Charles,
Here are some quick and dirty readings from my Field Day K3 which is
equipped with a 400 Hz filter, but nothing narrower.
Both sets of S meter readings below start with the K3 in CW mode tuned
to 3550.000 with the S meter reading S9+40 from a 3550.0 signal supplied
by an HP8640B. As you suggested, I then tuned the K3 away from the
signal from the generator.
400 Hz filter in "normal" configuration (400 Hz DSP also):
+40 = 3550.000
+35 = 3550.134
+30 = 3550.166
+25 = 3550.177
+20 = 3550.182
+15 = 3550.185
+10 = 3550.190
+5 = 3550.195
S9 = 3550.198
S8 = 3550.204
S7 = 3550.208
S6 = 3550.213
S5 = 3550.224
400 Hz filter with DSP narrowed to 200 Hz:
+40 = 3550.000
+35 = 3550.068
+30 = 3550.080
+25 = 3550.094
+20 = 3550.104
+15 = 3550.112
+10 = 3550.120
+5 = 3550.126
S9 = 3550.130
S8 = 3550.138
S7 = 3550.142
S6 = 3550.145
S5 = 3550.150
I only had time this morning to measure two filter settings on one slope
of each filter. I'll let you plot the data.
I hope you find this information useful until you get some better
information.
73,
Bill - NA5DX
[Elecraft] K3S DSP filter plots
*charles at k5ua.com*charles at
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Thanks for the reply Joe.
I'm hoping that the constant slope you described is not the way the DSP
filters are implemented, because that would mean the 50hz filter has a
5.625:1 shape factor, the the 100hz filter has a 5:1 shape factor, the
200 hz filter has a 3:1 shape factor and the 400hz filter would have a
2:1 shape factor. To achieve better than 2:1 shape factor at 30dB per
100hz, the width of the DSP filter would need to exceed 400hz.
I wonder if anyone has put their K3 or K3S in the 1 hz tuning mode with
a signal generator and ploted out the approximate response curves using
the S meter. It's a rather crude way to do it, but in the absence of
more accurate test gear it will give some idea of the shape factor of
the DSP filters.
I will be ordering a K3S today and will ask Elecraft if they have plots
for the 50, 100, 150, and 200 hz DSP filters. If not, I will get the
little signal generator and report my findings on the reflector.
If anyone reading this thread has plotted out the 50, 100, 150, or 200
hz DSP filter response curves, please let me know.
Charles K5UA
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