YO3ITI • Alauda Projects

Ham Radio

Here is a collection of articles related to Ham Radio, one of my hobbies. You can find here various build projects but also software applications designed for experiments or radio operations. I posted also some articles on various field activities with my friends.

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SA818 radio node – version 2.0

By AP,

I was pretty busy since August 2024 with a lot of other tasks, mostly job-related and did not have too much time for DIY and tinkering. And this included my SA818 project.

Fan control with dtoverlay on Raspberry

By AP,

Another day working a bit for my SA818 radio node project. Today I tried active cooling with a 5V fan driven from RPIs 5V rail and controlled from GPIOs with a MOSFET (2N7002).

Adalm Pluto ? Don’t think so

By AP,

I have a love-hate relationship with Adalm Pluto. I bought it from Mouser in 2020 when it was roughly 100 euros (now it is almost double that price !) and I never managed to do anything useful with it.

Raspberry Pi serial interface issues

By AP,

There is a problem I forgot to take care before creating the custom image for my radio node project. Programming SA818 module via Raspberry Pi’s UART interface cannot be done unless the UART interface is released from any interaction in console mode. I was banging my head for hours because of sustained DMOERROR message for […]

I am learning morse

By AP,

I was always interested in learning morse but I did not have my mind seriously set on it until recently. My shack conditions do not allow me do much DX-ing on SSB and I am not very keen of FT8 and other digital modes so I consider CW as the only possible way to get […]

Field Day, Tuzla, September 2025

By AP,

The autumn 2025 edition of Tuzla Field Day, Constanța, Romania, took place between 16 and 22 september. A lovely event, an occasion to meet old friends and make new ones.

Raspberry Pi compatible, SA818 radio node

By AP,

My new radio node that I designed last month is back from production at jlcpcb. Designed in Romania and built in China 😁. This is my first attempt using jlcpcb for the entire manufacturing chain, from PCB creation to part selection and assembly.

New radio node

By AP,

Today I finalzied the designed for my new Raspberry Pi Zero-based radio node. Designed around SA818 and CM108B sound codec, will replace my old dead-bug style radio node that I used for so many years.

I2S Raspberry Interface (4)

By AP,

More work today. Some wires got loose and I did some experiments with .asoundrc and ALSA settings. I added a 39 Ω ballast resistor on SDIN and SDOUT lines and put a ferrite core on both wires. The radio node works as expected, absolutely no issues with one exception, a periodic pop that is audible […]

I2S Raspberry Interface (3)

By AP,

Update July 11, 2025 Some thoughts and tasks today. The project is the same I2S interface.

A Si5351 DIY oscillator project

By AP,

I have some Si5351 chips that I never used for any projects. I purchased them from Mouser, I believe for an APRS project, long-standing and overdue. That APRS project I started some time ago but I never completed and maybe I should strongly consider to complete. But this is another topic.

Field Day, Tuzla, May 2025

By AP,

These days we are at Tuzla, in the sunny Dobrogea, on the Black Sea coast, for the sixth edition of Tuzla Ham Radio Field Day. From May 21st to May 25th. Amazing for this event is our desire to meet and socialize. In a world and time when people spend more time with bots and […]

Significant Svxlink power consumption

By AP,

While testing my I2S project I ran into some boot issues on the Raspberry Pi 4 host. For what seemed to be some unknown reasons the boot process was completely chaotic, sometimes running well, sometimes hanging. I banged my head for some time looking for a solution until it came to my mind to change […]

I2S Raspberry Interface (2)

By AP,

Update September, 2024. Activities and notes while developing the I2S interface for my radio node.

I2S interface for Raspberry Pi (1)

By AP,

Today I managed to connect the Digilent Pmod I2S2 to a Raspberry Pi 4 and have all frequencies generated. This is part of an older project that I left abandoned for a while: a radio node built on Raspberry Pi and using Svxlink. As known, Raspberry boards do not have a proper audio interface and […]

Controller for DR-1X repeater

By AP,

I made this for a friend. Is a remote controller for Yaesu DR-1X repetear that is installed on Summit Heniu (145.725 Tx -6khz Rx). This is a mixed digital (C4FM) and analogue repeater that is covering almost all northern half of Transyvania and can also be accessed via Echolink YO5D-R, node 54452. This version is […]

Harris 300W UHF pallet — how good could this be as a QRO for 70cm amateur radio band ?

Harris 300W UHF Pallet

By AP,

A couple of days ago I received from a friend of mine a Harris RF power pallet salvaged from a scrapped equipment. This pallet would be able to dissipate apx 300W PEP (black) on a 50 ohm load on ∼800 Mhz. Unfortunately I have no documentation for this. I do have the schematic but is […]

How to use Matlab PCBReader objects

By AP,

Recently I installed a trial version of the new PCB toolbox from Matlab. From Mathworks website: RF PCB Toolbox provides functions and apps for designing, analyzing, and visualizing high-speed and RF multi-layer printed circuit boards (PCBs). You can design components with parameterized or arbitrary geometry, including distributed passive structures such as traces, bends, and vias. […]

Malamute SDR

By AP,

I have to confess that I fail to comprehend this obsession for cheap chinese devices. Although I understand the “cheap” part of the rationale, what constantly amaze me is the fact that usually people that buy such stuff are not necessarily financially challenged — a fact that could justify such a choice. Let’s be honest: […]

Cold shrink tubes

By AP,

I discovered this technology rather recently on YouTube and I was instantly hooked by the opportunities. I bet most of you who had to insulate connectors or sections of hardware (like antenna segments, for example) relied heavily either on self vulcanizing tape or on electrical insulation tape. Both had disadvantages but for me the deal […]

Field Day, Tuzla, 2023

By AP,

The fourth edition of Tuzla Field Day took place this year on 14-17 September, 2023. Some pictures:

Multipurpose RF Proto Board v2.0

By AP,

This is a general purpose PCB that I designed in KiCad as a helper board for my Manhattan-style mounted RF projects. It allows connection via SMA connector (vertical or edge mount) and BNC. The two completely separated prototyping sections can be interconnected by using the SMAs in the middle or, if you want to save […]

Motor drivers for antenna rotator

By AP,

I made some progress on my antenna rotator project and installed the stepper drivers and the Raspberry Pi computer. I bought two drivers from ardushop.ro and these should work just fine. They are based on Toshiba TB6560AHQ, PWM Chopper-Type Bipolar Driver IC for Stepping Motor Control. The datasheet can be downloaded from here. My projects […]

Mini N connector – timelapse in Fusion360

By AP,

I needed this 3D design for a mini N connector that I have in my shack but I was unable to find any 3d file (.STEP etc) online. The connectors are used for my 101dB attenuator project. Enjoy ! Greetings.

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