Drake 300VMF+ Fixed Modulator - Manual (Page 4)

4 Front Panel Description
F1 F2 F3 F4 F5 F6 F7
F1 - POWER Indicator
Lights when the unit is connected to a source of AC
power.
F2 - OUTPUT TEST Connector
Provides a reduced level sample of the RF output signal.
The level at this connector is approximately 30 dB lower in
level than the RF OUTPUT signal. It is used to monitor
the active signal without affecting the level or quality of the
RF output signal.
F3 - CHANNEL Designation
The label indicates the fi xed channel output for your
particular model. The 300VMF+ is capable of fi xed
channel output (factory tuned) within the following
ranges: Channel 2 through 78 and 95 through 99.
F4 - RF OUTPUT LEVEL
This screwdriver adjustment permits decreasing the RF
output level a minimum of 12 dB below its specifi ed
output level as the control is rotated counterclockwise.
The maximum output level of +55 dBmV is set with the
adjustment approximately fully clockwise.
NOTE: If an output level of less than +43 dBmV is
required, add an attenuator of the appropriate value at
the modulator output.
Example: For an output level of +35 dBmV, add a 12 dB
attenuator pad to the modulator output and set the
output level to +47 dBmV.
F5 - A/V RATIO Control
This screwdriver adjustment varies the level of the aural
carrier over a range from 12 to 20 dB below the visual
carrier. The aural carrier should normally be adjusted to
approximately 15 dB below the visual carrier (normal
operation). Clockwise rotation increases the aural carrier
level and thus decreases the A/V ratio.
F6 - AUDIO LEVEL Control
The setting of this screwdriver adjustment determines the
peak aural carrier deviation. Clockwise rotation
increases the carrier deviation. After installing the unit,
and with an audio source connected, adjust the AUDIO
LEVEL control for 25 kHz deviation. If an audio
modulation meter is not available, use a TV set and
adjust for equal volume as compared to a known off-air
broadcast. Monitor for a few minutes to assure that
maximum volume of the audio source program does not
cause an over-modulation condition.
F7 - VIDEO LEVEL Control
The setting of this screwdriver adjustment determines the
video modulation level. Clockwise rotation increases the
modulation depth. After installing the unit, and with a
nominal 1 Volt P-P video source connected, adjust the
VIDEO LEVEL control for the correct percentage of
modulation (87.5%). If test equipment is not available for
such measurements, then adjust for proper picture
contrast when viewed on a TV set (compare with known
off-air broadcast picture quality).