Receiver Operation (Front End Block Diagram) - Yaesu FT DX 3000 Operating Manual

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The FT 3000 includes a wide range of special features to suppress the many types of interference that may be encoun-
DX
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 3000 interference-fighting circuitry begins in its "RF" stages, and continues throughout the entire receiver
DX
section. FT 3000 allows configuration of the features described below.
DX
R. FLT ( IF Roofing Filters )
Three Roofing filters, of 15 kHz, 6 kHz, 3 kHz, and 600
Hz bandwidths, are provided in the 9 MHz First IF, right
after the first mixer. These filters are automatically se-
lected to provide narrow-band selectivity to protect the
following IF and DSP stages. The automatically selected
filter may be manually changed by the operator, if de-
sired, for special operating circumstances.
CONTOUR Filter
The DSP Contour filter has the unique ability to pro-
vide either a null or a peak in tunable segments of the
receiver passband. You may suppress interference and
excessive frequency components on an incoming signal,
or you may peak those tunable frequency segments. The
level of the null or peak, and the bandwidth, over which
it is applied, are adjustable via the Menu.
IF SHIFT
The passband center frequency of the IF DSP filter may
be moved up or down by adjusting this control.
IF WIDTH
The width of the IF DSP filtering may be adjusted using
this control.
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IF NOTCH
The IF Notch filter is a high-Q notch filter that can elim-
inate, or significantly reduce an interfering carrier.
DNF ( Digital Notch filter )
When multiple interfering carriers are encountered dur-
ing reception, the Digital Notch Filter can significantly
reduce the level of these signals.
DNR ( Digital Noise Reduction )
The DSP's Digital Noise Reduction (DNR) feature uti-
lizes 15 different 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, and allows the signal to rise
up out of the noise.
AGC
The AGC system is highly adaptable to changing signal
and fading characteristics, making reception possible
under the most difficult conditions.
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