thermal kompensator

Do somebody know how thermal compensators are constructed in big CATV amplifiers, forward direction ? (control range is about 3 -5 dB for 60 deg C change)
Thanks
g579

As a rule, they are using special pilot tone (for example 110 MHz with level -10 dB to usefull signal) and measuring amplifier/detector with control by variable attenuator in the input of cable amplifier.

More complicated amplifiers for big networks are using two pilote tones (for example 110 and 240 MHz) - in high and low parts of frequency band - they are using for automatic level stabilization and automatic compensation of frequency response curvature in cable.

All these pilot tones are added to spectra in head station.

Klug,

Thanks for your reply.
But either I asked not precise enough, or you misunderstood me.
I am looking for circuit details of controllable (diode, NTC ?) attenuators, controlled either by the ambient temperature or by the AGC circuit of the amplifier. But in this case the controllable attenuator's linearity is also important.
Thanks.
g579