7MHz Transmitter with AVR Soft-keyer abram, March 3, 2019October 19, 2021 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… Continue Reading
7MHz Crystal Oscillator Design abram, February 6, 2019March 22, 2019 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… Continue Reading
DOD FX55B SupraDistortion – BigBuff Mod abram, September 16, 2014August 9, 2019 Here’s another in a line now of DOD pedal mods. For this FX55B, I decided to go for more of a BigMuff sound. Playing around with this pedal initially, I found it to be like most mass-produced distortion/fuzz effects. It had a very thin sound and that notorious volume drop… Continue Reading
Class AB amplifier test abram, September 12, 2014September 12, 2014 this was an attempt at designing a simple transformer-less class AB amplifier using two BJT power transistors. i setup the USB fan to protect against thermal runaway and cool off the transistors during operation. it took me looking over several schematics to realize that the the emitters of both the… Continue Reading
LFO modulated simple VCF abram, May 23, 2014 this is a rough draft of a circuit i’ve been working on based of the Simple VCF circuit floating out there. a big thanks to the original author for that. i’m sure there are some mistakes in here. it’s an odd one for sure, but it works on the breadboard…. Continue Reading
initial test of a modulated PT2399 circuit… abram, June 12, 2012June 12, 2012 a breadboard version of some PT2399 modifications i’ve been working on. there are a lot of DIY schematics that utilize the PT2399 (Magnus Modulus, Echo Base delay, Rebote, etc.). i’ve been interested at trying my hand at modulation techniques recently. i made a simple LFO circuit based on the findings… Continue Reading
experimental PTT signaling switch… abram, May 21, 2012May 22, 2012 this is an experimental circuit i threw together today. i’ve been working on getting a VOX circuit to work with the Yaesu FT-60R (VX-3R, VX-5, etc.) and Soundmodem on the ol’ Gentoo box. it’s working well, but test packets have been a little iffy. Continue Reading
PT2399 build… abram, May 19, 2012May 20, 2012 this is an older build now, but i wanted to post it while i’ve been on the subject to record the process. believe it or not, i still have some work to do on this one. i used a TL082 as a buffer for the mixing circuit. getting the gain… Continue Reading
ngSpice: single frequency FM modulated signal generation abram, May 13, 2012May 13, 2012 ever wanted to see how that 2N2222 might hold up as a linear RF amplifier? here’s a handy feature of ngSpice that i found recently. i’m rather new to ngSpice and at first was somewhat frustrated by its differences from other SPICE variants. however, i’ve earned a deep appreciation for… Continue Reading
Boss Tremolo TR-2 w/ C4 Mod +Gain Boost abram, July 15, 2010August 26, 2016 This little guy is currently on eBay. I always thought that this tremolo wasn’t bad, but the volume drop was insatiable and drove me nuts sometimes. I thought I would try modding this one by cutting out the C4 cap (a 0.1uF bypass cap) which is the alleged cause of… Continue Reading