Operating instructions

I
ciuctivell-
to the
tuned
secondary
winding
in
the
gricl
circuit of
converter
tube
V3.
d.
When
BAND
SW. switch
S1
is
placed
in
the band
2
position
(fr,g.2a),
the follorn'ing
cir-
cuit changes
are
effected
to
allorv coverage
of
the
2.7-
to 5-mc
band.
(1)
Section 5, rear,
selects
the D rvinding
of T2 in
place
of
the
C
r,r'inding
as tlie
grid
r-f
coil. In
paraliel
r,vith
the D
winding
ís
a
22-ppf
flxed
tuning
capac-
itor.
(2)
Section 5, front,
removes
the
grouncl
from
the D winding
and
trimmer
ca-
pacitor
C8
(fig.
48),
and
places
a
ground
on
the
C
rvinding
and
capaci-
tor
C9
(3)
Section
6, front,
selects
the D rvinding
of T3
in
place
of the
C
r,vinding
as the
plate
load for
Y2.
e.
When BAND
SW. switch is
placed
in
band
3
position
(fig.
24),
coverage
of thc
5- to 9.b-
mc
band
is
provided
through
circuit
changes
similar
to those
detailecl
for
band 2.
Sections
5. Lear,
and
6, front,
select
the D rvinding
of
T6
and
the
C
winding
of T7
as the
V2
grid
coil
and
plate
coil, respectir,'el.v.
A 25-ppf
capacitor
acts as
the fixed
tuned
capacitor
in
parallel
x'ith
the D winding
of T6.
Section 5, front.
groulrcls
the
unused
r-f
coils.
f. When
BAND
S\Y. sr,r'itch
is
set to
band
4
position (fig.2a)
u'indings
E
of T6
(paralleled
b1'
an
18-ppf
fixed
tuned
capacitor)
and D
of
T7
are selected
to
provide
coveralre
of the 9.5-
to 18-mc
band.
Section 5, front,
grounds
the
trntrsed
coils. A 2,400-pp.f
capacitor
(connected
in
series r'vith
secondary r,r'inding
E
of TG)
is
the
padder
to
provide
proper
tracking.
54.
Locol
Oscillotor
of
V3
(fiss.
24
ancl 25)
The
local oscillator
covers the
range of
the
receiver tuning
at a
frequencl'
455 kc
above
the
iticoming
signals on
all four bancls. In
the fol-
lou'ing
analvsis,
the circuit for bancl 1 is
dis-
cussecl in
detail, and
the anal-vses of bands 2,
3,
ltntl 4
discuss only the
-"'ariations
which
are
riccomplished
by band sr.r,itching.
a. The
local oscillator uses a tapped Hartley
.:::::with the
prate
circuit
(second grid
of
V3)
at r'-f
glouncl (fig.
25).
The
grid
circuit
is
tnneci
lrv
the ^\ l'incling
of T4,
a 27-ppÍ
fi,xeci
tunir-rg
caltaeitor.
trimmer
capacitor
C50, ancl
I\{ANUAL-PRESET
TU);ING
capacitor
C1D.
ó.
Sectic,n
S. ir,,nt.
o1 BAND
S\\r. switch
51
connects
the
t:i1r
of the
A
u'inrling
to
the fila-
ment
cathode,
ancl section
Í.). rerti'.
connects
the
tuned
output
of
the tank
across
CID
ancl
thence
to
the
grid
circuit.
The 220K-ohm gi'icl
cl-c re-
turn
resistor
and
the 820-ppf
fixed
ltacklet'
ciÌpac-
itor
are
connected
internalll.'
in
the
coil
as-
sembly.
Resistor
R8
and capacitor
C20 folm
the
grid-leak
bias network
for
the
o-scillator.
Section
9,
front,
of BAND
SW.
su-itch
31
grounds
the unused
winding
E
of T4
and
r.incl-
ings
A and E
of T8
(fis.
2D.
c.
The
local
oscillator
uses
the filament
ancl
first
two
grids
of
a
1R5
pentagrid
converter
tube
(fig.
25).
Filament
voltage
for
the tube is
ob-
tained
frorn
the 1.4-volt
d-c
potential
at
pin
11
of
J4, through
r-f
choke L1.
L1 maintains
the
filament
above
r-f
grouncl
potential.
Oscillator
plate (pin
3) voltage is
supplied
through volt-
age-dropping
resistor
Rg
from
the 90-volt
cl-c
potential
appearing
betu'een
pin
6
of J4
and
ground.
Capacitor
C21
places
the oscillator
plate
at r-f
ground
potential.
d.
When
BAND
SW. switch is
placed
in
band
2,
the follou'ing
circuit
changes
are
effected
(fig.24)
:
(1)
Section 8, front,
removes
rvinding
A
of
T4
from
the cathode
circuit
and
connects
in winding
E
of T4.
(2)
Section 9, rear,
removes
wincling
A of
T4
from the
grid
circuit
and connects
in
rvinding
E
of T4.
(3)
Section 9, front,
grounds
rvinding
A
of T4,
and removes
the
ground
from
winding
E.
(4)
A 1,2A0-y.pf
capacitor
is
the
padcler',
and
the
220K-ohm
resistor
plor-irles
the oscillator
grid
d-c
letuln.
fhi-s
parallel
netr,vork
is
connerterl
to the
gricl-leak
bias netu'ork.
tinrl
tt'inrnrel
capacitor
C51
is.sulrstitLìted
in
tl-re
tuning circuit
ífig.
-1ll).
e.
When BAND
S\\'.
su-itch
Sl
is
placecl
in
band 3
position
(fi.q'.
2l).
cilcLiit
chan.ges
ale
provided
similar
to those rletailecl
for
band
2.
+l