INTERFERENCE REJECTION(SIGNALS OFF FREQUENCY BY JUST A FEW KHZ)

R.FLT (ROOFING FILTERS)

Narrow-band Roofing Filters of 15 kHz, 6 kHz, and 3 kHz bandwidths are provided in the first IF, right after the first mixer. These filters provide protection fort the 2nd mixer, DSP, and other circuitry that follow and can dramatically improve reception on a very crowded band (during a contest, etc.). Typically, the AUTO selection mode is satisfactory for most operating situations, but in an extremely crowded phone band you may wish to select, for example, the 3 kHz roofing filter for SSB operation.

Press the [R.FLT] button to toggle the Roofing Filter selection.

AUTO ￿15 kHz ￿6 kHz ￿3 kHz ￿AUTO

ADVICE:

￿The Roofing filter selection affects the Main band (VFO-A) only. The Sub band’s (VFO-B) Roofing fil- ter is fixed at a bandwidth of 15 kHz.

￿As you repeatedly press the [R.FLT] button, you will observe changes in the notation in the R.FLT column of the Receiver Configuration Indicator on the display,

denoting the Roofing Filter currently in use.

￿Typically, this selection will be set to “AUTO.”

￿The Roofing Filter selection will be memorized inde- pendently on each VFO in the VFO stack.

QUICK POINT:

￿The “AUTO” selection of the Roofing Filter is based on the operating mode. However, you may override the automatic selection, if band conditions warrant a different (usually, a tighter) selection.

￿The AUTO mode Roofing Filter selections are shown below:

AM/FM/FM-PKT: 15 kHz

LSB/USB/PKT:

6 kHz

CW/RTTY:

3 kHz

￿When the Roofing filter mode is set to “AUTO” and the Noise Blanker is turned On, the Roofing Filter band- width will automatically be set to 15 kHz, as this set- ting provides the most effective noise blanking. How- ever, you still may override the automatic setting, and select a more narrow Roofing Filter. Noise blanking may be compromised, however, with a tighter Roofing Filter in the line.

TERMINOLOGY:

A “Roofing Filter,” as its name implies, places a “Roof” over the receiver’s IF system bandwidth. This “Roof” protects the circuitry downstream from the first mixer from interference, just as a roof on a house protects the contents from rain and snow.

Receiver Configuration Indicator

[R.FLT] Button

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FT-2000 OPERATING MANUAL