Recent content on K3XEC
Interested in future updates? Follow me on mastodon at @paul@soylent.green . Posts about hz.tools will be tagged #hztools . 🐶 Want to jump right to the draft? I'll be maintaining ARF going forward at /draft-tagliamonte-arf-00.txt . It’s true – processing data from software defined radios can be a bit complex 👈😏👈 – which tends to keep all but the most grizzled experts and…
Interested in future updates? Follow me on mastodon at @paul@soylent.green . Posts about hz.tools will be tagged #hztools . It’s well known and universally agreed that radios are cool. Among the contested field of coolest radios, Software Defined Radios (SDRs) are definitely the most interesting to me. Out of all of my (entirely too many) SDRs I own, the rtlsdr is still my #1. It’s…
After years of thinking about and learning about how radios work, I figured it was high-time to start to more aggressively share the things i’ve been learning. I had a ton of fun at DistrictCon year 0, so it was a pretty natural place to pitch an RF-focused introductory talk. I was selected for Year 1, and able to give my first ever RF related talk about how to set off restaurant pagers…
Some of you may remember that I recently felt a bit underwhelmed by the last pager I reverse engineered – the Retekess TD-158, mostly due to how intuitive their design decions were. It was pretty easy to jump to conclusions because they had made some pretty good decisions on how to do things. I figured I’d spin the wheel again and try a new pager system – this time I went for a…
It’s been a while since I played with something new – been stuck in a bit of a rut with radios recently - working on refining and debugging stuff I mostly understand for the time being. The other day, I was out getting some food and I idly wondered how the restaurant pager system worked. Idle curiosity gave way to the realization that I, in fact, likely had the means and ability to…
Interested in future updates? Follow me on mastodon at @paul@soylent.green . Posts about hz.tools will be tagged #hztools . If you're on the Fediverse, I'd very much appreciate boosts on my toot ! While working on hz.tools , I started to move my beamforming code from 2-D (meaning, beamforming to some specific angle on the X-Y plane for waves on the X-Y plane) to 3-D. I’ll have more to say…
The asterisk VoIP project has a protocol built-in called “AudioSocket”. AudioSocket is built on top of TCP, streaming int16 values at a sample rate of 8 kHz, neither of those options are configurable (by design). AudioSocket will stream audio from the connected phone to the tcp server, and play audio samples sent from the tcp server to the phone. This documentation is a work in…
Interested in future updates? Follow me on mastodon at @paul@soylent.green . Posts about hz.tools will be tagged #hztools . If you're on the Fediverse, I'd very much appreciate boosts on my announcement toot ! Ever since 2019, I’ve been learning about how radios work, and trying to learn about using them “the hard way” – by writing as much of the stack as is practical (for…
Before you go on: I've been warned off implementing this in practice on a few counts; namely, the space tradeoff isn't worth it, and it's unlikely to correct meaningful errors. I'm going to leave this post up, but please do take the content with a very large grain of salt! My initial efforts to build a PHY and Data Link layer – from scratch using my own code – have been progressing…
AX.25 is a tough protocol to use on UNIX systems. A lot of the support in Linux, specifically, is pretty hard to use, and tends to be built into the reptilian brain of the kernel. KZ3ROX built a userland AX.25 stack called patty , for which I have now built some Go bindings on top of. Code needed to create AX.25 Sockets via Go can be found at github.com/k3xec/go-patty , and imported by Go source…
🐀 This post is part of a series called "PACKRAT". If this is the first post you've found, it'd be worth reading the intro post first and then looking over all posts in the series . In the last post , we left off at being able to send and receive PACKRAT frames to and from devices. Since we can transport IPv4 packets over the network, let’s go ahead and see if we can read/write Ethernet…
🐀 This post is part of a series called "PACKRAT". If this is the first post you've found, it'd be worth reading the intro post first and then looking over all posts in the series . In the last post , we we were able to build a functioning Layer 1 PHY where we can encode symbols to transmit, and receive symbols on the other end, we’re now at the point where we can encode and decode those…
🐀 This post is part of a series called "PACKRAT". If this is the first post you've found, it'd be worth reading the intro post first and then looking over all posts in the series . In the last post , we worked through how to generate a BPSK signal, and hopefully transmit it using one of our SDRs. Let’s take that and move on to Receiving BPSK and turning that back into symbols! Demodulating…
🐀 This post is part of a series called "PACKRAT". If this is the first post you've found, it'd be worth reading the intro post first and then looking over all posts in the series . In the last post , we worked through what IQ is, and different formats that it may be sent or received in. Let’s take that and move on to Transmitting BPSK using IQ data! When we transmit and receive information…
🐀 This post is part of a series called "PACKRAT". If this is the first post you've found, it'd be worth reading the intro post first and then looking over all posts in the series . When working with SDRs, information about the signals your radio is receiving are communicated by streams of IQ data. IQ is short for “In-phase” and “Quadrature”, which means 90 degrees out of…
Hello! Welcome. I’m so thrilled you’re here. Some of you may know this (as I’ve written about in the past), but if you’re new to my RF travels, I’ve spent nights and weekends over the last two years doing some self directed learning on how radios work. I’ve gone from a very basic understanding of wireless communications, all the way through the process of learning about and…
Over the last few years, I’ve often wondered what the true power output of my SDRs are. It’s a question with a shocking amount of complexity in the response, due to a number of factors (mostly Frequency). The ranges given in spec sheets are often extremely vague, and if I’m being honest with myself, not incredibly helpful for being able to determine what specific filters and amplifiers I’ll need…
Over the course of the last year and a half, I’ve been doing some self-directed learning on how radios work. I’ve gone from a very basic understanding of wireless communications (there’s usually some sort of antenna, I guess?) all the way through the process of learning about and implementing a set of libraries to modulate and demodulate data using my now formidable stash of…
This post is all about the E4000 (e4k) RTL-SDR Tuner, commonly found in the Nooelec RTL-SDR. It’s one of my favorite RTL-SDR tuners, but it can be incredibly frustrating to work with if it’s not left on AGC . This documentation is a work in progress, and a result of source code spelunking or reverse engineering. It may contain errors or outright lies. The names may not match the…
rfcap is a file format with extremely small ambitions. rfcap files contain a fixed size header, and then a stream of raw IQ data. The rfcap header contains information about the IQ format type, and capture metadata. The header is aligned to a 128 bit boundary, so most iq formats can choose to ignore the header and throw out the first window, meaning existing tools like gqrx can read a subset of…
The rtl_tcp program will allow a client to remotely receive iq samples from the rtl sdr over a tcp connection. This document describes the mechanism by which the client and server communicate. This documentation is a work in progress, and a result of source code spelunking or reverse engineering. It may contain errors or outright lies. The names may not match the original name, but it's been…