Biomedical telemetry


Soviet sources reported about biomedical telemetry from the Vostoks: "...For continuous monitoring of the pulse rate during flights of many days an electrocardiophone was used. This was an instrument which transforms the bioelectrical potentials of the heart in square wave with a period of about 0.15 seconds......" Interestingly signals from Vostok 3-6 on 19.995 MHz and other similar channels near 20 MHz consisted of a continuous wave keyed "off" at varying intervals. The "off" period was 0.15 seconds! So the 19.995 MHz channel was a simple heart rate monitor. Each 0.15 second off pulse represented one heartbeat and the rate at which such pulses occurred was the heart rate! The HF signal propagated over very long distances and the basic health state of the cosmonaut could be monitored with very simple means:

Vostok heart rate telemetry


For Voskhod 1 and 2 this system was able to transmit "pulse and respiration combined". When examining recordings of signals on 19.9944 MHz from Voskhod 1 it is evident that the length of the "off" period varies in a slow cyclic pattern and this is obviously the respiration rate:

Voskhod heart and respiration rate telemetry
By plotting the length of the "off" pulses (in millimeters) from a pen recording the graph below was obtained. It shows a respiration rate of about 18 per minute.

Voskhod 1 respiration telemetry

This beacon signal changed into a pure CW carrier during the landing phase according to observations made at the Bochum radio observatory in Germany. This makes sense - when the re-entry vehicle separated form the orbital module the keying impulses from the crew was removed!

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Copyright © 1996 Sven Grahn