Wireless telemetry with magnetic induction field

A self-contained data transmitting system adapted for implantation in an in situ oil shale retort, the system comprising:

• a transmitter package;
• a wand extending from the package;
• a temperature sensor mounted on the end of the wand;
• a transmitter disposed in the package, the transmitter including means responsive to the temperature sensor for generating data pulses having constant duration and a temperature representative frequency and modulating means for turning a carrier on while a data pulse is present and for turning the carrier off while no data pulse is present;
• and
• a transmitting antenna disposed in the package including an inductive winding having an electrical length significantly smaller than the wavelength of the modulated carrier, the antenna being connected to the modulating means to transmit the modulated carrier.

A transmitter for use in determining the temperature at a remote point in a fragmented in situ oil shale retort comprising:

• a housing configured for insertion into an oil shale deposit, said housing being further configured for protecting components disposed therein from shocks due to fragmentation of the oil shale deposit surrounding the housing after insertion of the housing into said oil shale deposit;
• temperature sensing means disposed exterior of said housing for sensing the temperature in said oil shale deposit proximate the housing and for generating an electrical signal corresponding thereto;
• means disposed within said housing for generating a carrier wave of a preselected wavelength;
• means disposed within said housing for modulating said carrier wave with the electrical corresponding to the sensed temperature, to produce carrier wave pulses of equal duration having a frequency representative of the sensed temperature;
• and
• antenna means disposed within said housing for generating a magnetic induction field corresponding to the modulated carrier wave, said antenna means includes a winding having an electrical length significantly smaller than the wavelength of the modulated carrier wave.