Bedienungsanleitung Yaesu FT-DX9000MP (Seite 152 von 164) (Englisch)

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Page 150 FT DX 9000MP OPERATION MANUAL

RF µ-TUNING UNITS

(

MTU-160, MTU-80/40, MTU-30/20

)

The optional RF µ-Tuning Units provide ultra-sharp RF selectivity for the Main (VFO-A) band. The high Q is made

possible by the narrow-band design; one µ-Tune module is required for the 1.8 MHz band (MTU-160), while the 3.5 and

7 MHz bands are covered by the MTU-80/40, and the 10.1 and 14 MHz bands are covered by the MTU-30/20.

When one of three optional units is installed, it will automatically be adjusted so as to center on your operating frequency.

The narrow bandwidth is especially useful on the low bands, where many strong signals being received via NVIS propaga-

tion (Near Vertical-Incidence Signals) within a narrow bandwidth, and the added protection at the RF stage is especially

helpful in preventing IMD and blocking.

The µ-Tuning circuitry, with a Q and shape factor much higher than that afforded even by VRF, can also be manually

adjusted to provide relief against interference as close as 10 kHz away. The insertion loss of the µ-Tune filters is higher than

that of the VRF circuit, so if Noise Figure is a concern you may select the VRF circuit, instead of µ-Tuning, via the Menu.

Note

The µ-Tuning modules are available only for the Main (VFO-A) band, and only function up through the 14 MHz band. On

the 18 MHz and higher Amateur bands, the VRF circuitry is utilized.

µ-Tune Operation on the Main (VFO-A) band Receiver

1. Press the VRF/µ switch (# ). The imbedded Red

LED will light up.

H The µ-Tune circuit will automatically align itself

onto your operating frequency.

H Remember that µ-Tune only operates on the VFO-

A band on the 14 MHz and lower bands.

2. Now rotate the VRF/µ knob (# ) to peak the re-

sponse (background noise) or reduce interference.

H The amount of change in the center frequency of

the µ-Tune filter, when rotating the VRF/µ knob

by one click, can be configured using Menu item

[GENERAL 035 µTUNE DIAL STEP].

3. Press the VRF/µ switch (momentarily) once more

to disengage the µ-Tune filter; the imbedded Red LED

will switch off. In this mode, only the fixed bandpass

filter for the current band will be engaged.

Advice

H The µ-Tune filters are the most advanced, selective RF preselector filters ever incorporated into an Amateur Radio

transceiver. 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 a

few dozen kHz at -6 dB, at the expense of a few dB of system gain on bands where noise figure is seldom an issue. You

will notice that the S-meter deflection, when µ-Tune is engaged, is slightly less than when it is out of the circuit; this is

normal. 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.

H As you tune around on an amateur band with µ-Tune engaged, the microprocessor automatically commands the stepper

motor driving the toroid core stack to center the filter on your current operating frequency (the tuning resolution is 5

kHz). You may, however, use the VRF/µ knob (# ) to skew the filter response to one side or the other from your

operating frequency, to deal with heavy interference on one side. To re-center the µ-Tune filter on your operating

frequency, and eliminate any offset, press and hold in the VRF/µ switch (# ) for two seconds.

H While µ-Tune is a superior RF preselection circuit, it may be disabled via the Menu; if this is done, the VRF circuit will

engage when the VRF/µ switch is pressed. To disble µ-Tune, go to Menu item [GENERAL 035 µTUNE DIAL

STEP

] and set the selection to “OFF.”

Quick Note

The permeability-tuning concept utilized in the µ-Tune circuit dates back many decades, as it was incorporated in such classic

transceivers as the FT-101 and FT-901 series, in addition to the FT DX 400 and similar models. The µ-Tune circuit in the FT DX

9000MP is the highest development of this circuit concept ever employed in an Amateur transceiver.

VRF/µ Switch

VRF/µ Knob

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