CREG Journal (ISSN 1361-4800)

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Contents of journal 55
March 2004

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CREG Journal (PDF 5.8MB)        Individual articles may be available below

Contents

 

An Earth-Current-Based Cave Intruder Alarm

John W. Newman and his wife Jane own a cave in Kentucky, USA, which is home to an endangered species of grey bat (myotis grisescens). As warning notices were insufficient to keep out intruders, an electronic alarm system was devised.

 

Nothing New Underground - WW1 Trench Communications

Cave radio, like trench communications in WW1, depends on the propagation of electrical signals through the earth, and we still have things to learn. The diaries of Ernest H Hinrichs (US Signal Corps 1917-1919) are reviewed by John Rabson.

 

High Resolution Mapping in the Digital Age

The British Ordnance Survey now makes its mapping products available digitally through various software publishers. Mapping for other countries is available in digital form too. Mike Bedford considers the advantages and looks at some products currently available.

 

Noise-Cancelling Headphones: A Review

Originally developed for use by airline pilots, noise-cancelling headphones reduce the level of noise reaching the ear. This allows the user to relax in a quiet environment or to listen to music at a lower volume level than would otherwise be possible. David Gibson reviews three brands of noise-cancelling headphones and wonders if they would be any use for cave communications.

 

Web Watch

Peter Ludwig lists some earth resistivity sites and takes another look at batteries.

 

Figaro - Fireground Apparatus for Radio Operations

This induction radio system was used in 1975 at the London Underground Moorgate station, but little was heard of it thereafter. Rosy and John Rabson tried to find out what happened to it.

 

Turns Ratio Adjustment Aid for Earth-Current Transformer

To pass sufficient power into an earth-current electrode system requires either a high-voltage power amplifier or, more usually, an output transformer to boost the voltage. For versatility this transformer may have taps for different turns ratios. Here Rob Gill describes a signal-powered aid to confirming that the transformer has a turns ratio to suit the prevailing operating conditions.

 

Information on Talk-Through Boxes

A talk-through box enables a cave communications system to be linked to a 'surface' system such as a VHF radio or a mobile phone. David Gibson summarises the requirements and gives a list of further reading from CREG journals.

 

A Talk-Through Box for System Nicola

The emergency services are showing an increasing interest in being able to link cave radios to their own radio systems. Graham Naylor describes a PIC-based talk-through box that he designed for System Nicola.

 

David Gibson: PhD in Cave Radio

In February last year, David Gibson completed his PhD in 'Cave Radio'. We asked him to tell us something about his work.

 

A High-Performance Flashbulb Firer - part 2

Flashbulbs are still the professionals' choice for cave photography. This project by David Gibson - which is an update to his article in CREG journal 45 (Sept. 2001) - describes a compact, microprocessor-controlled bulb-firer that includes 'seated' and 'fired' indicators and a boost circuit to produce 24V from the 3V supply.

 

Slave Unit for Digital Cameras

The built-in flashguns in digital cameras often emit a double pulse, which causes a problem when they are used with conventional slave units. David Gibson describes an upgrade to his slave unit that aims to solve this problem.

 

Wet and Dry

Mike Bedford reviews the Sony DSC-U60 waterproof camera, and describes mini-maillon-rapides and John Hey describes the problem of waterproofing a mic. socket.

 

An Alternative Loop Antenna for the Ogofone

There are many good designs of cave radio loop antenna, but some take a while to build. Christopher Ross needed several in a hurry, for the Ogofones he maintains.

 

Student Project Suggestions: 2

From time to time, we have produced lists of projects suitable for undergraduates to undertake as part of their degree course. Here David Gibson gives some further suggestions.

 

Electronic Detection of Carbon Dioxide

Concerns have been expressed about the high levels of carbon dioxide found in some caves. Further research is needed, and this would be an ideal application for a cave data logger. Unfortunately, it is not easy to detect CO2 with an electronic sensor. Following on from David Gibson's article in CREGJ 53, Ian Drummond outlines two methods, based on infrared absorption and the conductivity of an aqueous CO2 solution, which might be worth pursuing.

 

Other items

We Hear, Letters.