RadCom April 2024, Vol. 100, No. 4

Regulars April 2024 33 The Antenna Notebook Edited by Lorna Smart, 2E0POI This book delivers innovative and novel design ideas for antennas that you may or may not have heard of – based on a previous book edited by the late Giles Read, G1MFG. The art of antenna design and building has long been the domain of the advanced amateur radio enthusiast, but it need not be. The content of these pages contains a wealth of information which make the practical application of building antennas simple. Designs are based mostly upon previously-published RSGB articles but are also drawn from other sources such as the ARRL and G-QRP Club. The various chapters address possible scenarios that are likely to be encountered by amateurs. For example, you might have a small garden, no garden at all or antenna hight restrictions etc. The methods employed show that home-constructed antennas can be as efficient or better than purchased versions. An interesting example of this is the use of wire in place of aluminium elements in the construction of a beam antenna. By constructing a frame made of UPVC tubing, and stringing it with wire in a specific way, the same or better performance than with a beam can be achieved. Dipoles that are featured suit both internal and external installation in a variety of domestic situations. The broad spectrum of over 50 antenna designs covered within the book should mean that there is something for everyone whether it be random end-fed wires or full-wave loops. The variety of materials used throughout the book is testament to the ingenuity of the radio amateur. Chopping boards, pipe clips and shelf brackets are all fair game when the design of a good antenna is at stake. Even such odd materials as Slinky Springs can be used! Another aspect of antenna design that is covered in the book is the use of a tuned antenna solution where antennas are designed to be resonant at a particular frequency. The book discusses the fact that receiving and transmitting antennas are fundamentally quite different and that the use of an ATU can dramatically enhance the performance of an antenna. The minimisation of reflected power is more critical for a transmitting antenna, of course, but when receiving any amount of gain that can be produced is a bonus. The book explains that an antenna can also be coupled with a pre- amplification stage to really pull in those distant signals. This book will take you, step by step, through designs that will allow you to build a great variety of antennas – it is a very useful reference and one that will often be referred to rather than simply gathering dust on a shelf in the shack. Size 174x240mm, 288 Pages, ISBN: 9781 9139 9552 2 Non Members: £15.99, RSGB Members: £13.59 Gravitational Waves By Brian Clegg Gravitational Waves (part of the same series as Origins of the Universe which we featured last month) seek to tell the story of the race to detect and prove the existence of this elemental force. It starts by setting out the history of gravitational waves and Einstein’s theory of relativity. Two laboratories were set up to form the LIGO project or, more formally, The Laser Interferometer Gravitational Wave Observatory. The object of the investigations was to determine the existence of gravitational waves, however this was to be a most difficult exercise as the theoretical waves are very small. To put them into perspective, the size of an atom is measured at 10 -10 m, the nucleus of an atom is (10 -15 m) and a gravitational wave is 10 -17 m. Thus, the method of detection devised was that of taking a long vacuum tube, passing a laser light down it and splitting the beam, diverting the second beam and, when eventually bringing the two back together, measuring any movement between the two. Two facilities were built to conduct the experiment, one at Livingston, Louisiana and the other at Hanford, Washington. These sites consisted of pairs of tubes 2.5 miles long, set at right angles, forming an L shape and the facilities set 1,865 miles apart. At each site, a laser passes along the pair of tubes to reflect off mirrors at the ends many times before the beams are brought together to form an optical interference pattern – a tiny set of fringes that gives a visible warning of incredibly small changes. The slightest variation of the beams will produce a detectable effect. This is the change that was expected to happen in the presence of gravitational waves. Gravitational Waves is a fascinating read and is an interesting window into the world of particle physics. The determination and ingenuity of the scientists and physicists involved is very compelling and can be likened to the parallels in research and experimentation being done by amateurs at the forefront of the radio spectrum in SHF engineering. Gravitational Waves is written in a clear and accessible way and does not require deep mathematical knowledge to follow it along. However, an appreciation of physics will help the reader get the most out of the book. This book will be enjoyed anyone who wishes to expand their knowledge of fundamental forces that are becoming understood more fully as research progresses. Size 128x196mm, 176 pages, ISBN: 9781 7857 8320 3 Non Members: £10.99, RSGB Members: £7.69 (30% OFF) Book Review RadCom Team radcom@rsgb.org.uk