CREG Journal (ISSN 1361-4800)

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Journal 128 has gone to press and is due for publication in December 2024

[1] News and Notes, CREGJ 126, p2. June 2024. (PDF 550KB)     

Note from your Temporary Editor Mike Bedford, Future CREG Events, Other Events for your Diary David Gibson

 

[2] News and Notes, CREGJ 125, p2. March 2024.   For download see previous item

Editor, Delay - Rob Gill, Erratum: QDX-M - Ian Drummond, June Field Meeting - David Gibson

 

[3] News and Notes, CREGJ 124, p2. December 2023.   For download see previous item

Change, David Gibson.

 

[4] Reciprocity and Radiation, CREGJ 124, pp17-20. December 2023. (PDF 348KB)     

Reciprocity is a property of passive electrical networks and electromagnetic fields. In a previous article David Gibson showed that nonradiating cave radio antennas behave as passive networks and obey simple reciprocity laws. In this follow-up article he demonstrates the wellknown observation that radiating antennas also obey the reciprocity principle. This is a slightly more complex demonstration as it requires a discussion of radiation resistance, impedance matching and fundamental thermodynamics.

 

[5] Reciprocity in Cave Radio Antennas, CREGJ 123, pp12-14. September 2023. (PDF 359KB)     

Reciprocity is a property of passive electrical networks and electromagnetic fields. It is sometimes loosely cited as being why a radio antenna can be used interchangeably as a transmitter or receiver; but what does that actually mean? David Gibson demonstrates that although cave radio antennas obey reciprocity laws, we have to be careful what we mean by reciprocity.

 

[6] Field Equations in Conducting Media, CREGJ 123, p20. September 2023. (PDF 263KB)     

When studying the fields from a small dipole antenna (electric or magnetic) in a conducting medium, it is sometimes helpful to use complete field expressions rather than the simpler quasi-static approximations. It is not always easy to find these in a textbook, so David Gibson has set them out here, as a useful reference.

 

[7] Comparing Loop and Line Antennas for Cave Radio Applications – 1, CREGJ 122, pp14-16. June 2023. (PDF 381KB)     

An induction-loop transmitter can operate at a higher current than a grounded electric dipole because the loop has a relatively low resistance when compared to the resistance between two earthed electrodes. However, the magnetic field from a loop falls off more rapidly with distance, so it is not straightforward to say that one antenna is better than the other. Several other factors, both physical and practical, come into play. In this article, David Gibson outlines how we might go about making a comparison. This is a nonmathematical article – a more complete treatment will be given in part 2 of this article.

 

[8] Current Problems in Cave Radio, CREGJ 121, p11. March 2023. (PDF 221KB)     

Although through-rock radio is now well established, there are a number of puzzles that David Gibson asserts would benefit from further study.

 

[9] Digital Object Identifiers - Part 1, CREGJ 120, p20. December 2022. (PDF 251KB)     

Digital Object Identifiers (DOI) are persistent long-lasting references, usually bound to a URL and intended to identify an online document. This makes them slightly different to, for example, an ISBN (book number), which merely identifies a product, because a DOI can also deliver a product. In this brief overview, David Gibson explains the DOI system used by the British Cave Research Association and, in part 2, will give examples of the webserver coding. He notes that BCRA does not use an official DOI implementation because surely, a URL is just a URL?

 

[10] Position Encoder Uses Single-Track Gray Code: Update, CREGJ 119, p19. September 2022. (PDF 227KB)     

This is an update to David Gibson's article in Journal 118 where he described an unusual single-track position encoder that encoded absolute position using a Gray code.

 

[11] Poster-Sized Stereo Photos: Update, CREGJ 119, p20. September 2022. (PDF 343KB)     

David Gibson makes some further comments about viewing poster-sized stereo photos and asks for feedback on how other people manage with this technique.

 

[12] Letter to the Editor, CREGJ 118, p12. June 2022. (PDF 272KB)     

Hunting Phosphorescence, Rob Gill; How Not to Lay a Telephone Cable, Chris Ross; Journal Back Issues, David Gibson.

 

[13] The Circle of Least Confusion, CREGJ 118, pp16-17. June 2022. (PDF 290KB)     

David Gibson describes a term in optics and photography that is used to derive the range of distances – the depth of field – over which a subject remains in good focus. This does not, of itself, require restating here, although there are some circumstances, such as the construction of stereoscopic and stacked-focus images, where a recap is useful. Additionally, there is a modification to the standard formula that extends its use to small-format digital cameras.

Corrections: please note that, in the paragraph headed Appendix, on page 17, "j117" should read "j118". Also, equation 1 on page 17 is incorrect, although the rest of the equations are OK. The equation is corrected in the online appendix (see below).

 

[14] The Circle of Least Confusion: Appendix, CREGJ 118, ppA1-A2. June 2022. (PDF 250KB)     

This appendix to the article in CREGJ 118 by David Gibson provides the derivation of the Depth of Field formula and a further discussion on modifying the formula to deal with digital cameras with varying image formats. This document was revised and updated to version 4 on 5 October 2022.

 

[15] Position Encoder Uses Single-Track Gray Code: Part 2, CREGJ 118, pp19-22. June 2022. (PDF 382KB)     

There are many examples, in electronic equipment design, where it is necessary to measure a linear or rotary position, which is often achieved using an optical or magnetic encoder. Simple encoders only detect changes in relative position; multi-track encoders can measure absolute position but, as David Gibson explains, a single-track encoder can, under the right conditions, also encode absolute position. An online demonstration program accompanies this article at bcra.org.uk/cregj/more/j118. Corrections: Appendix 2 on page 22 contains some errors. A corrected version will be uploaded here in October 2022.

 

[16] Cyclic Single-Track Gray Codes – Demo for CREGJ 118, CREGJ 118 (see supporting webpage). June 2022. (PDF 6.2MB)        Individual articles may be available below

This online demonstration program by David Gibson accompanies the above article. Please note that this supplement is in preparation and will be available in October 2022, hopefully.

 

[17] Applications of Chain Codes for Position Encoders, CREGJ 117, pp16-18. March 2022. (PDF 397KB)     

Linear and rotary position encoders can measure position using a single-track binary sequence known as a chain code. In a follow-up to his article in CREGJ 116, David Gibson gives some further explanation of how chain codes can be used. An online demonstration program accompanies this article at bcra.org.uk/cregj/more/j117

 

[18] Cyclic Binaries / Chain codes – Demo for CREGJ 117, CREGJ 117 (see supporting webpage). March 2022.

This online demonstration program by David Gibson accompanies the above article.

 

[19] Letter to the Editor, CREGJ 117, p21. March 2022. (PDF 319KB)     

Underground 'Radio' Powered by Compressed Air, David Gibson

 

[20] Viewing Poster-Sized Stereo Pairs, CREGJ 117, pp22-24,1. March 2022. (PDF 2.2MB)     

Stereoscopic pairs are traditionally viewed using a handheld 3D viewer. But when printed in a magazine or shown on a display board, such images are difficult to view unaided, as well as being necessarily very small because the centrelines of the images must match that of the eye. For stereo pairs to have an impact, they must be larger, but a traditional method of viewing larger images requires them to be printed in false colours, thus making them impossible to appreciate without special tinted glasses. In this article, David Gibson describes a simple technique that avoids this problem and allows poster-sized full-colour photos to be viewed without any artificial aid. Significantly, this allows them to be fully-appreciated both as flat images and as stereo pairs. Examples are shown on the covers of this Journal and in the online file bcra.org.uk/cregj/more/j117/3d.html.

 

Please note: i) The final page of this article is the front cover, page 1. ii) To view the stereo pair on p24 and p1 correctly online, you must instruct your browser's PDF plug-in to display the pages in 'two-page view'. How to do this will depend on your browser and, if it is not obvious how to achieve that, try looking for a menu icon (☰).

 

[21] Letters to the Editor, CREGJ 116, p12. December 2021. (PDF 279KB)     

SSB Generation, Ian Drummond; Router Problems at the British Cave Science Centre, David Gibson.

 

[22] Class-D SSB Modulator - Demonstrator Code Listing, CREGJ 116, pp20-21. December 2021. (PDF 275KB)     

As an appendix to his article in CREG Journal 115 that described a class-D SSB modulator, David Gibson gives a brief introduction to MATLAB and its free alternative GNU Octave, and then lists the code that produced the plotted graphs featured in the article.

 

[23] Position Encoder Uses Single-Track Gray Code: Part 1, CREGJ 116, pp22-24. December 2021. (PDF 371KB)     

There are many examples, in electronic equipment design, where it is necessary to measure linear or rotary position, which is often achieved using an optical or magnetic encoder. Simple encoders detect only changes in relative position; multi-track encoders can measure absolute position but, as David Gibson explains, a single-track encoder can, under the right conditions, also encode absolute position.

 

[24] A Simple Class-D Single-Sideband Modulator, CREGJ 115, pp10-13. September 2021. (PDF 657KB)     

David Gibson describes how the output pulses from two class-D double-sideband modulators using carrier-frequency PWM (CF-PWM) can be interleaved to create a class-D single-sideband modulation. The method, assumed to be novel, is simple enough to be implemented on a standard micro-controller, which means that it is more accessible to hobbyist designers than a DSP implementation.

 

[25] Data Protocol and Coding Examples for the British Cave Science Centre, CREGJ 115, pp16-20. September 2021. (PDF 452KB)     

The British Cave Science Centre (BCSC) at Poole’s Cavern in Derbyshire has been fitted with sensors and data loggers in support of a number of cave science projects. The sensors transmit their data to the Internet via a broadband telephone connection. Two data protocols are used, essentially a ‘push’ and a ‘pull’ operation, which David Gibson describes as ‘Source-As-Browser’ and ‘Source-As-Server’. Each method has its advantages and disadvantages, which are explained in this article, that also gives examples of the code needed to handle the operations.

 

[26] Update: Energy Harvesting, CREGJ 114, p10. June 2021. (PDF 233KB)     

Further notes on energy harvesting and human-powered lighting by David Gibson.

 

[27] The SSB Paradigm for Cave Radio is Outmoded - Is it Time to Move On?, CREGJ 114, pp12-14. June 2021. (PDF 375KB)     

If you want to build a cave radio that extends the art and doesn’t just repeat earlier work, then David Gibson argues that SSB techniques are outmoded. Not only is DSB modulation simpler, but it offers additional opportunities - including receiving SSB signals, if that is still required. Expressly, Gibson suggests that trying to implement traditional analogue SSB methods on a DSP platform is without merit, because tailored DSP techniques (such as the CORDIC used in Graham Naylor's Système Nicola) will perform so much better.

 

[28] Cave Radio antennas, CREGJ 114, p19. June 2021. (PDF 234KB)     

In another of our Fundamentals series (#5), David Gibson explains why we use induction loops and grounded electrodes as cave radio antennas.

 

[29] Update: Battery Polarity Protector, CREGJ 113, p12. March 2021. (PDF 248KB)     

Further to his notes on building rugged equipment, David Gibson describes a simple addition to a battery connector that prevents cells being inserted in reverse.

 

[30] Correction, CREGJ 113, p12. March 2021.   For download see previous item

Correction to David Gibson's Letter regarding Addressable Electrodes in Journal 112.

 

[31] Update: Pressurised Enclosures, CREGJ 113, p12. March 2021.   For download see previous item

As a follow-up to his notes on building rugged equipment, David Gibson further describes the use of a pressurised enclosure to prevent moisture ingress.

 

[32] Energy Harvesting with Electrets, CREGJ 113, p16. March 2021. (PDF 230KB)     

David Gibson envisages a portable energy-harvesting device utilising a wristwatch-style automatic winder, with the mainspring driving an electrical power generator that uses an electret material. The mainspring provides a method of regulating the power transfer, not unlike the concept of 'power matching'.

 

[33] Letters to the Editor, CREGJ 112, pp20-21. December 2020. (PDF 724KB)     

Earth Resistivity Surveying, Mike Cowlishaw; Earth Resistivity - Correction; Addressable Electrodes, David Gibson.

 

[34] Update: Regenerative Brake, CREGJ 112, p21. December 2020. (PDF 283KB)     

In an extension of his notes on regenerative braking, David Gibson describes how to build an LED lamp that is powered by a falling weight.

 

[35] The Parallel-Fed Voltage Multiplier, CREGJ 111, pp10-12,22. September 2020. (PDF 377KB)     

Voltage doublers and the Cockcroft-Walton voltage multiplier are examples of devices that use capacitors as charge-pumps to generate a high voltage at a low power in a relatively simple circuit. The conventional voltage multiplier is series-fed, acting as a 'bucket brigade' to pass the charge from one element to the next. This is difficult to analyse, as well as being inefficient, with a law of diminishing returns applying. A better scheme is the less well-known parallel-fed device, which has several advantages. David Gibson analyses this device, arguing that it deserves to be better known, and suggests some possible cave electronics applications.

 

[36] The Mystery of the Missing Energy, CREGJ 111, pp20-22. September 2020. (PDF 356KB)     

Whenever a capacitor is charged, energy seems to go missing. This has consequences when designing equipment that makes use of capacitor charging, such as a charge pump. David Gibson explains the phenomenon and challenges the reader to say where the supposedly missing energy might have gone.

 

[37] Letters to the Editor, CREGJ 110, p9. June 2020. (PDF 287KB)     

PIC Microcontrollers Mike Bedford, Flashgun Slaves David Gibson.

 

[38] Regenerative Brake Charges Your Caving Lamp Whilst You Abseil, CREGJ 110, pp13-16. June 2020. (PDF 337KB)     

A caver abseiling down a pitch will lose potential energy, which is converted into heat in his abseiling device; but what if it were converted into useable energy instead? David Gibson explains the principles behind regenerative braking and how you might use the braking energy to charge a battery. However, this is for theoretical interest only, and definitely not something to try out in practice!

 

[39] Flashgun Slave Redesign Notes, CREGJ 110, p21. June 2020. (PDF 239KB)     

David Gibson’s design for a flashgun slave unit first appeared in the CREG journal almost 30 years ago. It had a number of unique features that meant it was ideal for cave photography. Nowadays, cheap wireless slave units are readily available and there is probably no need for a home-built optical design. But, were a ‘retro’ optical device ever to be needed, David Gibson explains how he would modify his earlier design.

 

[40] Building Rugged Equipment for Use in Caves, CREGJ 109, pp19-22. March 2020. (PDF 410KB)     

In another of our Fundamentals series (#3), David Gibson describes the problems of building equipment for use in caves. Waterproofing is a big issue, but he also considers the choice of battery and some problems associated with switches and connectors. These notes are aimed at student electronic engineers who might be building equipment for use in caves as a practical element of their degree course.

 

[41] The Hidden Earth Projector Shutters, CREGJ 108, pp21-22. December 2019. (PDF 393KB)     

The UK's annual caving conference – Hidden Earth – required a remotely-operated shutter for its video projectors. David Gibson came up with a solution, using pieces of cardboard, motors, reed switches, and a generous quantity of steering diodes.

 

[42] The Inductance of a Wire Hoop, CREGJ 107, p6. September 2019. (PDF 251KB)     

Many textbooks and webpages quote a formula for the inductance of a thin wire hoop, but few actually give the derivation. David Gibson had been confused by formulas that appeared to differ by a factor of two but has eventually decided where the subtle difference lies. This leads to an interesting possibility for the design of a wideband loop antenna with a lower Q-factor than is normally achievable.

 

[43] The Radiation Efficiency of a Small Loop Antenna, CREGJ 107, pp17-18. September 2019. (PDF 313KB)     

For cave radio applications, we are not normally interested in the radiation from a loop antenna because the distance over which we are working is small (relative to a wavelength) and so only near-field effects need to be considered. However, it is still interesting to consider the radiation field, and to express the radiation efficiency in terms of the specific aperture where, just as for near-field operation, the number of turns on the antenna does not affect the result. David Gibson explains radiation resistance, summarises the equations and shows how the skin effect in the wire and the proximity effect between turns of the antenna winding can be taken into account.

 

[44] Data Transmission at the Cave Monitoring Centre, CREGJ 107, p23. September 2019. (PDF 415KB)     

The British Cave Research Association has teamed up with Buxton Civic Association to provide a facility at Poole’s Cavern show cave, in Derbyshire, UK, known as the British Cave Monitoring Centre. Tinytag data loggers supplied by Gemini Data Loggers can be monitored remotely via a web browser. David Gibson describes some of the problems encountered during the set-up – including difficulties with the router, firewall and PC.

 

[45] Simple Enclosure is Waterproof to 400 Metres, CREGJ 104, pp3-6. December 2018. (PDF 529KB)     

David Gibson describes a low-cost equipment housing for underwater use at depths of, potentially, up to 1000m although caving applications would normally be at a shallower depth of under 100m. Possible uses of this housing would be as part of a data-logger designed to monitor water depth (via a pressure sensor), as well as temperature, electrical conductivity and possibly turbidity and fluorescence.

 

[46] The Hidden Earth Timetable Display – Part 3, CREGJ 104, pp13-15. December 2018. (PDF 282KB)     

David Gibson continues with his series of articles on using Raspberry Pi computer modules as the basis for a network of computers that can provide information displays. This article includes an example of how to run a web browser in 'kiosk mode' on the Raspberry Pi, and how the Raspberry Pi can report its id to the system's web server.

 

[47] Letters and Announcements, CREGJ 104, p16. December 2018. (PDF 273KB)     

Caving Conferences, Peter Cousins, Optical Flash Slave Update David Gibson.

 

[48] The Hidden Earth Timetable Display – Part 2, CREGJ 103, pp22-24. September 2018. (PDF 466KB)     

The UK's annual caving conference – Hidden Earth – has experimented with a network of computers that provide timetable displays, as well as news and information. The Raspberry Pi module makes a very useful web client for such a system. In this article, David Gibson describes how to get started with the Raspberry Pi. A future article will give actual code examples.

 

[49] The Hidden Earth Timetable Display, CREGJ 102, pp5-7. June 2018. (PDF 439KB)     

The UK’s annual caving conference – Hidden Earth – has experimented with a network of computers that provide timetable displays, as well as news and information. The latest iteration uses a Raspberry Pi computer at the heart of each ‘information point’, which operates a web browser, pulling information from a local web server. The software and hardware are being developed by David Gibson, a member of the Hidden Earth organising team, who here outlines the salient points.

 

[50] Letters to the Editor, CREGJ 101, p7. March 2018. (PDF 162KB)     

Search Engines (Mike Cowlishaw, David Gibson).

 

[51] The British Cave-Monitoring Centre, CREGJ 101, p8. March 2018. (PDF 152KB)     

The British Cave Research Association is teaming up with Buxton Civic Association to provide a facility to be known as the British Cave Monitoring Centre at Poole's Cavern show cave, in Derbyshire, UK. Equipment will be provided to allow students to undertake projects to provide long-term monitoring of cave climate and to facilitate cave-related studies and scientific research. David Gibson describes how this is also an opportunity for BCRA's Cave Radio and Electronics Group to provide tailor-made equipment for sensing, logging, and the transmission of data to a website. The British Cave-Monitoring Centre uses Tinytag data loggers.

 

[52] 100 and Beyond: Readers Recall, CREGJ 100, pp16-17. December 2017. (PDF 223KB)     

What are the most memorable moments over the last 100 issues of CREGJ? We asked subscribers for their highlights. Contributions from: Stuart France, Rosy Rabson, Rob Gill, Mike Bedford, John T. M. Lyles, John Rabson, Ian Drummond, Brian Pease & David Gibson.

 

[53] The CREG Journal Search Engine, CREGJ 100, pp23-24. December 2017. (PDF 214KB)     

Click on the search icon at bcra.org.uk/cregj and you will be taken to the CREG Journal Search Engine. This is still under development but is already a useful tool for searching through the 100 issues of the CREG Journal, which contain some 1500 articles. As well as plain-text and wildcard searches, the engine offers powerful 'regular expression' searches. It scans the article titles and abstracts and allows the user to display the results in different ways. Popup boxes provide help at a number of places. In this article David Gibson provides some technical background information to his coding but, as he says - this is not a User Manual because it doesn't need one.

 

[54] Cave Radio and the Loran-C Spectrum [cregf], CREGJ 97.   March 2017. See further reading on the CREG forum

David Gibson takes issue with some of the points in Robin Gape's article, and gives some further information on the Loran-C spectrum, and how the interference might be countered. He also notes that the CREG search engine reveals a significant amount of prior discussion in the CREG journals. See the posting on the CREG forum, bcra.org.uk/cregf).

 

[55] Radio Propagation in Standedge Tunnel, CREGJ 94, pp3-5. June 2016. (PDF 285KB)     

Back in 2003, CREG was invited by Network Rail to investigate radio propagation in Standedge tunnel. During these tests, some unexpected results were obtained. Various hypotheses were discussed, but the work was never followed up. David Gibson asserts that a lack of 'experimenter's diligence' in the original work prevents us from drawing any useful conclusions, and he warns of the danger of making a 'wishful' hypothesis.

 

[56] Letters and Notes, CREGJ 94, p19. June 2016. (PDF 274KB)     

Calling Elderly Radio Amateurs [The author describes the concept of a "Naive Hoax"] David Gibson, Diary Dates.

 

[57] Searching the CREG Journal Contents Lists, CREGJ 94, p24. June 2016. (PDF 715KB)     

David Gibson describes a search routine that he is developing for the CREG Journal database.

 

[58] Signal Phase Cannot Be Determined from a Fourier Transform of Sampled Data, CREGJ 93, pp8-9. March 2016. (PDF 241KB)     

The Discrete Fourier Transform is a well-established tool for obtaining a frequency spectrum from a set of sampled data. The coefficients obtained from the DFT are complex-valued and so both phase and amplitude can be extracted. However, David Gibson asserts that if the sampled data originated in the real world (say, as a recording from a broadband radio antenna) the phase of the spectral components cannot be determined. This, he claims, is an 'obvious' observation, but one that is not emphasised in textbooks. The details of the problem are left for the reader to work out, as an interesting 'examination question' in DSP.

 

[59] Using AMSS on BBC Radio 4 to Send Data to Subsurface Locations, CREGJ 90, p6. June 2015. (PDF 217KB)     

AMSS (AM Signalling System) was originally developed by the BBC to transmit data, using a subcarrier, on a long-wave broadcast transmission. Similar in concept to the more well-known RDS (Radio Data System) that operates on VHF stations, AMSS was standardised in 2006 by ETSI as an extension to the Digital Radio Mondiale system. Because long-wave broadcasts can be received underground, AMSS may, as David Gibson explains, provide a convenient method of broadcasting emergency data to miners trapped underground.

 

[60] Stereoscopic Vision with Reduced Definition in One Eye, CREGJ 90, p9. June 2015. (PDF 161KB)     

Practical experiments with stereo pairs show that an adequate stereoscopic image can be formed by the human brain even when one of the images is considerably defocussed or pixelated. In a digital data transmission, the reduced-definition image can have a bandwidth (pixels x palette size) as low as 1/48th that of the full-definition image. David Gibson suggests that this could have useful implications in the transmission of stereoscopic images over reduced bandwidth channels.

 

[61] Determining the Photographic Guide Number of an LED, CREGJ 89, pp13-16. March 2015. (PDF 385KB)     

White LEDs are increasingly being used as sources of illumination for cave photography, both as modelling lamps and as alternatives to flashguns. Clearly, a simple way to determine the effectiveness of such illumination - the guide number - is to calibrate the light source in a series of practical tests. However, we can also determine the guide number theoretically. David Gibson goes through the steps in this exercise, which brings together several aspects of physics and photometry that the reader may have forgotten. (See CREG forum).

 

[62] How Earth-Current Antennas Really Work, CREGJ 88, pp13-14. December 2014.   For download see previous item

With cave radio equipment, there has been a trend away from the use of induction loop antennas to the use of so-called earth-current antennas, i.e. long wires grounded at both ends. Both the HeyPhone and Nicola system use this type of antenna. However, the popular explanation for how this antenna works is fallacious. The antenna does not operate by allowing the current to flow in a 'big loop' in the ground, nor is it a 'conduction mode' of operation. In fact, it does not depend, fundamentally, on current flow in the ground at all. The fact that the popular explanation is wrong is important because, if we do not understand how the antenna works, it is difficult to know the best way to use it, nor how to design a better one. In this short note, David Gibson outlines a more useful model - that of the Grounded Horizontal Electric Dipole - but without the mathematical justification, which will be given in a future article. (Also see CREG forum).

 

[63] Using Dispersion to Measure Ground Conductivity, CREGJ 85, pp7-8, 19. March 2014. (PDF 518KB)     

Several methods of remotely measuring ground conductivity are known, which depend on measuring the amplitude and phase of a received signal, relative to its transmitter. All of these methods require the separate transmission of a phase reference signal, with attendant difficulties. David Gibson proposes that by transmitting a suitably constructed signal, a phase measurement may be made without the need for a separate reference. This is achieved by making use of the phenomenon of dispersion, in which the phase velocity of a wave depends on its frequency. A related technique that makes relative measurements of signal amplitude is also described.

 

[64] LED lighting: how the world has got brighter [cregf], CREGJ 82.   June 2013. See further reading on the CREG forum

David Gibson reminisces on the bicycle lamps that were around in the 1960s, which used an Ever Ready number 800 battery, and suggests that assessing the light output and duration would be an interesting exercise. See the posting on the CREG forum, bcra.org.uk/cregf).

 

[65] Dowsing and the Doctrine of Naive Analogy [cregf], CREGJ 80.   December 2012. See further reading on the CREG forum

Followers of this doctrine, asserts David Gibson, disregard several basic principles of science. They assert that 'any hypothesis has value', and they do not obey the axiom 'Quod supplantandum, prius bene sciendum', or 'Whatever you hope to supplant, you will first know thoroughly'. Instead, they produce hypotheses in ignorance of basic physics, hence the 'Naive Analogy'. (See: Dowsing and the 'Doctrine of Naive Analogy', Letters CREGJ 82 and the expanded letter on the CREG forum, bcra.org.uk/cregf).

 

[66] Loop Antennas v. Ferrite Rods: A Case Study, CREGJ 77, pp10-14. March 2012. (PDF 401KB)     

An induction radio's transmitting antenna may be an air-cored loop or a ferrite-cored solenoid. Because there are so many variables involved it is difficult, in the general case, to compare the two types of antenna and it is not possible to state, unequivocally, which type of antenna will perform better. However, in specific practical situations, a comparison is possible. In this article David Gibson describes one such case.

 

[67] Novel Cave Radio Antenna uses Small Ceramic Tiles, CREGJ 71, pp14-15. June 2008. (PDF 1.2MB)     

Induction loop antennas are often inefficient due to skin and proximity effects, self-capacitance and tuning losses. However, an electric field antenna will generate a magnetic field which, in some circumstances, can exceed the field strength available from a loop antenna of similar mass and power dissipation. The main difficulty is in achieving efficiency at a small size. David Gibson explains how this may be achieved using high-permittivity ceramic tiles.

 

[68] Unusual Photographic Duotone Processing, CREGJ 71, p24. June 2008.

David Gibson describes the digital processing of the 2008 Hidden Earth poster, which used a MatLab program to achieve the desired reduction to two ink colours.

 

[69] Batteries for the 21st Century, CREGJ 70, pp18-19. March 2008.

A new type of nickel metal hydride rechargeable battery with a very low self-discharge and a primary battery using a lithium iron disulphide technology are both available at high-street retail outlets and, asserts David Gibson, they present the best performance of all small batteries and should be used in all caving equipment wherever possible.

 

[70] CREG Award 2007, CREGJ 69, p13. December 2007.

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 Phil Underwood.

 

[71] 2007 Cave Technology Symposium, CREGJ 69, pp21-23. December 2007.

Back in April 2007, BCRA's Special Interest Groups got together to organise a symposium. Cave surveying, electronics and the use of explosives in caving were discussed. David Gibson reports.

 

[72] Front Cover, CREGJ 68, p1. September 2007. (PDF 605KB)     

Front cover photo by David Gibson

 

[73] Treasurer's Report to AGM 2007, CREGJ 68, pp6-7. September 2007. (PDF 265KB)     

This 'interim' report by the Treasurer, David Gibson, is for the period ending 1 Sep 2007.

 

[74] Unusual Photographic Duotone Processing, CREGJ 67, pp23-24. June 2007.

David Gibson describes the digital processing of the 2007 Hidden Earth poster that appears on the outside cover of this Journal.

 

[75] A Digital Class-D Single-Sideband Transmitter, CREGJ 65, pp6-8. December 2006.   For download see previous item

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.

 

[76] CREG Award 2006, CREGJ 65, p9. December 2006.

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.

 

[77] How to Report Experiments, CREGJ 65, p19. December 2006.

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.

 

[78] Treasurer's Report for 2005/6, CREGJ 65, p21. December 2006.

David Gibson summarises his report to the 2006 AGM, held earlier in the Autumn.

 

[79] Remote Data Logging with Cell-Phones and the Internet, CREGJ 64, pp13-14. September 2006. (PDF 699KB)     

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.

 

[80] Cave Radio Notebook, CREGJ 63, pp8-10. June 2006.

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

 

[81] CREG 2004-2005 in Review, CREGJ 62, pp6-7. December 2005.

Richard Rushton provides a review of the last year and David Gibson summarises his financial report

 

[82] Cave Radio Notebook, CREGJ 62, p24. December 2005.

69: Voltage-Balancing Circuit for 2-Cell Battery Chargers, 70: Two ISB channels on the HeyPhone, 71: Carbon Dioxide Sensors. Edited by David Gibson.

 

[83] Letters to the Editor, CREGJ 62, pp26-28. December 2005.

New Ventures for David Gibson, Wireless Video in Caves, Design, Safely Rescued, Workbench Lighting, M3.5 Fasteners, Spanish HeyPhone Update, The Adventures of Greg.

 

[84] Newssheet, CREGJ 61, p3. September 2005.

Comment by David Gibson, HeyPhone Coils and PCBs, Diary Dates.

 

[85] Parallel v. Series Resonant Loops, CREGJ 61, p7. September 2005. (PDF 333KB)     

David Gibson fills in some of the background to Beat Heeb's article above.

 

[86] Noise Cancelling Microphones, CREGJ 61, p11. September 2005.

David Gibson attempts to lay to rest some of the myths that surround the term 'noise cancelling' when used to describe pressure gradient microphone capsules for close-talking applications.

 

[87] MatLab Synthesis of Loran Interference, CREGJ 61, pp13-15. September 2005.

As part of a programme of work to investigate methods of reducing Loran interference to cave radio transmissions, David Gibson describes how to synthesise a test sample using the MatLab software package.

 

[88] Update: A Flashgun Isolator, CREGJ 61, p16. September 2005.

Digital cameras can be damaged by connecting them to a traditional design of electronic flashgun. In this article, David Gibson describes the problem in more detail, and updates his isolator circuit from CREG Journal 60.

 

[89] CREG Award 2005, CREGJ 61, p17. September 2005.

We issue an annual award to recognize special contributions to the field of cave radio and electronics. David Gibson describes this year's award to Beat Heeb.

 

[90] Operating a Solar Panel at Maximum Power Efficiency, CREGJ 60, pp9-13. June 2005. (PDF 532KB)     

Solar panels have an optimum operating point that depends on illumination. David Gibson describes how, in a battery charger application, we can find this operating point and use it to make a more efficient charger.

 

[91] Low-Cost Implementation of a Speech Compression System, CREGJ 60, pp16-18. June 2005. (PDF 432KB)     

David Gibson reports a method first described over 30 years ago, for compressing the dynamic range of analogue speech waveforms without increasing the distortion. A modern implementation uses simple software and a low-cost RISC micro-controller. The technique claims to increase the intelligibility of speech, which is a point to be investigated.

 

[92] A Flashgun Isolator, CREGJ 60, p21. June 2005.

Digital cameras can be damaged by connecting them to a traditional design of electronic flashgun. David Gibson describe an isolator that will protect the camera's sensitive electronics from the possible high voltage of a flashgun.

 

[93] Update: Flashgun Slave Unit for Digital Camera, CREGJ 60, p26. June 2005.

By David Gibson.

 

[94] Double-Sideband v. Single-Sideband, CREGJ 59, p?. March 2005.

David Gibson explains the pros and cons of inter-operating DSB and SSB radios.

 

[95] A Sonic Flow-Rate Meter for Measurements in Air and Water, CREGJ 59, p?. March 2005.

When sound waves are transported by a medium that is, itself, in motion, the speed of sound can be used to determine the flow rate of the medium. David Gibson describes this well-established technique, suggesting a practical implementation that can measure micro-climatic air conditions and water flow rate without any moving parts.

 

[96] Cave Radio Notebook, CREGJ 59, p?. March 2005.

63: Alternative(?) HeyPhone Inductors, 64: The 3-Point Method for Measuring Earth Electrode Resistance, 65: Earth Potentials, 66: A Ferrite Antenna for the HeyPhone, 67: HeyPhone AGC, 68: Designing a Full-Duplex Single Wire Telephone. Edited by David Gibson.

 

[97] An Introduction to High Frequency Radio in Tunnels, CREGJ 58, p?. December 2004.

In recent CREG journals we have reported on experiments with HF, VHF and UHF radios in tunnels. The way these radio signals propagate is something of a mystery - does the tunnel act as a waveguide? If not, why not? In this article, David Gibson, Richard Rushton and John Rabson pool their thoughts. 1. How Propagation Varies with Frequency, 2. What is a Waveguide?, 3. A Bibliography of CREG information.

 

[98] Update: Digital Slave Unit, CREGJ 58, p?. December 2004.

There are some points to note during the construction and use of David Gibson's new slave unit for digital cameras.

 

[99] Slave Unit for Digital Cameras, CREGJ 57, p?. September 2004.

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.

 

[100] An Electronic Compass and Clinometer Using Optical Sensor, CREGJ 57, p?. September 2004.

David Gibson proposes another method of using an optical sensor to read the position of a compass or clinometer disc. Correction: The final column in Table 2 (p23) should read (top to bottom), 0-1-1-0 and not 0-0-1-1

 

[101] Single-Wire Telephones: Q&A, CREGJ 57, p?. September 2004.

For cave communications the emphasis is often on radio. But in many cases Single Wire Telephones should be considered as an alternative. David Gibson answers a few questions and summarises the state of the art.

 

[102] Update: Detecting CO2, CREGJ 57, p?. September 2004.

David Gibson invites comment on an electrochemical detector and Neville Michie describes the methods he has used.

 

[103] Cave Radio Notebook, CREGJ 56, p?. June 2004.

57: Metal Sheets as an Alternative to Earth Spikes (John Rabson). 58: Calculations for Plate Electrodes (David Gibson). 59: Wenner Array Measurements (John Hey). 60: Wenner Array Underground (Rob Gill). 61: Using DTMF signalling with a HeyPhone (Rob Gill). 62: LORAN Spectrum Analysis (David Gibson). Column edited by David Gibson.

 

[104] Electronic Detection of Carbon Dioxide in Caves, CREGJ 56, p?. June 2004.

Concerns have been expressed about the high levels of carbon dioxide found in some caves. A long-term study of CO2 levels would be an interesting project, but CO2 sensors are expensive. Here, David Gibson describes a possible method of constructing a cheap sensor that would be affordable by students and amateur scientists.

 

[105] Frequency Synthesis - Some Possibilities, CREGJ 56, p?. June 2004.

David Gibson discusses methods of adapting cave radios to work on different frequencies.

 

[106] Noise-Cancelling Headphones: A Review, CREGJ 55, p?. March 2004.

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.

 

[107] Information on Talk-Through Boxes, CREGJ 55, p?. March 2004.

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.

 

[108] David Gibson: PhD in Cave Radio, CREGJ 55, p?. March 2004.

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

 

[109] A High-Performance Flashbulb Firer - part 2, CREGJ 55, p?. March 2004.

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.

 

[110] Slave Unit for Digital Cameras, CREGJ 55, p?. March 2004.

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.

 

[111] Student Project Suggestions: 2, CREGJ 55, p?. March 2004.

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.

 

[112] Electronic Detection of Carbon Dioxide, CREGJ 55, p?. March 2004.

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.

 

[113] Equipment Review: The Nova Caving Lamp, CREGJ 54, p?. December 2003.

The Nova, from Speleo Technics, is the first commercially available caving lamp to use the Luxeon 5W single-chip LED. David Gibson describes how the lamp fared underground and offers some thoughts on how the design could be enhanced. See also www.speleogroup.org/attinya.html.

 

[114] What We Don't Know About Earth-Current Propagation, CREGJ 54, p?. December 2003.

The propagation of electromagnetic signals from an earth-current antenna, such as the HeyPhone uses, is difficult to model, and there are several questions that have not been adequately answered. David Gibson explains the problems.

 

[115] Electronic Detection of Carbon Dioxide, CREGJ 53, p?. September 2003.

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. But, as David Gibson explains, it is not easy to detect CO2 electronically.

 

[116] The Luxeon White LED, CREGJ 53, p?. September 2003.

David Gibson reports on LumiLed's new white LED - the 'Luxeon'.

 

[117] Bulb Firer: Progress Report, CREGJ 53, p?. September 2003.

David Gibson reports on the progress of his Bulb Firer and other cave photography projects, and suggests an interim solution.

 

[118] 3D Radiolocation Using a Single Station, CREGJ 52, p?. June 2003.

The satellite-based Global Positioning System (GPS) cannot be used underground, and similar low-frequency methods using time-of-flight are likely to be difficult to implement. The best method of achieving a similar 3D system is by monitoring field strength and direction. In this article, David Gibson describes how the distance, bearing and elevation of a surface-based transmitter beacon can (in theory) be determined from measurements at a single underground station.

 

[119] A Bibliography of Cave Radiolocation, CREGJ 52, p?. June 2003.

David Gibson explains the state-of-the-art in radiolocation, and gives a list of 'further reading'.

 

[120] Student Project Suggestions, CREGJ 52, p?. June 2003.

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

 

[121] Vision in Low-Lighting Conditions, CREGJ 51, p?. March 2003.

Previous definitions of scotopic or dark-adapted vision, used in the CREG journal, may have been wrong. David Gibson reports.

 

[122] Matching & Output Impedance: A Common Fallacy?, CREGJ 51, pp16-17. March 2003. (PDF 247KB)     

We often hear about 'output impedance' and 'matching' but David Gibson suggests that the terms are misunderstood by many designers, and he makes proposals for specifying low-frequency power amplifiers.

 

[123] Cave Radio Notebook, CREGJ 51, p?. March 2003.

54: Noise Shielding, 55: Measurement of V & I at LF. 56: Specific Aperture. Column edited by David Gibson.

 

[124] Making Sense of Atmospheric Noise Temperature Ratio, CREGJ 51, p?. March 2003.

The often-quoted CCIR noise data is probably irrelevant for predicting the performance of equipment with magnetic loop antennas. David Gibson explains why.

 

[125] Cave-to-Cave Radiolocation: a Generalised Algorithm, CREGJ 50, p?. December 2002.

Cave-to-cave radiolocation is more difficult than the conventional exercise of locating an underground transmitter by taking measurements on the surface and requires a different approach. David Gibson presents a generalised algorithm for solving the problem.

 

[126] Using Excel to Plot Cave Surveys, CREGJ 50, p?. December 2002.

Occasionally, when a Cave Survey Plotting program is not available, a general-purpose spreadsheet will suffice. David Gibson explains how Microsoft Excel can process the data, and plot the cave too.

 

[127] Magazine Reviews, CREGJ 50, p?. December 2002.

The hobbyist magazines, commercial catalogues and datasheets can all be a source of interesting project ideas. David Gibson describes some recent items that have caught his eye.

 

[128] CREG in Pictures, CREGJ 50, p?. December 2002.

David Gibson describes the montage of photos on the back cover.

 

[129] A Channel Sounder for Sub-Surface Communications, CREGJ 49, p?. September 2002.

Part 3 - Spectrum Survey: Preliminary Results. Channel-sounders are used to test radio-wave propagation in a specified band, often the short-wave (HF) or one of the UHF 'cell-phone' bands. In this series of articles, David Gibson describes a new design of sounder that operates from 0 - 200kHz with a wide-band induction loop antenna. The sounder can also be used as a spectrum analyser, and is intended to be part of a wideband adaptive digital communications system.

 

[130] Cave Radio Notebook, CREGJ 49, p?. September 2002.

51: Cave Radio Using a Broadcast Carrier, 52: A Goniometer for Angle Measurement (John Hey), 53: Cave Radio Notebook Index. Edited by David Gibson.

 

[131] Cave Radio Notebook, CREGJ 48, p?. June 2002.

49: Trigonometric Radiolocation, 50: Finding Ground Zero (Peter Martinez). Edited by David Gibson.

 

[132] Cave Surveying by Radio-Location - 3, CREGJ 48, p?. June 2002.

Cave radiolocation relies on magnetic fields and a crucial assumption is that these fields behave in a 'quasi-static' manner. David Gibson explains how the conductivity of the ground distorts the field lines, leading to error, and derives some new methods of eliminating these errors.

 

[133] Design Directory: Radiolocation and Cave Radio, CREGJ 48, p?. June 2002.

Under the classifications of 'building equipment', 'introductory articles', 'further reading' and 'historical reading', David Gibson lists some CREG journal articles that will give you some insight into the current state-of-the-art of radio-location beacons and cave communications using induction radio equipment.

 

[134] Flashgun Slave Unit for Digital Cameras, CREGJ 48, p?. June 2002.

Digital cameras often have a built-in flashgun that gives a small pre-flash in order to set the colour balance. A slave unit must respond to the second flash pulse. David Gibson describes how his slave unit can be adapted to achieve this.

 

[135] Bulb Firer Adaptor for Electronics Guns, CREGJ 48, p?. June 2002.

Flashbulb firers based on capacitor discharge circuits may damage, or be damaged by electronic flashguns. David Gibson describes a simple experimental adapter that allows a slave-driven bulb firer to be safely used with flashguns.

 

[136] Updates: Flashgun Slave & Bulb Firer, CREGJ 47, p?. March 2002.

Some updates to David Gibson's flashgun slave unit projects that were featured in journal 45.

 

[137] Cave Radio Notebook, CREGJ 47, p?. March 2002.

48: A DSP implementation of the Turner/ Weaver SSB modulator. David Gibson offers some comments on Graham Naylor's DSP proposals and looks at an alternative approach.

 

[138] Speleo Tools: A Toolkit to take Underground, CREGJ 47, p?. March 2002.

Following on from an earlier article by Mike Bedford, David Gibson suggests a toolkit for underground electronics repairs.

 

[139] Selected Further Reading, CREGJ 46, p?. December 2001.

If a topic in this issue interests you, this list from CREG journals, compiled by David Gibson, may help.

 

[140] Flashbulb Sockets, CREGJ 46, p?. December 2001.

David Gibson lists the sockets required for the common sizes of flashbulb.

 

[141] Online Subscription Payment, CREGJ 46, p?. December 2001.

Accepting subscription payments from overseas can incur high transaction charges. David Gibson explains how clubs and societies can benefit from Internet facilities now available.

 

[142] TETRA-based Multi-Media Radio Aids Mountain Rescue, CREGJ 46, p?. December 2001.

Using Terrestrial Trunked Radio (TETRA), mountain rescuers now have the capability to relay GPS positioning information, text and status messages, digital images and medical telemetry using a single system. HW Comms' press release is edited for CREG by David Gibson.

 

[143] A High Performance Flashgun Slave Unit, CREGJ 45, p?. September 2001.

David Gibson describes some recent upgrades to his design, which is now some nine years old and, being the basis of the Firefly II commercial unit, seems to have stood the test of time.

 

[144] Meet the CREGies, CREGJ 45, p3. September 2001.

Who are these people we keep reading about in this journal? And what do they look like? In the third of a series of reports Rosy Rabson interviews David Gibson, Ian Drummond and herself.

 

[145] A High Performance Slave Unit and Flashbulb Firer - part 1, CREGJ 45, p?. September 2001.

Flash bulbs are still the professionals' choice for cave photography. This project by David Gibson combines his well-established slave unit with a bulb-firer circuit. In part 1 he describes the evolution of the circuit. Part 2 will give constructional details in the style of the Slave Unit project that is also featured in this issue.

 

[146] Selected Further Reading, CREGJ 45, p?. September 2001.

David Gibson suggests other sources of material relating to the articles in this issue.

 

[147] The CREG Small Print, CREGJ 45, p?. September 2001.

In some 'small print', David Gibson sets out the context in which CREG journal articles are published; discussing legal liability and 'duty of care'. He also explains the operation of copyright, and 'design right' protection.

 

[148] Cave Radio Notebook, CREGJ 45, p?. September 2001.

45: Is 'Cave Radio' a radio phenomenon? 46: The role of 'skin depth' in cave radio 47: Writing a software radio. Column edited by David Gibson.

 

[149] Frequency Synthesis: A review, CREGJ 44, p?. June 2001.

Accurate frequency synthesis is needed for many purposes, from low frequency applications such as audio tone generation and stepper motor control, through to UHF radio. David Gibson reviews some common methods of LF frequency synthesis and suggests some methods of building a 'frequency-agile' cave radio.

 

[150] Further Reading, CREGJ 44, p?. June 2001.

If a topic in this issue interests you, this 'further reading' list, compiled by David Gibson, may be of use.

 

[151] Using a Scanner as a Digital Camera, CREGJ 44, p?. June 2001.

David Gibson observes that photographing PCBs and small components is much easier with a flat-bed scanner than with a conventional camera. He demonstrates this with a scan of his experimental through-rock channel-sounding equipment.

 

[152] Further Reading, CREGJ 43, p?. March 2001.

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

 

[153] Operating a Solar Panel at Maximum Power Efficiency, CREGJ 43, p?. March 2001.

Solar panels have an optimum operating point that depends on illumination. David Gibson describes how, in a battery charger application, we can find this operating point and use it to make a more efficient charger.

 

[154] The Future is not Orange, CREGJ 43, p?. March 2001.

In a follow-up to the article in journal 42, David Gibson answers some more questions, and reports on progress with LED lamp designs.

 

[155] Cave Surveying by Radio-Location - 1, CREGJ 43, p?. March 2001.

David Gibson discusses methods of radio-location as a prelude to a series of articles that will discuss the techniques and equipment used in more detail.

 

[156] Computer Simulation of a Grounded Wire Antenna, CREGJ 42, p?. December 2000.

The equations that describe the sub-surface fields due to a wire laid on the surface are complicated, both to define and solve. Reno Lippold explains his implementation of Hill & Wait's equations using the MathCad package. In a commentary, David Gibson suggests how we might interpret these results.

 

[157] Simple Flashbulb Firer, CREGJ 42, p?. December 2000.

Flashbulbs are still the professionals' choice for cave photography. This simple circuit by David Gibson allows you to fire flashbulbs manually or with a slave unit.

 

[158] Miniature Dichroic Lamps, CREGJ 42, p?. December 2000.

Low voltage tungsten halogen bulbs in a dichroic 35mm envelope are now becoming available. David Gibson reports.

 

[159] Further Reading, CREGJ 42, p?. December 2000.

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

 

[160] The Future is not Orange,... but White, CREGJ 42, p?. December 2000.

David Gibson and Stuart France describe the use of white LEDs for caving lamps and attempt to demolish a few myths. This article is the first of a series that will include practical circuits for LED caving lamps.

 

[161] Web Watch, CREGJ 41, p?. September 2000.

David Gibson explains how to avoid web-site-published e-mail addresses giving rise to junk e-mail.

 

[162] Further Reading, CREGJ 41, p?. September 2000.

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

 

[163] A Channel Sounder for Sub-Surface Communications Part 2 - Computer Simulation of a Small Buried Loop, CREGJ 41, p?. September 2000.

Channel-sounders are used to test radio-wave propagation in a specified band, often the short-wave (HF) or one of the UHF cell-phone bands. In this series of articles, David Gibson describes a new design of sounder that operates from 0 - 200kHz with a wide-band induction loop antenna. The sounder can also be used as a spectrum analyser, and is intended to be part of a wideband adaptive digital communications system.

 

[164] Selected Further Reading, CREGJ 40, p?. June 2000.

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

 

[165] 'Lech' on 4 D-cells, CREGJ 40, p?. June 2000.

Lechuguilla Cave seems to be a popular location to test 'high-tech' lighting systems. David Gibson reviews a report.

 

[166] Cave Radio Notebook, CREGJ 40, p?. June 2000.

43: LORAN Noise Filtering. 44: Channel Evaluation. Notes by Lev Bishop. Notebook editor David Gibson.

 

[167] Pulse discharge circuits for Flashguns, CREGJ 39, p?. March 2000.

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.

 

[168] Foot-candles, CREGJ 39, p?. March 2000.

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

 

[169] Photography News, CREGJ 39, p?. March 2000.

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

 

[170] Selected Further Reading, CREGJ 39, p?. March 2000.

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

 

[171] An On-line CREG Journal Digest, CREGJ 39, p?. March 2000.

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.

 

[172] Cave Radio Notebook, CREGJ 38, p?. December 1999.

41: Transition Zone & Rayleigh Distance. 42: Winding Accuracy of Radiolocation Antennas. Edited by David Gibson.

 

[173] Selected Further Reading, CREGJ 38, p?. December 1999.

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

 

[174] A Channel Sounder for Sub-Surface Communications, CREGJ 38, p?. December 1999.

Part 1 - Adaptive Digital Communications for Sub-Surface Radio Paths. Channel-sounders are used to test radio-wave propagation in a specified band. In this series of articles, David Gibson describes a new design of sounder that operates from 0 - 200kHz with a wide-band induction loop antenna. The sounder can also be used as a spectrum analyser, and is intended to be part of a wideband adaptive digital communications system.

 

[175] A Methodical Approach to Loop Antenna Design, CREGJ 37, pp17-20. September 1999. (PDF 370KB)     

Loop antenna calculations are simplified by the use of a 'figure of merit' term, known as the 'effective aperture'. David Gibson explains how it is used.

 

[176] Selected Further Reading, CREGJ 37, p?. September 1999.

If you are interested in this issue's topics, this list of further reading from CREG journals, compiled by David Gibson, may be of use.

 

[177] Selected Further Reading, CREGJ 36, p?. June 1999.

If you are interested in the topics covered in this issue, then this list of 'further reading' from past CREG journals, compiled by David Gibson, may be of use to you.

 

[178] Cave Radio Notebook, CREGJ 35, p?. March 1999.

36: Energy storage in Inductors, 37: Underwater Radiolocation, 38: Comms Reports, 39: Index to Cave Radio Notebook. Edited by David Gibson.

 

[179] Speleonics, CREGJ 34, p?. December 1998.

Recent topics included using salt to lower earth resistance, and the mechanism of magnetic field generation in earth-current systems. Review by David Gibson.

 

[180] EMC Type Examination for RF modules, CREGJ 34, p?. December 1998.

In addition to Type Approval, transmitters require EMC Type Examination. The RA has recently clarified these procedures for RF modules. David Gibson reports.

 

[181] Improvements to Caving Lamps, CREGJ 33, p?. September 1998.

David Gibson describes some existing 'high-tech' lamp drivers and introduces his 48-white-LED caving lamp.

 

[182] Cave Radio Notebook, CREGJ 32, p?. June 1998.

Edited by David Gibson - 29: The Thirds Rule for Radiolocation. 30: Experiments with Ground Electrodes. 31: ICs for Amplitude Modulation. 32: Fields from a Grounded Wire.

 

[183] LF Through-rock Induction - the Broader Picture, CREGJ 32, p?. June 1998.

David Gibson describes some of the commercial uses of ground-penetrating radio, based on a presentation he gave at the Radio Solutions conference in October 1997.

 

[184] Web Watch, CREGJ 32, p?. June 1998.

Peter Ludwig lists some more web sites to visit. David Gibson continues his review of Usenet, and brings us up to date with the Speleonics mailing list.

 

[185] A Phonetically-Balanced Speech Intelligibility Test, CREGJ 31, p?. March 1998.

The audio equivalent of an optician's eye chart is a specially constructed word list that is used to measure the articulation loss of consonants. David Gibson explains how it is used and why consonants are important.

 

[186] Cave Telephones - Q&A, CREGJ 31, p?. March 1998.

We often get asked questions about communications equipment. David Gibson answers some queries about using telephones in an 800m deep cave in Spain.

 

[187] Web Watch, CREGJ 31, p?. March 1998.

Regular author Peter Ludwig looks at communications and mapping. David Gibson introduces his 'Virtual Foyer' and looks at Usenet.

 

[188] PIC a Project!, CREGJ 30, p?. December 1997.

Some ideas for projects using PIC microcontrollers by David Gibson.

 

[189] Solar Charger FAQ, CREGJ 30, p?. December 1997.

Answers by David Gibson.

 

[190] Cave Radio - 'How to do it', CREGJ 30, p?. December 1997.

David Gibson gives an introduction to his cave radio design, bringing together some points discussed in previous Journals and suggesting how you might go ahead with the design.

 

[191] 1996/7 Treasurer's Report, CREGJ 30, p?. December 1997.

Based on David Gibson's report for the year to 31st March with additional personal comments.

 

[192] Foot-Candles: Photometric Units, CREGJ 29, p?. September 1997.

More footnotes on optical topics by David Gibson.

 

[193] Fluorescent Tube Drivers, CREGJ 29, p?. September 1997.

A selection of references to circuits for driving fluorescent tubes collected by David Gibson.

 

[194] Update: Flashgun Slave, CREGJ 29, p?. September 1997.

This short note gives an update on the constructional information for David Gibson's slave unit.

 

[195] Using LEDs as Photodiodes, CREGJ 29, p?. September 1997.

David Gibson shows that using an LED could reduce the cost, and increase sensitivity of his flashgun slave.

 

[196] The Cave Radio & Electronics Group - The First 10 Years, CREGJ 29, p?. September 1997.

Mike Bedford and David Gibson chart our progress over the first ten years.

 

[197] Spectrum, CREGJ 29, p?. September 1997.

News about the LF spectrum by David Gibson.

 

[198] The Resistance of Ground-electrode Arrays, CREGJ 29, p?. September 1997.

Using N electrodes in a ground array can reduce the resistance to 1/N but certain criteria have to be met. David Gibson explains the theory.

 

[199] The New CREG Journal Bar Code, CREGJ 29, p?. September 1997.

David Gibson.

 

[200] Ground Shorts with a Single-wire Telephone, CREGJ 28, p?. June 1997.

What happens when the conductor of a single-wire telephone is accidentally shorted to earth? David Gibson analyses where the current goes, and shows that shorts are not necessarily a problem.

 

[201] LF Utility Stations, CREGJ 28, p?. June 1997.

A list of transmitters operating in the LF spectrum, compiled by David Gibson from information supplied by Joerg Klingenfuss of Klingenfuss Publications, and others.

 

[202] Cave Radio Notebook, CREGJ 28, p?. June 1997.

Edited by David Gibson, with contributions from John Hey and Chris Trayner. Topic 15 : 73kHz monopoles. 16: The 'thirds rule' for radio location. 17: An automatic level control. 18: A mixer for cave radio signals. 19: Under-sampling in a digital receiver. 20: Ground proximity and antenna de-tuning. 21: Deformation of loop antennas.

 

[203] Hi-Z SWTs, CREGJ 27, p?. March 1997.

David Gibson takes a brief look at single-wire telephones, and compares Lovell's high impedance version with Michie's standard design.

 

[204] Single Wire Telephones for Mines Rescue, CREGJ 27, p?. March 1997.

David Gibson recently visited a Mining consultancy, to find out what commercial communications equipment was used by Mines Rescue teams, and whether it would be suitable for cavers.

 

[205] Foot Candles, CREGJ 27, p?. March 1997.

Footnotes to David Gibson's article 'Candlepower' in J26.

 

[206] Radio Speleohistory, CREGJ 26, p?. December 1996.

David Gibson has collected some examples of the early use of radio in caves and mines.

 

[207] New Usenet Newsgroups, CREGJ 26, p?. December 1996.

David Gibson reports on two new Internet newsgroups which will be of interest to cavers.

 

[208] 'Speleological Abstracts' on CD-ROM, CREGJ 26, p?. December 1996.

This annual world-wide caving bibliography is now available on CD-ROM. David Gibson was not impressed with the presentation.

 

[209] Choosing a Frequency for a Radio-Location Beacon, CREGJ 26, p?. December 1996.

Radio-location beacons tend to use a crystal oscillator and a power-of-two divider. David Gibson suggests that we can be a little more imaginative.

 

[210] An Introduction to Data Transmission, CREGJ 26, p?. December 1996.

Part 2 of David Gibson's summary of digital communications techniques.

 

[211] Candlepower!, CREGJ 26, p?. December 1996.

David Gibson explains lumens and candelas, and why the candlepower rating of a lamp can be misleading.

 

[212] Humidity Measurement, CREGJ 25, p?. September 1996.

Accurate humidity measurement in caves is not possible nor, says David Gibson, is it needed.

 

[213] Measuring Radiated Power at 73kHz LF, CREGJ 25, p?. September 1996.

David Gibson explains how cave radio experimenters can benefit from the very strong near fields that 1W e.r.p allows, and explains the problems in measuring the radiated power.

 

[214] 3-D Vector Processing of Magnetometer and Inclinometer Data, CREGJ 25, p?. September 1996.

Electronic sensors can be used to construct a cave surveying tool, but the data needs processing in 3 dimensions. David Gibson explains the maths.

 

[215] The Eartalker, CREGJ 25, p?. September 1996.

David Gibson briefly describes a combined earphone / microphone.

 

[216] Safety-Critical Use of the Induction Radio Band, CREGJ 25, p?. September 1996.

David Gibson reports on the latest proposals from the Radiocommunications Agency.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[217] An Introduction to Data Transmission, CREGJ 24, p?. June 1996.

An introduction to data communications as applied to cave radio, by David Gibson.

 

[218] Electronics in Surveying, part 2, CREGJ 24, p?. June 1996.

David Gibson elaborates on his article in the previous Journal. Global positioning and inertial navigation are discussed.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[219] Update - Type Approval of Modules, CREGJ 23, p?. March 1996.

David Gibson reports on the latest from the Radiocommunications Agency.

 

[220] Electronic Aids for Photographers, CREGJ 23, p?. March 1996.

David Gibson reports on a discussion held at the Autumn 95 CREG field meeting.

 

[221] An Improved Circuit for Firing Flashbulbs, CREGJ 23, p?. March 1996.

David Gibson's design allows slaves to be used more reliably with flashbulbs, and provides an indication that the flashbulb is correctly seated.

 

[222] A Slave for RALF: part 2, CREGJ 23, p?. March 1996.

Some further notes on construction, by David Gibson.

 

[223] Electronics in Cave Surveying, CREGJ 23, p?. March 1996.

David Gibson reviews the uses of electronic instrumentation for surveying and navigation in caves.

 

[224] Review: Electronic Compass Modules, CREGJ 23, p?. March 1996.

David Gibson lists a range of components and modules useful for the design of electronic compass / clinometers.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[225] A Slave for RALF, CREGJ 22, p?. December 1995.

Following on from Mike Bedford's article on the RALF concept in the last issue, David Gibson provides constructional information on a new slave.

 

[226] Designing an 'Outphaser', CREGJ 22, pp17-21. December 1995. (PDF 992KB)     

David Gibson introduces the outphaser method of SSB generation and provides design parameters and a circuit diagram.

 

[227] Literature Received, CREGJ 22, p?. December 1995.

David Gibson lists some items sent in by members.

 

[228] Automatic Battery Protector, CREGJ 22, p?. December 1995.

A circuit for preventing the deep-discharge of a NiCd battery by David Gibson.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[229] Cave Radio Notebook, CREGJ 21, p?. September 1995.

6: Ferrite rods, 7: noise-cancelling antennas, 8: range & power, 9: magnetic field detector. Notebook edited by David Gibson, with contributions from Nick Negus and Chris Trayner.

 

[230] A Design Procedure for Transmitter Loop Antennas, CREGJ 21, p?. September 1995.

David Gibson describes how a design needs to take account of bandwidth and effective aperture.

 

[231] Review: Fluorescent Lamp Driver, CREGJ 21, p?. September 1995.

David Gibson reviews an application note from Electronics World.

 

[232] Bandwidth of Tuned Antenna does not Affect Performance, CREGJ 21, p?. September 1995.

David Gibson shows that bandwidth may be set independently of effective aperture and is no longer a limit on performance of tuned antennas.

 

[233] Update - ETSI 300 330 Signal Strength Limits, CREGJ 21, p?. September 1995.

David Gibson reports the latest from the Radiocommunications Agency.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[234] Talk-through Boxes, CREGJ 20, p?. June 1995.

A 'talk-through box' is the correct terminology for the type of 'repeater' needed to interface a cave radio to devices such as HF radios, telephones and so on. Mike Bedford and David Gibson explain the principles.

 

[235] Simplex Protocols for Cave Radios, CREGJ 20, p?. June 1995.

In a glossary and draft specification, David Gibson discusses the operation of a PTT switch, cueing tones, hands-free operation, and talk-through boxes.

 

[236] High Power Switching Regulator, CREGJ 20, p?. June 1995.

David Gibson introduces a novel design.

 

[237] Sodium Lamps for Caving, CREGJ 20, p?. June 1995.

Nick Williams and David Gibson describe the characteristics of these lamps.

 

[238] Signal/Noise Ratio - Part 1 of a Series on Receiver Noise Topics, CREGJ 20, p?. June 1995.

David Gibson introduces this series and explains the steps leading up to an expression for the s/n ratio of an induction loop receiver.

 

[239] Cave Radio Notebook, CREGJ 20, p?. June 1995.

David Gibson's notes on 4: earth current communication, 5: circular polarisation, 5: [sic] ground conductivity.

 

[240] Wet & Dry, CREGJ 20, p?. June 1995.

Our regular(ish) column on waterproof electronics. More on waterproof speakers by David Gibson.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[241] Reviews of Literature Received, CREGJ 19, p?. March 1995.

David Gibson lists some papers which readers have sent in.

 

[242] Earth Current / Induction Field Experiments, CREGJ 19, p?. March 1995.

Following David Gibson's assertion that an earth current signal could be received inductively, Rob Gill put it to the test obtaining encouraging results.

 

[243] Lithium-ion Cells, CREGJ 19, p?. March 1995.

An overview of these new cells by David Gibson.

 

[244] Designing a Capacitive Coupler for an SWT, CREGJ 19, p?. March 1995.

Some theoretical guidance by David Gibson.

 

[245] Losses in Tuning Capacitors, CREGJ 19, p?. March 1995.

David Gibson described the effect of dielectric losses in the tuning capacitors of loop antennas and indicates which types of capacitor have the lowest loss.

 

[246] Update - Type-approved Transmitter Module, CREGJ 19, p?. March 1995.

Following some misunderstanding regarding articles in the last Journal, David Gibson clarifies his ideas for a type-approved transmitter module.

 

[247] Cave Radio Notebook, CREGJ 19, p?. March 1995.

In this new series, David Gibson presents notes on 1: aperture synthesis, 2: spectrum analysis, 3: digitised speech.

 

[248] Wet & Dry, CREGJ 19, p?. March 1995.

Our regular(ish) column on waterproof electronics. David Gibson describes Pelican cases, Hexseals and waterproof speakers.

 

[249] The Proximity Effect - part 1, CREGJ 19, p?. March 1995.

David Gibson describes this little-discussed effect which was described by Butterworth in 1926.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[250] Cave Radio - the Next Generation, CREGJ 18, p?. December 1994.

David Gibson looks at some factors which may prevent progress on the next generation of cave radio and suggests how a new design may come into being.

 

[251] Speech Communications at 27kHz FM, CREGJ 18, p?. December 1994.

Stuart France describes the design philosophy of his experimental FM cave radio, and gives some advice to budding cave radio designers. David Gibson gives some technical background to Stuart's design.

 

[252] Licence-free Home-construction of Induction Radio Equipment, CREGJ 18, p?. December 1994.

Is it possible to have a design type approved and then allow individuals to home construct units? David Gibson investigates.

 

[253] Type Approval News, CREGJ 18, p?. December 1994.

The latest information, reported by David Gibson.

 

[254] Broadening our Horizons, CREGJ 18, p?. December 1994.

Mike Bedford and David Gibson suggest some new applications of electronics to caving and urge us all to broaden our horizons.

 

[255] Sites for Testing Cave Radios at Depth, CREGJ 18, p?. December 1994.

David Gibson considers which British caves will present the biggest challenge for testing new radios.

 

[256] Designing an SSB Transmitter Module, CREGJ 18, p?. December 1994.

David Gibson outlines his thoughts for producing a basic type approved SSB module which could form the basis of new cave radios.

 

[257] Update on Cave Data Logging, CREGJ 18, p?. December 1994.

David Gibson reports on the progress of the project outlined in Journal 11.

 

[258] Reviews, CREGJ 18, p?. December 1994.

David Gibson reviews some recent articles on earth-current communications and data-logging.

 

[259] Update, CREGJ 18, p?. December 1994.

David Gibson updates recent articles on Earth Current communications, NiCd Charger/Conditioner, Caver Counter.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[260] An Introduction to Earth current Communication, CREGJ 17, p?. September 1994.

David Gibson provides some theory to back up Steve Clark's article in Journal 16.

 

[261] Ferrite Rods as Transmitting Antennas, CREGJ 17, p?. September 1994.

Part 2 of David Gibson's series, held over from Journal 16.

 

[262] Forthcoming Changes to Induction Radio Licence Specifications, CREGJ 17, p?. September 1994.

David Gibson describes the new ETSI 300 330 specification.

 

[263] A 200J Flashgun, CREGJ 17, p?. September 1994.

David Gibson describes his experimental 200J flashgun and discusses the features that could be incorporated into a finished product.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[264] A Toroidal Loop Antenna, CREGJ 16, p?. June 1994.

Part 2 of David Gibson's series on driving an untuned loop antenna.

 

[265] Water Tracing with VLF Radio, CREGJ 16, p?. June 1994.

Is it possible to design a VLF radio which can be dropped into a sump and tracked from the surface? David Gibson shows how the theory is applied to this problem.

 

[266] Locating Cavities Using Microgravity Techniques, CREGJ 16, p?. June 1994.

David Gibson reviews an article in Mine & Quarry.

 

[267] A More Accurate Dipole Field Pattern, CREGJ 16, p?. June 1994.

David Gibson suggests that previously published field patterns have been misleading and presents the new improved version.

 

[268] AM Radio Reception in Caves, CREGJ 16, p?. June 1994.

A review of a discussion which appeared in The Texas Caver. Review by David Gibson.

 

[269] Accuracy of Ultrasonic & Optical Rangefinders, CREGJ 16, p?. June 1994.

Henry Lyall comments on David Gibson's article in Journal 6.

 

[270] Alkaline Cell Failure, CREGJ 16, p?. June 1994.

David Gibson reviews and expands on an article in Speleonics 17.

 

[271] Wet & Dry, CREGJ 16, p?. June 1994.

In our regular column on making equipment cave-proof, David Gibson explains some of the thoughts behind his choice of components for his 2-way earth return telephone.

 

[272] A High Performance Flashgun Slave, CREGJ 16, p?. June 1994.

An update on David Gibson's design.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[273] Driving an Untuned Loop Antenna, CREGJ 15, p?. March 1994.

David Gibson considers the use of untuned loops as an alternative to the more common tuned antenna.

 

[274] Wet & Dry - Engineering a Cave Radio, CREGJ 15, p?. March 1994.

David Gibson takes time out from the subject of waterproofing to discuss more general requirements in this regular series.

 

[275] Ferrite Rods as Transmitting Antennas, CREGJ 15, p?. March 1994.

Following on from consideration of ferrite rods for receiving, David Gibson now investigates their use in transmitting antennas.

 

[276] A Caver Counter, CREGJ 15, p?. March 1994.

A practical design by David Gibson for a device to measure the amount of traffic in caves.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[277] Theoretical Considerations for a Low Noise Pre-amp, CREGJ 14, p?. December 1993.

Comment on David Gibson's article by Derek Potter.

 

[278] Designing a Low-noise Receiver Pre-amp, CREGJ 14, p?. December 1993.

David Gibson summarises the signal/noise and reception range equations and gives some worked examples.

 

[279] Flashgun Slaves for Flashbulbs, CREGJ 14, p?. December 1993.

David Gibson gives a circuit for adapting slave units to work with bulbs, and Steve Clark gives a design for a slave unit.

 

[280] Penetration of Magnetic Fields Underground, CREGJ 14, p?. December 1993.

In this, the third part of our 'optimum frequency' series, David Gibson derives graphs of s/n ratio against frequency for various rock conductivities.

 

[281] Expected Values of Atmospheric Radio Noise, CREGJ 14, p?. December 1993.

John Rabson presents the figures, and David Gibson gives some guidance on how to use them.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[282] Wet & Dry, CREGJ 13, p?. September 1993.

This regular column, by David Gibson, looks at rotary switches, enclosures, microphones and speakers.

 

[283] A Low-noise Earth Return Telephone, CREGJ 13, p?. September 1993.

A design idea by David Gibson as a prelude to a forthcoming constructional article.

 

[284] VLF Licence Regulations Explained, CREGJ 13, p?. September 1993.

David Gibson give a full explanation of the various licences relevant to VLF work in the UK.

 

[285] A Multi-drop Earth Return Telephone, CREGJ 13, p?. September 1993.

A design idea by David Gibson.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[286] Theoretical Considerations for a Low Noise Pre-amp, CREGJ 12, p?. June 1993.

David Gibson considers this, the most critical stage of a cave radio receiver.

 

[287] A New Technique for Speech Signal Enhancement, CREGJ 12, p?. June 1993.

David Gibson reports on a new technique which claims a 20dB increase in s/n ratio using a microprocessor.

 

[288] The State of Cave Surveyors, CREGJ 12, p?. June 1993.

David Gibson offers an opinion in the latest episode in this ongoing saga.

 

[289] Waterproof Housings & Components, CREGJ 12, p?. June 1993.

Housings, connectors, switches and indicators come under the spotlight in this, the first of a new series, by David Gibson.

 

[290] Loop Antenna Construction, CREGJ 12, p?. June 1993.

In our cover feature, David Gibson suggests some novel alternatives to loop construction.

 

[291] The Optimal Design of a Cave Radio, CREGJ 12, p?. June 1993.

Notes based on David Gibson's talk at last year's BCRA conference.

 

[292] Which is the Best Frequency for Cave Radios?, CREGJ 12, p?. June 1993.

Following Mike Bedford's look at the spectrum, David Gibson discusses some theoretical points.

 

[293] A NiCd Charger and Conditioner, CREGJ 12, p?. June 1993.

David Gibson discusses a possible practical design.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[294] Extending Battery Duration by Heating, CREGJ 11, p?. March 1993.

David Gibson investigates.

 

[295] Guide-wire Communications Review, CREGJ 11, p?. March 1993.

David Gibson gives a roundup of the various techniques referred to as 'guide-wire' communication.

 

[296] Choosing a Battery Voltage, CREGJ 11, p?. March 1993.

How many NiCd cells should you string together into a battery? David Gibson shows there is a limit to this.

 

[297] Ferrite Rods as Receiving Antennas, CREGJ 11, p?. March 1993.

David Gibson explains the salient points of using ferrite cores and compares them with air-core antennas.

 

[298] How Long Should a Wire Antenna Be?, CREGJ 11, p?. March 1993.

Despite the virtual universality of loop antennas for cave radio, there may be something to be said for using short whips. David Gibson reports.

 

[299] Biasing Op-amps for Single-supply Circuits, CREGJ 11, p?. March 1993.

David Gibson gives circuit suggestions for using op-amps when you don't have a split supply rail.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[300] A High-performance Flashgun Slave, CREGJ 10, p?. December 1992.

David Gibson presents a practical design which is compact, has a high range, in insensitive to caplamp beams and consumes a very low current.

 

[301] Cave Radio PA Design and a Digital PWM DSB Modulator, CREGJ 10, p?. December 1992.

David Gibson's experimental design.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[302] The Watsonlinc, CREGJ 9, p?. September 1992.

David Gibson reviews an inductive device for tapping into telephone cables.

 

[303] A Very Big Flashgun, CREGJ 9, p?. September 1992.

David Gibson explains how to make a big flashgun by connecting lots of little ones together!.

 

[304] No-nonsense NiCd Charging, CREGJ 9, p?. September 1992.

Sensible instructions on the use of rechargeable cells, from David Gibson.

 

[305] A Battery Discharger, CREGJ 9, p?. September 1992.

A circuit to safely pre-discharge a NiCd battery before charging, by David Gibson.

 

[306] Global Positioning Underground, CREGJ 9, p?. September 1992.

David Gibson explains how inertial navigation might work in a cave-surveying tool.

 

[307] An Aluminium Tape Antenna, CREGJ 9, p?. September 1992.

David Gibson outlines his experimental tape antenna, and discusses other designs that might be considered.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[308] Cave Detection with rho, sigma, mu, epsilon Part 2, CREGJ 8, p?. June 1992.

David Gibson continues with a summary of the effects of each parameter and a list of further reading.

 

[309] Modulation Methods and Signal/Noise Ratio, CREGJ 8, p?. June 1992.

David Gibson discusses the different modulation techniques suitable for cave radio, and explains how they affect the s/n ratio.

 

[310] SSB Modulation Review, CREGJ 8, p?. June 1992.

David Gibson explains the different methods of achieving single-sideband modulation.

 

[311] Project Greensites, CREGJ 8, p?. June 1992.

A review of the South Wales Caving Club 'Greensites' project for cave detection. Reviewed by David Gibson.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[312] Phased-array Sonar for Rangefinding, CREGJ 7, p?. March 1992.

David Gibson presents a computer-generated plot showing how the beam from a small ultrasonic transducer might be concentrated. (Front cover diagram).

 

[313] UK VLF Licence Regulations, CREGJ 7, p?. March 1992.

David Gibson summarises the MPT 1337 type-approval specification.

 

[314] Optimal Design of a Cave Radio, CREGJ 7, p?. March 1992.

David Gibson summarises some key points.

 

[315] Lighting: The Aven Explorer, CREGJ 7, p?. March 1992.

Small NiCd cells can be used with high wattage bulbs provided certain precautions are taken. David Gibson explains.

 

[316] Cave Detection with rho, sigma, mu, epsilon. Part 1, CREGJ 7, p?. March 1992.

David Gibson summarises the physical parameters that we could consider measuring in order to detect caves.

 

[317] Are Q-Multipliers Any Use for Cave Radio, CREGJ 7, p?. March 1992.

David Gibson questions the worth of the Q-multiplier, seen in several designs of cave radio receiver.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[318] Field Pattern of a Small Magnetic Dipole, CREGJ 6, p?. December 1991.

David Gibson presents a computer-generated plot of the near and far-fields and the transition-zone between them. (Front cover diagram).

 

[319] Digestive Biscuits, FX2s and Abseiling, CREGJ 6, p?. December 1991.

David Gibson muses on biscuits and gravity-powered lighting.

 

[320] Tips for Using Ni-Cd Cells, CREGJ 6, p?. December 1991.

Brief notes on charging and potting of NiCd cells, by David Gibson.

 

[321] Notes on a Laser Gyrocompass, CREGJ 6, p?. December 1991.

Can a gyrocompass be used in an electronic surveying instrument? Notes by David Gibson.

 

[322] Accuracy Problems in Ultrasonic and Light-beam Rangefinders, CREGJ 6, p?. December 1991.

Rangefinders based on 'time-of-flight' measurements may not always be accurate. Notes by David Gibson.

 

[323] Improving Directivity in Ultrasonic Rangefinders, CREGJ 6, p?. December 1991.

David Gibson explains how a parabolic reflector aids focussing.

 

[324] A Laser Rangefinder, CREGJ 6, p?. December 1991.

David Gibson outlines the design of a 'time-of-flight' opto-electronic rangefinder.

 

[325] How Big Should a Loop Antenna Be?, CREGJ 6, p?. December 1991.

Loop antennas do not necessarily need to be large; what is important is the signal/noise ratio. David Gibson investigates.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[326] Smaller Batteries Can Improve Loop Antenna Performance, CREGJ 4, p?. Summer 1989.

David Gibson extends the expression for loop antenna performance to include battery mass.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

[327] Number of Turns has no Effect on Loop Antenna Performance, CREGJ 3, p?. Spring 1989.

David Gibson derives an expression for the performance of a loop antenna and demonstrates that the number of turns is not a contributing factor.

 

[328] Feedback, CREGJ 3, p?. Spring 1989.

David Gibson provides some feedback on a letter about LEDs for distance measuring in issue 2.

 

[329] Terminations for Ribbon Aerials, CREGJ 3, p?. Spring 1989.

Some practical tips by David Gibson.

 

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.

CREG Journal Archive:
This issue is available on paper as part of a two-volume archive, covering issues 1 to 25. To purchase it, please visit Lulu.com.