dsp block 14 accepts and processes a data stream provided by either a data source transmit data streams or the terminal controller overhead data stream and performs data scrambling data interleaving and data encryption and forwards error correction coding and other functions the dsp blocks 14 can be realized separately or in a single device for example a custom dsp chip a general dsp chip a custom fpga or a custom asic dsp block 14 provides the processed data stream to the modulators 15 each modulator 15 accepts the processed data stream from the corresponding dsp block 14 and modulates the signal onto an intermediate frequency if carrier the modulation process includes data modulation using m ary psk m ary qam m ary fsk or any other digital modulation technique spectrum control such as square root raised cosine pulse shaping and if necessary distortion mitigation such as linearization each modulator 15 produces an analog signal modulated onto an if carrier which is then provided to the corresponding frequency converter 16 each frequency converter 16 upconverts the if signal provided by the corresponding modulator 15 to a unique rf frequency as an alternative the modulator 15 can perform direct modulation to modulate the data stream directly onto the rf carrier in such a design frequency converters 16 are unnecessary in addition if the if frequency is also one of the desired if frequencies the frequency converters 16 can be eliminated the output of each frequency converter 16 or modulator 15 when the frequency converter 16 is unnecessary is provided to a variable amplifier amp 17 the amp 17 is controlled by the terminal controller 8 to optimize channel performance by adjusting the signal level.