Telerad VHF High Power Transceiver

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The SE9000x16 transmission system has been designed for long range communication when there is no possibility to install a remote site for extended range. Compared with high output power transmitter systems using valves, the SE9000x16 system offers the following significant advantages:
● fully solid state system,
● wide-band design (no amplifier or filter tuning),
● utmost stability of transmission parameters (frequency, power and modulation),
● fully protection against load mismatch, including antenna short or open circuit,
● very limited maintenance is required.

Because the SE9000x16 is basically composed of 16 conventional transmitters and coupling devices, by design, the system is fully redundant and exhibits an exceptional operational availability (no service interruption despite the failure of one unit), thus allowing one installation without standby equipment. The exchange of most of the units composing the system can be achieved while the system remains in operation. All the vital functions using active elements are duplicated and monitored. At last, the transmission system SE900x16 is equipped with wide telemonitoring possibilities implemented in order to give the user a detailed view of the operation of each unit composing the system part.

Description

The 700W transmission system has been designed from an original concept developed by Telerad, and which has been adopted by the French Technical Services of the Civil Aviation (S.T.N.A) for more than 20 years. This concept
consists in transmitting on one frequency with two inter-coupled transmitters, so that the RF output powers can sum up.

Regarding the transmitters, the coupling implies an operation:
● from the same frequency driver,
● at the same power level,
● with the same modulation signal.

Once got the coupling of two transmitters, there is no more difficulty to inter-couple two pairs of transmitters. Telerad already supplied Spain and Morocco with several 200W transmission systems made by coupling 4 conventional 50W transmitters.

In the present case, for 700W carrier, 4 transmission 200W systems are coupled, just as in a 200W unit 4 transmitters are coupled. The component used to sum up the RF output powers delivered
by the transmitters is the -3 dB λ/4 hybrid coupler.This component has a structure of bi-coaxial quadripole with an electric length of λ/4.

Thanks to its properties, if any signals with determined phase and amplitude relations are introduced in two adjacent ports, the power of these signals is summed to a third port, whereas the fourth port remains isolated. If optimum phase and/or amplitude relations are not respected, a signal appears on this last port related with the imbalance level. This port is connected with a 50 ohms dummy load and has a detection device for imbalance signalling and alarm.