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·be
tried if its position is accidently
changed. The
neutralizing adjustment is
quite critical if optimum ol?eration on
c-w
telegraphy is
to
be obtained and
the adjustment
procedure
" somewhat involved and requires the use of
special instruments. The proper procedure will
be
described under
the
heading
..
SERVICING INSTRUCTIONS...
.
Having
adjusted the oscillstor stage
as
outlined ~ve
on
all
active
channels,
the
chassis now can be
r,,turned to the
case
and
the
antenna
conn'ected. Eithec the
rod ontonna or•
wire antenna up
to
¼
wave in
Jongth
may
be
used.
(The
length
in
ftet of a
¼
wave antenna
is equal to 246
d,v,ded by
the frequency in
mogacydes.) Simultaneous
loading of th• p-a
stage,
.and
tuning
of the p·t.
stage and the
antenna,
an now be ca.cried
out
The method
of
adjustmont
is the same
rrrespective
of which anteona is uied,
except that if
the
equipment is
to be used
for porttble operation the final
trimming of
the
p·•
tuning 2nd
loading
adjustments should
be
made with the
transmitter-receiver raised
a
few ftet off the ground,
otherwise
these adjust-
ments will
be
ufected when the equipment is transferred to the operator's
bade. Also, for 6xed,
or
semi-fixed operation,
using
either the rod or the
wire
antenn•,
a
ground conoection
should
be
made to oo• of the bolts
provided in the
bars under the
osc,
to increase the efficiency
of
the antenna,
and
so
radiUe
a muimum
of
d power.
The tronsmiller tuning
condenser
should
be
set
al
O
and the COUP UNG
control
set
at
position
I.
Select
one
of
the active channels
and press the
microphone
button.
Quickly route the tuning condenser
in
a clockwise
directron until the
p-•
plate
current rClches
a minimum
value (rCld with
the
meter switch
on
TRANS 1lJNE.) Now
further
advance the COUPLING
control
a
step
at a time, manipulating the tuning condenser after each step
to
obtain resonanct -
i.e.
minimum plate current. Jt will be found
that
as
this
process is continued the plate current
at resonance increases,
indicating
that the p•a
valve
is
being
loaded. The tronsmitter will
deliver
rated po•-'«
to
the output circuits when the p-a
plate
current
lies in
the range 25 to 35 ma.
The
unit should
not
be operattd for long
periods
either with the
output circuit
out
of
resonance
or
with
the p•a. plate
current
in excess of
40
ma,
u
this may
sc,iously shotten
the life
of the
valve.
Therefore,
continue
to advance
the COUPLING
control
until
a p-a
plate current of between
25 and
35 ma is obtained
after
having obnil\ed resonance with the nu.in
tuning condenser.
When
this condition
has
been
reached
tbt
tcan,mittec
is
ready
for
oper1tion on this
frequtncy,
and
the
adjustments
will not
change appreciably unless the length of
the
antenn•
is
changed.
11,e
proctdure outlined
above should
now be
repeated for
the other
two
channels
if
these are
to
be
used.
The
main points
to be borne
in mind when
tuning
and operating the
transmitter ace:-
.,
(1)
The 6Jamcnt
voltage
should
be
maintained
at
2.15
volu.
(2)
Tuning always should be
commenced
with the COUPLING ond
tuning controls
11
the low
end·
of
their stales,
9
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