UBS Axcera 835A-6 6000-Watt UHF Transmitter User Manual 835A

UBS-Axcera 6000-Watt UHF Transmitter 835A

Specifications

UHF Solid State Transmitters
835A-3, 835A-4, 835A-5, 835A-6
The 835A represents the state of the art in
solid state UHF transmitters. High
performance, redundancy, and simplicity are
combined in a very reliable unit.
Using parallel high gain amplifiers, the 835A
can be configured for 3kW, 4kW, 5kW, or
6kW operation. Combined aural/visual
amplification is achieved with very good
intermodulation performance, thanks to
highly linear amplifiers and extensive
correction capability.
Front panel samples, status, and metering,
most of which are remote controllable, allow
for convenient system monitoring. As with all
Axcera products, servicing is made easy with
slide out assemblies that require no extender
cards. This allows the circuits to be accessed
for maintenance or adjustments even while
on the air.
www.axcera.com • 724-873 -1500
UHF Solid State Transmitters
High Performance
Exciter
The exciter, designed and
built by Axcera, contains the
circuitry to convert the input
video and audio signals to a
combined, modulated RF
signal which drives two very
linear phase and gain
modules. An optional
second exciter with
automatic exciter switcher is
available for added
redundancy.
Video/Visual Modulation
The video signal is processed
in several ways prior to
modulation. Sync tip
clamping is provided to
restore proper DC level.
Sync and white clipping are
also included to limit
video
transient faults. Back porch
clamping is also available for
some scrambling systems.
The video signal is then
applied to a double
balanced diode modulator,
providing modulation
UHF Solid State Transmitters
capability to 1% at standard
intermediate frequency (IF).
A SAW filter is employed
for precise sideband
filtering with minimal group
delay error.
Audio/Aural Modulation
The audio signal is applied to
a very wideband, linear FM
modulator which operates at
intercarrier frequency (4.5
MHz for system M). The
high performance modulator
accepts a full range of
multichannel audio including
stereo, mono, and second
audio programming (SAP).
Standard aural IF is achieved
by heterodyne conversion of
the modulated intercarrier
signal with the visual IF.
IF Processing
The visual and aural
modulated IF signals are
combined and applied to IF
processing stages. These
stages provide outstanding
signal precorrection to yield
a very linear transmitter
output. Amplitude
linearity, incidental carrier
phase modulation (ICPM),
and frequency response
correction are all
adjustable.
Upconversion
The IF signal is upconverted
to final channel frequency
through heterodyning with a
very stable local oscillator.
The oscillator is crystal and
oven temperature controlled
for excellent frequency
stability. The exciter is
controlled with an Automatic
Level Control (ALC) loop
which ensures stable signal
levels. After upconversion
the signal is amplified to
provide the exciter output.
Power Amplifiers
The parallel 600 watt
power amplifiers are high
gain units (45-50 dB),
which provide redundant
paths from the exciter to the
output. Redundancy is
enhanced with independent
power supplies and cooling
for each amplifier assembly.
The output stage of each
amplifier module utilizes
eight transistors in parallel for
added redundancy and on-air
reliability.
A high degree of protection
is provided with each
amplifier. Individual
circulators, overdrive
protection, VSWR cutback,
and overtemperature
protection are all
included.
Automatic Gain Control
around each amplifier
ensures that the transmitter
output remains stable.
The output of each RF
cabinet is fed into a low loss
hybrid combiner. Output
bandpass and trap filtering is
included to provide superior
out of band rejection.
www.axcera.com • 724-873 -1500
UHF Solid State Transmitters
Features and Benefits
24 Hour Field Supprt
Standard with all Axcera products is 24 hour/day, 7 day/week field support. This service
operates as a direct telephone line during business hours, and on a pager system at all other
times. Since all our products are designed and built at our facility just south of Pittsburgh,
Pennsylvania, we are able to offer quick turnaround on most replacement modules, and
timely shipping from the Pittsburgh International Airport.
■Utilizes 100% solid state circuitry for high reliability and low maintenance costs
■Configured with parallel high gain amplifiers for total system redundancy and maximum
on-air reliability, including driver stages
■Provides standard ±1 kHz frequency stability for stations with an offset frequency
■Independent power supplies and cooling for cost-effective and reliable operation
■Configured with broadcast quality exciter that includes full BTSC sound
capability
■Provides output circulator amplifier protection and isolation for high VSWR conditions
■Experienced field service/support team is ready to help you 24 hours a day, 7 days a week
PA
PA
PA
PA
PA
PA
PA
PA
PA
PA
Splitter 5-Way
Combiner
IPA
Splitter
Hybrid
Combiner
Splitter 5-Way
Combiner
IPA
Exciter
Switcher
Exciter
Exciter
Bandpass/
Trap Filter
Optional Second
Exciter with
Automatic Exciter
Switcher
Combined RF
Combined RF RF Output 5kW Peak Visual
500W Average Aural
Video
Audio
Video
Audio
UHF Solid State Transmitters
Block Diagram - 835A UHF 5kW Transmitter
B0008 1101R1-E
835A-3, 835A-4, 835A-5, 835A-6
Visual Performance
Power Output (Peak) 3000, 4000, 5000, or 6000
watts
Output Impedance 50 ohms
Output Connector 3 1/8" EIA
Frequency Range 470 to 860 MHz
Carrier Stability ±1 kHz (standard)
±350 Hz (optional)
Regulation of RF Output Power 3%
Output Variation (over 1 frame) 2%
Sideband Response (System M/N-others on request)
-3.58 MHz -42 dB
-1.25 MHz and below -20 dB
-0.5 to +3.58 MHz ±0.5 dB
3.58 MHz to 4.18 MHz +0.5, -1.0 dB
Freq Response vs. Brightness ±0.5 dB
Visual Modulation Capability 1%
Differential Gain 5%
Incidental Phase Modulation ±3°
Linearity (Low Frequency) 5%
Differential Phase ±3°
Signal-to-Noise Ratio 55 dB
2t K-Factor 2%
Env. Delay Per CCIR or FCC Standard
Video Input 75 ohms (loop through)
Video AGC Range 1V, ±6 dB
Harmonics -60 dB or better
Intermodulation Products -52 dB or better
Spurious -60 dB or better
(>3 MHz from channel edge)
Aural Performance
Power Output (Average) 300, 400, 500, or 600 W
Frequency Deviation Capability ±75 kHz
Distortion 0.5%
FM Noise -60 dB
AM Noise -50 dB
Aural to Visual Separation 4.5 MHz, ±100 Hz
Composite Audio Input (multi-channel sound)
Input Level 1V peak, nominal
Input Impedance 75 ohms, unbalanced
Frequency Range
±0.1 dB response 50 Hz to 50 kHz
±0.5 dB response 30 Hz to 120 kHz
Monaural Audio Input
Input Level 0 to +10 dBm
Input 600 ohms, balanced
Freq Range (±0.5 dB resp.) 30 Hz to 15 kHz
Pre-emphasis 75µs
Subcarrier Input
Input Level 1V peak, nominal
Input Impedance 75 ohms, unbalanced
Freq Range (±0.5 dB resp.) 20 kHz to 120 kHz
General
Operational Temperature Range 0°C to +50°C
Operational Humidity Range 0% to 95%
Altitude 8,500 feet
Line Voltage 230V, ±10%,
1 phase or 3 phase,
50/60 Hz
Power Factor 0.95
835A-3
Size (H x W x D) 80" x 44" x 34"
Weight 1150 lbs
Power Consumption 10,300 W (50% APL)
835A-4
Size (H x W x D) 80" x 66" x 34"
Weight 1350 lbs
Power Consumption 13,700 W (50% APL)
835A-5
Size (H x W x D) 80" x 66" x 34"
Weight 1500 lbs
Power Consumption 17,000 W (50% APL)
835A-6
Size (H x W x D) 80" x 66" x 34"
Weight 1650 lbs
Power Consumption 20,200 W (50% APL)

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