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CREG Journal
Contents

Flood Pulse Measurement: Preliminary Results from DYO
A low-cost prototype flood-pulse logger, designed by Stuart France using PIC microcontrollers, has produced promising results in Dan-yr-Ogof.

Computer Simulation of a Small Buried Loop
Evaluating the magnetic fields from a buried loop antenna requires a large amount of computing power. Reno Lippold explains his implementation of Wait's equations in the MathCad package, and compares the results with Shope's earlier simulation.

Pulse discharge circuits for Flashguns
Electronic flashgun design is aided by knowledge of the characteristic of the energy discharge circuit. In these notes David Gibson gives a brief introduction to the modelling of the capacitor and inductor circuits.

Simple Caver Counter offers Improved Performance
Ian Drummond uses a low-cost, off-the-shelf data logger to implement a caver counter. Successful operation over a period of a year is reported.

LORAN - Know your Enemy
LORAN is a major source of interference to cave radios operating in the vicinity of 100kHz. John Hey provides some background information.

Digital Wall Mapping at Wakulla Springs, Florida
A surveying and inertial navigation tool for cave diving has been developed by Brian Pease. Here he describes its first trials to John and Rosy Rabson.

Foot-candles
Our occasional notes on photometry, optics and opto-electronics. David Gibson discusses pulsed light sources.

Photography News
David Gibson reports on the forth-coming field meeting, and on plans for a BCRA photography group.

Web Watch
Sites of interest to cave-electronics enthusiasts, listed by Peter Ludwig.

Selected Further Reading
If a topic in this issue interests you, this 'further reading' list from CREG journals, compiled by David Gibson, may be of use.

Flood Pulse Logger uses Low Cost Data Logger
Julian Coward describes a simple water level logger, using a commercially available HOBO logger and Motorola pressure sensor.

Wet & Dry
Cave radio in rugged plastic Pelican cases.

An On-line CREG Journal Digest
David Gibson describes his on-line database which includes a search-engine written in JavaScript. With the output in HTML and the data source in plain ASCII, this results in some cross-platform portability. The principles could be applied to the National Cave Registry database.

A Pre-Selector for a Cave Radio Receiver
The performance of a receiver can be much improved by careful control of signal levels and bandpass filtering applied before the mixer stage. Jean-Jacques Fauchez describes an add-on filter for his Cournouze receiver.

An Introduction to PSK31
PSK31 is a new digital coding scheme developed by radio amateurs for use on the shortwave band. Some cave radio experimenters have suggested that it might prove useful at LF. Mike Bedford provides the basic facts.

Speleonics
The prominent topic recently has been infrared films. Jeremy Davis reviews the past three months of postings.

Letters to the Editor
So where now?, Electronic publishing, SNAP beacon.