Tag Archives: amateur radio

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’.

Continue reading
Tagged , , , ,

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!

Tagged , , , , , , ,

QRP By The Bay, Chelsea Beach, Melbourne, 2nd Nov 2019

QRPers at play.

QRP By The Bay was held again at Chelsea Beach on Saturday 2nd November 2019. A crowd of QRP, homebrew enthusiasts, and amateur radio knockabouts gathered on a wet and windy day, some with show-and-tell items, some obviously shy of bringing a full scale portable station on account of what the unpredictable weather might do.

Continue reading
Tagged , ,

Dummy loads for an AM PWM transmitter build

My Pulse Width Modulated AM transmitter project required dummy loads to match the load impedance of the RF power stage (50 ohms) and the Pulse Width Modulator (12 to 16 ohms). Surely any self-respecting amateur radio station would have a decent 50 ohm dummy load, I hear you ask incredulously. I do have one at VK3HN … or I did.

Continue reading
Tagged , , ,

A 300 Watt DC Power Supply for a QRO AM Transmitter

This post describes construction of a 300 watt DC power supply for use in a 150 watt Class D AM transmitter. The transmitter design calls for about 150 volts DC at 2 amps continuous and up to 4 amps peak. This post describes the 240v mains DC supply. The switch mode regulator is described in another post. The other modules in this QRO transmitter project are to follow.

Continue reading
Tagged , , , ,

A 300w switching regulator for a QRO AM transmitter power supply

Laurie VK3SJ is an accomplished RF designer and homebrewer in Melbourne’s 160m scene. You can hear his excellent AM signal regularly on the 160m AM Coffee Break net most weekdays. Laurie has spent a great deal of time experimenting with Class D, E and Pulse Width Modulators. He has an interesting Class D AM transmitter design with a pulse width modulator. Laurie’s design has been built by Wayne VK3ALK, who I met online in the Class E Forum on AMFone. After lots of emails and a few calls with these homebrew AM experts, I decided to proceed with my build of a VK3SJ AM transmitter for 160m.

Continue reading
Tagged , , , ,

A Pulse Width Modulator for the FAT5 160M Class E Transmitter

After a few months of operating my FAT5 160m AM Class E transmitter with its linear modulator, it was time to try Dave and Eric’s Pulse Width Modular module (PuWMa). This is a PWM using the Texas Instruments’ UCC25701 PWM chip, with TC4421 drivers and IRF640 switching FETs, followed by the obligatory Low Pass Filter to clean the 170kHz AC off the modulated DC.

Continue reading
Tagged , , ,

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.

Continue reading
Tagged , ,

160m 100W Class-E AM transmitter (FAT5)

The FAT5 project is a 100 watt Class E AM transmitter from Dave GW4GTE and Eric GW8LJJ, dating back to 2011. The name derives from Dave’s desire to design a 100 watt AM workhorse using contemporary FETs to rival the ubiquitous AT5, a widely used war surplus boat anchor for low band AM.

Continue reading

Tagged , , ,
The Free Range QRP DX-er

Home of the "Free Range 300 QRP Challenge"

VK1DA on the net

Amateur radio experiences with VK1DA

Tj Lab

信号処理とラジオ

WA2MZE

Amateur Radio and unrelated technologies

Paul Gacek

W6PNG/M0SNA

Radio Engineering Projects powered by DK7IH (Peter)

Projects for the radio draftsman. Hardware, software, electronics and test equipment for the radio designer

VK3KR Workshop

Homebrew electronics and a bit about a Tandoor oven

W3JDR Bright Ideas

For Ham Radio Experimenters

ZL4SAE

Amateur Radio and Stuff