feet of cable is limited to 20 db if a uniform cable was used the dynamic range could be as high as 46 db for the same cable length this reduction in dynamic range has three beneficial effects first the dynamic range of the analog to digital converter is more optimally utilized second the system operational characteristics are more uniformly distributed over the cable length third the total attenuation is reduced as the cable attenuation increases with the coupling factor additional lengths of similarity gradated cable can be utilized provided appropriate line amplifiers are used for the four staged gradated cables in the example the amplifiers would require a total gain of 80 db 40 db in each cable further reduction in dynamic range is achieved if the cable is continuously gradated thereby eliminating all connectors the transmitter 16 initiates the rf pulse along one of the leaky coaxial cables a typical system operates with the following specifications carrier frequency 60 mhz bandwidth 2 5 mhz pulse width 400 nanoseconds repetition rate 30 khz and peak power 0 5 watts the carrier frequency and pulse widths are carefully selected considering cable attenuation and possible rf interference while typical leaky cables can operate from 30 mhz to 400 mhz and thus a transmitter operating in the range 30 400 mhz can be used it is desirable to select as low a frequency as possible to minimize the cable.