Crystal controlled radio receiver for high voltage alternating current sensing using frequency modulation with automatic frequency and output control

Claim 2

In a radio receiver responsive to a radio transmitter mounted on a high voltage electric power transmission line conductor and generating a transmitter carrier modulated by a signal corresponding to a variable in said conductor and likely to change its center frequency in combination: a receiver oscillator for generating a local oscillation having a frequency which is maintained substantially constant and beats with said transmitter carrier to generate an intermediate frequency; demodulating circuit means for receiving said intermediate frequency and tunable to operate at a receiver frequency, the output of said demodulating circuit means including a direct voltage component corresponding to the differential between the transmitter carrier and receiver center frequencies; automatic frequency alignment means responsive to said direct voltage component for applying to said demodulating circuit means a counterpart direct voltage component to shift the center frequency of said demodulating circuit means in the direction of said center frequency of said carrier, and capacitor means connected to said demodulating circuit means and charged to an extent depending upon the magnitude of said direct voltage component for maintaining said automatic frequency alignment means in operation to shift said center frequency of said demodulating circuit means for a substantial time after said transmitter ceases to operate.

Claim 3

The radio receiver according to claim 1 wherein means discharge said capacitor means a substantial time after removal therefrom of said direct voltage component whereby said counterpart direct voltage applied to said demodulating circuit is correspondingly reduced.

Claim 4

The radio receiver according to claim 1 wherein feedback circuit means in said automatic frequency alignment means increases the gain thereof with decrease in said direct voltage component to maintain said counterpart voltage at the required voltage.

Claim 5

The radio receiver according to claim 1 wherein said variable is 60 Hz current and said automatic frequency alignment means is substantially nonresponsive to that portion of said signal corresponding to 60 Hz.

Claim 6

The radio receiver according to claim 1 wherein said demodulating circuit means is characterized by having a tuning range of about + or - 20 kHz. to prevent response of said receiver to an adjacent channel.

Claim 7

Means for transmitting a signal corresponding to the magnitUde of a variable at the potential of a high voltage conductor and for receiving said signal at a remote point at ground potential comprising: a radio transmitter for operating at said potential of said conductor to generate a transmitter carrier frequency modulated by a signal corresponding to a variable in said conductor; a radio receiver at said remote point responsive to said signal modulated transmitter carrier frequency including: a receiver oscillator for generating a local oscillation having a frequency which is maintained substantially constant and beats with said transmitter carrier frequency to generate an intermediate frequency; intermediate frequency amplifier means for said intermediate frequency; demodulating circuit means for receiving said intermediate frequency and tunable to operate at a receiver frequency, the output of said demodulating circuit means including a direct voltage component corresponding to the differential between the transmitter carrier and receiver center frequencies; carrier level relay means coupled to said intermediate frequency amplifier means and responsive to receipt of said modulated transmitter carrier frequency; and automatic frequency alignment means controlled by said carrier level relay means and responsive to said direct voltage component for applying to said demodulating circuit means a counterpart direct voltage component to shift the center frequency of said demodulating circuit means in the direction of said center frequency of said transmitter carrier frequency.

Claim 8

Means for transmitting a signal corresponding to the magnitUde of a variable at the potential of a high voltage conductor and for receiving said signal at a remote point at ground potential comprising: a radio transmitter for operating at said potential of said conductor to generate a transmitter carrier frequency modulated by a signal corresponding to a variable in said conductor; a radio receiver at said remote point responsive to said signal modulated transmitter carrier frequency including: a receiver oscillator for generating a local oscillation having a frequency which is maintained substantially constant and beats with said transmitter carrier frequency to generate an intermediate frequency; intermediate frequency amplifier means for said intermediate frequency; demodulating circuit means for receiving said intermediate frequency and tunable to operate at a receiver frequency, the output of said demodulating circuit means including a direct voltage component corresponding to the differential between the transmitter carrier and receiver center frequencies; carrier level relay means coupled to said intermediate frequency amplifier means and responsive to receipt of said modulated transmitter carrier frequency; and automatic frequency alignment means controlled by said carrier level relay means and responsive to said direct voltage component for applying to said demodulating circuit means a counterpart direct voltage component to shift the center frequency of said demodulating circuit means in the direction of said center frequency of said transmitter carrier frequency.

Claim 9

The radio receiver according to claim 6 wherein relay control circuit means, responsive to said modulated transmitter carrier, control the energization of said relay means, and means control the level at which said relay control circuit means is responsive to said modulated transmitter carrier.

Claim 10

The radio receiver according to claim 6 wherein means delay energization of said relay means for a predetermined time after said modulated transmitter carrier reaches a predetermined level.

Claim 11

The radio receiver according to claim 6 wherein means cause said relay means to become deenergized when the level of said modulated transmitter carrier is reduced a predetermined amount below the level at which said relay means is energized.

Claim 12

The transmitting and receiving means according to claim 6 wherein: signal responsive means is driven in accordance with the output of said demodulating circuit means; and said relay means includes means for connecting said demodulating circuit means to said signal responsive means when said relay means is energized in response to said modulated transmitter carrier and also includes means for connecting said signal responsive means to ground when said relay means is deenergized.

Claim 13

In a radio receiver responsive to a radio transmitter mounted on a high voltage electric power transmission line conductor and generating a transmitter carrier modulated by a signal corresponding to current flow in said conductor and likely to change its center frequency, in combination: a receiver oscillator for generating a local oscillation having a frequency which is maintained substantially constant and beats with said transmitter carrier to generate an intermediate frequency; intermediate frequency amplifier means for said intermediate frequency; demodulating circuit means for receiving the amplified intermediate frequency and tunable to operate at a receiver frequency, the output of said demodulating circuit means including a direct voltage component corresponding to the differential between the transmitter carrier and receiver center frequencies; automatic frequency alignment means responsive to said direct voltage component for applying to said demodulating circuit means a counterpart direct voltage component to shift the center frequency of said demodulating circuit means in the direction of said center frequency of said carrier; and carrier level relaY means coupled to said intermediate frequency amplifier means and responsive to said transmitter carrier for controlling the application of said direct voltage component to said automatic frequency alignment means.

Claim 14

In a radio receiver responsive to a radio transmitter mounted on a high voltage electric power transmission line conductor and generating a transmitter carrier modulated by a signal corresponding to current flow in said conductor and likely to change its center frequency, in combination: a receiver oscillator for generating a local oscillation having a frequency which is maintained substantially constant and beats with said transmitter carrier to generate an intermediate frequency; intermediate frequency amplifier means for said intermediate frequency; demodulating circuit means for receiving the amplified intermediate frequency and tunable to operate at a receiver frequency, the output of said demodulating circuit means including a direct voltage component corresponding to the differential between the transmitter carrier and receiver center frequencies; automatic frequency alignment means responsive to said direct voltage component for applying to said demodulating circuit means a counterpart direct voltage component to shift the center frequency of said demodulating circuit means in the direction of said center frequency of said carrier; and carrier level relaY means coupled to said intermediate frequency amplifier means and responsive to said transmitter carrier for controlling the application of said direct voltage component to said automatic frequency alignment means.

Claim 15

The radio receiver according to claim 11 wherein relay control means, responsive to said modulated transmitter carrier, control the energization of said relay means, and means control the level at which said relay control circuit means is responsive to said modulated transmitter carrier.

Claim 16

The radio receiver according to claim 11 wherein means delay energization of said relay means for a predetermined time after said modulated transmitter carrier reaches a predetermined level.

Claim 17

The radio receiver according to claim 11 wherein means cause said relay means to become deenergized when the level of said modulated transmitter carrier is reduced a predetermined amount below the level at which said relay means is energized.

Claim 18

The radio receiver according to claim 11 wherein said carrier level relay means includes means for connecting said demodulating circuit means to signal responsive means when said relay means is energized in response to said modulated transmitter carrier frequency and also includes means for connecting said signal responsive means to ground when said relay means is deenergized.