Indholdsfortegnelse for May 2024 i Practical Wireless

I’ve tried and tested quite a wide range of portable, mobile and otherwise compact antenna kits in my time but never one quite like this. It arrived at Christmas but not quite in my stocking. I assumed it was yet another incarnation of the base-loaded whip idea from China. I was half right but had the country of origin wrong – it’s a neat idea from Taiwan. Neat is the word as the box contained seven well finished BNC terminated, very shiny black moulded coils approximately 1.8cm diameter and 8.5cm long from threaded shank to BNC tip. Six of the HF loading coils ranged from 2.63μH at 28MHz to 41.24μH at 7.00MHz. Each inductor designed and labelled for a single amateur band ranging from 10MHz - 50MHz. With a bit…

The first thing to do when investigating a source of QRM is to make sure your own station is clean. Switch off all of your household circuit breakers and using a battery powered receiver see if the noise is still there. If it is, then the offending device is not likely to be in your household although be aware of battery devices such as burglar alarms etc. If the noise disappears while your power is off, then switch each breaker back on, in turn, and see if/when the QRM returns. This should allow you to isolate what circuit the device(s) are on. Next, turn any items on the circuit on and off and hopefully the culprit may be found. An alternative approach would be to use something like a TinySA…

REVIEW – ALPHA DELTA ANTENNA SWITCHES: Richard Constantine G3UGF discusses antenna switch es and reviews the products from Alpha Delta. REVIEW – THE SDRPLAY RSP1B AND THE STAMPFL STRESSLESS: Georg Wiessala has been looking at a couple of interesting receivers. THE DIGITAL TUNEAID: Andrew Woodfield ZL2PD describes the construction of a Precise 1kHz Sinewave Test Oscillator. A 160 AND 60M ANTENNA FOR THE SMALL(ISH) GARDEN: Steve Telenius-Lowe PJ4DX describes the development of a 160m antenna suitable for a small plot (and it works on 60m too). BUILD A FIELD STRENGTH METER: Alpar Cseley HA8KT describes how to build a useful shack accessory. There are all your other regular columns too, including HF Highlights, World of VHF, Data Modes, Antennas, Book Reviews, What Next, The Morse Mode and Amateur Radio on…

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Kenwood first started building communications products in 1955 and entered the amateur radio market in 1958. Products were sold under both the ‘Kenwood’ and ‘Trio’ brand names. Their hybrid HF transceivers were popular from the mid-1970s to the 1980s and many are still in use today. Kenwood (Trio) also sold standalone receivers designed for the amateur radio and short-wave listener markets such as the early valve 9R-59RS, JR500 models and the later solid-state receivers such as the R600, R1000 and R5000. Many of these sets still command reasonable prices on the second-hand market. One Kenwood receiver that is less well known and about which there is limited information to be found on the internet, is the R-820, Fig. 1. It may be less well known because it was not in…

This project was introduced last month and we are starting the construction with the VFO as it is ‘the beating heart’ of any transceiver. “Why not use a crystal oscillator like the original?”, I hear you say. Well, crystal oscillators are very reliable but being stuck on one frequency can be hugely frustrating, especially when the station you want to work is just off that frequency. A VFO provides some frequency agility and so increases your chances of hearing other stations and making contacts. VFO circuit description The Rev. George Dobbs G3RJV used the same VFO circuit, or variations of it, in many of his projects over the years and often referred to it as his ‘Sunday Best’ VFO. This version uses the same circuit updated in that it uses…

This article will show you how you can make a single-band WSPR beacon with a power output of 10dBm, 0.01Watt, using the Arduino IDE, five components, and a phone charger power supply. The single band WSPR beacon only requires an ESP32 microprocessor, an si5351 function generator, a real time clock, a lowpass filter, and an OLED display but if your eyesight is like mine, you will also need a magnifying glass to read the display. Fig. 1 is a block diagram of the complete circuit, and yes, there are only seven wires plus the power. Total cost should be less than £50. Why Espressif ESP32? The ESP32 has built-in Wi-Fi to connect to your router and get to the internet. It is also very fast and has a lot of…

While I await the lovely 20°C of Scottish weather to appear (joke), I thought it best to put my time to good use and make that 145MHz lightweight portable Yagi that I need for some ARDF joy. I went into the shed where I keep the bits and bobs that I refuse to throw in the bin, or as my wife calls it, the junk pile. I pulled out some short lengths of 20mm diameter blue PVC pipe with end caps, an old tape measure and a strip of RG-58U coax that was left over from some homemade traps. These materials are the basis of the antenna that I decided to make and all of these parts can be seen in Fig. 1. I looked online and came across a…

In this article I am going to look at a professional fixed power supply and at a circuit to increase the utility of these supplies by adding a variable voltage option. The professional power supply This power supply, shown in Fig. 1, an Advance PMG-24-3 is still heavier than the semi-professional power supply I wrote about last month, weighing in at more than 5kg. The specifications are a fixed output voltage of 24V DC with a maximum continuous current supply of 3A. These 24V DC fixed power supplies are found in many industries where a 24V bus has been standardised and from which all other DC voltages are derived. These power supplies are built with high-quality components, large electrolytic capacitors, bridge rectifiers and the use of large external heatsinks. In…

What do antennas like the G5RV, folded dipoles, magnetic loops and the like have in common? They are all reminders of the undeniable fact that that the UK is a small country and that many of us have smaller gardens than we would really like in order to exploit our hobby to the full. But at a recent field day event I was delighted to meet Brian Hardy G4BIP who has no such problems, as the event took place on his farm-holding near Northampton where my eye was quickly drawn to an array that even included a lofty full-size top band dipole. When I learned that Brian’s wife Hilary held the call G0SOI and that their son Dan was M7DHR, I felt sure that readers might like to know more…

Perhaps the most significant news for all UK amateurs this month is the revised licence conditions announced by OFCOM on 21 February. From my perspective the changes are positive, Fig. 1. All licence holders are able to run more power than with their previous privileges. Although power is not everything, when you are looking at marginal paths, especially at VHF, good things happen when you are able to run more power. With Full licensees being able to run 1kW, this is good news for meteor scatter, EME and those really weak signals. Foundation and Intermediate licensees see their power limits increased to 25 and 100W respectively. This is really great news. One of my concerns with Foundation before was that a new licensee passed their exam, got their licence and…