Indholdsfortegnelse for May 2022 i Practical Wireless

The IC-705 has probably spawned more rig accessories than most radios in the last 20 years. ML&S think this one, the 705 Meter, is the most exciting though! Mode Filter settings Real-time display of operating frequency SWR, Real Power or S-Meter, in both text & a Needle on the usual radio-style scale. • For more information see: HamRadio.co.uk/705Meter The DigiRig Mobile is a tiny new digital modes interface that: combines audio codec, serial CAT interface and PTT switch supports full featured CAT interface: PTT, bands, tuning etc. (not just VOX based PTT) uses a single USB connection to computer minimising the cables mess serial computer aided transceiver (CAT) port can be configured for logic levels, RS-232, CI-V or TX-500 works with all major OS flavours: Windows, MacOS and Linux permanently…

practicalwireless@warnersgroup.co.uk The master unit is constructed with a commercially made case purchased from RS Components, Figs. 1 and 2. A supporting plate made from 1.5mm aluminium sheet was attached to the lower part of the case to support the main components in the master unit. The bias tee PCB is mounted on the rear panel, Fig. 3, as is the IEC mains socket with integrated switch and mains fuse. The bias tee PCB was used initially to mark out the position of the holes on the back panel for the RF sockets and mounting screws. The bias tee PCB is mounted away from the back panel with brass threaded spacers as is the RF switch board in the remote unit. Decoupling capacitors (C1, 2, 3 and 4) are mounted directly…

samuel.ritchie.8@gmail.com For a number of years, I used a Drake-2B receiver with the Q-multiplier option. The receiver was limited to the reception of 12 band segments, each of 600kHz. These segments were selected by switching between 12 crystals. Before you touched the tuning knob you would select the band via a bandswitch, adjust the preselector for maximum noise, then use the tuning knob to look for signals. When you heard a signal, you peaked the preselector for maximum signal. In this fifth part I look at using the quadrature product detector (QPD) described in the January 2022 issue with a preselector and a variable frequency oscillator (VFO) to provide continuous coverage of 3.3 – 30MHz. If you have built the QPD, or are intending to do so and perhaps have…

practicalwireless@warnersgroup.co.uk In this 21st century introductory microwave series the centrally most important component to discuss and consider, in depth, is the antenna. As with all RF systems from gamma rays to LF HF radio, radar, submarine, and any form of radio communications, receive and transmit, the antenna governs the overall performance, hence what is possible. A splendid, currently relevant, and extremely expensive place to start, by example, is with the recently launched James Webb ‘space telescope’ illustrated in Fig. 1. Let us call it more accurately, a large mechanically adaptable and adjustable reflector Terahertz antenna and receiver. Not exactly a Practical Wireless feasible project, taking 30 years to develop, several billions (~$10B), very many people, a huge powerful and highly sophisticated rocket launcher plus a wideband telemetry communications system from…

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practicalwireless@warnersgroup.co.uk Do you ever get to use both your hands just for holding your soldering iron and the thread of solder when building something? Most don’t. It’s commonplace for vendors at rallies or elsewhere to have the inexpensive lightweight metal stands with two alligator clips and a magnifying glass for sale. They work. But they tip over with any heavy object and can easily break if dropped on a hard surface such as a cement floor. They don’t function at all for SMD work, a growing part of kit-building and circuit board design. Surprisingly to many purchasers, you need more than a couple of extra ‘hands’ to get multiple parts and pieces together for connection by solder. Don’t sneeze or turn on a fan as Michael Jones GW7BBY’s article in…

teleniuslowe@gmail.com Propagation continues to improve, albeit slowly and there have been some poor days. The sun was fairly quiet most of February with the Solar Flux Index (SFI) hovering around the 100 mark. The Sunspot Number (SN) dropped to only 23 by 25 February before picking up again. By 11 March it was 90, still down on six months ago but up on the figure for March 2021 (see Table 1). Ukraine Amateur Radio Ban Due to the invasion by Russia, the whole of Ukraine with the exception of the Donetsk and Luhansk regions was put under a state of emergency on 24 February. One of the provisions was a ban on amateur radio transmissions. The state of emergency was due to last for 30 days initially. A few Ukrainian…

g0tmt@theshack.org.uk In this part I’ll walk you through the RF chain of the receiver, giving my sources as I go and hopefully an explanation as to how each key ‘module’ works. So, as always we’ll be studying the circuit diagram as we go, Fig. 1. By the way, the components list is for the whole receiver board, although I won’t be cover the audio stages until next time. Power Supply In the top left is U1, a common-all-garden 8V regulator IC. The NE602/SA612 mixer chip we’re going to use doesn’t like a supply voltage of much more than that and it also helps to have things nice and smooth. I fitted my regulator on the receiver board. An alternative approach would be to build a little power supply board. We’re…

teleniuslowe@gmail.com As regular readers of PW will know, I am primarily an HF operator. The summer 6m Sporadic E (Es) ‘season’ coincides with the period when I usually visit family and friends in the UK and Europe and therefore, I had never paid much attention to the 6m (50MHz) band. However, Covid meant I was unable to travel during the summer of 2020 so I tried some SSB and CW on 6m, with what could best be described as ‘limited’ success. At the end of the year, though, I started to use FT8 on HF and, still unable to travel in May-June 2021, then also on 6m. Love it or loathe it, FT8 is where (nearly) all the DX activity is on 6m these days (even more so than on…

practicalwireless@warnersgroup.co.uk Spring is in the air, and it’s time to get ready for some of the enhanced propagation conditions we will be experiencing. In this month’s column, I’ll be looking at how we can use specialist data modes to make the most of these conditions. Let’s start by looking at a couple of propagation modes you may not have tried. Tropospheric Scatter Propagation Conventional radio links on the VHF and higher frequencies are usually considered effective only for line-of-sight operations. However, another propagation mode can provide reliable communications over much longer routes. That mode is tropospheric scatter or troposcatter and has often been used for long-distance UHF and microwave radio links. Let me just briefly explain how troposcatter propagation works. I’ve illustrated the process in Fig. 1. The troposphere is…

practicalwireless@warnersgroup.co.uk How do you define ‘DX’? If you are a novice, operating QRP under poor conditions, a successful contact at the other end of the country might well qualify. If you’re a seasoned amateur with a 400W linear, you’d be disappointed not to reach the antipodes on a good day. But, as we shall see, it’s entirely possible to have a contact over 230,000 miles away – if you are Ian Morison G0DMU and can draw upon the resources of the mighty Jodrell Bank radio telescope. Ian, who was brought up near Bognor Regis, had a traditional start in amateur radio, building crystal sets and in due course his first one-valve receiver. As a schoolboy, he joined the Combined Cadet Force and encountered for the first time the famous Wireless…

bgtaylor@ieee.org For over 50 years, SSB has proved the dominant mode for analogue phone communication on the HF bands. So much so that young SWLs could be forgiven for believing that the ‘communications speech quality’ resulting from audio pre-emphasis, brick-wall sideband filters, digital dynamic pre-distortion and range compression, envelope power overshoot (and often a slightly mistuned carrier insertion oscillator) is an unavoidable shortcoming of contacts by amateur radio. SSB is undoubtedly an efficient voice mode for clocking up DXCC countries and winning phone contests in difficult conditions on crowded wavelengths. But at times when the bands are quiet and propagation is good, the richer and more natural audio quality of older AM rigs incites warmer, longer and more memorable ragchews. Many radio amateurs first discovered the hobby when they accidentally…

military1944@aol.com Carrying on from my first part about repairing old valved radios, about getting some tools together, some test equipment items and finding a nice warm, brightly lit place to work we can now look at valves and start with power supplies. Safety A quick reminder. Safety at all times. You may well have invested in an isolation transformer. Another useful item is an RCD. This is another device that can add a factor of safety to your workshop. Many people have plug-in units inserted in the wall socket into which they then plug their lawnmower and such and cost just a few pounds online. A residual-current device (RCD), or residual-current circuit breaker (RCCB), is a safety device that quickly breaks an electrical circuit to protect equipment and to reduce…