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# format auto-updated on access: Mon 27-Nov-2017 11:29:27 +01:00 CREG Journal Contents Newssheet Cave Radio Test Sites; CREG Award; HeyPhone PCBs. A Resistance Meter for Earth-Current Systems Measurement of the loop resistance of an earth-current system with a d.c.-based meter is not practicable because of the presence of d.c. potentials. John Hey describes an a.c. meter that gets round this problem. Radio Tests in Essex Road Railway Tunnel CREG was recently approached by Railtrack (now Network Rail) and asked to advise on management and safety communications for a casualty evacuation exercise in a railway tunnel. John Rabson reports. LF Propagation on Simulated Railway Tracks Propagation tests in tunnels have indicated that the tracks themselves may guide low frequency radio waves. As it is not always easy to get access to a railway line, some experiments have been performed above ground. John Rabson reports. Vision in Low-Lighting Conditions Previous definitions of scotopic or dark-adapted vision, used in the CREG journal, may have been wrong. David Gibson reports. Amateur Radio Licensing - an Update Over the past year more than 6000 of the new amateur radio Foundation licences have been issued. John Rabson, G3PAI, explains the new arrangements and why this development is significant for cave radio. Practical Battery Management How should batteries used for essential rescue equipment be stored? Mike Bedford gives some advice on battery management in response to queries from the cave rescue community. Portable Fuel Cells to Replace NiMH and Li-ion Cells? Stephen Voller, of Voller Energy, became frustrated with the short life of the batteries in his mobile phone and laptop computer, so he set up a company to develop miniature fuel cells to replace them. Web Watch Another list of sites from Peter Ludwig. Check Your Resistors A cautionary tale by John Rabson. Wet & Dry Mike Bedford reviews some more items of rugged equipment - a laptop, a walkie-talkie and a camera. Matching & Output Impedance: A Common Fallacy? (16-17) We often hear about 'output impedance' and 'matching' but David Gibson suggests that the terms are misunderstood by many designers, and he makes proposals for specifying low-frequency power amplifiers. Cave Rescue Wish List Jopo asked the BCRC committee what new items of cave electronic equipment would be helpful to them. HeyPhone Testing in the Lamprechtsofen Fay Hartley of Four Iron Caving Club took two HeyPhones on a trip to Austria and shows that performing the actual testing can be less than half the battle. CREG's Equipment Initiative Mike Bedford describes how CREG is now starting to serve the wider caving community by loaning equipment and by providing PCBs for projects at cost. HeyPhone Documentation: More Updates Mike Bedford outlines new and updated documentation, which is available on the HeyPhone Website. Speleonics Lumileds Lighting, Flashgun Slave Unit and more. Contributions summarised by John Rabson. Piecewise Modelling of Antennas The NEC series of programs is used for calculating the behaviour of antennas. Brian Pease discusses his experiences with the latest version. Cave Radio Notebook 54: Noise Shielding, 55: Measurement of V & I at LF. 56: Specific Aperture. Column edited by David Gibson. Making Sense of Atmospheric Noise Temperature Ratio The often-quoted CCIR noise data is probably irrelevant for predicting the performance of equipment with magnetic loop antennas. David Gibson explains why. Letters to the Editor Letters.