6. CHANNEL SELECTION
a. The CT-FMM is a fixed channel modulator. Channel adjustment is possible, but only
within the band for the specific CT-FMM purchased.
b. The optional CT-FCP frequency control panel is required to adjust a CT-FMM’s
channel within its specific band.
c. Remove the panel covering the CT-FMM’s In-band Channel Adjustment port.
d. Power up the CT-FMM.
e. Attach the CT-FCP wiring harness to the CT-FCP, then attach the CT-FCP to the CT-
FMM’s In-band Channel Adjustment port.
f. Push the respective Up / Down Buttons to set the desired channel. After about 15
seconds the channel will be automatically stored in the modulator’s memory. In the
event of a power outage the channel will be automatically recovered.
g. Disconnect the CT-FCP from the CT-FMM and replace the In-band Channel
Adjustment port panel.
7. ADJUSTMENT
a. After installation and completing all hardware connections power the unit and wait 20
minutes before making the following adjustments.
b. For testing purposes no more than 15dB from the RF Output should be going to a
TV or RF input monitor. Use an attenuator to reduce the signal level if testing with an
RF Input monitor. Individual CT-FMM setup and level settings can be tested from the
RF Output port. However, system level testing should be done from the combiner.
c. With a nominal 1 Vp-p video source connected, use the Video Modulation Index
Level control to adjust the video modulation level for correct percentage of
modulation (87.5%) if the video input is greater than 1.5 Vp-p. If test equipment is
not available then adjust for proper picture contrast when viewed on a TV monitor
and compare with known Off-Air broadcast picture quality. Turn the level control
clockwise to increase the video modulation index, counter-clockwise to decrease the
video modulation index.
d. With audio source connected, adjust Audio Modulation Deviation Level control on
the front panel for 25 kHz deviation. If you do not have an audio modulation meter
and a precision demodulator, use a TV set or a signal level meter with an audio
speaker and adjust for equal volume as compared to a known Off-Air broadcast.
Monitor for a few minutes to assure the maximum volume does not over modulate,
which can cause picture distortion. The audio modulation deviation can be increased
by turning the level control clockwise, counter-clockwise to decrease the audio
modulation deviation.
e. To adjust the picture carrier to audio sub-carrier ratio of the output signal, rotate the
A/V Adjustment on the front panel. Clockwise to increase the audio carrier level,
counter-clockwise to decrease the audio carrier level.
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