Yaesu FTDX-9000MP Operation Manual

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Page 68 FTDX9000MP OPERATION MANUALB CACONT (CONTOUR) C ONTROL O PERATIONThe Contour filtering system provides a gentle perturbation of the IF filter passband, so as to suppress or enhance certainfrequency components modestly, so as to enhance the natural-sounding received signal.I NTERFERENCE R EJECTION (S IGNALS WITHIN 3 KHZ )Using Contour on the Main (VFO-A) Receiver1. Press the Main (VFO-A) CONT switch (# ). TheLED imbedded in the switch will glow Red to con-firm that the Contour filter is engaged.2. Rotate the Main (VFO-A) CONTOUR knob (# )to achieve the most natural-sounding audio reproduc-tion on the incoming signal. To cancel Contour tuning,press the Main (VFO-A) CONT switch once more.Using Contour on the Sub (VFO-B) Receiver1. Pressing the Sub (VFO-B) band’s RX switch (# )will engage Dual Receive operation.When the imbedded LED grows green, this is yourconfirmation that Dual Receive is in operation.2. Press the Sub (VFO-B) CONT switch (# ). TheLED imbedded in the switch will glow Orange, con-firming that the Contour filter is engaged.3. Rotate the Sub (VFO-B) CONT knob (# ) toachieve the most natural-sounding audio reproductionon the incoming signal. To cancel Contour tuning, pressthe Sub (VFO-B) CONT switch once more.Advice The TFT’s Audio Scope (on the “Oscilloscope” page)is particularly useful when adjusting the Contour con-trol. Not only can you see the effect of the notch/peakof the Contour system, but you also can see the posi-tion of the notch/peak with respect to frequency com-ponents of interest on the incoming signal. You maythen observe (on the Audio Scope) the effect of theContour control while listening to the effect on thesignal, and this will help build your intuition on howbest to use Contour tuning in the future. The Width of the Contour filter effect, and the degreeof nulling or peaking, may be adjusted using the menu. The Contour filter’s level (either nulling or peak-ing) may be adjusted using Menu Item [RX DSP078: MAIN-CONTOUR-LEVEL] for Main(VFO-A) band and [RX DSP 080: SUB-CON-TOUR-LEVEL] for Sub (VFO-B) band. The fac-tory default setting is –15. The bandwidth over which the Contour filter ef-fect is applied may be adjusted using Menu Item[RX DSP 079: MAIN-CONTOUR-WIDTH] forMain (VFO-A) band and [RX DSP 081: SUB-CONTOUR-WIDTH] for Sub (VFO-B) band. Thefactory default setting is 10.With reference to Figure (B), note the initial posi-tion (12 o’clock) of the CONTOUR control whenthe CONT switch is pushed. You may observe the“indentation” in the receiver passband where theContour filter is placing a low-Q “notch” (per thesetting of Menu #078 and 080, referenced above).Counter-clockwise rotation (to the left) of the Con-tour knob causes the indentation to move toward alower frequency within the passband, while clock-wise rotation (to the right) causes the indentation tomove toward a higher frequency within the passband.By removing interference or unwanted frequencycomponents on the incoming signal, it is possible tomake the desired signal rise out of the backgroundnoise/interference, enhancing intelligibility.IFBANDWIDTHIFBANDWIDTHIFBANDWIDTHCONT SwitchCONTOUR KnobCONT SwitchCONT KnobMAIN (VFO-A)SUB (VFO-B)Quick PointThe steep slopes of the DSP filtering can, when adjusted aggressively, impart an unnatural sound to an incoming signal.Oftentimes, though, a narrow bandwidth is not the key to improving copy; the incoming signal itself may have undesirableor excessive frequency components, especially in the low-frequency range around 400 Hz. By judicious use of the Contourfilter, the “shoulder” of the passband response may be altered, or components removed from within the passband, allowingthe desired signal to rise above the background noise and interference in a manner not obtainable with other filteringsystems.