Yaesu FT DX 9000 CONTEST Operation Manual page 177

RF μ-T RF μ-T RF μ-T
RF μ-T RF μ-T
UNING UNING UNING
UNING UNING
μ-T
UNE AND
μ-T
UNE
Inspection of the illustrations to the right will demonstrate
the profound advantage of the μ-Tune circuit. In illustration
[ A ] , the gray area represents the passband of a typical fixed
bandpass filter covering the 1.8 ~ 3 MHz range; this is typi-
cal of the kind of bandpass filter found in many high-quality
HF receivers today. Note also the hypothetical distribution of
signals across the 160-meter band.
In illustration [ B ] , note the narrow white segment within the
gray passband of the fixed BPF. These narrow segments rep-
resents the typical bandwidth of the μ-Tune filter, and one
can see that the passband has been reduced from about 750
kHz 9in the case of the fixed BPF) to a few dozen kHz when
μ-Tune is engaged. The vast majority of the incoming signals
are outside the passband of the high-Q μ-Tune filter, and they
will not impinge on any of the RF/IF amplifiers, the mixers,
or the DSP. Very strong out-of-band signals like this can cause
Intermodulation, blocking, and an elevated noise floor for a
receiver.
VRF
In this example, illustration [ a ] depicts a typical fixed bandpass
filter covering 14.5 to 22 MHz, and once again the gray shaded
area depicts the fixed bandpass filter's frequency coverage.
The vertical lines in the illustration, once again, represent hy-
pothetical signals throughout this frequency range.
Figure [ b ] shows the same fixed BPF, with the white area
representing the typical passband of the VRF filter operating
in the same frequency range. Although the selectivity of the
VRF is not as tight as that of the μ-Tune filter, the RF selec-
tivity of the VRF preselector is still magnitudes better than
that of the usual fixed bandpass filter, affording significant
protection against the ingress of high signal voltage from
strong out-of-band signals.
FT 9000 C O
DX ONTEST
U U U U U
NITS NITS NITS
NITS NITS ( MTU-160, MTU-80/40, MTU-30/20 MTU-160, MTU-80/40, MTU-30/20 )
MTU-160, MTU-80/40, MTU-30/20 MTU-160, MTU-80/40, MTU-30/20
MTU-160, MTU-80/40, MTU-30/20
VRF: C
OMPARISONS TO
M
PERATION ANUAL
F B F
IXED ANDPASS ILTERS
[ A ]
1.8MHz
FRONT-END BAND WIDTH
[ B ]
1.8MHz TUNE BAND WIDTH
μ
[ a ]
14.5MHz
FRONT-END BAND WIDTH
[ b ]
14.5MHz VRF BAND WIDTH
2.5MHz
2.5MHz
22MHz
22MHz
Page 175