Endoradiosondes: Further Notes

This paper is to supplement last year´s summary on swallowable radio transmitters. Included are general comments on procedure as well as specific items such as temperature sensitivity, the use of tunnel diodes in pH measurement, the use of multiple transmitters, and the design of a nondirectional receiving antenna system. The latter not only simplifies unattended recording in some cases but also helps in relaying the signal from a small booster transmitter carried by the subject. The frequency shift needed in relaying action is here a frequency doubling provided by suitable nonlinear receiver circuits.