General Instrument C6M-II, Installation Manual

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Installation 3-5
C6M-II Installation Manual
For audio, this function maintains a preset audio deviation despite changes in audio input level
resulting from audio source variations or from audio switching. To activate the audio AGC, go
to the Audio menu and choose Audio AGC (AAGC). Change from AAGC OFF to AAGC ON.
When the optional stereo encoder is in operation, Audio AGC cannot be changed.
Audio Parameters
Audio Impedance
Audio impedance has two settings, 600 Ohms and greater than 15 kohms. The value is set
through the Audio menu. Go to the Audio menu and choose either Audio Impedance Low
(AUDZ LOW) which is 600 Ohms, or Audio Impedance High (AUDZ HI) which is greater than
15 kohms.
Audio Level
There are two ranges for the input audio signal:
−
10 to +10 dBm and +5 to +25 dBm. The
range is set through the Audio menu. Go to the Audio menu and choose Audio Range Low
(AUDR LOW) which is
−
10 to + 10 dBm, or Audio Range High (AUDR HI) which is + 5 to
+ 25 dBm.
Stereo Encoder (Optional)
When the stereo encoder option is installed in the unit, the following audio parameters cannot
be changed: audio input range, input impedance, pre-emphasis, and AGC. Audio A can be
stereo encoded while Audio B is always monaural.
Selecting the RF Channel Frequency Plan
The C6M-II meets the FCC Part 76 Frequency Rules.
The C6M-II operates in STD, HRC, EIA or IRC modes. The difference between the IRC and
Standard frequency plans is the following:
n
For the HRC and IRC Phaselock Mode, channels 54, 55 and 56 are used in the low band in
place of channels 5 and 6.
n
For the Standard Mode, channels 5 and 6 are located at the standard frequency
assignments. Channels 54, 55 and 56 are at the IRC frequencies. Channels 42, 60 and 61
have the + 25 kHz FCC frequency offsets built in.
The C6M-II has the capability to output any frequency in increments of 12.5 kHz if needed. If
AUX IF
and/or
PRGM IF
is used in HRC, IF frequency must be 45.7522875 MHz.
To select a mode, go to the Option menu and choose Tuning mode. Select either MODE IRC,
MODE HRC, MODE STD, MODE EIA or MODE FREQ.
Appendix B, Frequency Plan shows the relationship between channel and frequency for the
four modes.