(
)
Connect the
output
of the audio
generator
to the
microphone
input
on
the SB-10. Set
the
frequency
to
1000
cps and
adjust the output
voltage
to approximately
30 millivolts.
If out-
put
voltage
control or
calibration is not
provided,
use
a
500
KQ
control
to divide
the output
voltage down
to a level
low enou
gh
to insure
that
the $peech-amplifier
is not
being over-
driven.
(
)
Connect
the
vertical input
of the oscilloscope,
if available,
across
the
transmitter dummy
Ioad. A
direct
connection
may be used since, due
to the low
output impedance,
the voltages
developed
will not
be excessive.
If additional vertical
attenuation
is
required.
use
a
b0-100
mmf coupling
capac
i
tor.
)
Tune
up
the
transmitter
and adapter
on
BOM
and
load
the transmitter
final
to
250
ma.
)
If
an oscilloscope
is not
availattle,
or
as an additional
indicator
of
unwanted
suppression,
insert
some
carrier
and
tune an
SSB
receiver
to
zero-beat
the
carr:ier"
Now null
the
carrier.
ff
excessive
radiation
from
the
exciter stages
of
the
transmitter,
which
is
operating
on
pre
fundamental
frequency,
tends toblock
orover.l"oad
the
receiver, physically
separate
the
re-
ceiver
from
the
transmitter
until
the feedttrrough
is
minirnized.
Shorting
the receiver
antenna
input
terminals
may
help.
NOTE:
When using
the
sing.le tone test as described
in the following
steps, keep
the intervals of
test
"on
time"
to a
minimum to avoid exceeding the
average
plate
dissapation
o{
the 6146
finat
amplifier
tubes.
(
)
Now
advance
the audio
gain
control
until
about
125
ma
of final amplif
ier
plate
current is
indi-
cated.
Adjust
the
vertical
gain
of the oscilloscope for full scope-face
height. If an SSB
re-
ceiver is
being
used, select
the
unwanted sideband
on
the
receiver.
(
)
Now
adjust the
phase
balance and audio
balance
contlol for minimum
ripple ou the scope
pattern
or for
minimum S-meter reading,
if an
SSB reeeiver
is
being
used. This method
of adjustment
is based on the
principle
that for
a single audio tone
input, the RF output
consists
of a single
RF
signal, the desired sideband.
On an oscilioscope, this
RF
signal
looks
like a
CW signal, that
is,
a smooth
strip.
(
)
During
the
adjustment
of the
phase
balance and
audio
balance control,
note
that the spacing of
the ripple
peaks
due
to carrier
is
twice that oI those
due to unwanted
sideband.
Thus,
it is
possible
to
tell what kind of
adjustment
is needed.
The
carrier null
controls
affect carrier
suppression
and
the audio and ratio balance controls
affect
unwanted sideband
suppression.
(
)
Once
maximum suppression
has
been obtained for one sideband,
select
the
other
sideband
on
the SB-10.
The
suppression on
this
sideband
will
probably
notbe
as
good
as on the other
sideband.
Readjust
the balance controls until a compromise
is reached
where
the
suppression
of
either sideband
is
equally
good.
This is
important
even though
operation
onone
particular
sideband
is never
intended.
(
)
Refer
to
the table in
Figure 2l on
page
56. If
an oscilloscope
is being used, reference
to
this
table
will
give
a
good
approximation of the
amount of unwanted sideband
suppression
obtained. When
adjusted and operating
properly,
the SB-10 will
exhitlit about 30 db un-
wanted
suppression
on either sidebzurd. The suppression
obtained during
this
procedure
on
80M
will
hold for
all other bands and no further
adjustment is required.
(
)
To demonstrate
the
relationship
of
actual RF
peaks
to
indicated
plate
current
peaks,
dis-
connect t}le audio
generator
from the microphone
input
and
reconnect the
microphone.
While
speaking
into the microphone, adiust the
audio
gain
to
the
point
where
about
125 ma
peaks
are
indicated
on
th€r meter, Notice that the
RI'
peal<s
on
the
scope are
just
beginning
to
"flat-top".
These
RF
pea.ks
correspond to actual
plate
current
peaks
of
about 250
ma
but the
meter
cannot fol]o1\ fast enough, Thus, the
maximum
indicated
plate
current
peaks
are
much lower,
(
)
Turn
the transmitter plat.," po\/er
OFF and
place
the SB-10
function switch
in STANDBY.
Disconnect
the oscilloscr)!:o
lrom
the
dummy load
and
the audio
generator
from
the
micro-
phone
input.
Connerci thl: ::rl""opnon"
to the mict'ophone
input.
Page
5 5
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