Andy Fletcher Old Homebrew Projects
Here are some notes on some home-brew projects I have done, roughly in chronological order. There is nothing new here, just projects I’ve enjoyed doing. All comments are welcome. At school I was the despair of my woodwork and metalwork teachers, and my talents in making holes in boxes have not improved over the decades. They are usually not in the place I wanted them to be. At least I seem to be able to make round holes of the correct size. Rectangular holes are another matter. I show my projects for interest rather than attempting to inspire praise.
- Medium Wave receiver, using a 1L4 pentode valve – and a 69 V battery!
- Audio Processor, mostly op amps.
- C. M. Howes 20m DCRX – a direct conversion receiver kit.
- Crystal Calibrator
- A 2m to 10m Receive Converter
- 40m CW Transmitter
- RF Sampler and AM Demodulator – as described by Alan, W2AEW in his YouTube video. I recommend his videos. He has a way of explaining designs that makes them clear and easy to understand. I boxed this up using a sweetie tin (Mixed Fruit Drops for the curious).
- AM Modulator– simply to test the AM Demodulator
- RF Sniffer
- Inductance tester – to measure home-brewed inductances. This is based on the tester in section 25.8.3 of the ARRL 2013 Handbook. I didn’t bother with the internal meter, using an oscilloscope instead.
- 40m Low Pass Filter
- CWKtiny keyer from WiMo Antennen und Elektronik GmbH. This is just boxed up with an idiot diode on the power connection and 33 ohm resistors on the key inputs. I use this with my Bencher key.
- SDR Mixer – used with the Gqrx application to display HF signals in the frequency domain. The main part is a RealTek RTL2838-based dongle. As the dongle only handles from 24 MHz up, the HF signal is up-converted using a 100MHz oscillator and a diode ring mixer. Based on Alan’s video. Boxed up in a Glenfiddich whisky miniature tin. I’ll probably get back to this and add an LNA to the input.
- A ramp generator to drive the sweep input of my TG120 function generator.
- An Aerial Analyser
- An audio Frequency Doubler
- A Hellschreiber Modem
- An Internet Radio based on a Raspberry Pi and the audio stages of an old DAB radio
- An AD9851-based VFO
- A CW Decoder based on the Goertzel algorithm running on an Arduino
- An FT60 PTT Circuit for connecting an FT–60 VHF/UHF transceiver to a Raspberry Pi 3B+ acting as a TNC
- Keeping a old MacBook Pro going by using OpenBSD
- A failed attempt to make a PSK Modem on breadboard
I use the commercial test gear listed here.
The components and other hardware to make these projects were bought mostly at