KING KR 21 - SECTION III OPERATION; 3.1 MARKER BEACON (KMA 20 AND KR21)

KING
KMA
20 /KR 21
MARKER BEACON
RECEIVER/
TSOLATION
AMPLIFIER
SECTION
III
OPERATION
3.1
MARKER
BEACON(KMA20
AND
KR21)
Marker
beacon
receivers
are
used to
provide
accurate
fixes by
informing
the
pilot
of
his
passage
over
beacon stations
located on
airways
and
ILS
approach
courses. Three types
of beacons are
used.
They
are the
inner
marker,
the
outer marker
and
the middle
marker.
The
outer,
middleand inner markers are
used
in conjunction with the radio
instrument
landing
systems.
The
outer
marker
is
normally
positioned on the
front
localizer
course
near
the point
where
the glideslope
approach
path intersects
the minimum
inbound
altitude
after
the
procedure
turn. Distance
from
the
airport will
vary
from
4
to 7
miles.
Radio
frequency
from
the
marker
is
projected
vertically
in
an elliptical cone shaped
pattern.
The marker
signal
is
modulated
at 400Hz
and
is
keyed
to emit dashes at a
rate of two
per
second.
When
passing
the
outer marker
the
blue light will flash "on/off" at
a
two
per
second rate
and the pilot will
hear
a series of low tone
dashes.
The middle
marker
is
normally located
on the front localizer course
about 3200 feet
from
the
approach
end
of
the
ILS runway.
The radiated
pattern
is
similar
in
shape
and
power
to the
outer
marker. The middle
marker
signal
is
modulated with 1300Hz and the
modulation
is keyed
to
identify by
alternate
dots
and
dashes.
When the KMA
20
(KR 21)
equipped
aircraft
passes
the
middle marker
the pilot
hears
a medium
pitched tone in a
series of dots and
dashes
and the amber light
flashes
synchronously
with
the
tones.
The
inner
marker
is located close to the end of the
runway.
The
beacon
transmitter
and
antenna
are
designed to
project
a cone
shaped
pattern of 75MHz
energy, vertically.
The
radio
frequency
output of the
transmitter
is modulated with an audio tone of
3000Hz.
An
aircraft
equipped
with
the KMA
20
(KR
21)
will
receive a 3000Hz
tone in headphone
or
speaker
and
the white
lamp will be
lighted
while
over
the
station.
The
inner marker
is
used
to
indicate a
point
approximately
1500
ft. from the
runway
and if on
proper
glide
path the
altitude
above the
runway
should
be
approximately
100
feet.
The
marker
beacon
function in the KMA 20 provides the
pilot with
audio
switching
control
and the
Hi-Lo
Switch
in
the KR
21
and
KMA
20 provide
sensitivity switching control.
Many
marker receivers provide
only a
"low sensitivity" position. The effect of the high
sensitivity
position
is
to
greatly
enlarge
the size of the
cone shaped
"area
of
indication"
above
the
station.
An
aircraft
flying at
high altitude or
slightly off
course
may fail
to
receive
the signal
when in the low
sensitivity
postion.
It is
suggested that the KMA 20
Rev.
1, August,
1972
Page
3-1