1 ST-40 System
1.1Overview
Hardware Specifications
Operating Frequency Range 30-60 MHz
Peak Envelope Power 40 KW PEP (minimum)
VSWR(Input/Output) 1.5:1 (minimum)
Maximum PRF Dependent on pulse width and maximum Duty Cycle
Pulse Shape Gaussian Square
Maximum Duty Cycle 10 % Gaussian 12% Square
Output Spurious and Harmonics Better than –60 dBc
Impedance (Input/Output) 50Ω
Output Level Adjustable from 0 to 100%
Power Supply 50V DC (typical) 10KW (for max. Duty Cycle)
Ambient Temperature +5 to +35 oC
Sub-Rack Temperature +65 to +95 oC (60 oC rise for max. Duty Cycle)
Sub-Rack Mounting 19” rack mount
Cooling Forced air-cooled
1.2Rack Layout
The ST-40 VHF Transmitter is composed of a number of sub-systems here referred to as sub-racks. The
three main sub-racks are
1. DC Power Supply (x2)
2. RF Power Combiner (x1) and
3. ST-20 (x2) ( which is itself a VHF Transmitter).
Other components of the ST-40 include a Circuit Breaker/Distribution Panel Ethernet Switch and a Medium
Power 2-1 RF splitter. Please refer to Block Diagrams 1 & 2 for the front and rear view of these sub-racks in
the ST-40 cabinet.
Modularity is an important feature of the ST-40 design and as such critical sub-racks are modular. In
particular the ST-20 is composed of [1-6] RF PA Modules also a RF PA Driver Controller and Fan
module. The DC Power Supply is composed of a Controller module and [1-4] Rectifier modules. The
benefits of this modularity include:
1. Scalability in RF Output Power. From 4 KW to 40KW in steps of 4 KW.
2. Scalability in Duty Cycle. 0-10% with 4 Rectifier modules installed i.e 2 Rectifiers per ST-20 sub-
rack. With reduced PEP then operation with a Duty Cycle > 10% may be possible.
3. Maintenance upgrades & repairs.
4. Easy of Transport.
Please refer to the various sub-rack sections for module installation instructions also see Block Diagram [1-
2] and Pictures [1-4].
P/No: 15-05004 Issue 2 5
