Receiver Operation (Front End Block Diagram) - Yaesu FTDX-9000D Operation Manual

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The FT 9000D includes a wide range of special features to suppress the many types of interference that may be encoun-
tered on the HF bands. However, real world interference conditions are constantly changing, so optimum setting of the
controls is somewhat of an art, requiring familiarity with the types of interference and the subtle effects of some of the
controls. Therefore, the following information is provided as a general guideline for typical situations, and a starting point
for your own experimentation.
The FT 9000D's interference-fighting circuitry begins in its "RF" stages, and continues throughout the entire receiver
section. The FT 9000D allows configuration of the features described below independently on the main band (VFO-A)
and sub band (VFO-B), except for the µ-TUNE (Narrow-bandwidth High-Q RF Filter) feature; the sub band (VFO-B)
receiver does not have provision for a µ-TUNE module or modules.
µ-Tune Filters (See page 64)
The µ-Tune filters provide ultra-sharp RF selectivity on the 1.8 ~ 14
MHz Amateur bands on the Main (VFO-A) receiver. Automatic tuning
of the µ-Tune filters is provided via a precision motor drive.
VRF (See page 66)
On the 18 MHz and higher Amateur bands on the Main (VFO-A) re-
ceiver, and on all Amateur bands on the Sub (VFO-B) receiver, Yaesu's
powerful VRF (Variable RF Filter) preselector circuit provides excel-
lent suppression of out-of-band interference, with a passband much nar-
rower than that provided by traditional fixed bandpass filters.
R. FLT (IF Roofing Filters) (See page 67)
Three automatically-selected Roofing filters, in bandwidths of 15 kHz,
6 kHz, and 3 kHz, are provided in the 40 MHz First IF, right after the
first mixer. These filters provide narrow-band selectivity to protect the
following IF and DSP stages, and the filters' automatically-selected band-
widths may be manually changed by the operator, if desired, for special
operating circumstances.
CONTOUR Filter (See page 68)
The Contour filter is a unique capability of the FT
either nulling or peaking of tunable segments of the receiver passband,
so as to suppress interference or excessive frequency components on an
incoming signal, or to peak those tunable frequency segments. The
amount of nulling/peaking, and the bandwidth over which it is applied,
are adjustable via the Menu.
IF SHIFT (See page 69)
The passband center frequency response of the IF DSP filtering may be
adjusted using this control.
IF WIDTH (See page 70)
The width of the IF DSP filtering may be carried using this control.
µ-TUNE
VRF
VRF
Page 60
F
O F
9000D, providing
Main Band ( VFO-A )
RF
IPO "OFF"
BPF RF AMP
1st Local
RF
IPO "OFF"
BPF RF AMP
1st Local
E B D
IF NOTCH (See page 71)
The IF Notch filter is a high-Q notch filter that can significantly reduce,
if not eliminate, an interfering carrier. The Q (sharpness) of the filter
may be adjusted using the Menu, and the exact tuning of the filter may
be monitored visually using the Audio Scope page on the TFT (espe-
cially useful is the "Waterfall" display).
DNR (Digital Noise Reduction) (See page 72)
The DSP's Digital Noise Reduction (DNR) feature utilizes sixteen dif-
ferent mathematical algorithms to analyze and suppress different noise
profiles encountered on the HF/50 MHz bands. Choose the selection
that provides the best noise suppression, which concurrently will allow
the signal to rise up out of the noise.
DNF (Digital Notch filter) (See page 74)
When multiple interfering carriers are encountered during reception, the
Digital Notch Filter can significantly reduce the level of these signals.
AGC (See page 75)
The AGC system is highly adaptable to changing signal and fading char-
acteristics, making reception possible under the most difficult conditions.
SLOPED AGC (See page 76)
The Sloped AGC system, instead of clamping a fixed upper bound on
audio output across a wide range of input signals, actually allows the
audio output to rise, very gently, with ever-increasing signal strength.
This capability allows you to separate signals, using your brain, accord-
ing to signal strength in addition to slight frequency differences.
IF Filter Quality Adjustment (See page 140)
The "Q" (quality factor) of the IF DSP filters may be adjusted indepen-
dently for the Main (VFO-A) and Sub (VFO-B) receiver IF DSP filters,
using the Menu.
Variable IF Filter Shape Factor (See page 140)
You may adjust the shape factor of the Main (VFO-A) and Sub (VFO-
B) receiver IF DSP filters, using the Menu.
1st IF
40.455 MHz
ROOFING
FILTER
1st
CF
IF AMP
3k/6k/15k
2nd Local
Sub Band (VFO-B)
1st IF
40.450 MHz
ROOFING
FILTER
1st
CF
IF AMP
3k/6k/15k
2nd Local
FT 9000D O
2nd IF 3rd IF (DSP)
455 kHz 30 kHz
2nd DSP
IF AMP UNIT
3rd Local
3rd IF (DSP)
2nd IF
450 kHz 30 kHz
2nd DSP
IF AMP UNIT
3rd Local
M