Receiver Operation (Front End Block Diagram) - Yaesu FT-450D Operation Manual

R
ECEIVER
The FT-450D includes a wide range of special features to suppress the many types of interference that may be
encountered 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-450D's interference-fighting circuitry begins in its "RF" stages, and continues throughout the entire
receiver section. FT-450D allows configuration of the features described below.
R. FLT
IF Roofing Filters
The Roofing filter, with a bandwidth of 10 kHz is pro-
vided in the 68 MHz First IF, right after the first mixer.
This filter provides narrow-band selectivity to protect
the following IF and DSP stages, for special operat-
ing circumstances.
CONTOUR Filter
S
EE PAGE
The DSP Contour filter provides a unique capability
on the receiver, providing either nulling or peaking of
tunable segments of the receiver passband, so as to
suppress interference or excessive frequency com-
ponents on an incoming signal, or to peak those tun-
able frequency segments. The amount of nulling/
peaking, and the bandwidth over which it is applied,
are adjustable via the Menu.
IF SHIFT
S 29
EE PAGE
The passband center frequency response of the IF
DSP filtering may be adjusted using this control.
IF WIDTH
S 30
EE PAGE
The width of the IF DSP filtering may be adjusted
using this control.
FT-450D O
PERATION
C
ONVENIENCE
( F
O
PERATION
28
M
ANUAL
E B
RONT ND LOCK
IF NOTCH
S
EE PAGE
The IF Notch filter is a high-Q notch filter that can
significantly reduce, if not eliminate, an interfering
carrier.
DNR
D N
IGITAL OISE
The DSP's Digital Noise Reduction (DNR) feature uti-
lizes eleven different mathematical algorithms to ana-
lyze and suppress different noise profiles encountered
on the HF/50 MHz bands. Choose the selection that
provides the best noise suppression, which concur-
rently will allow the signal to rise up out of the noise.
AGC
S 27
EE PAGE
The AGC system is highly adaptable to changing sig-
nal and fading characteristics, making reception pos-
sible under the most difficult conditions.
F
EATURES
)
D
IAGRAM
31
R S 32
EDUCTION EE PAGE
Page 25