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CREG Journal 64 (0-24)
Contents

Newssheet (3)
CREG Mailing List, CREG Field Meetings, Caption Competition, Diary Dates.

Improved Automatic Gain Control for the HeyPhone (4)
The HeyPhone design has a simple AGC system which does not protect against overload of the RF stages. John Hey describes the development of an improved AGC system that controls the gain of the RF stage of the HeyPhone receiver.

Reviewing the RETRO 2 (5-6)
A LED upgrade for Oldham and Speleo Technics headsets has been launched by the Mine Explorer Society. Mike Bedford tries it out and reports on his findings.

We Hear (7-8)
A round-up of new from the world of cave-related radio and electronics. Column edited by Mike Bedford.

A Robotic Surveying Vehicle for Hazardous Conditions (9-11)
James Jobling-Purser describes a tracked robotic surveying platform, which may be controlled via a Zigbee wireless mesh network. The unit is easily transported and assembled on site. He also considers alternative robotic platforms that may be more appropriate to the cave environment.

Web Watch (11)
Peter Ludwig highlights web sites featuring big LEDs, advances in battery technology and more.

HeyPhones and Système Nicola in Cueva del Gato, Málaga (12)
Lino del Campo and colleagues have performed some comparative tests on HeyPhones and Système Nicola radios. He also reports on the development of their own version of the HeyPhone.

Remote Data Logging with Cell-Phones and the Internet (13-14)
By means of the GSM cell-phone network and the Internet, data can be delivered from remote locations to anywhere in the world. Using this existing infrastructure can be an advantage over the more traditional point-to-point radio telemetry. An obvious use in speleology is the remote monitoring of long-term cave-based experiments or water levels and the progress of flood pulses. David Gibson outlines the principles.

230V AC Supply in the Field (15)
John Rabson describes a low cost palm-size 150W inverter that allows mains-driven equipment to be powered from a vehicle battery. The device produces a modified sinewave.

PMR 446 Eight Years On: Update on Licence-free Radio (16-18)
Licence-free PMR 446 radio has have been available in Europe for almost eight years but things are not standing still. Mike Bedford looks at what it offers to the caver, both at home or on expedition, with particular emphasis on the latest developments.

CREG at the BPC Winch Meet (19-20)
Richard Rushton reports on the CREG Spring 2006 field meeting which included a winch trip into Gaping Gill and trials of leaky feeder cable at 27MHz and 446MHz.

Speleonics (21-22)
A report on a commercial temperature and humidity monitor led to an extensive discussion on the best ways of measuring temperature and humidity for cave science purposes. Discussion summarised by John Rabson.

Letters to the Editor (23-24)
Unconventional Earth Electrodes, When Radio Links are Poor, Evanescent Mode, Gwent RAYNET, Power Amplifier, What To Call It?, Logging Compass, Head Absorption, Small Ads, The Adventures of Greg.