual
correctly, they are followed by another much wider 2-pole
filter to reduce wideband IF amp noise which probably doesn't
contribute much to the FL1-4 CW shape factors (correct?).

         I'm really just trying to understand the K2's CW crystal filter
characteristics by themselves.  Sorry my questions were not clear!

                                                 73,  Bill  W4ZV

P.S.  My original questions:

> > 1.  What is the actual 6 dB BW, combined 6/60 dB shape factor (X7-11
> > plus X5-6) and passband ripple for various "selected" bandwidths from
> > minimum (200 Hz?) to about 1 kHz?  What I'm looking for is actual data
> > from measurements (Spectragram if it has 60 dB DR or spectrum analyzer)
> > similar to the following:
> >
> > Selected BW   Actual BW  Shape Factor  Passband Ripple
> >       700            350         2.1:1           3 dB
> >
> > 2.  What is the minimum "selectable" BW  (Spec sheet says only "~200 Hz")
> > and what is its actual BW?
> >
> > 3.  Why aren't "selectable" and "actual" bandwidths closer?