Tabla de contenidos para April 2022 en Practical Wireless

Keylines Firstly, my thanks to those of you who congratulated me on having edited 100 issues of PW. If nothing else, it shows you read my editorials! It’s good to see that many rally organisers are biting the bullet and announcing events for this year. I am writing this on the day that the government has announced the ending of Covid restrictions, so hopefully even more organisers will feel confident in planning for events later in the year. While I realise that many radio amateurs are older and potentially vulnerable, many others of us consider that losing two years of events at our age is more than enough and it’s time to get out and about again! Weather In mid-February I had planned a 15m entry in the ARRL CW…

Data Modes More on SDR-Console Mike Richards G4WNC has a mixed bag of goodies for readers, but begins by finishing off the signal analysis tools in Simon Brown’s SDR-Console. Mike Richards G4WNC practicalwireless@warnersgroup.co.uk Last month I showed you how to make spectrum recordings as the first analysis stage. Once you have the recordings, SDR-Console’s powerful playback tools let you play back the spectrum so you can home-in on the area of interest. From that point, you can use the data editor tool to extract a narrower slice of the recorded spectrum. Not only does this make analysis more accessible, but it will significantly reduce the file size, so the next stage of analysis will be much quicker. With the smaller file, you can use the playback tool to loop over…

The World of VHF VHF/UHF Net Information Tim Kirby GW4VXE adds to the list of VHF/UHF nets as well as bringing readers the latest news from around the world. Tim Kirby GW4VXE longworthtim@gmail.com The PW initiative to help VHF/UHF activity by compiling a list of regular nets has really taken off this month. Thanks to everyone who has emailed with information. We now have a list of nearly 100 regular nets taking place on the VHF/UHF bands. Some of them happen every day, some of them might be once a month, but what is clear is that the VHF/UHF bands are being used widely on FM as well as on the digital modes. Rather than repeat last month’s list, Table 1 this month lists additional nets that I have become…

Feature Remote Manual HF ATU (Part I) Ken Ginn G8NDL describes the construction of a manual ATU that operates remotely. Ken Ginn G8NDL practicalwireless@warnersgroup.co.uk In an HF radio installation we have a choice as to where an antenna’s ATU (if used) can be sited, either in the shack or closer to the antenna. The best position for an Antenna Tuning Unit (ATU) is to have the ATU at the antenna end of the installation rather than being local to the radio in the shack. This offers the best solution where the feeder is matched all along the signal path to the ATU. Even when matched, a shack sited ATU will have a degree of mismatch from the ATU along the coaxial feeder to the complex impedances offered by the antenna.…

Valve and Vintage The Hallicrafters S20R Sky Champion Communications Receiver Philip Moss describes an elderly but interesting set from the USA. Philip Moss practicalwireless@warnersgroup.co.uk I bought this set, Fig. 1, from eBay, for £45 in 2012. Seeing at the time yet another ubiquitous DAC 90 was up for £51, I don’t think I did too badly. The radio was in OK but not wonderful condition. Probably the many honest caveats the seller put in the description put people off, including that it was probably for 110V, which was true. Much more about the transformer later. He also said the speaker cone was jammed. The pictures, which were in-focus, showed that it was not too bad, but some corrosion was visible and it would turn out that it had probably got…

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Feature Using the NanoVNA as an Antenna Analyser The NanoVNA costs a fraction of the amount of even the cheapest antenna analyser. Although it’s a bit fiddly to do so, Steve Telenius-Lowe PJ4DX explains how this diminutive device can be used to measure an antenna’s SWR. Steve Telenius-Lowe PJ4DX teleniuslowe@gmail.com I consider an antenna analyser (sometimes called an SWR analyser) to be an almost essential piece of test equipment for every amateur who likes to experiment (or just ‘mess about with’) antennas – and isn’t that all of us? I have owned a few such analysers over the years, starting with the trusty old MFJ-259, which I used for many years and which worked faultlessly until one day I dropped it from a not inconsiderable height on to a concrete…

HF Highlights Propagation Gets Better Steve Telenius-Lowe PJ4DX has plenty of HF news as band conditions continue to improve. Steve Telenius-Lowe PJ4DX teleniuslowe@gmail.com We are now seeing a definite upward trend in the solar flux and sunspot number month by month and, with them, a welcome improvement in propagation on the higher HF bands such as 24 and 28MHz. However, although several people have commented to me that “10 metres is wide open”, I would beg to differ. When 10m is ‘wide open’ we should be seeing both short path and long path openings from the UK into Hawaii and the South Pacific and that has not happened yet, despite more frequent openings to Australia and occasionally also to New Zealand. The solar flux was around 125 in early February…

Practical Building the VFO Board Mark Tuttle G0TMT moves this month on to the VFO board of the 40m transceiver project. Mark Tuttle G0TMT g0tmt@theshack.org.uk The VFO section is an amalgamation of quite a few designs; taking what I believed to be the best parts of each. The bulk of it was published by PA2OHH in his article entitled A Nice Rig (see first URL below), which in turn lifts ideas from the NE-QRP Club’s 40-40 rig. The expression ‘There’s nothing new under the sun’ springs to mind here. The latter was included in a publication entitled QRP Power, a great little book that is getting harder to find. I get the impression one of the forerunners using a similar layout is a well-known design called the 2N2/40+ by K8IQY…

Feature Fixed Frequency Operation In this fourth part, the author has a look at using the quadrature product detector (QPD) described in the January 2022 issue for fixed frequency operations. Dr Samuel Ritchie EI9FZB samuel.ritchie.8@gmail.com This article covers the one element shown in blue in the block diagram Fig. 1, that is the fixed frequency oscillator (FFO) used to tune to a specific frequency, or perhaps a limited number of spot frequencies. You may recall in the previous article that I advised it was good practice and often useful to include a bandpass filter (BPF) to attenuate strong out-ofband signals, which helps to prevent unwanted spurious responses at the output. However, the QPD is fairly robust and resistant to very strong out-of-band signals on its own merit. To demonstrate this…

News Newsdesk Have you got something to tell our readers about? If so, then email practicalwireless@warnersgroup.co.uk SOUTHERN FUSION: Phil Bridges G6DLJ reports that owners of Yaesu C4FM transceivers may be interested to learn of a new Wires-X room, Southern Fusion, currently room 41893. Focusing primarily on repeater and gateway users in Southern England and, of course, Wires-X users anywhere on the planet! At the time of writing RF access is available (by default) via a growing number of C4FM repeaters, including the donor repeater GB7IV (Southampton), GB7CM (Blandford), GB7IE (Plymouth), GB7TM (Ipswich) plus Gateways in Reading, Hastings and Ringwood with more joining every week. The room also hosts a regular Sunday morning one-hour net at 1100UTC, which all are encouraged to participate in. NEWS FROM JERSEY: Jersey Club President Rob…

Review RadioAnalog PTRX-9700 Sam Jewell G4DDK takes a look at an add-on board to allow a second receiver to be added to the IC-9700. Sam Jewell G4DDK practicalwireless@warnersgroup.co.uk When I reviewed the then-new IC-9700, back in the July 2019 issue of Practical Wireless, it was not clear how popular the new VHF/UHF transceiver would be. At close to £1800 it would have to offer a lot of value to prospective buyers. Subsequently sales seem to be doing well, judging from the number of people I have worked who use one. Without doubt the IC-9700 has some shortcomings in terms of RF performance and ‘missing’ facilities. This article describes one of the accessories I have used to enhance my own IC-9700. PTRX-9700 A second receiver, on the same band, with a…

Doing it by Design An 80m to 40m AM Receiver Eric Edwards GW8LJJ describes the build of a single conversion AM receiver for 80 through 40m. Eric Edwards GW8LJJ ericgw8ljj@outlook.com This is a single conversion (455kHz IF) receiver covering from 3MHz to 8MHz in one continuous tuning. It covers the 80m, 60m and 40m bands and all in between and a bit over on both sides so that interesting continental broadcast stations transmitting AM (Amplitude Modulation) on the ‘short wave band’ can be listened to. The main component is a car radio chip (integrated circuit) TDA1072A, and although considered obsolete I have a large stock for all that want to build this project. This integrated circuit (IC) contains all the circuitry from the bandpass filter (BPF) input to the audio…

What Next SSTV pictures from the ISS Colin introduces readers to Slow Scan Television and Satellites by showing how to receive SSTV pictures from the International Space Station. Colin Redwood G6MXL practicalwireless@warnersgroup.co.uk While there are several aspects of amateur radio that need to be brought together to receive SSTV pictures from the International Space Station (ISS), it certainly isn’t difficult, and neither does it require a lot of expensive equipment. If you have a way of receiving 2m FM signals and have a computer, then you are well on your way. The first aspect to consider is receiving SSTV pictures, and the second is Satellites. Subsequently, each of these can be pursued separately as you wish. What Is SSTV? The pictures that are transmitted from the ISS use Slow Scan…