Josh Stone's blog, recording information security observations, hacking techniques, and penetration testing tool information.
I’m playing around with some ideas for VHF and UHF experiments, and need a good signal source. Before implementing a fancy PLL myself on my own boards, I thought I’d pick up an ADF4351 board from Amazon. I could poke at it with my Bus Pirate , but that’s not really a viable approach for making benchtop experiments easy in the future! So I designed a “backpack” control board to mate with the…
I don’t see a lot of people using high-speed opamps in RF circuits, but I wonder what they are useful for. After sketching out a few ideas, I thought I’d pick up the LT1818 from Analog Devices. It’s a pretty snazzy one… putting it on a little test board and putting it through some paces suggests it’s quite usable for HF and low VHF, at the very least! Introduction Several articles I found seemed…
I’m always hoping to find modern, in-production parts that can be used as RF power devices. Proper RF power transistors are crazy expensive, but it does seem like some parts (like the popular IRF510) can be made to work for RF purposes, despite not being properly intended for it. This post is about trying out the 2SCR573 – a general purpose BJT power transistor that weighs in at about $0.70…
My son and I are starting a project to build the ultimate ham radio cyberdeck . Of course, this will require a custom HF SDR , so my head has been filled with ideas. I’ve built an IQ modulator for TX, and a few different IQ mixers for RX. And of course, I’ve got a halfway decent QRP+ HF power amplifier that I realize I haven’t written up here yet… But a few pieces remain slightly outside my…
I’ve been playing with some different attempts to venture into the VHF and UHF bands (in terms of homebrew projects), and hit a lot of dead ends. This post is my first real success getting something going on the 70cm band, playing with Silicon Labs’ Si4467 chip. How I got to this point I’ve done a lot of HF projects, as should be evident from the posts here. And HF is really fun, don’t get me…
I’ve harmonized some of my thinking around the various experiments I’ve done recently, and decided I was ready to bring a bunch of ideas together in a big experiment. This post details my adventure trying to use the full 10x10cm of a JLC PCB order… or… how I made a double conversion superhet SDR transceiver and learned a whole lot! Level set expectations So, right off the bat it’s important I make…
Continuing from my last post, where I built a digital IQ modulator for generating a carrier at any amplitude and phase… this post is about some investigation of phase detection and demodulation. I carried out three separate experiments, which make me hopeful that I could actually build a non-coherent demodulator for low baud-rate amateur radio digital modes. Premise Consider an incoming carrier…
I was greatly inspired by this video from W2AEW , where Alan shows the use of an IQ modulator to generate amplitude and phase modulated signals. I’ve enjoyed playing with simple FSK modes, using an Si5351 and changing its frequency to modulate data (played with Hellschreiber, WSPR, and RTTY, for example). But the idea of trivially generating PSK and QAM signals with a couple of mixers was…
While working through some questions around impedance matching amplifiers, one of my mentors asked how confident I am in the measurements I get from the NanoVNA. I haven’t really run into a situation where it severely mislead me, but I had never really done anything to test its reliability. He suggested I measure a few values of resistors and capacitors and just check to make sure what we were…
This blog post is about the first step in what feels like a big project for me – but one that I hope will resolve a lot of outstanding questions I have about impedance matching and power amplifiers. This is my journey to create an in-home DIY load-pull analysis lab for characterizing and understanding transistors. Since I started on this ham radio home brew journey, I’ve been unsettled by many…