"Development of the Nicola System in the Isère region of France (which incorporates the Vercors and Chartreuse caving areas) is being undertaken to develop underground communication systems. This work is being performed with the help of the ADRASEC 38 (an association of radio amateurs who provide emergency communication services – equivalent to the British RAYNET) and several British cavers (Paul Mackrill, Paul Rice and myself). The development of communications systems is motivated by the requirements of the department’s cave rescue team the SSSI. The tragic flooding of the Gouffre Berger in 1996 led to the loss of two lives, Torda Istvan and Nicola Dollimore. Nick Perrin (Nicola’s husband) set up a fund to finance research into the development of communication systems for use in caves and in particular to allow a warning message to be given in the Gouffre Berger. The importance of prompt communication of the status of a victim in the early stages of a rescue has long since been recognised by French rescue teams – especially in the Isere where a return to the surface can take up to 10 hours in certain of the deeper systems. Following very fruitful input from others working in the same area in Switzerland, Britain, the USA and Canada, we have produced four cave radios using the original John Hey SSB LF transmitter and receiver boards (Hey, 1995). The first two were prototype devices with which we used to demonstrate the principle. A further two were produced to rather higher standards by F6EGY (these latter devices are currently kept in the CRS Alpes headquarters ready for use by the emergency services). A simple bridge amplifier using two TDA2006s drives a transformer similar to the one Rob Gill described recently (Gill, 1998). The efficiency of the earth current technique has been demonstrated at 87kHz vertically through over 500m of rock in the Gouffre Berger and horizontally through over 900m of rock in the Dent de Crolles cave system as Jean-Jacques of the ADRASEC 38 reported in a previous issue of the CREG Journal (Fauchez, 1998a). The requirement of the Nicola system as defined by the SSSI was reliable communications through over 500m of rock. Recently a new generation System Nicola radio has been developed called system Nicola MK II. "
Full article: Cave Radio