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H 52005-301D
(3)
Set the FINE TUNE control to the mark
on the
panel,
i.e. the centre
of its range of
adjustment.
13.
The
tuning elements are ganged wire
wound
resistors.
As
a result
of the contacts passing
over
the discrete turns of wire, some
fluctuation of output may occur.
Stabilization of the output
level
will
take place after any adjustment.
14.
The FINE TUNE control gives
gradual and precise frequency adjustment over a
limited
range in
the region
of the
setting of the main
FREQUENCY control.
It
can be used
to
minimize
the frequency
calibration
error
of the main dial
at a
particular
frequency
and
its
vicinity;
by
adjusting
the FINE TUNE control, the reading
of the
main
dial can
be
standardized
against the
indication of a counter
connected to the
output
.
The
FINE
TUNE control also
facilitates
setting
the instrument
exactly to
the optimum
pass or rejection
frequency
of a highly selective circuit,
such as
a filter having a narrow frequency
response.
OSCILLATOR OUTPUT
15.
Before
connecting a sensitive
load
to the instrument, turn
the
SET OUTPUT
controls fully
counter-clockwise
to
avoid applying
too much
output.
16
.
Output from an
oscillator can be
taken
from
the
front panel OUTPUT
terminals,
or
from
the OUTPUT coaxial socket at the
re~r,
depending on the setting of the
OUTPUT switch
above
the terminals on the front panel.
Set
this to the
right for
front terminals output, or to the left
for use of the
rear coaxial socket.
The front terminals
contain sockets
for
4
mm
plugs
and
will accept
a twin plug
having 19
mm pin
spacing.
Note
.•.
The 'live' front
panel terminals and the centre socket of the rear
coaxial
outlet
are
fed
internally through
a
reversible electrolytic capacitor.
Damage
may result if the
load
applies more than
±25 V d.
c
.
back
to
the instrument.
17.
The OUTPUT switches situated
above
the front panel
terminals
of
each
oscillator
can
be
used to bring the oscillators into
c
ircuit independently
when
they
are both connected to the
moni-
tored
attenuator.
As the
two oscillators
are
connected simply in
parallel it is necessary when
setting the output
level
of one to
simulate the
shunt impedance
of
the other
.
This
is
done by
making use
of the fact that the attenuator
internal load resistor
when
switched
in with
zero
attenuation appears
directly
across
the attenuator
input.
18
.
To set
output level
proceed
as
follows
:-
(1)
Connect the
load
to
the
appropriate attenuator OUTPUT terminals.
(2)
Turn the
LOAD
switch to
INT
.
(3)
Turn the
a
ttenuator
switches to 0 dB.
(4)
Connect one oscillator only
t
o
the
attenuator by pressing the OUTPUT switch of
one
oscillator to
the
left
(REAR) and the other OUTPUT
switch to
the
r
ight.
(5)
The
oscillator that is connected may
now
be brought up to the
desired
level,
as in-
dicated by the input
voltmeter
of
the
attenuator.
(6)
Interchange
the
oscillators
by reversing the
settings
of
both the OUTPUT
switches
and
adjust
the output
level
of
the other oscillator.
(7)
Now
connect
both oscillators by pressing both OUTPUT switches
to
the
left (REAR)
and
disconnect the
internal load
by
turning
the
LOAD
switch to EXT
.
19.
When the SET
OUTPUT control
has
been
rotated
through
a
small
angle
from the
extreme
Nov
.
79
Chap.
3
Page 5
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