Swann 400 - Antenna Matching and Selection; Mobile Antenna Considerations

I
MODEL 4OO
TRANSCEIVER
B. Installation
(Cont)
seLector
s\ritch should
be installed
to
select
either the broadcast
receiver
or
tranaceiver
output.
MICROPHONE
The rnicrophone input
is designed lor
high impedance
rnicrophones
only. The
choice
oI microphone
is imporlant,
for
good speech
quality, and ehould
be
given
serious
consideration.
Th€ crystal
lattice filter in the
transceive!
provides
all the
restriction necessary
on audio
response, and
fr.rrther
restriction in the
microphone
is not required.
lt is more
irnportant
to have a mic
rophone with
a
smooth,
flat response
throughout
the
speech
range.
The microPhone
PIug
should
be
a
standard
l/4 in. diamete!
three-contact
type. The tiP
connection
is for
push-to-talk
relay
control, the
ring connector
is for
the microphone
terminal,
and the
sleeve is for
the com-
rnon chassis
ground. The manufactu!elis
instructions
should be
followed in
connect-
ing
the lnicrophone
cable to the
Plug.
With
many
microphone6,
the
push-to-talk
button
rnust be
pressed to make
the
rnicrophone
operative,
even
though
the
panel function
switch
i5 in the transmit
position.
This leatule
rnay be
disabled,
iJ desired,
by opening
the microphone
case
and
permanently
connecting
the
contacts
which
control the microPhone.
ANTENNA
Any
of the
common antenna
systems
de-
signed
for uEe
on the high frequency
amateur
bands may
be used with
th€
Swan
transceiver,
provided the input
impedance
of the transmission
line
is not
outside
the capability
ol the
pi-output
matching
network, An antenna
which
reflects
a standing wave
!atio on 50
or
?5
ohm
rransmiss;on
line, below aPproxi
-
matety
4:
I at the
proposed
oPerating fre
-
quency,
or a
system
tha! results
in a
transmission
line iiput
impedance
that
is essentially
resistive
and
between l5
and 500
ohlns
will take
power from
the
transceiver
with
little ditficulty.
If
tuned
open-wire
trallslnission
line
is used to
excite the antenna,
a suitable
antenna
tuner should
be used
between the
trans
-
ceiver and
the antenna
to
Provide
a
reasonable
irnpedance
match
between the
unbalanced
coaxial
output and
the balanced
open-wire
line. Methods
oI constructing
and
operating such
tuners ale described
in detail
in the ARRL
Antenna Handbook,
and sihilar
publications. Fo! oPeration
on the 75- and
40-meter
bands, a simPle
dipole antenna,
cut
to resonate in the
rnost
used
poltion oI the
band' will
Per-
forrn satisfactorily.
For operation
on
the
10, I5, and
20 meter
bands, the
efficiency
of the station will
be
Sreatly
increased
if a
good di!ectional
rotary
antenna is
uBed.
MOBILE
ANTENNA
Mobrle
antenna
rnstallations are
critical,
since any
mobile antenna
fo! use
on the
high frequency
bands
repre6enta a
num_
ber
oI cornpromiBe6.
Many alnateurs
Iose the
ef{iciency
oJ their antenna
through
improper
tuning.
Points to remernber
about the
rnobile antenna
used with the
Swan
400 are:
I, The
rO"
o{ the antenna
loading coil
BhoIrId
be a6
high as
possible. There
are several
comme rcial
models
available
which
use high
"Q"
coils,
including
the Swan
Model 45 and
Model
55 5
band
"Swantennas.'
2.
The loading
coil must be
caPable oJ
handling
the
power of the Model 400
without
overheating.
In TUNE
position, the
power outPut of the
transceiver Inay
exceed 250
watts.
wide spaced,
heavy
wire loading
coils are
e s sential,
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