Scratch-built 8-band HF SSB/CW transceiver (EI9GQ) – Part 2 – Receiver completion

There’s a reason why most homebrew transceiver kits and scratch-built projects are monoband and single mode — theres a chance you’ll finish it, or at least, get it working for a while. Building a multiband HF transceiver is a big job, as any homebrewer who has attempted it will tell you. It may take years.

20 meters, 200mW & 12,000 miles: WSPR magic!

Weak Signal Propagation Reporter is a global radio propagation monitoring and reporting network comprised of thousands of low power beacons operating on the amateur radio bands. WSPR beacons can be detected from the lowest of Medium Wave frequencies (137kHz) all the way through the HF spectrum (all the bands from 160m to 10m are popular) to the VHF bands, 50 and 144MHz. WSPR receivers decode the tiny beacon packets and upload them to a central database, at WSPRNet.org, where anyone can literally ‘see’ the propagation paths that are currently open.

40m AM Transmitter (120 watts, PWM/Class D)

This AM solid state Class D single band transmitter was assembled over a three year period. Started in 2018, it’s first configuration used a 100 watt push pull RF module published by Drew Diamond VK3XU in Amateur Radio magazine, modulated by a 200 watt linear power amplifier driving a reversed mains transformer, available as a kit from local supplier Jaycar. I built up the RF board, 50 volt power supply (using a stock 300VA toroids mains transformer, no regulator) and proceeded to destroy half a dozen power FETs (STW20NM50) in the RF power stage. Realising I didn’t really know what I was doing, I wisely put it aside.

SP-X, a pocket rig for the CW activator in a hurry!

I’ve long been interested in compact and fairly minimal SSB and CW rigs with good performance. I’m not into bells, whistles or menus. Menus are for restaurants! When hiking, walking or bouncing around summits I want to minimise things that are not absolutely necessary, things that can go wrong. Less is more when it comes to a transceiver for portable work.

Social distancing project #1: Lightweight Linked Dipole

The coronavirus has stopped just about everything, and is undoubtedly changing our lives forever. With almost every group or event cancelled, there are predictions of mass boredom and social isolation. Many people apparently have no idea what they’ll find to do with their time. How odd. That’s never been a problem for makers like me. So in the interests of the bored and isolated, I offer this story of something useful that can be made in an afternoon — a linked dipole.

200 watt Class D and Pulse Width Modulated AM Transmitter

This post wraps up a series describing the construction of a 200W Class D AM transmitter for 160m, built, tested and put on air over 6 months from August 2019. The transmitter consists of a digital PLL VFO and driver circuit, an Arduino controller, a microphone amplifier, a Pulse Width Modulator, two H-bridge Class D RF modules each capable of at least 100 watts of carrier, an RF power combiner, Low Pass Filter, a 300W power supply and a switching regulator. At the Australian legal limit of 120W carrier, all parts of the transmitter run cool due the use of switching designs. Previous posts describe the switching regulator, 300 watt DC power supply and dummy loads for this project.

QRP By The Bay, Chelsea Beach, Melbourne, Saturday 8th February 2020

QRP By The Bay is a regular meet-up of amateur radio operators, makers and experimenters , Chelsea Beach, Melbourne. On Saturday 8th February the weather was summery, a warm 28 degrees C, but windy, 35km/h blow from the south-east. A strong turn out resulted in lots of conversation, show-and-tell, and general story telling. The video shows some of the faces and activity. If you want to know more about any of the people or projects drop a comment below.

I was expecting Peter VK3YE to take his wade-tenna into the shallows for some pedestrian mobile contacts, but the wind made that option risky. No matter, there was plenty to see and discuss at the tables.

Thanks to Peter VK3YE for continuing this series of ‘eyeball’ QSOs, a now regular and much appreciated date on the amateur radio calendar in Melbourne.

8 Band Superhet AM Receiver

Amplitude Modulation holds a fascination for me. It dates back to those hours spent as a teenager listening to the big broadcast-like amateur AM stations in the 1970s and 80s, on 160, 80 and 40 meters. Signals that seemed as wide and loud as medium wave commercial broadcast stations, bearing sonorous, paced voices that projected a wealth of wisdom and experience, and in many cases, a grandfatherly manner. Back then, AM was known as ‘The Gentleman’s Mode’.

Two activators, two summits in the Yarra Ranges (25/10/2019)

On the 25th October 2019 I dragged David VK3KR out to the Yarra Ranges for some SOTA fun. The story is told by the video. Thanks to all chasers!

Microphone Compressor from 1978 lives again (ETI490)

Whilst sorting electronics junk recently I unearthed this board. My build of the Electronics Today International microphone compressor, ETI490, published in the magazine in December 1978. I remember preserving my copy of this magazine for many years, long after the pages faded and cover tattered, as it contained the construction article for this useful amateur radio station component.