DRAKE MN2700 Manuale di istruzioni - Pagina 13
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Stampa la paginaREACTIVE tuning control clockwise. Readjust the
RESISTIVE tuning for a dip. If this dip is
downscale from the first dip, you are tuning in the
right direction, and should continue to alternately
move the REACTIVE tuning control clockwise and
tune the RESISTIVE tuning for a dip, until a
minimum VSWR indication is obtained. If the sec-
ond dip found reads higher on the meter than the
first dip, the REACTIVE tuning control must be
turned counterclockwise a short distance, and the
RESISTIVE tuning adjusted for a dip. Continue
alternating these actions until a minimum VSWR
reading is reached. Again, if additional tuning
range is needed, switch in or out the range
capacitors to obtain minimum VSWR reading.
If the dips found during the tuning procedure are so
far downscale that i t becomes difficult to tell
whether a particular dip is lower or higher than the
preceding one, you can increase the meter sensitivi-
ty and get readings that are fartherupscale by turn-
ing the VSWR SET knob clockwise. With this add-
ed sensitivity it may not be possible to dip to the
meter zero, but any residual reading will represent a
very small power level, probably less than 0.1 watt.
b5.
OFF-THE-AIR
TUNING.
If
a
50
ohm
dummy
load
that
is
capable
of
handling
full
transmitter
power
output
is
available,
i t
and
the
MN-2700
can
be
used
to
tune
up
with
minimdm
in-
terference.
Connect
the
50
ohm
dummy
load
to
DL
connector
on
the
MN-2700,
switch
the
ANTEN-
NA
switch
to
GNDIDL,
switch
theBAND
switch
to
DIRECT,
and
turn
on
the
transmitt@r.
The
transmitter
(and
high-power
amplifier,
if
used)
can
now
be
tuned
to
match
the
50
ohm
dummy
load.
Then
turn
off
the
amplifier
and
reduce
the
transmit-
ter
power
output,
without
changing
the
transmitter
I
tuning.
As
little
as
10
watts
input
to
the
MN-2700
is
enough.
Set
the
BAND
switch
to
the
desired
band,
the
ANTENNA
switch
to
the
desired
antenna,
tune
the
matching
network
for
minimum
VSWR,
and
then
increase
the
transmitter
power
to
normal
operating
level.
3-6. REFLECED POWER.
I t
is
possible
to
read
reflected
power
with
the
When
the
matching
network
has
been
adjusted
MN-2700,
although
the
instrument
was
not
primari-
the
lowest
possible
dip,
it
is
properly
tuned
to
pre-
ly
designed
to
do
this,
T~
read
reflected
power,
first
sent
a
50
ohm
resistive
load
to
the
transmitter.
Ad-
rotate the
VSWR
SET
knob
fully
counterclockwise,
just
the
transmitter
plate
tuning
and
loading
con-
and
press
either
the
200
WATTS
or
2000
WATTS
trols
as
directed
by
the
transmitter
instruction
meter
switch,
Increase
transmitter
Dower
to
the
manual.
desired level (do not exceed full scale on the meter).
then press the VSWR SET button. Rotate the
Make a note of the settings of the RESISTIVE and
VSWR SET knob clockwise until the meter in-
tuning and
range
and the
dicates the same forward power. Press the VSWR
BAND switch. The next time you operate on this
READ button, The meter now indicates reflected
band, you can tune up quickly by returning the
power,
MN-2700 controls C o the same settings.
With the range switch in 0-10 position, the tuning
control would be recorded as the number on the
knob dial between 0 and 10. With the range switch
in the 10-20 position, 10 should be added to the
number on the dial
-
record a number between 10
and 20. In the 20-30 switch position, add 20 and
record a number between 20 and 30.
Push the VSWR SET button and rotate the VSWR
SET knob clockwise until the meter needle lines up
with the SET mark (full-scale) on the meter face.
Push the VSWR READ button. The meter will now
indicate VSWR.
3.7.
USE
WI
rRANSCElVERS
OR
TIR
COM-
BINATIONS.
Adjustment
of
the
MN-2700
with
a
transceiver
is
done
exactly
as
described in
Sections
3-4and
3-5
Since
the
received
signal
will
be
passed
through
the
matching
network,
i t
is
necessary
to
change
the
BAND
switch
to
either
DIRECT,
or
to
the
band
the
receiver
is
tuned
to.
If
this
is
not
done,
the
received
signal
will
be
attenuated
by
the
matching
network
whenever
the
BAND
switch
setting
is
not
the
same
as
the
band
being
tuned.