Tabla de contenidos para March 2024 en Practical Wireless

The better weather will soon be here, affording us the opportunity of some outdoor amateur radio activities such as Amateur Radio Direction Finding (ARDF), also known as fox hunting. One useful piece of equipment for use during ARDF is an Offset Attenuator. Where you have tracked down the beacon to a local area but due to the signal strength of the beacon you are unable to identify a more accurate location, then it is time to use the offset attenuator. More on the use later, let us get into the construction. I first did some research online where I came across a few designs, but looking to keep things simple I picked and drew the schematic as seen in Fig. 1. This uses a 4MHz crystal and only contains 16…

While measuring voltages and currents in a circuit can tell us a lot about what is going on, an oscilloscope can provide a visual image of the voltage or more rarely, the current that we’re interested in. This article is intended to provide someone who has never used an oscilloscope with an introduction to the controls found on a basic single-or double-beam oscilloscope and how to make some basic measurements. Oscilloscopes are available with a wide range of capabilities and performance – reflected by the price. Modern oscilloscopes tend to have LCD displays and may have four or more traces. They are usually also able to carry out certain mathematical operations on the waveforms. Here though we will assume that you’re using one of the older analogue oscilloscopes. Basic oscilloscopes…

The invention of the superheterodyne receiver, Fig. 1, was a major milestone in the evolution of radio technology. History tells us that the theoretical basis of a development is often derived long before its practical applications flourish. For example, George Boole published his Mathematical Analysis of Logic in 1847, but it was only with the arrival of the digital age in the 20th century that his binary logic was applied extensively. And James Clerk Maxwell had formulated the classical theoretical foundation for the understanding of electromagnetic radiation as early as 1865, but only in 1888 did Heinrich Hertz confirm the existence of radio waves and measure their properties. Even Hertz thought that his work had no practical use, and it was a further nine years before Guglielmo Marconi and others…

In Part I, I described new data on HF transmit noise that I compiled from public sources. These data covered many modern HF transceivers appearing in the famous Sherwood Table of receive performance and in my previous articles (Howell 2021a,b). The finding was that many modern HF transceivers, some of which would be considered among the best available today, vary considerably in the noise they put into their transmitted signals. These differences were perhaps surprising to the reader, partly because they represent new data in a consolidated, compiled form. But how do these HF transceivers compare on measured receive performance? Can money buy a ‘cleaner’ HF transceiver? Altogether, how well does the amateur say they like these ‘cleaner’ transceivers? In Part II, I analyse these questions using visual charts and…

By their nature, radio amateurs the world over tend to be enthusiastic collectors and most shacks contain an impressive array of transceivers, tuning units, power supplies, test equipment and the like. But this month, I was delighted to meet Mark Stuckey G0SQK, Fig. 1, whose Aladdin’s Cave of modern and vintage equipment was in a class of its own. It was no surprise to me that he was the obvious choice when, in 2018, the producers of the popular BBC 1 show The Repair Shop enlisted him as its resident electronics and electrical restoration expert. How it all began “It all started with my fascination with Dr Who,” explained Mark. “He seemed to know a bit about everything, and I really admired that!” And so started his long voyage of…

My interest in radio started as a shortwave broadcast bands listener in the late 1960s. One of the stations that was very popular back in those days was Radio Nederland. 55 years ago, in March 1969, Radio Nederland opened its first overseas relay station on Bonaire, in what was then the Netherlands Antilles. As a keen listener (and lapsed philatelist – radio had taken over from stamp collecting as my main interest) I applied to Radio Nederland for the commemorative first day cover shown in Fig. 1. Little did I know then, as a 13-year old SWL, that decades later I would spend ten wonderful years living on Bonaire! However, all good things come to an end and, after nearly 20 years abroad, Eva PJ4EVA and I have decided to…

For the non-English speaking world, the BBC’s External Services reported the Coronation on 2June 1953, in no fewer than 41 different languages. Europe was served during the day by ‘live’ commentaries broadcast over five networks in 15 languages. Recorded commentaries and studio reconstructions of the day’s events were given in a further ten languages. The pattern of multi-language broadcasting for the Middle and Far East, and for Latin America, was similar. Some months before the Coronation, requests were received from France, Western Germany and the Netherlands for facilities to relay the BBC’s television broadcast of the event. The possibility of such a relay had been demonstrated by the BBC a year earlier when it successfully transmitted a number of programmes over a temporary television link established between Paris and London,…

Mauritius Dear Don, I was very interested in your Mauritius visit. The RN had a large radio station (GXO) in the 1960s, known as ‘the hub of the wheel’. Never went there but did visit Elephant Island, one of the Chagos Chain, in a ship RFA Gold Ranger to land an inter-services expedition. The only ship I ever sailed in with a shack on deck. Incidentally how we now call our radio stations ‘the shack’. There was no cabin space below for a radio station so a shack was built on deck back in the day. Dr David Bellamy was part of that team and their RAF radio operator was using a KW2000 transceiver, which we repaired before he went ashore. Luckily, we carried the correct valve. My daughter-in-law’s mother…

I’ve just spotted an exciting new design for a low-cost HF transmitter using the Raspberry Pi Pico (£4) microcontroller board. The design has been developed by Bryan Cockfield and published on the popular HACKADAY site: http://tinyurl.com/4w8wxupd One of the features that sets the Pico apart from many other microcontrollers is its programmable I/O pins. These can be programmed to operate independently of the central processor core using their four dedicated state machines. These state machines are ideal for handling repetitive tasks such as generating an RF carrier for a transmitter. Bryan’s design has taken full advantage of the Pico I/O pins. I’ve shown a simplified block diagram in Fig. 1. It uses one programmable I/O for the RF carrier and a second to generate a PWM (Pulse Width Modulation) signal…

Last month I started to describe the construction of a lightweight two-element Yagi for use on the 10m band (loosely) based on the W6SAI model in the Beam Antenna Handbook. To recap; the antenna had to be as light as possible because it was my intention to mount it on my LMA-33 telescopic mast. I decided on a reflector and driven element configuration and for simplicity a feedpoint close to 50Ω was desirable. Also wanted was a good VSWR bandwidth to cover as much of the band as possible. It needed to be constructed from materials that I had to hand. I had some 24x24mm timber for the boom, 65x10mm for the elements support and 8mm dia thick wall aluminium tube for the elements themselves. I would 3D print the…

REVIEW ICOM ID-50E: Richard Constantine G3UGF takes a long walk with the ID-50E. PORTABLE MILITARY RADIO COMMUNICATIONS OF WWII: Graham Caldwell looks at the rapid development of American portable radio equipment during WWII, their collecting potential and cost for immediate use or restoration. THE G3RJV SCD QRP TRANSCEIVER: Steve Hartley G0FUW starts a series revisiting a classic QRP transceiver from the late George Dobbs G3RJV. POWER SUPPLIES: Dr Samuel Ritchie EI9FZB continues his three-part series looking at reusing various types of fixed power supply. ENCLOSURES FOR NANOVNA AND TINYSA: Michael Jones GW7BBY/GB2MOP has a solution for improving the use and life of your NanoVNA or similar test equipment. There are all your other regular columns too, including HF Highlights, World of VHF, Data Modes, Antennas, Book Reviews, What Next, The…