Textron Cessna 172R - Page 391

CESSNA
MODEL
172R
SECTION
9
-
SUPPLEMENTS
SUPPLEMENT
6
-
FAA
APPROVED
ADF
OPERATION
NOTES:
r
ERRONEOUS
ADF
BEARING
DUE
TO
RADIO
FREQUENCY
PHENOMENA:
In
the
U.S.,
the
FCC,
which
assigns
AM
radio
frequencies,
occasionally
will
assign
the
same
frequency
to
more
than
one
station
in
an
area.
Certain
conditions,
such
as
Night
Effect,
may
cause
signals
from
such
stations
to
overlap.
This
should
be
taken
into
consideration
when
using
AM
broadcast
station
for
navigation.
Sunspots
and
atmospheric
phenomena
may
occasionally
distort
reception
so
that
signals
from
two
stations
on
the
same
frequency
will
overlap.
For this
reason,
it
is
always
wise
to
make
positive
identification
of
the
station
being
tuned,
by
switching
the
function
selector
to
ANT
and
listening
for
station
call
letters.
ELECTRICAL
STORMS:
In
the
vicinity
of
electrical
storms,
an
ADF
indicator
pointer
tends
(
to
swing
from
the station
tuned
toward the
center
of
the
storm.
NIGHT EFFECT:
This is
a
disturbance
particularly
strong
just
after
sunset
and
just
after
dawn.
An
ADF
indicator
pointer
may
swing erratically
at
these
times.
If-
possible,
tune to
the
most
powerful
station
at
the
lowest
frequency.
If
this
is
not
possible,
take the
average
of
pointer
oscillations
to
determine relative
station
bearing.
MOUNTAIN EFFECT:
Radio
waves
reflecting
from
the
surface
of
mountains
may
cause
the
pointer
to
fluctuate
or
show
an
erroneous
bearing.
This
should
be
taken
into
account
when
taking bearings
over
mountainous!
terrain.
f**
COASTAL
REFRACTION:
Radio
waves
may
be
refracted
when
passing
from
land
to
sea or
when
moving
parallel
to
the
coastline.
This
also
should
be
taken
into
account.
Feb
28/00
S6-11
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