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| Model No.: TW/VHFPA/50W |
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| 100W VHF POWER AMPLIFER |
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 The 50W VHF Power Amplifier subsystem
described in this. 10 mW (+10 dBm) sync peak
RF input (From selected Exciter) is
amplified to 100W sync peak power at antenna
port, by two Class AB solid state 50W Power
Amplifiers in parallel.
These power amplifiers have high gain and
can be operated in any of the VHF band III
TV channel, provided used as part of system
is aligned to the corresponding channel.
Two 50W power amplifiers along with combiner
forms a 100W Power Amplifier sub-system. The
50W Power Amplifier sub-system is mounted in
a single rack and consists of mainly of, Two
50W Power Amplifiers in each power
amplifier.
The Amplifiers are powered from +28V DC
Power. The subsystem is configured for
operation with high reliability, low MTTR,
and state-of-the-art components. Visual
indication, metering and monitoring points
are provided for ease of operation and high
quality picture transmission. Automatic
level control ensures stable power output,
and absorbs gain variation of power
amplifiers.
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| 50W POWER AMPLIFIER
(CLASS-AB) |
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50W power amplifier consists of the |
- 70W power amplifier pallet
- 1 Nos. circulator
- Directional coupler
- Monitoring card
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| 70W AMPLIFIER PALLET |
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This amplifier is Class AB and incorporates micro strip technology and push-pull
MOSFET to enhance ruggedness and reliability. This Amplifier provides 70W sync
peak output power. Data sheet is encl. For the details.
Such 2 nos. of 70W power amplifier are combined and we can get the 100W sync
peak power from the amplifier.
3Db, 90 degree in phase Divider and combiner are wide band through out the VHF
frequency band.
A circulator is installed in each path of the 70W Pas to protect the Reflection
from the combiner side.
This coupler is used for sensing output power of PA and is given to detect the
levels of Forward and Reflected power in Monitor Board. The distinct feature is
that it has got repeatability built in the design. It has coupling of 32dB to
34dB in VHF Band.
In monitoring card following controls and monitoring points are available. |
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- Forward power control
- Reflected power control
- Power amplifier heat sink
temperature.
- Metering the Forward and reflected
power
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| Specifications of 50W Power
Amplifier Subsystem: |
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| No. |
DESCRIPTION |
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SPECIFICATIONS |
| 1 |
Frequency Range |
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| 2 |
Power Gain (Min) |
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54dB |
| 3 |
Power Output |
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50WATT (Peak to SYNC at 1% SYNC Compression) |
| 4 |
Frequency Response |
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± 0.2 dB in any band III channel |
| 5 |
IMD |
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Better than 48 dB |
| 6 |
Harmonics |
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< -60 dBc |
| 7 |
Spurious |
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< -55 dBc |
| 8 |
VSWR Trip |
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10W Black |
| 9 |
Input Return Loss |
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>16dB |
| 10 |
DC Input (Black Burst)
(At rated output power) |
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28V / 25A |
| 11 |
Indications |
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PA OK LED
GREEN |
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When PWR OK |
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FWD HIGH LED, RED |
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When FWD PWR Exceeds 1030W (SYNC PEAK) |
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RFL HIGH LED, RED |
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When RFL PWR Exceeds 32.5W (SYNC PEAK) |
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TEMP HIGH, RED |
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When Thermistor Temp Exceeds 75°C |
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HEALTH |
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TTL High When PA Fails |
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TTL Low When PA OK |
| 12 |
Metering Indication |
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FWD |
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Indication in Green Range for PWR O/P 1000W |
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RFL |
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Indication in Red Range for RFL PWR >20W |
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