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CREG Journal 65 (0-24)
Contents

Newssheet (3)
Postage Stamp Problems, Automation of CREG Administration, Colour Cover, the Internet of Things, Diary Dates

BCRA Cave Technology Symposium (4)
Presentations of short topics on cave surveying, electronics, computing, lighting, photography, cave radio, radio-location and other aspects of caving technology.

We Hear (5)
A round-up of news from the world of cave-related radio and electronics. Column edited by Mike Bedford.

A Digital Class-D Single-Sideband Transmitter (6-8)
Graham Naylor has discovered a novel method of SSB synthesis that makes use of digital techniques, for which he has received the 2006 CREG award. Together with David Gibson, he describes how it works.

CREG Award 2006 (9)
We issue an annual award to recognise special contributions to the field of cave radio and electronics. David Gibson describes this year's award to Graham Naylor.

Designing an Efficient LED Caving Lamp (10-12)
The efficiency of an LED lamp not only depends on the type of light emitting diode but on the method of power regulation, the optical components (lens, reflectors) and the type of power source. Henry Schneiker explains how a knowledge of these factors can lead to a better design of lamp.

Field Exposure Limit for a Body-Worn Cave Radio Loop (13)
If might sometimes be convenient to use a cave radio when on the move. John Rabson looks at the implications for magnetic field exposure.

Communications in Show Caves - Appraising the Options (14-17)
Mike Bedford looks at the challenges in providing communication systems for tourist caves and suggests some solutions.

Web Watch (17)
Peter Ludwig offers an eclectic selection of web sites ranging from big LEDs to submarines.

Speleonics (18)
It seems to be widely expected that HF, VHF and UHF signals will not usually travel far in caves or between underground and surface. From time to time, however, exceptions are encountered. Discussion summarised by John Rabson.

How to Report Experiments (19)
David Gibson and Rob Gill consider that good experimental technique and a structured approach to reporting results is essential. They identify some simple principles and highlight some common pitfalls.

Letters to the Editor (20)
Ukrainian Library Fire, Time for a New Cave Radio?

Treasurer's Report for 2005/6 (21)
David Gibson summarises his report to the 2006 AGM, held earlier in the Autumn.

Reassessing the HeyPhone Output Transformer Ratio (22-23)
John Hey reconsiders the fixed 10:1 transformer ratio used in the HeyPhone and reports on field strength tests with a variable ratio transformer. He concludes that a higher ratio may be of benefit in some operational circumstances.

The Adventures of GREG (23)
Illustrated by Adrian Higgins with words by Mike Bedford.

Cave Surveys in Colour, rear cover illustration (24)
This survey of Steinbrückenhöhle in the Austrian Alps, by Martin Green and Dave Loeffler features the use of colour to distinguish levels in what is a very complex cave. The survey also demonstrated the state-of-the art in computerised survey-drawing software, using TunnelX, written by another Cambridge University Caving Club member, Julian Todd.