I MODEL
4OO TRANSCEIVER
C, Operation
(Cont)
the MIC. GAIN control
until occa-
sional
peak reading oI l?5 to
200
ma. are obtained.
With
most
rnicrophones, the MIC.
GAIN
con-
trol will be set
between
9
and
l2
orclock, but it rnay
vary
consider-
abry. The ALC circuit will help
limit cathode current to about 200
rna., but
turning the MIC. GAIN
{rp too high will still
produce
flat-
topping and 6purious
siBnals,
so
it
is important to hold it down. The
meter is
quite heavily damped, and
its reading *ith average
voice modu-
lation may nol look
very impressive,
but the
voice
peak6
are
going
well
ower the 400
$att
Po\"er
rating of
your Swan tlan6ceiver, and
signal
reports
will verify this fa(t.
8.
TRANSMITTER
TUNING WITH
SWR
BRIDGE
OR FIELD STRENGTH
METER.
lf either oI the6e instru-
ments is available,
they
are
highly
recommended
as a better method
o{
tuning
the PA AmpliJier, since
they
provide
a
direct indication
of rela-
tive
output. With the SWR
Bridge
in Forward
position, or
with
the
Fie]d Strength
Meter 5et to
pick up
a
portion of the radiated
power,
simply
adjust the PA TUNE
and PA
LOAD
controls for rnaxirnurn
output.
This
rnust be done
quickly, limited
to about
30 seconds,
to limit tube
di6sipation as
previously
mentioned.
This method will
result in rrraxr-
lnum
possible output
and
efficiency,
as well as
rnaxirnum linearity.
You
witl
probably find that cathode
current
readings
end uP somewhat
less than 500
ma. on l0 meters
becau6e
grid
drive is
the
least
on
this
band.
On
80
rneters where
grid
drive
i6 the
greatest, rnaxinurn out-
put will
be reached at rnore than
500
rna. These are
a normal condi-
tion.
16
NOTE
-
The cathode
cur.ent level
to which
the PA
is loaded will
have
no bealing
on tube life, When
transmitting
with nolrnal voice
modu_
lation, average
Povwer
inPut
rrill
be
the sarne
regardless
of how high
or
1ow
the PA was loaded
while
tuning.
Peak output,
Iinearity, and lowe8t
distortion
will
go along with maxi-
mum
loading. In
other words,
You
will
not extend
tube life by loading
to a lesser
degree, The
secret to
long
tobe life
is simply to keep
TUNE-up
periods short and
not too
frequent.
AM
OPERATION
(Single
Sideband
with Carrier)
L
Tune up
transmitter
to full output
on single
sideband on desired
fre-
quency band as described
above,
2,
Rotate MIC GAIN
contlol to
lull
counter-clockwiae
Position.
3. With
Function Switch
in TRANSMIT,
rotate CAR BAL
control until
cathode current
rs apptoximately
150 ma.
4. While
talking
in a nollnal
tone oI
vorce into the
rnicrophone,
increa6e
MIC GAIN setting
until variation
is
just
discernible
on meter.
This
setting
will result
in adequate hodu-
lation with
one sideband.
CW OPERATION
l. Tune transmitter
to
firll output a6
described
above.
2.
Insert CW
key in
the key
iack Pro-
vided
on
the back of the 400.
Use
a standard
I/4 inch diamete!
2
circuit
phone plL1g.
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