Fig. 17 Ilhowl a 'flIriation
on
the
dual..convenlon
receiver
j....t eJ:plained. In thia receiver, an additional
Itage
of
amplification
it
present
between
the
fint
and
AUTOMATtC
NOISE
UtKTER
Moo
recei~n
contain
lOme
type
of
noile
wppreuion
circuit..
The
moo
common
type
ill
an
Automatic
Noile Limiter (ANL).
This
Itage
1II\1&1ly
COlUiIII
of
a
diode
in
leria
with the
detect«.
The
diode
iI.lightly
forward
bi..-I
which
alIo_
the
audio
IIignaI to
puI
tbroueh
durinC normal
opentKln.
II
a noiae
'Pike
iI
AUTOMATtC
NC:MSE
BI..ANKER
second
minr
Itages.
Alia
note
that
the
fint
IF
frequency ill 7.6
MH1,
due
to a differt'nt
fint
local
OlICillator frequency
than used
in
the
fmt
enmple.
applied
to
the
cathode
of
the
diode,
the
'Pike revene-
b'-
the
diode
cauatna
it
to
Jtop
eonduction
for
the
time
the
noile
'Pike
II
p~t.
111ia
eatlllell
a
mom-
entary
interruption
of
the
audio
being
fed to
the
audio
amplifier.
Iniecl
RF
and
Noise
-,~
N"O'
1@.:::.}-J-n.:::.?J.
"
"""
.....
tL...-...J
O>ed<
wid.
ScoPt
,,,
0scl11a10f
""
OodllalOf
~
•
AN~'
AN'
tl.~:-=::'
t IF t
Do_Of
"""
"""
PuIM$
I,om
NL204 Uoing
J9Gl10
u'minl'lld ctbIe.
FfI.
18-Eztrlil
circuitry
UHd
(or
Automlltic
Noix
BlIlnlHr.
..."
•
•
Fill:.
18
aho..... a
more
effecti..e
type
of
noi3e
RlppreI-
aion ill
proftded
with an
Automatic
NoW. Blanker
(ANB). Rather
than
aampling the
detected
"llIio
out-
put,
the
noise infotmlltion ill
tabn
from
the
output
of
the
Rf'
amplifier OJ'
the
tint
lD.i.zer.
Thit
-.ignaI
if;
fed
throuata
a
trpU&1oe
IF
I}'Stem
tuned
to
fre-
quencin
lela 1ban
300
H1.which
noiIe
pu1Iea
UIUa1Iy
OOCIIpy (ignition noiae,
AC
paWl!'!' line
noile,
etc.l
.
SINGLE SIDEBAND OPERATION
Many
lBn_iven
are
equipped for Single Sideband
(SSB) operation.
In
thil
mode
of
opention,
the
carrier
of
the
tlanomitted llignal
is
removed
hup-
preMed) with only one
or
the
lkIebanm
beinS
broad·
cut.
sse lranl1tliuionl have
two
main Ildvantages.
Firlt,
lince
only one sideband il
neeeaary
for
Iftn
...
miNion, twice u many conversation. can be
pre.ent
on
the
40
CB
channel.
at
one
time. Half
of
the
con·
venation.
are on
the
upper
sideband.
(USB) and half
2S
'nIe
output
of
thill amplirlcaUon ltage
ill
detected,
and
red
to.
"NoiM
Switch".
Thil
no_twitch
may
be between any
of
the
If'
.tqeI
or
betwNn
the
If'
AageI:
and
detector.
Any
time
there
is an
output
at
the
ANB detector,
the
noile
switch
ill
turned
off,
eliminatinc
the
noile
apikK
from
beinI
puaed
to
the
detoeetc.'
cin:uit.
IIJ'e
on
the
lower
.ideband
(LSB)
of
each
channel.
Secondly,
sse
trammluionl
are
leu
IIIlllCl!ptible
to
interference.
In
operation,
the
transmitter
must
produce
the
nec·
essary
sideband, and remove mOllt
of
the
camer
.is·
nal.
The
receiver, on
the
oUler
hand,
mlllt
re-insert
this missins carrier befort' beinS
detected
as a
nonnal
AM
.ignal.
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