Yaesu FT-991 User Manual

Page 44 FT-991 OperaTing Manual
convenience features
receiver operAtion
(
Front end block diAgrAM
)
The
FT-991
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-991
interference-ghtingcircuitrybeginsinits“RF”stages,andcontinuesthroughouttheentirereceiversec-
tion.
FT-991
allowscongurationofthefeaturesdescribedbelow.
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of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ltermay
bemovedupordownbyadjustingthiscontrol.
IF WIDTH
ThewidthoftheIFDSPlteringmaybeadjustedusing
this control.
IF NOTCH
TheIFNotchlterisahigh-Qnotchlterthatcanelim-
inate,orsignicantlyreduceaninterferingcarrier.
DNF
(
Digital Notch lter
)
When multiple interfering carriers are encountered dur-
ingreception, theDigital NotchFilter cansignicantly
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proles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 automatically adapts to changing sig-
nalandfadingcharacteristics,makingreceptionpossible
underthemostdifcultconditions.
Front end block diAgrAM
HF/50MHz
HF/
50MHz
ANT
VHF/
UHF
ANT
ATT BPF
RF
1st IF
69.450 MHz
2nd IF
9 MHz
2nd IF
450 kHz
FM C4FM
3rd IF
24 kHz
MCF
144MHz
LPF
430MHz
LPF
BPF
RF AMP/
IPO
1st
IF AMP
3rd
IF AMP
DSP
UNIT
ROOFING
FILTER
RF AMP
RF AMP BPF FM DET
1st Local
3 kHz
15 kHz
2nd Local
3rd Local
1st Local
2nd Local
C4FM
DSP UNIT

Yaesu FT-991 Specifications

General

Frequency Range Transmit	1.8 MHz - 54 MHz, 144 MHz - 148 MHz, 430 MHz - 450 MHz
Antenna Impedance	50 Ohms
Antenna Connector	SO-239
Supply Voltage	13.8 V DC ±15%
Modes	SSB, CW, AM, FM, C4FM Digital
Display	3.5-inch color TFT LCD
Weight	4.3 kg