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Page 64 FTDX9000D OPERATION MANUALUSING THE μ-T UNE F EATUREThe μ-Tune system is an advanced preselector for the RF front end of the Main (VFO-A) receiver, providing a much narrowerpassband than the VRF circuit. The Q of the μ-Tune filter is so tight as to provide significant suppression of signals little more than10 kHz away from your current operating frequency, and manual adjustment of the μ-Tune filter's center frequency allows you toposition the shoulder of the filter in such a way as to enhance interference rejection to one side or another of your current frequency.Because the insertion loss of the μ-Tune is somewhat higher than that of the VRF, we have also provided the capability to disengageμ-Tune, and engage VRF, should your antenna and noise environment lead to system noise figure concerns when using μ-Tune.The FT DX 9000D’s Main (VFO-A) band receiver is equipped with μ-Tune modules covering the 1.8 ~ 14 MHz Amateurbands. On the 18 ~ 50 MHz bands on the Main (VFO-A) receiver, and on all bands on the Sub (VFO-B) side, the VRFcircuit is provided.μ-Tune Operation on the Main (VFO-A) Receiver1. Press the VRF/μ-T switch (# ). The imbeddedRed LED will light up. The μ-Tune circuit will automatically align itselfonto your operating frequency. Remember that μ-Tune only operates on the Main(VFO-A) band on the 14 MHz and lower bands.2. Now rotate the VRF/μ-T knob to peak the response(background noise) or reduce interference. A pictorial representation of the tuning positionof the μ-Tune filter will appear on the bar graphon the TFT. The amount of change in the center frequency ofthe μ-Tune filter, when rotating the VRF/μ-Tknob by one click, can be configured using Menuitem “GENERAL 035 μTUNE DIAL STEP.” If you have performed manual adjustment of theμ-Tune filter’s center frequency, you may pressand hold in the VRF/μ-T key for two secondsto re-center the filter response on your current op-erating frequency.3. Press the VRF/μ-T switch (momentarily) once moreto disengage the μ-Tune filter; the imbedded Red LEDwill switch off. In this mode, only the fixed bandpassfilter for the current band will be engaged.MAIN(VFO-A)VRF/μ-T switchMAIN(VFO-A)VRF/μ-T knobMAIN (VFO-A)μ-Tune filter will appearon the bar graphμ-Tune filter will appearon the bar graphQuick NoteThe permeability-tuning concept utilized in the μ-Tune cir-cuit dates back many decades, as it was incorporated in suchclassic transceivers as the FT-101 and FT-901 series, in ad-dition to the FT DX 400 and similar models. The μ-Tunecircuit in the FT DX 9000 is the highest development of thiscircuit concept ever employed in an Amateur transceiver.Advice The μ-Tune filters are the most advanced, selective RF preselector filters ever incorporated into an Amateur Radiotransceiver. The RF selectivity provided by μ-Tune can be of tremendous value in ensuring quiet, intermod-free recep-tion even in the most crowded bands on a contest weekend. The μ-Tune filters provide RF selectivity on the order of afew dozen kHz at -6 dB, at the expense of a few dB of system gain on bands where noise figure is seldom an issue. Youwill notice that the S-meter deflection, when μ-Tune is engaged, is slightly less than when it is out of the circuit; this isnormal. If your antenna system gain is so low as to make it impossible to hear band noise when μ-Tune is engaged(highly unlikely), just switch it out or revert to the VRF system, which has slightly less insertion loss. As you tune around on an amateur band with μ-Tune engaged, the microprocessor automatically commands the steppermotor driving the toroid core stack to center the filter on your current operating frequency (the tuning resolution is 5kHz). You may, however, use the VRF/μ-T knob (# ) to skew the filter response to one side or the other from youroperating frequency, to deal with heavy interference on one side. To re-center the μ-Tune filter on your operatingfrequency, and eliminate any offset, press and hold in the VRF/μ-T switch (# ) for two seconds. A pictorial representation of the tuning position of the μ-Tune filter will appear on the bar graph on the TFT. While μ-Tune is a superior RF preselection circuit, it may be disabled via the Menu; if this is done, the VRF circuit willengage when the VRF/μ-T switch is pressed. To disble μ-Tune, go to Menu item “GENERAL 035 μTUNE DIALSTEP” and set the selection to “OFF.”The FT DX 9000D includes an unmatched array of RF selectivity-enhancing features. Please study the material belowcarefully, so as to understand the various features complete.Advanced Interference-Suppression Features: RF Front End