Yaesu FT DX 3000 Operating Manual

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Page 50 FT DX 3000 O peraTing M anualinTerFerence rejecTiOnR.Flt (R ooFiNg FilteRS)Narrow-band Roofing Filters of 15 kHz, 6 kHz, 3 kHz, 600 Hz, and 300 Hz (requires optional XF-127CN CW NarrowFilter) bandwidths are provided in the first IF, right after the first mixer. These filters provide protection for the 2nd mix-er, DSP, and other circuitry that follow and can dramatically improve reception on a very crowded band (during a con-test, etc.). Typically, the AUTO selection mode is satisfactory for most operating situations, but in an extremely crowdedphone 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 Filterselection.AUTO*1  300 Hz* 2  600 Hz  3 kHz  6 kHz  15 kHz  AUTO .....*1: The “AUTO” selection mode selects the optimum bandwidth ofthe Roofing filter for the reception mode.In this case, the selected bandwidth in the R.FLT column of theBlock Diagram Display glows yellow (Normally glows Blue).*2: Requires optional XF-127CN CW Narrow Filter.A dvice : In the AM/FM mode, only the 15 kHz Roofing Filteris utilized. As you repeatedly press the [R.FLT] button, theselected Roofing Filter bandwidth will be displayedin the R.FLT column of the Block Diagram Displayon the TFT display, denoting the Roofing Filter cur-rently in use. Typically, this selection will be set to “AUTO.” The Roofing Filter selection will be memorized inde-pendently on each VFO stack of VFO-A and VFO-B.QuicK poiNt:The “AUTO” selection of the Roofing Filter is based onthe operating mode. However, you may override the au-tomatic selection, if band conditions warrant a different(usually, a tighter) selection.[R.FLT] ButtonteRMiNology:A “Roofing Filter,” as its name implies, places a “Roof”over the receiver IF system bandwidth. Starting at thefirst mixer, the Roofing filter protects the circuitry down-stream from strong signals, just as a roof on a houseprotects the contents from rain and snow.blocK diAgRAM diSplAyIndicates the receiverIF Roofing Filter