Receiver Operation (Front End Block Diagram) - Yaesu FTdx5000 Series Operating Manual

C
R
ECEIVER
The FT 5000 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.
Yaesu provides the optional RF-µTUNING Unit (Narrow-bandwidth High-Q RF Filter) for additional protection from
strong signal interference.
VRF
S 54
On the 1.9 - 28 MHz amateur bands, Yaesu's powerful
VRF (Variable RF Filter) preselector circuit provides ex-
cellent suppression of out-of-band interference. The pass-
band is much narrower than that provided by traditional
fixed bandpass filters.
R. FLT
IF Roofing Filters
On the VFO-A receiver, Roofing filters, in bandwidths of
15 kHz, 6 kHz, 3 kHz, 600Hz, and 300 Hz (optional in
some models), are provided in the 9 MHz First IF, right
after the first mixer. These filters provide narrow-band se-
lectivity to protect the following IF and DSP stages. The
15 kHz, 6 kHz, or 3 kHz filters are automatically selected
for typical operating modes, and may be manually changed
by the operator, if desired, for special operating circum-
stances.
The VFO-B receiver 40 MHz IF includes three Roofing
filters, with bandwidths of 15 kHz, 6 kHz, and 3 kHz.
CONTOUR Filter
S
The DSP Contour filter is a unique capability of the
FT 5000, providing either nulling or peaking of tunable
segments of the receiver passband. The Contour filter can
suppress interference, or excessive frequency components
on an incoming signal, or it can peak those tunable fre-
quency segments. The amount of nulling/peaking, and the
bandwidth over which it is applied, are adjustable via the
Menu.
IF SHIFT
S 60
The passband center frequency response of the IF DSP
filtering may be adjusted using this control.
IF WIDTH
S 61
The width of the IF DSP filtering may be adjusted using
this control.
ATT
ATT
Page 50
F
O
PERATION
S 56
58
RF
THRU
OPTION
RF AMP/
µ-TUNE
BPF
IPO
VRF
RF
THRU
RF AMP/
VRF BPF
IPO
F E B
RONT ND LOCK
IF NOTCH
S
The IF Notch filter is a high-Q notch filter that can signifi-
cantly reduce, or eliminate, an interfering carrier. The Q
(sharpness) of the filter may be adjusted using the Menu.
DNR
D N
The DSP's Digital Noise Reduction (DNR) feature uti-
lizes sixteen 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, which concurrently will allow the
signal to rise up out of the noise.
DNF
D N
When multiple interfering carriers are encountered during
reception, the Digital Notch Filter can significantly reduce
the level of these signals.
AGC
S 67
The AGC system is highly adaptable to changing signal
and fading characteristics, making reception possible un-
der the most difficult conditions.
SLOPED AGC
Instead of limiting a wide range of audio output signals to
a fixed upper bound, the sloped AGC system actually al-
lows the audio output to rise, very gently, with ever-in-
creasing signal strength. This capability allows you to men-
tally separate signals, according to signal strength, in ad-
dition to slight frequency differences.
IF Filter Quality Adjustment
The "Q" (quality factor) of the IF DSP filters may be ad-
justed using the Menu.
Variable IF Filter Shape Factor
You may adjust the shape factor of the receiver IF DSP
filters using the Menu.
VFO-A Receiver
SCOPE IF OUT
1st Local
VFO-B Receiver
1st IF
40.455 MHz
ROOFING
FILTER
1st
IF AMP
3kHz
1st Local 6kHz 2nd Local
15kHz
FT
D
IAGRAM
63
R S 64
S 64
S 68
S
S
1st IF 2rd IF (DSP)
9 MHz 30 kHz ( SSB/CW )
24 kHz ( AM/FM )
ROOFING
FILTER
1st 2nd
IF AMP IF AMP
300Hz
600Hz
2nd Local
3kHz
6kHz
15kHz
2nd IF 3rd IF ( DSP )
455 kHz 30 kHz ( SSB/CW )
24 kHz ( AM/FM )
3rd
CF
IF AMP
3rd Local
5000 O
DX
131
131
DSP
UNIT
DSP
UNIT
M