Transmission/reception installation for microwave radio signals comprising: - a transmission/reception unit comprising means for receiving the electric signals from the conversion of radioelectric signals received via a terrestrial or satellite channel, referred to as forward-link signals; - at least one box including a modulator; - a coaxial cable connecting the transmission/reception unit and the box capable of conveying said forward-link signals from said transmission/reception unit to said box; the transmission/reception installation being characterised in that: - the transmission/reception unit comprises: o a demodulator able to demodulate electric signals according to a first modulation/demodulation protocol; o a modulator of electric signals according to a second modulation/demodulation protocol that is different from said first protocol, said second protocol being a spread spectrum protocol, said modulator modulating the signals demodulated by said demodulator; o means for converting said electric signals modulated according to said spread spectrum protocol, referred to as return-channel signals, into radioelectric signals capable of being transmitted via a satellite channel; - the modulator of the box is capable of modulating electric signals according to said first modulation/demodulation protocol, said electric signals being intended to be demodulated by the demodulator according to said first protocol then modulated by the modulator according to said second modulation/demodulation protocol; - the coaxial cable is capable of conveying the electric signals from said modulator according to said first protocol from said box to said transmission/reception unit. - a transmission/reception unit comprising means for receiving the electric signals from the conversion of radioelectric signals received via a terrestrial or satellite channel, referred to as forward-link signals; - at least one box including a modulator; - a coaxial cable connecting the transmission/reception unit and the box capable of conveying said forward-link signals from said transmission/reception unit to said box; the transmission/reception installation being characterised in that: - the transmission/reception unit comprises: o a demodulator able to demodulate electric signals according to a first modulation/demodulation protocol; o a modulator of electric signals according to a second modulation/demodulation protocol that is different from said first protocol, said second protocol being a spread spectrum protocol, said modulator modulating the signals demodulated by said demodulator; o means for converting said electric signals modulated according to said spread spectrum protocol, referred to as return-channel signals, into radioelectric signals capable of being transmitted via a satellite channel; o a demodulator able to demodulate electric signals according to a first modulation/demodulation protocol; o a modulator of electric signals according to a second modulation/demodulation protocol that is different from said first protocol, said second protocol being a spread spectrum protocol, said modulator modulating the signals demodulated by said demodulator; o means for converting said electric signals modulated according to said spread spectrum protocol, referred to as return-channel signals, into radioelectric signals capable of being transmitted via a satellite channel; - the modulator of the box is capable of modulating electric signals according to said first modulation/demodulation protocol, said electric signals being intended to be demodulated by the demodulator according to said first protocol then modulated by the modulator according to said second modulation/demodulation protocol; - the coaxial cable is capable of conveying the electric signals from said modulator according to said first protocol from said box to said transmission/reception unit.