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If by
the
time
you have found the
trouble
you have blown
a
number
of
fuses,
now
investigate your fuse
box to be
sure
the clips
are
clean
and not
charred.
If
they
are charred,
fuse
blowing will continue anyway and
it
will
be
necessary
to
replace
the
clips that hold the
fuses.
i
1.
UNEXPLAINED OUTAGES. This one
puzzles
the
best
of
them.
A
transmitter
that
goes
off
the
air
for
no
reason
and can be
turned back
on by
pushing the
start
button brings the query, "What caused
that?
If
this
happens
very infrequently, it is probably caused
by a
power line dip,
a jump
across
the
arc
gap
at
the tower
base,
or
other normal things that activate the protective relays
in the
transmitter
as they
should.
Your
transmitter
always looks like the offender. It is the device with
meters
and
it
is the device that
complains or quits
if
there
is
a
failure
anywhere
in the
entire system.
An
open
or
short circuit
in
a
transmission
line only
reacts
at the
transmitter.
A
faulty
insulator
in an
antenna
guy
wire or
a
bad
connection in the tuning unit or ground
system reacts
only
at the
transmitter.
Here
again the dummy
antenna is
of
great
value.
If
these unexplained outages
do
not
appear
in
operating
into
a
dummy antenna,
then you must look
elsewhere for
the
problem. It is always well
to
remember
that the
transmission
line
tuning units and
associated connections, including
the tower chokes,
are
somewhat like
the
drive shaft
between the automobile motor and the
rear
wheels.
If the
drive shaft
fails, it
does not mean
that the
motor is defective.
12.
STEP
BY
STEP
TROUBLE SHOOTING.
Never trouble -shoot
on
the
basis
of
"it
might
be
this or that ".
Instead,
start
from
the beginning.
If
the
transmitter
was
satisfactory
on
the dummy
antenna, then the
question becomes "Where is the trouble
?"
If
a
transmission
line connects the
transmitter
to the
antenna coupler, then disconnect the antenna coupler
and
provide
a
dummy antenna
at
the
far
end of
the
transmission
line and
repeat
the
test.
If you
noticed the outage at this point, then
the
trouble
is in
the
transmission
line.
If not,
reconnect it
to the antenna coupler unit and put the dummy antenna at the
output
of
the coupling unit. This is known as
step
by
step checking to locate problems.
The
same process
is used in
trouble-
shooting the
transmitter.
In
checking
voltages,
you
start
with the
oscillator
and go
through
to the power
amplifier
and with the
first
audio
stage
to the
final
audio
stage.
Other outage conditions not affecting the
transmitter
are listed
below
for your checking:
Under
certain
conditions, especially at higher
altitudes,
the
guy
insulators
will
arc,
usually caused
by
static
conditions. This will
nearly
always
cause
an outage as
it
changes the antenna
characteristics.
This is
hard
to find as
it is hard
to
see.
Use
of
field glasses at
night is the
best
way. If
it happens,
the
insulator
should
be
shunted with
a
resistor.
Write
our
Engineering Depart-
ment for advice,
giving
full antenna detail
when
writing.
At
times
the
arc
gap
at the base
of
the tower is
set
too
close or has accumulated
dirt.
This
causes
an
arc
to ground
under
high modulation.
A
crack
in the
tower base
insulator
is
very unlikely
but
it should
be
inspected
and
keeping the base
insulator
clean is
necessary.
A
low
resistance
path at
this point is highly
undesirable.
Look
at
the tower chokes. Though they
are
husky, they
are
in
a
vulnerable
position for lightning.
You
might find
a
charred
point that is causing the
trouble.
.
Shunt fed
towers
or
those
with
no
base
insulator are usually more sensitive
to
static bursts
than
series
fed
towers.
The
best
method is
to
try
and
make
the
feed line to the tower equal
the
impedance
of
the
transmission
line. Talk
to
your consultant about
this.
One
side
of
the
tower lighting
circuit
shorted
to
the tower
itself, either
permanently
or
intermittently,
can cause
trouble
even though the lights may
function
perfectly.
13.
OTHER OUTAGES.
If
the
transmitter
is the
offender, such as acting improperly
on
a dummy antenna, the
process
of
elimination
by
starting
at the
first
and following
through
is
preferred,
unless
of
course
the
cause is actually
known. The following may be helpful:
(FALL OUT) The
transmitter turns
off
at
high modulation.
Possibly
the
overload
relay
is
set
too
sensitive.
The
transmitter
may not
be
properly
neutralized
where
neutralization
is
required.
(HARD TO
MODULATE)
Cause can
be
either improper impedance match
between
transmitter
and the
transmission
line or
low
grid drive
to the
final
power
amplifier.
Consult the
instruction
book
for
correct
grid drive.
The
correct
match
of
the
transmitter
to load
is covered in the
instruction
book.
Usually
an
antenna
current meter that
does not move
up
freely
with modulation
indicates
a
mismatch between
the
transmitter
and
its
loading equipment.
(BAD
REGULATION) The
size
of
the
primary
lines between
the
meter
box
and the
transmitter
is extremely important.
If
they
are
too
small,
bad
regula-
tion will
exist.
In
some
instances
the power line has bad
regulation
too. This
C
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