Índice para June 2022 em Practical Wireless

Another month gone by! And I’ve actually been to a couple of gatherings – quite a change after all those lockdowns! The first was a belated centenary dinner for my old University Wireless Society (G6UW, Cambridge), a very pleasant gathering where it was encouraging to meet some of the present crop of undergraduates as well as old lags such as myself. The second was the GMDX Convention in Stirling, well attended and with some excellent talks although the main pleasure was actually meeting old friends in person and sitting down to the evening dinner with many of them. And there are quite a few more in-person events to look forward to over the coming months as ‘normal’ life continues to resume. Radials Update A few months ago (in my March…

The Sharman MD-3500 Slider 80-6m (3.5-50MHz) Mobile Antenna is a complete antenna with simple slide tuning giving coverage of all bands 80 through to 6m. The MD-3500 is an excellent choice for temporary field operations. Frequency: 3.5-30/50MHz Band Max. Power Rating: 130W (SSB) Impedance: 50Ω Length: approx. 2.6m (max.) Connector: PL259 Type: 1/4 wave reduced type (HF Band), 1/4 wave (50MHz) The antenna uses a PL259 mount so you can use this on your existing car mount. Resonance is achieved by sliding the antenna for minimum SWR. https://tinyurl.com/4avn37ct Also, the Sharman HLP-270 Dual Band (2 & 70) Halo Antenna, a ‘Super Light-weight Half Wave Dipole Square Loop Antenna’. Mounted horizontally Frequency: 140 – 150, 400 - 470MHz Gain: 4dB(VHF) /5dB(UHF) VSWR: 1.5 Max. Power: 800W Impedance: 50Ω Weight: 0.36kg Connector:…

practicalwireless@warnersgroup.co.uk CTCSS is used in many analogue two-way VHF and UHF FM radio systems all around the world. A continuous low-level tone in the range of 67.0 – 254.1Hz is mixed with audible 300 – 3000Hz speech when transmitting. This CTCSS tone is detected by a matching CTCSS decoder in the repeater or transceiver receiver. This ‘unsquelches’ or unmutes the receiver, allowing users listening to the receiver to hear the speech. A highpass filter in the decoder ensures the CTCSS tone remains inaudible to users. The use of CTCSS can reduce interference, increase frequency utilisation, and expand radio services. For example, CTCSS can permit shared voice and data use of a repeater, ensuring voice users avoid hearing any data transmissions. CTCSS was first developed during the latter half of last…

samuel.ritchie.8@gmail.com This article covers two elements shown in red in the block diagram, Fig. 1. The first is a module that provides some protection to the front end, an attenuator and a preamplifier. Second is a switchable bandpass filter (BPF) arrangement, and the manner in which it is drawn reflects that the bandpass filter needs to be inserted after the protection and attenuator, but before the preamplifier. In my implementation, the protection, attenuator and preamp are in one enclosure, and the BPF is in a separate enclosure. This reflects the development of each module as a standalone item. Protection The schematic of my protection circuit is given in Fig. 2. When the receiver is not switched on, relay K1 is not energised, and the input passes through C1 and then…

practicalwireless@warnersgroup.co.uk In my view, the general coverage receiver is the heart of a good shack, but for many, especially in recent years, I believe that is not so much the case. When I first became interested in radio, it was as a Short Wave Listener (SWL). I was 13 years old and on holiday at my Great Aunt’s in Suffolk. She had an old Pye domestic radio, which I still own, Fig. 1, and I spent many evenings with a length of scrap wire in the antenna socket, tuning around the SW broadcast bands amazed at what I could hear. As I tuned around I was entranced with Radio Sweden, Voice of America, HCJB, Swiss Radio International and many others. In short, I was hooked. I guess many of us…

practicalwireless@warnersgroup.co.uk Before looking at the 6m (50MHz) band, I thought it would be a good idea to introduce readers to Sporadic E propagation. Every year amateurs in the northern hemisphere are blessed with some enhanced propagation known as Sporadic E. This rather erratic enhancement can result in much stronger signals and better propagation than is usually encountered at sunspot minimum on the 10m, 6m and 4m bands. A previously dead band can suddenly become alive with strong signals from distant stations. Occasionally the enhancement can extend as high as the broadcast FM band II frequencies and even up to the 2m (144MHz) band. Most years the Sporadic E season runs from about mid-May to early August. With this in mind, I thought it would be timely to look at the…

practicalwireless@warnersgroup.co.uk Regular readers will know that I am a bit of a Xiegu fan. I already own the G90 and X5105 radios and have also reviewed the G1M. I was delighted, therefore, when Alan at Sinotel asked if I would like to review the latest offering. It was nice to see that when the rig arrived, Xiegu have updated their packaging, giving a more professional appearance, and there was a proper printed manual to get you started. The rig comes with a fist microphone, allowing quite a few operations to be performed from it, a USBto-USB C cable, a dedicated mains charger (but the two-pin European variety and no adapter) and a power cord. The rig itself, Fig. 1, is of a very similar size and weight to the existing…

practicalwireless@warnersgroup.co.uk Last month I looked at tropo and meteor scatter modes, so this time I’ll move on to what is one of the most significant VHF propagation modes for the summer months, Sporadic E. This propagation mode occurs in the E layer of the ionosphere, which extends from approximately 90-160km above the Earth’s surface. Sporadic E is commonly known as Es and occurs in three distinct areas, which are: Auroral, Equatorial and Mid-latitude, Fig. 1. Auroral Es are caused by additional electrons being injected into the E layer as they follow the earth’s magnetic field lines into the polar regions. This form of Es tends to be at its peak in the early hours of the morning and supports transpolar contacts. Equatorial Es occurs due to plasma instabilities in the…

practicalwireless@warnersgroup.co.uk The particular radio I describe here is in the collection of the British Vintage Wireless & Television Museum, Dulwich. The KW201 was specifically intended for amateurs using SSB, but also catered for CW and AM. I think it fair to say that in the sixties SSB was still more a coming than fully arrived mode, so the KW 201 and other KW sets were ahead of their time. Britain was slow to adopt SSB despite the fact it was a British invention in about 1929. It was developed by Rediffusion, not for conventional broadcast but for power-line transmission of radio, to consumers. The idea was that the listener could have a simpler radio, by using signals sent along power lines, and it would be possible to get more signals…

roger@g3ldi.co.uk I have had quite a bit of feedback on the subject of Morse protocols and as suggested in my last column; I shall be presenting the code without calling procedural signals ‘prosigns’ in a future update to my book. I am not sure when the next version of Morse Code for Radio Amateurs will be published or even if it will be published, so my revisions may not appear in the next version, the text for which has already been accepted. Signalling Lamps Don’s picture last time created quite a stir! It seems that there were quite a number of people involved in sending ‘visual’ Morse so this month has been devoted to the feedback I had. Paul G3VPT, who lives locally to me, sent a picture of a…

ericgw8ljj@outlook.com This is a fun to build and use, very sensitive receiver for the serious builder. It is a regenerative receiver that uses a different method to create the regeneration of the received input signal compared with what is normally used. It uses commonly available transistors, and is a complete receiver with all the parts from the antenna preamplifier to the loudspeaker (LS) audio amplifier fitted on a single PCB. The Circuit The circuit is shown in Fig. 1. All the controls are fitted on a custom-made PCB to avoid any ‘flying’ leads that can cause instability and frequency variations. It is intended to operate from a regulated 12V power supply with about 500mA current capability as the circuit consumes an average of around 200mA, but more than 300mA with…

practicalwireless@warnersgroup.co.uk Over the last few years I have enjoyed renovating old communication receivers. There has been quite a lot of information recently in PW about Eddystone Receivers and I have renovated several of my own. Not long ago I acquired an Eddystone EB35 receiver, Fig. 1. This is a broadcast receiver meant for the domestic radio market rather than a communication receiver. One big difference between the two types being that broadcast receivers are for receiving AM or FM transmissions and communications receivers for AM, CW and SSB. Older communications receivers were fitted with a ‘Beat Frequency Oscillator’ or BFO, which is used to resolve CW and later, SSB transmissions. Broadcast receivers such as the EB35 do not have a BFO fitted, making it difficult to listen to CW or…

TRANSATLANTIC TESTS: The RSGB and ARRL have been celebrating the centenary of the Transatlantic Tests. The Society has just released a video that highlights the fantastic exhibition put on by the National Heritage Centre in Saltcoats, the 1921 message re-enactment by the Kilmarnock and Loudoun Amateur Radio Club and also the 160m Transatlantic QSO Party: www.youtube.com/watch?v=L1Ww7QDwDI4 EMF HELP VIDEO: The RSGB has recently published a very short video outlining the new EMF regulations and the help/tools the RSGB provides for radio amateurs. https://youtu.be/pbslKR_NEpM RSGB ANNOUNCES FURTHER DETAILS OF JUBILEE GB70 SES: As part of the forthcoming Jubilee celebrations, the RSGB has announced further details of its GB70 special event station activities. The seven SES callsigns will be active across the Jubilee weekend, from 2-5 June, on multiple bands and modes. After…

Nevada Radio have announced a new Digital Audio Filter from XIEGU. The XIEGU GNR1 incorporates both Audio Digital noise reduction and Audio digital filtering. It will effectively reduce background noise, improve signal-to-noise ratio and make received voice transmissions more clear and intelligible. The unit will work with both HF and VHF/UHF radios to give a big improvement in reception. The Filter has independent adjustments of both input and output levels to work with headphones or an external speaker, giving up to 3W audio output. The XIEGU XRN1 sells for £229.95 and is available from UK importers Nevada: www.nevadaradio.co.uk or Waters& Stanton: www.hamradiostore.co.uk…

practicalwireless@warnersgroup.co.uk The popular Practical Wireless 144MHz QRP Contest is the ideal way for newcomers to the VHF bands and contesting to get a good feel for many aspects of amateur radio contests. It is an excellent way to experience the thrill of making contacts over many km on the 2m band. Power The power limit will again be 5 Watts at the transmitter so that participants with all types of UK licence can participate equally. Equipment The only equipment you’ll need is a low-power 2m transceiver and an antenna. While you can expect to make some contacts with a basic 2m FM handheld transceiver, most of the activity is likely to take place using single sideband (SSB). Most stations use horizontally polarised Yagi antennas when operating on SSB or CW.…

Longworthtim@gmail.com Last month I mentioned that some interesting QSOs were being made on 50MHz using Trans Equatorial Propagation, not only from the Mediterranean but from Eire. Mark EI3KD has continued to make some great contacts into South America. On the evening of 4 April there was a really excellent opening when Mark made 58 QSOs into South America, including two new DXCCs, ZP and CX. It wasn’t only well-equipped stations making contacts either. Here at GW4VXE I came up to the shack to see if anything was happening and was surprised to see LU5FF and CX6DRA on my screen at decent strength. I was really excited to work LU5FF, LU8GMM, ZP9HTL and PY5BW while running 100W to my vertical antenna. Clearly, I was in the right place at the right…

CAISTER MARCONI RADIO STATION CON-TACTS MORE THAN 160 AMATEURS IN 25 COUNTRIES: Radio amateurs at Caister Lifeboat in Norfolk managed 162 contact in 25 different countries on Saturday 23 April when they took part in the annual International Marconi Day (IMD) event to mark the inventor’s birthday. Using the call GB0CMS and a mixture of Morse code, telephony and data (FT8), contacts were made with other radio amateurs across the UK, Europe, the USA, Canada and Australia. Notable contacts were made with other IMD stations in Newhaven, East Sussex and Chelmsford – the home of Marconi’s original factory. Other long-distance contacts were made with Ian VK3MO near Melbourne in Victoria, Australia and John VK6WC in Chidlow, Western Australia. The Norfolk Amateur Radio Club (NARC) ran the all-day special event station…

g0tmt@theshack.org.uk In the last part we followed the signal path from the antenna through to the product detector. The differential output of this stage resulted in a low-level audio signal. We now need to do a little work on this signal before we can put it into the audio amplifier we built at the start of the series. We’re also going to use the audio level to automatically adjust the incoming signal. So, let’s make a start describing the audio chain circuits, see Fig. 1. Audio Limiter The first few stages of the audio chain are taken from a great little book called QRP Power, an ARRL publication, which is getting a bit difficult to find these days. The circuit is featured in a design from QST magazine, November 1994…

geofftheasby@gmail.com The first suggestion describes a simple, resistive SWR meter, which is not frequency conscious, in that no tuned lines or pickup loops need to be fabricated or etched, but which is good up to 30MHz. This was described by G3ROO and G4WIF, and originally appeared in the G-QRP Club magazine Sprat. A sensitive meter is not required, I tried several up to 1mA full scale deflection. The circuit was first built ‘in mid-air’ to prove my construction and component values, Fig. 1, then rebuilt on 0.15in Veroboard, Fig. 2. It works like a charm! www.gqrp.com/resistive_swr_bridge.pdf The second returns to the original theme of these occasional articles, being a ready-built module, Fig. 3, available from the usual suspects for about £7 (£7.79 from Banggood at the time of writing – Ed).…

Send your letters to: Practical Wireless Letters, Warners Group Publications plc West Street, Bourne, Lincs PE10 9PH E-mail: practicalwireless@warnersgroup.co.uk What a Treat Dear Don, Well, what a treat this month’s (May 2022) PW was. Something for almost everyone. Microwave, millimetre wave and terahertz antennas, a nostalgic trip down ‘The Panda Cub’ road, Valve Radio Repair, the machinations of Jodrell Bank and last but not least, construction projects. And of course, no ham magazine would be complete without rig reviews. This time, a D-STAR handheld but this one has got a ‘waterfall’ display. I wondered how long this innovation would take to migrate from an HF rig to something you can caress in your hand. Yes, it is indeed the VOA 80th Anniversary as commented on by Steve PJ4DX. And no…