INTERFERENCE REJECTION(SIGNALS WITHIN 3KHZ)

CONTOUR CONTROL OPERATION

The Contour filtering system provides a gentle perturbation of the IF filter passband, so as to suppress or enhance certain frequency components, thus enhancing the sound and/or readability of a received signal.

1.Press the [CONTOUR] button. The Contour notation will appear in the display to confirm that the Contour filter is engaged.

2.Rotate the [CONTOUR] knob to achieve the most natural-sounding audio reproduction on the incoming signal.

3.To cancel Contour tuning, press the [CONTOUR] but- ton once more.

CONTOUR Indicator

[CONTOUR] Button

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[CONTOUR] Knob

ADVICE:

￿ The Contour filter affects the Main band (VFO-A) only. ￿ You may observe the graphically-depicted peak position of the CONTOUR Filter in the CONTOUR indi-

cator on the display.

[CONTOUR] button

[CONTOUR] button

 

Fully Clockwise

 

Fully Clockwise

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[CONTOUR] button

[CONTOUR] button

 

 

 

Center

 

 

 

 

 

Center

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[CONTOUR] button

[CONTOUR] button

Fully Counter-Clockwise

Fully Counter-Clockwise

CONTOUR GAIN “MINUS”

CONTOUR GAIN “PLUS”

￿The Contour filter’s level (either nulling or peaking) may be adjusted using Menu item “090 rdSP CNTR LV.” The factory default setting is for a null of “–15” (dB).

￿The bandwidth over which the Contour filter effect is applied may be adjusted using Menu item “091 rdSP CNTR WI.” The factory default setting is “10.”

￿When the optional DMU-2000Data Management Unit is connected, the Audio Scope (on the “Oscilloscope” page) is particularly useful when adjusting the Con- tour control. Not only can you see the effect of the null/peak of the Contour system, but you also can see the position of the null/peak with respect to frequency components of interest on the incoming signal. You may then observe (on the Audio Scope) the effect of the Contour control while listening to the effect on the signal, and this will help build your intuition on how best to use Contour tuning in the future.

QUICK POINT:

With reference to Figure “B,” note the initial position (12 o’clock) of the [CONTOUR] knob when the [CONTOUR] button is pushed. You may observe the “indentation” in the receiver passband where the Contour filter is placing a low-Q “notch” (per the setting of Menu item “090,” referenced above). Counter-clockwise rotation (to the left) of the [CONTOUR] knob causes the indentation to move towered a lower frequency within the pass- band, while clockwise rotation (to the right) causes the indentation to move toward a higher frequency within the passband. By removing interference or unwanted frequency components on the incoming signal, it is possible to make the desired signal rise out of the background noise/interference, enhancing intelligibility.

A B C

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IF

 

 

 

 

IF

 

 

 

 

IF

 

 

 

 

BANDWIDTH

 

BANDWIDTH

 

BANDWIDTH

 

 

The 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 undesirable or excessive frequency components, especially in the low-frequency range around 100-400 Hz. By judicious use of the Contour filter, the “shoulder” of the passband response may be altered, or components removed from within the passband, allowing the desired signal to rise above the background noise and interference in a manner not obtainable with other filtering systems.

FT-2000 OPERATING MANUAL

Page 55