VT50/OM Rev-A
9
VT50 Series Transmitters operating at 5 Watts or higher incorporate an automatic power
“fold back” circuit to protect the unit in case of high VSWR loads (such as RF short, RF
open, broken antenna, wrong antenna, etc.). In the event of a high VSWR load causing
approximately 2.5 Watts power reflection for L/S/C-band units and 5 Watts for UHF
units, the RF output power is automatically reduced to approximately 2 Watts to avoid
excessive heat and potential damage to the unit. The “fold back” circuit attempts to
restore the RF output power to its normal level every 1 millisecond, checking each time
whether the high VSWR load has been repaired.
4.2.3 Video Inversion Switch:
All AMP Transmitters and Receivers are standard equipped with video inversion,
selectable with a slide switch accessible through the chassis lid. When selected, the
phase of the video signal is inverted (shifted 180
o
) in the transmitter and re-inverted in
the receiver, providing a basic level of security. If an inverted video signal is detected by
a receiver not configured for inversion, the resulting picture is scrambled.
To select standard video (no inversion), position the slide switch to VIDEO STD as
indicated on the unit label. To select inverted video (phase inversion), position the slide
switch to VIDEO INV as indicated on the unit label.
The video inversion switch position on AMP’s Receivers must match that of the
transmitter or the picture will appear scrambled. If using AMP’s Transmitters with other
receivers or vice-versa, position the Video Inversion slide switch to VIDEO STD.
4.2.4 Audio On/Off Switch(es):
VT50 Series Transmitters are optionally equipped with up to two audio subcarriers. Each
subcarrier is individually enabled / disabled with a slide switch accessible through the
chassis lid. When enabled, the audio signal applied to the audio input is transmitted.
When disabled, the subcarrier signal is not produced, and no audio is transmitted.
To enable audio transmission, position the corresponding slide switch to AUDIO ON as
indicated on the unit label. To disable audio transmission, position the corresponding
slide switch to AUDIO OFF as indicated on the unit label.
When two subcarriers are specified, Audio On/Off switches are designated as AUDIO-1
ON / AUDIO-1 OFF and AUDIO-2 ON / AUDIO-2 OFF on the unit label.
4.2.5 Line / Mic Audio Level Switch(es):
VT50 Series Transmitters with audio subcarriers accept either Line or Microphone Level
audio inputs. Audio level for each subcarrier is individually controlled with a slide
switch accessible through the chassis lid. When set to Line, the audio input circuitry
adjusts to accept standard Line Level (-10 dBV) audio. When set to Mic, the audio input
circuitry adjusts to accept typical Microphone Levels (-70 thru -20 dBm) with automatic
level control (ALC).
