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I MODEL 4OO TRANSCEIVER
C ,
O p e r a t i o n ( C o n t )
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
o r c l o c k , b u t i t r n a y v a r y c o n s i d e r -
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-
t o p p i n g a n d 6 p u r i o u s s i B n a l s , s o i t
is important
to hold it down.
The
meter
is quite heavily damped,
and
its reading *ith
average voice modu-
l a t i o n m a y n o l l o o k v e r y i m p r e s s i v e ,
but the voice peak6 are going well
o w e r t h e 4 0 0 $ a t t P o \ " e r r a t i n g o f
your Swan tlan6ceiver,
and signal
r e p o r t s w i l l v e r i f y t h i s f a ( t .
8.
TRANSMITTER
TUNING WITH
SWR BRIDGE OR FIELD
STRENGTH
M E T E R .
l f e i t h e r o I t h e 6 e i n s t r u -
ments is available,
they are highly
r e c o m m e n d e d a s a b e t t e r m e t h o d o {
tuning the PA AmpliJier,
since they
provide a direct
indication
of rela-
tive output.
With the SWR Bridge
i n F o r w a r d
p o s i t i o n , o r w i t h t h e
F i e ] d S t r e n g t h M e t e r 5 e t t o p i c k u p
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
l e s s t h a n 5 0 0 m a . o n l 0 m e t e r s
b e c a u 6 e g r i d d r i v e i s t h e l e a s t o n
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.
1 6
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
t o a l e s s e r d e g r e e , T h e s e c r e t t o
long tobe life is simply to keep
TUNE-up periods short and not too
frequent.
AM OPERATION
( S i n g l e S i d e b a n d w i t h C a r r i e r )
L
T u n e u p t r a n s m i t t e r t o f u l l o u t p u t
o n s i n g l e s i d e b a n d o n d e s i r e d f r e -
quency band as described above,
2, Rotate MIC GAIN contlol to lull
c o u n t e r - c l o c k w i a e P o s i t i o n .
3. With Function Switch in TRANSMIT,
rotate CAR BAL control until
c a t h o d e c u r r e n t r s a p p t o x i m a t e l y
1 5 0 m a .
4.
While talking in a nollnal tone oI
v o r c e i n t o t h e r n i c r o p h o n e , i n c r e a 6 e
MIC GAIN setting until variation is
j u s t d i s c e r n i b l e o n m e t e r .
T h i s
setting will result in adequate hodu-
lation with one sideband.
CW OPERATION
l.
Tune transmitter
to firll output a6
d e s c r i b e d a b o v e .
2 .
I n s e r t C W k e y i n t h e k e y i a c k P r o -
vided on the back of the 400.
Use
a standard
I/4
inch diamete!
2
circuit
phone plL1g.
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