Category Archives: Arduino

Homebrew 50 watt amplifier for 80-17m (W6JL)

Don W6JL’s 50 watt FET amplifier is a popular afterburner for FT817s and other QRP rigs and exciters. Don won the QST Homebrew contest in 2009 with this design. The amp offers a useful order of magnitude (12dB) power lift over QRP levels, and apart from the power FETs can be built from an averagely stocked junk box. The FETs are commonplace and cheap — they can be bought for as little as 98c each!

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A compact Arduino, si5351 VFO with Keyer and OLED display

The remarkable compact transceivers of Peter DK7IH inspired me to dream up a compact transceiver of my own. This project would be an experiment on a shirt-pocket scale — not as dense as some of Peter’s rigs, but small on my scale. Starting with the PLL VFO/controller along the familiar lines of Raduino (Arduino Nano and si5351), I sketched out a physical design, and it became clear that the display choice would dictate the size of this module. Where small displays are concerned, there’s only one option … OLED.

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A scratchbuilt G6LBQ BiTx ‘Walkie-Talkie’ for 40 and 20m SSB/CW

After completing a 6-band SSB/CW QRP transceiver (Summit Prowler IV) I found myself thinking about a more compact QRP SSB/CW rig for SOTA, with two of the main day-time SOTA HF bands (40/20m). The design driver this time was to try a different ‘form factor’ — I wanted a rig with a narrow and long case, such that it would easily slide inside a backpack, and on a summit sit vertically against a rock or be hand held. All my SOTA rigs so far use both front and back panels for connections and controls, so they need to sit level on a horizontal surface. As most rocks or tree stumps are low, you can’t easily read the display. Some designers get around this by putting the display on the top of the box, a sensible adaptation but one that makes the rig look like a flounder. Because I spend a lot of time building and using these radios at home on the shack bench as well as on a summit, I wanted a design for use in both situations.

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Scratch-built 8-band HF/6m transceiver (EI9GQ) – Part 1 Receiver

Eamon EI9GQ’s book (‘Building a Transceiver’, RSGB 2018) started me down the path of another modular transceiver project. For this build I wanted to continue working with surface mount but without the compulsion to pack it all in tight. More space and the freedom to replace a module later. It would be a Shack Sloth rig (a base station), not a Summit Prowler, so the space, weight and power budget shackles fell off from the start.

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Arduino GPS experiment for SOTA

How could a GPS unit integrated with a SOTA transceiver assist in activations? I’ve been turning that thought over for a while now after seeing David VK5KK’s GPS and Arduino based grid square locator (posted to the ‘VK Homebrew’ group on facebook).   The ready availability of cheap GPS units with a simple serial interface makes the option straight-forward.  As my homebrew rigs are using Arduino Nanos and si5351 breakout boards, the GPS is just another (serial) attachment.

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‘Summit Prowler IV’ — Homebrew 160m to 17m QRP SSB/CW transceiver for portable and SOTA use

‘Summit Prowler IV’ is a scratch-built six-band SSB and CW transceiver, designed for portable and SOTA activations. It is based on Leon VK2DOB’s MST3 (Minimal Sideband Transceiver, third version) from 2016, with alterations to support multiple bands, my Arduino-based digital VFO/controller and keyer, and a few extras to support portable operating. The transceiver is a conventional single-conversion superhet with 12MHz IF and an si5351 and Arduino Nano-based digital VFO. This project comes after having done more than 50 activations with my 2013 MST Mk I kit radio on 40m SSB. This rig has performed well on 40m SSB (and CW after I added it) and has launched my interest in SOTA activating, turning me into an occasional weekend ‘summit prowler‘.

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My second homebrew Arduino/si5351 Digital VFO-Controller

Back in February 2017 I scratch-built my first Arduino and si5351 VFO. Here’s my second one. It is a generic Nano/si5351 module wired up to Farhan’s Raduino circuit. The si5351 is on an Adafruit breakout which includes a 3.3v regulator and crystal. Everything else is as per Raduino other than the presence of a second 7805 regulator for the LCD (and a 1000uF electrolytic storage capacitor) which will allow testing of Pavel CO7WT’s scheme for saving the VFO frequency to the Arduino’s EEPROM when the power drops.

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DIYODE Issue 1 July 2017

DIYode, a new Australian DIY electronics magazine has just launched. I picked up my first edition from the Jaycar counter. It’s thick, glossy and oozes high production values. There’s an nostalgia in having a current electronics magazine on the coffee table. It takes me back to the 1980s when Electronics Australia, Silicon Chip and Electronics Today International bought circuits, components, kits and articles, not to mention ads and specials from hobbyist-focused advertisers like Dick Smith into our lives every few weeks.  Those days are gone forever.  Smartphones and the internet have put every circuit diagram and datasheet at our fingertips, and have spawned global communities which put world experts just minutes or hours away.  So in July 2017, where does a glossy DIY electronics magazine fit in this smorgasbord of information and community?

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Homebrew 40m SSB rig gets CW, keyer, break-in, AGC and metering

A couple of ‘solder sessions’ finished all the wiring, debugging and testing required to deploy my Arduino Nano keyer and SWR/power meter, and the LED LDR AGC and S-meter modules into my homebrew 40 meter SSB rig (MST Mk1 from OzQrp).  Before reassembly I sprayed the front and rear panels, and added my preferred DecaDry white lettering and a protective coat of  clear satin sealer. It’s now resplendent with all the expected features of a SSB/CW monoband portable rig.

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Saving an Arduino-controlled Digital VFO frequency over a power cycle

Following the success of My First DDS VFO, complete with Arduino script programming, I found myself interested in mimicking more of the features of the digital dials in ‘real’ rigs. Like dynamic incremental speed-tuning, where the tuning rate increases or decreases dynamically depending on how fast you spin the dial. More on this later. A more achievable feature is to have the band, mode and VFO come up on the frequency where you left it at the last power-down. This involves writing these parameters into the Arduino’s EEPROM, using the EEPROM library.

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