Hi Carl!
I'm surprised at the variation in shape factors at very
low bandwidths and believe you are seeing the combined effect
of cascading the DSP filter with the roofing filter. Otherwise,
I can think of no reason why the shape factor of the DSP filter
alone would vary by bandwidth as it seems to. Remember that
Orion automatically selects the next higher roofing filter
whenever you select a DSP bandwidth. This could explain why
the shape factor appears to improve as selected BW approaches
each roofing filter BW (1.0, 2.4, 6.0 kHz) in your results.
Could you try an experiment for us? I assume you have
only the stock roofing filters (15 kHz, 6 kHz, 2.4 kHz and 1.0 kHz),
with the automatic mode enabled.
1. FIrst disable automatic mode.
2. Set the DSP BW to 1000 Hz and enable the 1000 Hz roofing filter.
3. Record your measurements.
4. Repeat keeping the DSP BW fixed at 1000 Hz but successively
enabling the 2.4, 6 and 15 kHz roofing filters (15 kHz might not be
possible if it is only available for FM mode...will be interesting
to learn if it will work for CW).
I expect the 1000 Hz shape factor will degrade as you select the
higher roofing filters and have less cascaded effect. If you select a
DSP BW and enable a roofing filter much higher, you should be truly
measuring the DSP shape factor alone, assuming the roofing filters
center response is relatively flat.
73, Bill W4ZV
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