E–1
Appendix E. Es/No
MEASUREMENT
Although
the
CDM
‐
750
Advanced
High
‐
Speed
Trunking
Modem
calculates
and
displays
the
value
of
receive
Es/No
on
the
front
panel
of
the
unit,
it
is
sometimes
useful
to
measure
the
value
using
a
spectrum
analyzer,
if
one
is
available.
The
idea
is
to
accurately
measure
the
value
of
(Co+No)/No
(Carrier
density
+
Noise
density/Noise
density).
This
is
accomplished
by
tuning
the
center
frequency
of
the
Spectrum
analyzer
to
the
signal
of
interest,
and
measuring
the
difference
between
the
peak
spectral
density
of
the
signal
(the
flat
part
of
the
spectrum
shown)
and
the
noise
density.
To
make
this
measurement:
•
Use
a
vertical
scale
of
1
or
2
dB/division.
•
Set
the
Resolution
Bandwidth
of
the
Spectrum
Analyzer
to
<
20%
of
the
symbol
rate.
•
Use
video
filtering
and/or
video
averaging
to
reduce
the
variance
in
the
displayed
trace
to
a
low
enough
level
that
the
difference
can
be
measured
to
within
0.2dB.
•
Place
a
marker
on
the
flat
part
of
the
signal
of
interest,
then
use
the
MARKER
DELTA
function
to
put
a
second
marker
on
the
noise
to
the
side
of
the
carrier.
This
value
is
(Co+No)/No,
in
dB.
•
Use
this
value
of
(Co+No)/No
in
the
table
on
the
following
page
to
determine
the
Eb/No.
You
will
need
to
know
the
operating
mode
to
read
from
the
appropriate
column.
•
If
the
(Co+No)/No
value
measured
does
not
correspond
to
an
exact
table
entry,
interpolate
using
the
two
nearest
values.
Note
that
the
accuracy
of
this
method
degrades
significantly
at
low
values
of
(Co+No)/No
(approximately
less
than
6
dB).
Summary of Contents for CDM-750
Page 76: ...CDM 750 Advanced High Speed Trunking Modem Revision 2 Updating Firmware MN CDM750 4 12 Notes...
Page 224: ...CDM 750 Advanced High Speed Trunking Modem Revision 2 Appendix A MN CDM750 A 4 Notes...
Page 234: ...CDM 750 Advanced High Speed Trunking Modem Revision 2 Appendix B MN CDM750 B 10 Notes...
Page 256: ...CDM 750 Advanced High Speed Trunking Modem Revision 2 Appendix C MN CDM750 C 22 Notes...
Page 280: ...CDM 750 Advanced High Speed Trunking Modem Revision 2 Appendix D MN CDM750 D 24 Notes...
Page 300: ...2114 WEST 7TH STREET TEMPE ARIZONA 85281 USA 480 333 2200 PHONE 480 333 2161 FAX...
