Users Manual 7

FCC ID: K6620461X50

Users Manual

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FCCID_1770322

Interference Rejection FCC ID: K6620461X50 / IC: 511B-20461X50 CONTOUR Control Operation The Contour filtering system provides a gentle perturbation of the IF filter passband. The Contour is set to either sup- press, or boost specific frequency components, and thus enhance the sound and readability of a received signal. 1. Press the [CONT/APF] button to activate the Con- tour filter. The LED inside the [CONT/APF] button glows orange and the current “null” (or “peak”) po- sition of the Contour filter will appear in the CON- TOUR indicator on the display. 2. Rotate the [CONT/APF] knob to achieve the most natural-sounding audio reproduction on the incom- ing signal. Advice: The display will show the Contour frequency for 3 [CONT/APF] Knob [CONT/APF] Button seconds whenever the [CONT/APF] knob is turned. 3. To cancel Contour tuning, press the [CONT/APF] button momentarily. Advice: Alternate presses of the [CONT/APF] button, will switch the Contour filter between on or off. Refer to Figure “B”, this illustrates an “indenta- Advice: tion” of the Contour filter in the center of the  The Contour filter selection will be memorized inde- passband. The Contour filter is placing a low-Q pendently on each VFO stack of VFO-A and VFO-B. “notch” (per the setting of Menu item “069  The Contour filter level (either a null or a peak) may RGEN CNTR LV”, referenced above) in the pass- be adjusted using Menu item “109 RX DSP CON- band. Counter-clockwise rotation (to the left) TOUR LEVEL”. The factory default setting is for a of the [CLAR/VFO-B] knob causes the notch null of –15 (dB). to move towered a lower frequency within the  The bandwidth over which the Contour filter effect is passband, while clockwise rotation (to the right) applied may be adjusted using Menu item “110 RX causes the notch to move toward a higher fre- DSP CONTOUR WIDTH”. The factory default setting quency within the passband. By removing inter- is 10. ference or unwanted frequency components of  When the optional DMU-2000 Data Management the incoming signal, it is possible to make the Unit is connected, the Audio Scope (on the “Oscil- desired signal rise out of the background noise/ loscope” page) is particularly useful when adjusting interference, enhancing intelligibility. the Contour control. Not only can you see the effect of the null/peak of the Contour system, but you also A B C 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: The steep slopes of the DSP filtering, when adjusted aggressively, can impart an unnatural sound to an incoming sig- nal. Often, 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 may be 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 DX 3000 Operating Manual Page 49

Interference Rejection FCC ID: K6620461X50 / IC: 511B-20461X50 IF SHIFT Operation (SSB/CW/RTTY/PKT/AM Modes) IF SHIFT allows you to move the DSP filter passband higher or lower, without changing the pitch of the incoming sig- nal, and thus reduce or eliminate interference. Because the carrier tuning frequency is not varied, there is no need to re- tune the operating frequency to eliminate the interference. The total passband tuning range for the IF SHIFT system is ±1 kHz. 1. Rotate the [SHIFT] knob to the left or right to re- duce the interference. Advice: The display will show the shift value of the IF SHIFT for 3 seconds whenever the [SHIFT] knob is turned. Advice: The center position of the IF passband will be memo- rized independently on each VFO stack of VFO-A and VFO-B. [SHIFT] Knob Referring to Figure “A”, note the depiction of the IF DSP filter as the thick line, with the [SHIFT] knob in the 12 o’clock position. In Figure “B”, an interfering signal has appeared inside the original passband. In Figure “C”, you can see the effect of rotating the [SHIFT] knob. The interference level is reduced by moving the filter passband so that the interference is outside of the passband. A B C Page 50 FT DX 3000 Operating Manual

Interference Rejection FCC ID: K6620461X50 / IC: 511B-20461X50 WIDTH (IF DSP Bandwidth) Tuning (SSB/CW/RTTY/PKT Modes) The IF WIDTH tuning system allows you to vary the width of the DSP IF passband, to reduce or eliminate interference. Moreover, the bandwidth may actually be expanded from its default setting, should you wish to enhance incoming sig- nal fidelity when interference on the band is low. 1. Rotate the [WIDTH] knob to the left or right to re- duce the interference. Advice: The frequency display will show the bandwidth of the IF passband for 3 seconds whenever the [WIDTH] knob is turned. Advice: [WIDTH] Knob The IF Bandwidth will be memorized independently on each VFO stack of VFO-A and VFO-B. Referring to Figure “B”, you can see the default bandwidth on the SSB mode. By rotating the [WIDTH] knob to the left, the Using IF SHIFT and WIDTH Together bandwidth will narrow (see Figure “A”, while The IF SHIFT and Variable IF WIDTH features rotation of the [WIDTH] knob to the right, as together form a very effective interference-fight- depicted in Figure “C”, will increase the band- ing filtering system. width. For example, in Figure “A”, you can see how in- terference has appeared both on the high and low A B C sides of the desired signal. Rotate the [WIDTH] knob, the interference from one side can be eliminated (Figure “B”). Next, rotate the [SHIFT] knob to re-positioning the passband (Figure “C”), the interference on the opposite side can be re- moved, without re-introducing the interference previously eliminated in Figure “B”. A B C The default bandwidths, and total bandwidth ad- justment range, will vary according to the operat- ing mode: SSB Mode: 1.8 kHz ~ 4.0 kHz (default: 2.4 kHz). CW Mode: 500 Hz ~ 2.4 kHz (default: 2.4 kHz) RTTY/PKT Modes: 500 Hz ~ 2.4 kHz (default: 500 Hz) Advice: For best interference reduction, the WIDTH and SHIFT features are the primary tools you should use. After narrowing the bandwidth (WIDTH) and/or adjusting the center of the passband (SHIFT). The Contour control may then yield additional signal-enhancement benefits on the net residual bandwidth. Even more, the IF NOTCH Filter (described later) may also be used, in conjunction with these filter systems, to significant advantage. FT DX 3000 Operating Manual Page 51

Interference Rejection FCC ID: K6620461X50 / IC: 511B-20461X50 NARROW (NAR) One-Touch IF Filter Selection Pressing the [NAR] button provides one-touch, mode-specific, selection of a narrow IF DSP filter setting that does not require resetting the [WIDTH] knob. Pressing the [NAR] button once more returns the band- width control to the WITDH/SHIFT system. The factory default bandwidths are: Operating Mode [NAR] Switch “ON” “OFF” SSB 200 Hz ~ 1.8 kHz 1.8 ~ 4.0 kHz (1.5 kHz) (2.4 kHz) CW 100 ~ 500 Hz 500 Hz ~ 2.4 kHz (500 Hz) (2.4 kHz) RTTY/PKT-L/PKT-U 100 ~ 500 Hz 500 Hz ~ 2.4 kHz (300 Hz) (500 Hz) [NAR] Button PKT-FM 9 kHz 16 kHz AM 6 kHz 9 kHz FM (28/50 MHz Bands) 9 kHz 16 kHz : Depends on the [WIDTH] knob ( ): Default Bandwidth Advice:  When the narrow bandwidth is selected, the “ ” icon will appear in the display.  Even if the [NAR] button has been pressed to en- gage the narrow filter, you may adjust the narrow IF bandwidth by rotating the [WIDTH] knob. The IF SHIFT still is operational. For many applications, you may find that simply pressing the [NAR] button instead of adjustment of the [WIDTH] knob, may be satisfactory for interference reduction.  When you press the [NAR] button in the FM mode, both transmit and receive bandwidths are narrowed. Page 52 FT DX 3000 Operating Manual

Interference Rejection FCC ID: K6620461X50 / IC: 511B-20461X50 IF NOTCH Filter Operation (SSB/CW/RTTY/PKT/AM Modes) The IF NOTCH filter is a highly effective system that allows you to slice out an interfering beat note or other carrier signal from inside the receiver passband. 1. Press the [NOTCH] button to activate the Notch fil- ter. The LED inside the [NOTCH] button glows or- ange and the current “null” position of the NOTCH filter will appear in the NOTCH indicator on the display. The [NOTCH] knob functions as the Notch adjustment knob. 2. Rotate the [NOTCH] knob to adjust the “null” posi- tion of the Notch filter. Advice: [NOTCH] Button The frequency display will show the Notch frequen- cy for 3 seconds whenever the [NOTCH] knob is turned. 3. To cancel the NOTCH filter, press the [NOTCH] button momentarily. The graphic disappears from the NOTCH indicator on the display, confirming that the The performance of the IF NOTCH filter is NOTCH filter is no longer operation. shown in Figure “A”, where the effect of rotation Advice: of the [NOTCH] knob is depicted. In Figure “B” Alternate presses of the [ NOTCH ] button, will you can see the notching effect of the IF NOTCH switch the NOTCH filter between on or off. filter as you rotate the [NOTCH] knob to elimi- nate the incoming interference. Advice:  The IF NOTCH Filter selection will be memorized independently on each VFO stack of VFO-A and A B VFO-B.  When the optional DMU-2000 Data Management Unit is connected, the effect of the IF NOTCH filter may be observed on the Audio Scope (on the “Os- cilloscope” page). The Notch will be observed as a “dip” in the noise platform observed. What’s more, the “Waterfall” display may be used to observe the effect of the IF NOTCH filter, which will appear as a white area in the colored background area. FT DX 3000 Operating Manual Page 53


Document Created: 2012-08-10 19:01:43
Document Modified: 2012-08-10 19:01:43
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