CREG Journal (ISSN 1361-4800)

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Contents of journal 63
June 2006

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CREG Journal 63 (0-24) (PDF 3.7MB)        Individual articles may be available below

Contents

 

Newssheet (3)

CSTRI Award, CREG Prize, Cover Photographs, Caption Competition, Diary Dates.

 

An Introduction to Low Data-Rate Speech Codecs (4-5)

Speech codecs are devices that digitally encode and decode analogue speech for transmission over a communications link, making use of compression algorithms to reduce the bandwidth. Mike Bedford outlines the state-of-the-art.

 

Improving Cell-Phone Signal Strength in Marginal Areas (6-7)

Cell-phone (GSM) coverage can be marginal in rural areas where it might be used for cave rescue. It is sometimes suggested that signal strength improves with height above ground. Rob Gill set out to investigate if this claim was true at UHF frequencies. He looks at amplifiers and high gain antennas and uses Nokia's 'Net Monitor' to gauge signal strength. Initial tests did not support the hypothesis.

 

Cave Radio Notebook (8-10)

72: Eliminating Loran Interference, 73: Waveguide v. Transmission Line Propagation, 74: Full-Length v. Centred Ferrite Rod Windings. Edited by David Gibson.

 

Communications Tests in the Severn Railway Tunnel (11)

Recent communications tests by Gwent RAYNET in Britain's longest railway tunnel bore out our findings that, for long tunnels, frequencies in the region of 1.3GHz are likely to be much more effective than those of 433 or 446MHz. Kevin Snelling summarises the main report.

 

We Hear (12-13)

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

 

A Ready-Made Power Amplifier for Cave Radio (14-15)

Audio amplifiers can be used at the low radio frequencies typically used by cave radios. Chris Trayner describes a ready-built amplifier for this application.

 

Through-Rock Radio: A Professional Perspective (16-17)

Through-rock induction radios are not used only by cavers. Mining companies employ systems to provide an emergency warning system. These systems are able to work through much less favourable geology than cave radios by operating on a significantly lower frequency, as Mike Bedford reports.

 

Introducing Nathan B. Stubblefield - Induction and Earth Current Pioneer (18-19)

Nathan B. Stubblefield was an early pioneer of wireless telephony. Mike Bedford investigates the man and his work and discovers techniques that were much the same as those used today for through-rock communication systems.

 

Web Watch (19)

Peter Ludwig highlights web sites featuring big LEDs, the care of Li-Ion cells and more.

 

Speleonics (20)

Electronic clinometers, laser rangefinders and an emerging new battery technology have been discussed on the Speleonics mailing list recently, as reported by John Rabson.

 

Robust Text and Data Exchange with Earth-Current Transceivers (21-22)

Jacques Hurni, Felix Ziegler HB9CPZ and Christian Ebi HB9ZG describe the development of a pollution warning system using robust earth current data transmission linked to a GSM modem to monitor water level, flow and fluorescence. Link status and battery levels are also reported, with data presented on a regularly updated web page.

 

Review (23)

Air Navigation: from Balloons to Concorde by Walter Blanchard (ed.) is reviewed by Chris Trayner. The book covers the history of Loran in detail.

 

Letters to the Editor (23-24)

Zigbee, Microphones, Workbench Lighting, Journal of Speleo-Electronics, Flash Slave Upgrade PCBs, The Adventures of Greg.