Sommaire pour July 2024 de Practical Wireless

Having experienced damage to one of my favourite QRP radios some time ago and for which there isn’t a viable cure, I was anxious to find out how to avoid a potential repeat at some time in the future. The most likely culprit seemed to be a faulty antenna switch that had allowed RF from one radio to pass directly into the antenna socket of another… could I prove it? I say antenna switch as I hesitate to call such things coaxial switches. I prefer to think of them as ‘switches for coax’. A genuine coaxial switch is a slightly different animal that provides a constant impedance. That said, for most practical amateur radio use, unless you’re talking GHz bands a commonly available switch unit normally does the job ….…

Just as a quick recap, part 1 of this series provided the basic project overview and some advice on construction methods, PCBs, etc. Part 2 covered the construction details for the Variable Frequency Oscillator, or VFO. Part 3 covered the receiver side of the project. This part is only required if you are going to add the transmitter to your project; the circuit switches the antenna and 12V power from the receiver section to the transmitter section and back again. It also provides Receiver Independent Tuning (RIT) and sidetone so you can hear your own Morse Code when sending. Changeover module circuit description This module, block diagram in Fig. 1 and circuit diagram in Fig. 2, includes a sidetone circuit that means you can hear what you send. I find…

Welcome to the July HF Highlights. I was a little saddened to read the open letter issued on 25 April by Martin Jue K5FLU, the founder of well-known amateur radio manufacturer MFJ. In it Martin stated that after 52 years in the business he would be retiring and with effect from 17 May MFJ, along with its sister companies Ameritron, Hygain, Cushcraft, Mirage and Vectronics, would be closing its manufacturing facility in Mississippi. There can’t be many HF operators who haven’t used an MFJ product or perhaps a Hygain or Cushcraft antenna over the years. My first experience was with an MFJ ATU, which I bought from the then fledgling company nearly half a century ago. In those early days MFJ had a reputation for perhaps not the highest quality…

In the June issue of PW, I announced news of the release of the latest version of AN-SOF antenna simulator, namely AN-SOF DX. Tony at AN-SOF has kindly made available to me a fully working version of AN-SOF DX so I can bring a full review to PW readers; consequently, I have carried over my intended subject for this month to next month. AN-SOF DX is a fully featured electromagnetic antenna modelling simulator for Windows operating systems. This special version has been aimed specifically for use by radio amateurs, for noncommercial use, and offers a more affordable lower-tiered alternative to the Professional edition of the software with a 500/50/5 combination that is: Up to 500 Segments + Connections, up to 50 frequencies in a linear sweep and 5 degrees of…

Some years ago, I developed a ‘TuneAid’, an audio oscillator with a 20 second timer driving a tiny speaker (see URL below). I placed this little box near my SSB transceiver’s microphone to help me tune my antenna tuner. www.zl2pd.com/tuneaid.html I used to adjust the controls on my antenna tuner while whistling briefly into the microphone to generate a suitable signal for tuning, after delivering the essential voice station identification, of course! But one day, a really bad cold left me with a decided lack of ‘whistlepower’. Those who suffer from asthma can probably appreciate this problem all too well. The original TuneAid solved the problem. Rather than whistle, I just pressed the button on the TuneAid. It generated a loud and far from sinusoidal (!) tone around 700Hz for…

If you enjoy experimenting with the many types of SDR and supporting software, you will soon discover that much of the software uses Linux as the preferred operating system. This can be a major deterrent as most radio amateurs use Windows-based computers for their main stations. The other problem with a changeover to Linux is the relatively steep learning curve to get to a point where you can confidently compile and configure the software. However, a great solution was devised during the Covid pandemic. Known as DragonOS, the author (@cemaxecuter) has utilised the portability, security and power of the Lubuntu Linux distribution to create a suite of pre-installed SDR software and utilities. Close to 180 applications are pre-installed, so they should keep you interested for a while! This makes DragonOS…

First I must say thanks for all the emails, tips and QSL replies from experimenters who have followed my journey to try and improve their radiated signal and enable them to still enjoy the wonderful world of amateur radio. It’s not been easy and I have had great obstacles in my way and other problematic things that I have had to try and master, like living in a Faraday Cage! So I have had to try and re-adapt myself and antenna design to overcome these obstacles that I have inherited. I have been amazed at the prices that some companies and other sellers are asking for their magnetic loop antennas. Somehow I feel that I am in the wrong business (hi)! Seriously though, I was never very good at skin…

When I joined the BBC straight from college in 1963 my first posting was to the television outside broadcast base at the Palace of Arts in Wembley, opposite the old Wembley Stadium. No, it was not normal practice for BBC engineers to be offered palatial workshops – the building was actually a left-over from the 1924 exhibition, which had become surplus to the nation’s requirements. I soon learned on the grapevine that the BBC was putting out experimental colour TV transmissions after close-down from the nearby Lime Grove studios. With the self-confidence that comes from youth, I thought this merited further investigation and decided to see for myself. In those halcyon days, a BBC pass would get you into premises anywhere in the country, probably even with a little salute…

23 June NEWBURY RADIO RALLY: Newbury Showground, next to junction 13 of M4 motorway in Berkshire, RG18 9QZ This is the 35th year of The Newbury Radio Rally and is the ideal event for anyone interested in radio communications, computing and electronics. There will be a display area with an amateur radio station, exhibits, special interest groups, clubs and societies. Open to sellers at 08.00hr and visitors at 09.00hr. Massive Free parking. On-site catering. Disabled facilities. Entry is £3 visitor, £15 sellers pitch. ADVANCE BOOK-INGS (with discount) can be made via: www.nadars.org.uk/rally.asp Email: NewburyRally@nadars.org.uk www.nadars.org.uk 28-30 June HAMRADIO FRIEDRICHSHAFEN www.hamradio-friedrichshafen.com 30 June DUNSTABLE DOWNS ANNUAL CAR BOOT SALE: The Dunstable Downs Radio Club are holding their Annual National Amateur Radio Car Boot Sale at the usual venue, Stockwood Park in…

Latest news from Icom Icom report over 100,000 sales worldwide for their acclaimed IC-7300 HF transceiver since its launch in January 2016. The press release states, “From Day one, the 7300 etched a significant place in Icom’s amateur radio lineup boasting our ‘first-ever’ model with RF direct sampling system. This technology converts RF signals directly into digital data, which is then processed within the FPGA (Field-Programmable Gate Array). Using this clever approach the 7300 offers the perfect blend of high performance whilst using a simplified circuit design, all housed in an attractive, compact, and user-friendly end product. “Previously the domain of high-end models, the 7300 also boasts an integrated real-time spectrum scope and waterfall function, which considerably enhances receiver performance and maximises QSO opportunities. These features, coupled with its competitive…

Many readers will know the HRO range of receivers built by the US firm National. They produced many variations of the famous receiver with the rather odd looking main tuning control, which gave you numbers as you rotated it. You then had to look at a chart on the plug-in coil pack front, which had a graph of frequency verses numbers. This looks rather dated now with modern digital and SDR readouts but at the time, it was a rather clever way of doing things. With plug-in coil packs for each band they eliminated the need for complex band switching, which would have had a myriad of wires and contacts for the RF, mixer and oscillator coils, all prone to fail under constant use, not a good idea for a…

The main commentary for the Coronation Service on 2 June 1953, was provided by doyen television broadcaster, Richard Dimbleby, from a position high-up in the Triforium, Fig. 2. After the service, the unit outside the Abbey covered the departure of the various international Prime Ministers, the Colonial Rulers, Queen Elizabeth The Queen Mother, and Her Majesty The Queen together with HRH The Duke of Edinburgh. Viewers then saw the procession in all its splendour, initially from a high vantage point in Hyde Park where the commentators were Bernard Braden and Brian Johnston. Coverage concluded with the RAF fly-past and salute at the Victoria Memorial. Vintage coronation television equipment This month’s trip through vintage copies of uncared for newspapers and magazines has gleaned an advertisement by Ferranti for their Coronation 12in…

Worldwide shortwave contacts are based on diffraction (more precisely refraction and diffraction) of radio waves in the ionosphere. This is an area of the upper atmosphere in which solar energy in particular splits the gases into positive ions and free electrons. This ‘cold plasma’ then becomes conductive for radio waves. The mechanisms are already well researched. Since the 1940s, this has led to increasingly refined models that can be used to predict propagation for certain frequencies, over certain distances and at certain times and boundary conditions such as sunspot and geomagnetic activity. Since the advent of PCs and the release of models initially developed for the military, radio amateurs and shortwave listeners have also benefited from this science [1]. These are always so-called climatological forecasts, which, as with the weather,…

The best aurora in years was the considered opinion of many VHF operators who were able to take part in the aurora which occurred on the evening of Friday 10 May. Solar forecasts predicted that it was going to be a ‘big one’ but you never know until it arrives. Most parts of the country could see the aurora – for me it was a mesmerising sight! Auroral contacts were made on 40, 50, 70, 144 and 432MHz – I’m happy to be able to include details in some of the band reports this month. The majority of contacts appear to have been on CW with one or two stations trying out Q65C which seems to cope with auroral distortion. On 50MHz, where doppler shift is less than on 144MHz,…