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# htmlentities() run on access: Tue 03-Sep-2019 10:54:37 +01:00. Delete this line to re-run it. # format auto-updated on access: Tue 03-Sep-2019 10:54:37 +01:00 CREG Journal 107 (0-24) This issue has a cover date of September 2019 and was published on 1 September 2019. Front Cover (1) The Flyability Elios 2 drone following a flight. The external cage prevents damage to critical moving parts, despite some evidence being visible that the drone came into contact during the flight. Photo: Contents (2) List of contents and masthead information. CREG Autumn 2019 Field Meeting. Introducing the Elios 2 Drone for Aerial Inspections of Confined Spaces (3-5) Elios 2 is an aerial drone for carrying out inspections in confined spaces, which is protected from collisions by a carbon cage. , Marketing Manager at Flyability, outlines this new product and highlights its use in a recent exercise at the Aven d’Orgnac cave in France. The Inductance of a Wire Hoop (6) Many textbooks and webpages quote a formula for the inductance of a thin wire hoop, but few actually give the derivation. had been confused by formulas that appeared to differ by a factor of two but has eventually decided where the subtle difference lies. This leads to an interesting possibility for the design of a wideband loop antenna with a lower Q-factor than is normally achievable. Determining Ammonia Concentrations in Bat Caves with Passive Air Samplers (7-9) Caves that are home to large colonies of bats may have atmospheres with significant concentrations of gaseous ammonia. describes an approach to measuring concentrations over time using Radiello diffusive air samplers. Wet & Dry (10) reports on rugged, waterproof, and generally cave-proof equipment for use in conjunction with cave data logging. Response Characteristics of Instruments and Sensors (11-12) discusses the response characteristics that instruments and sensors can exhibit, and considers how, unless properly understood, this can result in erroneous conclusions being drawn when using data loggers and similar instruments. Building Blocks (13) Some considerations if wireless connectivity is required for a project, by . Using Cave Radios for Combined Speech and Radiolocation (14-16) Transporting radiolocation equipment as well as cave radios can sometimes be impractical. shows that, in some circumstances, cave radios are adequate for radiolocation, despite operating on relatively high frequencies. The Radiation Efficiency of a Small Loop Antenna (17-18) For cave radio applications, we are not normally interested in the radiation from a loop antenna because the distance over which we are working is small (relative to a wavelength) and so only near-field effects need to be considered. However, it is still interesting to consider the radiation field, and to express the radiation efficiency in terms of the specific aperture where, just as for near-field operation, the number of turns on the antenna does not affect the result. explains radiation resistance, summarises the equations and shows how the skin effect in the wire and the proximity effect between turns of the antenna winding can be taken into account. Using Avalanche Beacons in Cave Exploration (19-20) Avalanche beacons are low-cost transceivers operating on 475kHz. describes how he has used them for finding new entrances into large cave systems, and to identify dig locations for joining two caves. Letters to the Editor (21) Spot the Polarity , Maintaining Concentration . Web Watch (21) Every search of the Internet seems to turn up interesting gems. reveals the results of some of his recent explorations... We Hear (22) Roundup of news and events – brings us the latest to impact the world of cave radio and electronics. Fuel Cells to Become Mainstream? Rotating Magnet Antennas, Gas Sensor Donation to BCRC Data Transmission at the Cave Monitoring Centre (23) The British Cave Research Association has teamed up with Buxton Civic Association to provide a facility at Poole’s Cavern show cave, in Derbyshire, UK, known as the British Cave Monitoring Centre. Tinytag data loggers supplied by Gemini Data Loggers can be monitored remotely via a web browser. describes some of the problems encountered during the set-up – including difficulties with the router, firewall and PC. The Adventures of GREG (24) Illustration by , and words by .