Automatic compensation of cable television systems

Claim 2

In a cable television system, a cable to transmit multiple channel television signals for distribution to subscriber equipment, the signals being subject to attenuation during said cable transmission, multiple solid state wideband r.f. amplifiers electrically connected in series with the cable at predetermined intervals to amplify the transmitted signals and thereby compensate said attenuation, the system being subject to additional signal attenuation that varies as a function of signal frequency, and equalizer means to compensate said additional attenuation and including a fixed reference signal source and a comparator responsive to the reference signal and to the cable transmitted signals to produce an error signal, said means also including a network connected in series with said cable and responsive to a version of said error signal to control cable transmitted signal level and frequency response, the network including impedance to compensate for changes in cable effective length.

Claim 3

The system of claim 1, in which said network includes a bridge circuit having legs containing variable capacitance diodes and a transformer tapped to supply said error signal as a voltage acting to drive the bridge toward increased attenuation whereby transmitted signal level and frequency response are temperature compensated.

Claim 4

The system of claim 1, including housings for said amplifiers having integral cable connections, the amplifiers having pre-aligned construction, the cable including main trunk sections, and including equipment connected to deliver substantially constant level television signals to the head end of the main trunk cable.

Claim 5

In a cable television system, a cable to transmit multiple channel television signals for distribution to subscriber equipment, the signals being subject to attenuation during said cable transmission, multiple solid state wideband r.f. amplifiers including control amplifiers and repeater amplifiers electrically connected in series with the cable at predetermined intervals to amplify the transmitted signals and thereby compensate the attenuation, the system being subject to temperature change productive of additional signal attenuation that varies as a function of signal frequency, and means connected with said control amplifiers to alter the gain thereof in respoNse to said temperature change so as to overcompensate said additional attenuation, said means including impedance comprising at least one adjusted variable impedance element and a thermistor connected with said element, repeater amplifiers being spaced between said control amplifiers, said overcompensation determined by the adjusted impedance of said element and characterized by raising the control amplifier transmitted signal by an amount approximately 1/2 epsilon above the normal temperature maximum signal levels in response to temperature increase above said normal temperature, where 1/2 epsilon is the difference between the actual minimum signal level at the input side of a control amplifier due to said temperature increase in the absence of said means and normal temperature minimum signal level at the input side of the control amplifier.

Claim 6

In a cable television system, a cable to transmit multiple channel television signals for distribution to subscriber equipment, the signals being subject to attenuation during said cable transmission, multiple solid state wideband r.f. amplifiers including control amplifiers and repeater amplifiers electrically connected in series with the cable at predetermined intervals to amplify the transmitted signals and thereby compensate the attenuation, the system being subject to temperature change productive of additional signal attenuation that varies as a function of signal frequency, and means connected with said control amplifiers to alter the gain thereof in respoNse to said temperature change so as to overcompensate said additional attenuation, said means including impedance comprising at least one adjusted variable impedance element and a thermistor connected with said element, repeater amplifiers being spaced between said control amplifiers, said overcompensation determined by the adjusted impedance of said element and characterized by raising the control amplifier transmitted signal by an amount approximately 1/2 epsilon above the normal temperature maximum signal levels in response to temperature increase above said normal temperature, where 1/2 epsilon is the difference between the actual minimum signal level at the input side of a control amplifier due to said temperature increase in the absence of said means and normal temperature minimum signal level at the input side of the control amplifier.

Claim 7

The system of claim 4 in which said means includes a D.C. amplifier having an input connection providing voltage input that varies with said impedance and with the rectified output of said control amplifier, the D.C. amplifier output connected in feedback relation with the input to the control amplifier.

Claim 8

The system of claim 5, in which said D.C. amplifier includes a transistor wherein said input connection includes a control electrode, said impedance comprising a thermistor connected in biasing relation with said control electrode.