A method and apparatus for transmitting information-encoded, telemetry signals percutaneously between an implanted medical device and an external device as telemetry RF pulses which are modulated in pulse position and/or in pulse width within a telemetry frame comprising at least a telemetry frame boundary RF pulse and a telemetry frame data RF pulse. Data to be transmitted in a given telemetry frame is encoded into a PPM code for positioning at least certain telemetry RF pulses at pulse positions of the telemetry frame and a PWM code for establishing the pulse widths of at least certain telemetry RF pulses of the telemetry frame. The telemetry frame is formatted from the PPM code, and the telemetry RF pulses are generated at the formatted pulse positions within the telemetry frame. The pulse widths of the telemetry RF pulses are controlled in accordance with the PWM code for the certain telemetry RF pulses. The PWM and PPM combinations of RF pulses of a telemetry frame can convey the data type, the telemetry frame frequency, number of pulse positions of the telemetry frame, data type and data content, including the identification of the implanted medical device. The selective PWM of certain or all RF pulses of the telemetry frame allows its data content to be increased or the telemetry frame size to be shortened or telemetry frame energy reduced by reducing the number of RF pulses of the telemetry frame or the range of possible pulse positions in the telemetry frame. The PWM may be reduced or disabled in noisy conditions.