K3S DSP filter plots

[Bill Breeden]

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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[Bob McGraw - K4TAX]

Here is a site that provides free computer based spectrum displays. I
use Spectrum View in conjunction with the USB soundcard within the K3S.  
It can be run in real time and you observe the changes that occur as the
various parameters of BW and Shift are utilized.  Easy to use and best
of all, its FREE!

http://www.hotamateurprograms.com/previews.htm

With this application one can see the effect of the BW and Shift
changes.  Also with the markers, one can measure, with reasonable
accuracy and repeatability, the results between different configurations.

I'm sure there's other applications. This one just happens to be one of
my favorites and thus I don't move the HP Spectrum Analyzer from the
shop to the station.  {By the way I figured out what HP stands
for............it's "Hernia Producing"}

73
Bob, K4TAX


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