Taking a look at Yaesu's latest firmware feature - version Main 0124 + EDSP 0546
All tests were conducted with 3 Khz roofing filter, 2.4 Khz DSP width.
The "S. NARROW" menu option is identical to the prior APF implementation. Shown below are plots of the APF before and after the firmware update. Of the 4 choices now available, only this option has a traditional analog look.
The remaining 3 choices are of a similar filter implementation, with varying bandwidths. Shown here, the "NARROW" option.
Menu option MEDIUM here.
And menu option "WIDE"
Comparing the 4 choices made available in the firmware update.
Measured data for each APF mode:
The APF filter choices may be combined with other filtering options. For example, in this plot we can see the filter spectrum of the 300 Hz DSP only, the MEDIUM APF only, and also the result of using both together in combination.
With the addition of the APF options, the filtering available can be a combination of any of these:
- Standard DSP (rectangular filter shape)
- APF (peaking filter shape)
- Contour (boost or null shape)
- Notch (sharp null)
- AF high/low pass roll-off with up 18 db/octave
And of course, the roofing filters - which provide selectivity - but who's primary function is to prevent overload of the 2nd mixer and subsequent stages.