Author: abram
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Amongst Projects: Therematron
Here’s an beautiful synth project I found by Steve Roberts at Amongst Projects that utilizes some work I did back in 2012 with my Arduino LFO. It’s always a pleasure to find my own work buried in someone else’s. I recommend heading over and checking out the post. You won’t be sorry.
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7MHz Transmitter with AVR Soft-keyer
In my last post, I went over the design of a Colpitts crystal oscillator design that put out a moderately clean 7 MHz signal. In order to match the output impedance to 50 Ω, an NPN feedback pair (at least that’s what I’m calling it) was designed. While meeting the specs for driving an ADE-1…
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7MHz Crystal Oscillator Design
After constructing a 40m wire dipole that works with my SDR setup, I needed to start working on a transmission system. At the heart of virtually any RF system lies a stable oscillator, and crystal oscillators are ubiquitous in many low-power (QRP) rigs simply because they are so stable. After some rough math and a…
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Testing a 40m Wire Dipole on Mt. Hood
Here’s a quick video showing how I deployed a DIY 40m dipole antenna on Mt. Hood a while back. Though not the most interesting video, I think it shows the results pretty well. I used an AirSpy HF+ supplied by KK7B for a project I’m working on. A Panasonic Toughbook CF-30 helped stave off the…
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2m AM Exciter
Here’s a project that I’ve been working on for a class recently. This is a very basic 2m AM Transmitter that operates from 144.25 to 144.31 MHz. It does put out a low powered RF signal (around 5 mW PEP) that has been copied over 1 mile from the transmitter. This is an ongoing project…
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Basic Voltage-Controlled Amplifier
I’ve been looking at the theoretical principles that govern the voltage-controlled amplifier (VCA) recently and came across some simple VCA designs that caught my attention. A common technique involves a JFET and an opamp to achieve VCA type operation by using the JFET as a voltage-controlled resistor somewhere in the input path. I’ve seen a…
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Milling PCBs with Linux…
This is a quick outline of my LinuxCNC setup. Basically, I have an old HP Compaq Pentium IV that’s running Xubuntu 14.04. I had to install the Xenomai real-time kernel in order to make it work with LinuxCNC 2.5.2 which controls my Chinese CNC3020T. I’ve been using 0.1mm 30° engraving bits for etching which have…
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#NoDAPL
I believe it’s time to put an end to this kind of insanity. There can be no economic growth if human beings continue to be reckless with the environment that supports them. Clean air, water, and soil are necessary for all life to flourish. That ought to be a priority.