Índice para July 2022 em Practical Wireless

gm6dx@outlook.com For years I have been reading in amateur radio magazines the various ways of creating PCB designs via homebrew means and although this was explained clearly, I wanted to create my own PCBs for amateur radio projects but I wanted them produced professionally as I never had the time nor material to fully homebrew my own PCB. I started to explore PCB designing and after some discussion with a friend, Ross MM0OBT, I downloaded a simple to use PCB design software known as Fritzing. Available at: https://fritzing.org/download or you can download a version from my one drive here: https://tinyurl.com/3xdf7dpe The software is very easy to use and allows you to export the finished design as a Gerber file type, which you then turn into a .zip file and upload…

samuel.ritchie.8@gmail.com This article covers the one element coloured red in Fig. 1, a direct digital synthesiser driven by a Microchip microcontroller. The two main requirements for this element were to provide coverage across 0.1 – 30MHz, and to control which of the eight bandpass filters (presented last month) is selected. It quickly became apparent that finding a kit or module to accomplish both of these functions would not be easy. While in the 1980s I had formally learned assembler programming, and had developed hardware and software around a number of imbedded controllers, this was my least favourite part of playing with electronics. In addition, my skills were decades out of date and I have zero enthusiasm for attempting to ascend the learning curve. However, in the February 2021 edition of…

practicalwireless@warnersgroup.co.uk Issue 1000 of PW back in 1990 had a supplement with several valve (tube) circuits including a crystal oscillator/power amplifier (COPA) transmitter. The valves were the directly heated type developed for early handy–talkies in WWII. Power output on 7MHz was a modest 500mW. Vacuum tubes were at the heart of early amateur radio and still have a certain enduring mystique. Lockdown gave me the chance to build two little valve transmitters. One was a ‘straight through’ COPA like the original PW design. With two 3A4 valves in parallel in the PA it ran about 1.5W on 80 and 40. However there was a tendency to ‘chirp’, a well-recognised problem when oscillator and PA tank are tuned to the same frequency. The second design, using half a 3A5 twin triode…

practicalwireless@warnersgroup.co.uk As Jeff approached the lab he noticed that the lights were already on. Unusual thought Jeff as he was normally the first in because he liked to consume a couple of cups of tea and have a read of either his newspaper or the latest issues of Practical Wireless or RadCom before starting work. As he entered the lab he saw that the lab’s apprentice Natalie had beaten him as the first arrival this morning. “Morning Natalie, what brings you in at this hour?” Jeff asked. “Oh, morning Jeff”, Natalie replied. “I came in early to have a quick look at the electronics reference books we have to see if there is anything about decibels in them”. “I see”, said Jeff, “Would this have anything to do with your…

Send your letters to: Practical Wireless Letters, Warners Group Publications plc West Street, Bourne, Lincs PE10 9PH E-mail: practicalwireless@warnersgroup.co.uk What is a Communications Receiver? Dear Don, I cannot agree with your definition of a Communications Receiver (hereafter Comms Rx), namely a facility to mute an associated transmitter. This in any event assumes that one only ever uses a Comms Rx in association with a transmitter. If I follow that, then the following Comms Rx sets known to me are not Comms Rxs. Marconi CR100/B28, Murphy CR150/B40, R107, Eddystone 734 and 770, and EC10, although the/2 at least has a spare pair of contacts on the standby switch that one can wire for the purpose, through a grommeted hole in the rear. R209, Hallicrafters S20R and S 38A. Redifon R50 and…

Regrettably, to offset the increases in costs of energy, raw materials and postage charges the cover price of Practical Wireless has increased to £5.49; but you don’t have to pay that!2022 We’ve frozen our subscription prices meaning you can save even more than before when subscribing to Practical Wireless! Take out a digital subscription today https://pktmags.com/pw-sub22 PREFER PAPER? Have the magazine posted direct to your door each month. To find our latest subscription offers please visit bit.ly/pw-sub22 or call 01778 395161 Telephone lines are open Monday to Friday 8am – 6pm and Saturdays 9am – 5pm…

practicalwireless@warnersgroup.co.uk If you ever find yourself working G4AEH on phone for the first time and think the voice sounds familiar, there’s a good reason. Its owner is Nuneaton-born Jim Lee, Fig. 1, who regularly modulates the BBC’s transmitters as a freelance continuity announcer and newsreader on BBC Radio 4 and the BBC World Service. Licensed since the age of 17, Jim told me that he has his mum to thank for his introduction to amateur radio. “As a teenager, I was a keen listener to pirate stations like Radio Caroline and my mum got fed up with my monopolising the family radio,” Jim recalls. “So, one day she came back from a church jumble sale and presented me with an enormous old valve radio.” Jim soon noticed to his delight…

teleniuslowe@gmail.com The solar flux peaked at 164 and the sunspot number at 119 on 22 April after which both declined somewhat. However, the trend is still upwards, as can be seen in Table 1 and solar cycle 25 is continuing to be higher than predicted for this stage of the cycle. Silent Keys Unfortunately, hardly a month goes by without news of well-known and respected radio amateurs becoming Silent Keys. Last month it was Zorro JH1AJT and this month comes news of two more SKs. Roger Western G3SXW became a silent key in April at the age of 75. A superb CW operator, Roger had taken part in numerous DXpeditions. He was a former President and was a Life Vice-President of FOC, the First Class CW Operators’ Club, and had…

Brickworks is an exciting and fun way to build on what you’ve learned while studying on your Foundation Course, returning to the hobby after a break, or wanting to explore new aspects of the hobby you’ve never experienced before – all in the friendly supportive environment of a Brickworks Accredited Club. It helps you build your confidence, expand your knowledge, gain a greater understanding of how to get the best out of your hobby, and enjoy new experiences. Brickworks – Why the Relaunch? Originally launched in 2020 as the ‘Beyond Exams Club Scheme’, Brickworks is a framework that clubs can use to support members as they explore different facets of the hobby. Unfortunately, soon after the launch, the pandemic resulted in clubs shutting down physical meetings and the amateur radio…

practicalwireless@warnersgroup.co.uk While sitting outside on these balmy summer evenings, imbibing in your favourite beverage, you’ve probably caught sight of the occasional bat flickering in your peripheral vision. Bear with me on this; I’ve not lost the plot as this will lead to a working example using Simon Brown’s SDR Console Data Analyser! These fascinating, protected, creatures can be found throughout the UK and are usually seen at twilight as they start their hunt for flying bugs. I have a particular interest in bats because my daughter is an environmental surveyor and has been specialising in bat habitats recently. She uses commercial monitoring kit to detect bat activity and identify the species. It seems you can identify the bat species by the frequency of the sonar pulses they use for navigation.…

A SMALL MAGNETIC LOOP FOR THE HF BANDS: Maurice Webb GW0UGQ describes a small magnetic loop suitable for use by those with restricted space. MOVING HOME AND A FRESH START WITH AMATEUR RADIO: In Part 1 of a new series, Richard White G6NFE recounts the trials and tribulations of starting afresh. THE MARCONI 2955 RADIO TEST SET: Gary Clark G0BKR takes a look at the Marconi 2955 Radio Communications Test Set. THE PW PASTON: Mark Tuttle G0TMT brings readers the final part of the build by adding the antenna changeover circuit. VALVE & VINTAGE: Philip Moss M0PBM takes a look at the once popular Eddystone EC-10 receiver. There are all your other regular columns too, including HF Highlights, World of VHF, PW at 90, The Morse Mode, Doing it by…

New from Nevada Radio Nevada Radio have announced that they now have the new Tecsun DEGEN DAB119x portable radio in stock. This radio covers DAB+, FM stereo (with RDS display), Medium Wave and Shortwave and features Bluetooth 4.0 capability. It will automatically tune and store stations into memory, has an alarm clock, date/time display and a built-in charging function. Shortwave coverage is from 2300kHz to 26100kHz with an extra-large LCD display to aid tuning and an external antenna input for DX reception. The Bluetooth 4.0 enables linking to other Bluetooth enabled devices for streaming music or other material through the radio. The radio can be charged from the included mains charger or through its USB socket. It will sell for £139.95 and is available from UK Distributors Nevada Radio: www.nevadaradio.co.uk…

michael@internalfire.org One piece of equipment coveted by radio amateurs is the Spectrum Analyser. Until recently these would be laboratory grade instruments which would set you back £1000s. You would have needed deep pockets even for a second-hand one. I have had long term plans to build one, but other more pressing projects have kept it on the back burner. However, prices of small spectrum analysers on eBay, among other sites, are falling, RF explorer has been around for a while now, but at £200+ it is still out of my price range. Others take the form of an add-on for a PC and are not unreasonably priced (£60 to £80), but the lowest frequency of operation is about 35MHz, which is no use for HF measurements. Relatively new on the…

Longworthtim@gmail.com I’ve mentioned digital hotspots in the past, but in the last few weeks, I’ve had the opportunity to try an ‘analogue hotspot’ in the shape of an Allstar node. This is a box that contains a Raspberry Pi, a soundcard, a power supply and a Baofeng radio. It connects to your internet router by Wi-Fi or wired Ethernet connection. Once you have set up an account on the Allstar network, you can create a node on the network and use these credentials on your Allstar node. I used the ‘Microhub’ built by Peter G7RPG, Fig. 1, and the process couldn’t have been more painless, it was literally a question of plugging it in to 12V, tuning a 70cm FM handheld to the frequency of the hotspot and off you…

practicalwireless@warnersgroup.co.uk Antenna characteristics and radiowave propagation are inexorably linked, one way or another, at all frequencies. This applies to terrestrial, or earth space based or indeed spaced based applications such as the Webb antenna introduced in a previous part of this series. Especially and including microwave, millimetrewave and terahertz bands which are all addressed, albeit briefly, here. There are ways to do antenna modelling cheaply, yet thoroughly, compared to current commercial EM software products of which there are several [1] and they can run to £30k+ software just for rentals, then you need to become an expert to effectively use them. However, it is true to say that we are only at the beginning of the widespread application of these EM tools, which offer much potential. The characteristics to be…

g0tmt@theshack.org.uk In the last part we finished the receiver board and with it coupled to the audio board we built in Part 2 we should have a working receiver. Now we turn our attention to the companion transmitter board that, in my rig at least, is mounted directly above the receiver board. It’s the same physical size, 100mm x 75mm. In my rig this board not only houses the transmitter but also the antenna changeover circuit. In this penultimate part I’m going to cover just the transmitter circuit. I’ll cover the antenna changeover in the final part. However, there’s no reason why it can’t be built on a separate board if you prefer and have space. The Transmit Mixer As usual, let’s follow the circuit diagram, Fig. 1. The first…