INTERFERENCE REJECTION(SIGNALS WITHIN 3KHZ)

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, so as to eliminate interference. Moreover, the bandwidth may actually be expanded from its default setting, should you wish to enhance incoming signal fidelity when interference on the band is low.

Rotate the [WIDTH] knob to adjust the bandwidth. Counter-clockwise rotation reduces the bandwidth, while clockwise rotation increases the bandwidth.

ADVICE:

￿The IF Width affects the Main band (VFO-A) only.

￿The bandwidth of the IF can be observed on the dis- play.

CAUTION:

When rotating the [WIDTH] control fully counter-clock- wise, the transition between 50 Hz and 25 Hz bandwidth may be accompanied by a “ping” sound, depending on the amount of noise present. This is a normal condition, and you should turn down the volume, when wearing head- phones, to minimize the amplitude of this momentary sound.

Referring to Figure B, you can see the default bandwidth with the [WIDTH] knob set to the 12 o’clock position.

By rotating the [WIDTH] knob to the left, the bandwidth will narrow (see Figure “A”), while rotation of the [WIDTH] knob to the right, as depicted in Figure “C,” will widen the bandwidth.

A B C

IF

IF

IF

BANDWIDTH

BANDWIDTH

BANDWIDTH

The default bandwidths￿, and total bandwidth adjustment range, will vary according to the operating mode:

SSB Mode: 200 Hz ~ 4.0 kHz (2.4 kHz￿)

CW Mode: 25 Hz ~ 2.4 kHz (2.4 kHz￿)

RTTY/PKT Modes: 25 Hz ~ 2.4 kHz (500 Hz￿)

￿: bandwidth at 12 o’clock position of [WIDTH] knob.

WIDTH Indicator

[WIDTH] Knob

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Using IF Shift and Width Together

The IF Shift and Variable IF Width features together form a very effective interference-fighting filtering system.

For example, in Figure “A” you can see how interference has appeared both on the high and low sides of the desired signal. By rotating the [WIDTH] knob, as shown in Figure “B,” the interference from one side can be eliminated, and by re-positioning the [SHIFT] knob (Figure “C”), the interference on the opposite side can be removed, without reintroducing the interference previously eliminated in Figure “B.”

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 also yield additional signal- enhancement benefits on the net residual bandwidth. What’s more, the IF Notch Filter (see the next sec- tion) may also be utilized, in conjunection with the three other filter systems, to significant advantage.

A

B

C

Desired Signal

Desired Signal

Desired Signal

QRM

QRM

QRM

QRM

QRM

QRM

IF

IF

IF

BANDWIDTH

BANDWIDTH

BANDWIDTH

FT-2000 OPERATING MANUAL

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