Tag Archives: homebrew

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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Remembrance Day Contest 2018

Remembrance Day Contest is a 24 hour amateur radio operating contest conducted each year by the Wireless Institute of Australia, to commemorate those Australian licensed amateur radio operators who lost their lives in World War 2. It is ‘designed to encourage friendly participation and help improve the operating skills of participants‘, and is held on the weekend closest to the 15th August, the date on which hostilities ceased in the southwest Pacific. This year it commenced at 1pm local time on Saturday August 11th.

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Desklamp conversion to 12v DC 20w power supply

Picked up a halogen desk lamp from a street hard rubbish pile the other day. This particular desk lamp model has been a popular product for many years and appears to be still available. As I stood on what Melburnians strangely refer to as a ‘nature strip’, starting at someone else’s pile of junk, I faced a familiar dilemma– take it and do something with it, or walk away.

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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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Hard-to-find faults and other homebrew ‘Gumption traps’

I recently cut this small piece Veroboard to hold two vertically aligned miniature potentiometers on a receiver front panel. The three soldered tracks to the right allow connection of the audio signal to the volume control using shielded twin conductor cable. Very standard stuff, I’ve been wiring up audio amplifiers to volume controls like this for about four decades. But this one wouldn’t work. It has a fault — it’s there, in the picture above, right in front of your eyes… can you see it?

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Veroboard at radio frequencies

Charlie ZL2CTM has been pushing out a series of excellent videos on his YouTube channel that take you through the circuit design, making and testing of superhet SSB transceiver modules.  Yesterday my eyebrow involuntarily raised ever so slightly at his use of Veroboard as the substrate for his latest 8MHz crystal filter.  Veroboard? At radio frequencies?  Veroboard et les fréquences radio ne sont pas compatibles!

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An SSB receiver from an Arduino/si5351 VFO/BFO

Having finished my latest Arduino Nano/si5351 VFO/BFO/Controller, I wanted to hook it up to some receiver stages to realise a SSB receiver. My grand plan for these modules is to build a multiband SSB/CW transceiver for SOTA and portable operation (another rig in my established ‘Summit Prowler’ series). The architecture will be a single conversion superhet with an IF of 12 MHz. For a base design I chose Leon VK2DOB’s MST3, a proven design which I am very familiar with, having used the MST (circa 2013) on nearly all of my SOTA activations to date.

I scratch-built two boards. The first is the MST3 product detector (SA612), audio filter (NE5534) and audio amplifier (TDA7052A). This module includes receiver muting, sidetone injection and audio-derived AGC which controls the gain of the TDA7052A. The second board contains the transmit and receive mixers (both SA612s), some SA630D RF switches to switch the bandpass filter between transmit and receive signal paths, as well as two 5-pole crystal filters (one for SSB, one for CW), each switched by another pair of SA630Ds. There is no IF gain stage, although I put some pads on the end of this board for one or two MOSFET stages, if needed.

As per other recent scratch building efforts these boards are a curious jumble of thru-hole and SOIC ICs, soldered to the copper side of a Muppet style hand drawn and etched board, largely populated with junk box and surplus sales components.

Once the boards were debugged, temporarily adding a 40m bandpass filter and connecting the VFO/BFO up brought the little receiver to life. I used no si5351 clock filtering or buffering, just CLK0 and CLK2 square waves straight into the SA612 Gilbert cell active mixers, which have some useful gain. The sound of the receiver is pleasant, to me at least. The video includes a range of DX and local signals on 40m from my QTH in the north-eastern suburbs of Melbourne, received over a day.
Next, I will add a third board with a bank of switched bandpass filters and switching logic, all controlled by the Arduino. More to follow.

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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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WA2MZE

Amateur Radio and unrelated technologies

Paul Gacek

W6PNG/M0SNA

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