Orban OPTIMOD-FM 8700, Operating Manual

Page: 99 / 390

OPTIMOD-FM DIGITAL INSTALLATION
2-37
this case, we advise you to set the output level using the 8700i’s refer-
ence 400Hz tone.
In the United States, F.C.C. Rules permit you to add 0.5% modulation for
every 1% increase in subcarrier injection. For example, if your subcarrier
injection totals 20%, you can set the total modulation to 110% (

82.5
kHz deviation). This implies that you must set the 8700i’s composite out-
put level for the equivalent of 90% modulation, not counting the subcar-
riers. (90% + 20% = 110%.) This will mean that pilot injection will be
about 8% modulation instead of the desired 9%. From the Input/output
> Composite screen, adjust
P
ILOT
L
EVEL
control as necessary to produce
9% modulation (

6.75 kHz deviation). This will ordinarily require you to
set the
P
ILOT
L
EVEL
parameter to “10%.”
12. Set up Dante AES67 audio-over-IP output (optional).
See step 3 on page 2-101.
13. Set preemphasis mode of Output meters (optional).
When the
M
ETER
S
ELECT
switch (in
I
NPUT
/O
UTPUT
> HD D
IGITAL
R
ADIO
) is set to
FMO
UT
L
EVEL
, the 8700i’s Output meters normally indicates the peak output level
of the FM analog processing, which is always pre-emphasized. If you wish to ap-
ply de-emphasis before these meters, navigate to
I
NPUT
/O
UTPUT
> U
TILITIES
and set
the
FM O
UTPUT
M
ETER
to
D
E
-E
MPH
.
The default is
P
RE
-E
MPH
.
14. Set the polarity of the analog FM processing (optional).
In HD Radio installations, this command is useful when switching the 8700i be-
tween transmitters if the transmitters’ exciters produce opposite FM modulation
polarities when driven by identical digital audio input signals. This setting affects
any output emitting the analog FM processed signal, including the composite
output.
A) Navigate to the I
NPUT
/
OUTPUT
> U
TILITIES
screen.
B) Set the FM P
OLARITY
control to P
OSITIVE
or N
EGATIVE
as appropriate for your
transmitter.
15. Configure composite outputs.
[Skip this step if you are not using the composite baseband outputs.]
A) Navigate to the
I
NPUT
/
OUTPUT
>
C
OMPOSITE
screen.
B) Adjust the composite level at the composite output(s) you are using so that
the FM carrier is modulated to 100% on modulation peaks. Alternately, you
can use tone.
If you are using subcarriers, this screen allows you to specify the amount
by which the 8700i automatically reduces main and stereo subchannel
modulation to accommodate the subcarrier within the modulation limits
specified by the governing authority.
See step (8.C) on page 2-22 for a more detailed discussion.