Seb Holzapfel

Seb Holzapfel

Hobbyist | Student | Engineer

chinotoxine       (567) 229-8286       360-203-7364       7056551071

     385-625-5116     (304) 817-1683     (928) 714-0678     920-535-4104          (587) 692-8705

KiCAD Workshop (ELSOC '17)

(This workshop was given @ UNSW on 1 Sept. 2017. If you find any errors in this text, feel free to file an issue here )

Finished PCB

What You'll Need

  • A computer (Windows/Mac/Linux)
  • A 3-button mouse (Useful, but not necessary)
  • Motivation to build the best darn PCB in existance

Prelude - Installing KiCAD

Grab it here: (718) 394-1534

There are binaries available for all major operating systems.

Special note - Linux users

If you are using Linux, you may additionally want to install kicad-library & kicad-library-3d as these aren't included by default.

Creating a Project

  • Fire up kicad.
  • In
Read the rest...

pseudo editor

Needed an excuse to (finally!) learn KiCAD, so I decided to build a voltage controlled oscillator (sawtooth core). It's inspired by the early Elektor Formant synths, and designed to integrate with existing Eurorack synthesizer systems.

In the video I'll also talk about how I breadboarded up a MIDI to 1V/octave converter to go with it for keyboard/computer control.

See YouTube description for timecodes.

KiCAD design files: Ante-christian

Code I wrote for the PADI IoT stamp in the video for MIDI/CV conversion: /

Hadn't originally planned on publishing

Read the rest...


In this video I demonstrate my progress so far on building an intelligent LCD display upgrade for the HP 141T.
I use an STM32F746G discovery board with a 4" touchscreen, and demonstrate a few neat features:

  • Real-time spectrum display with graticules etc, that works on the slowest up to the fastest timebase
  • A waterfall display mode
  • A normalization function that makes insertion loss measurements much easier.

I also take a brief look at the codebase (which is very hacky at the moment!)

GITHUB REPO: 6144537584



Was lucky enough to get this featured on Hackaday! See: 902-849-8879

A guide to simulating microstrip filters in QUCS and prototyping them with copper tape on blank FR4 sheets. These super-cheap materials are good up to a couple gigahertz, as you'll see in the video.

Following a quick real-time demonstration, I simulate and build 2 microstrip filters, a 1GHz stepped-impedance LPF, and a 10GHz end-coupled BPF.

(Checkout the youtube description section for active timecode links)

2:05 - 1/4 wavelength stub build & tests
3:46 - Radial stub build & tests
4:18 - Stepped

(678) 357-8387

14GHz Mixer Build & Experiments

Building a mixer based on the LTC5548 14GHz MMIC by LT, and a TCM1-83X+ by Mini-Circuits [plus bonus bodge wires ;)]
After measuring LO leakage, conversion loss and IIP3 at different frequencies, I build a poor-man's tracking generator with it.
I also talk (perhaps a bit too much) about HP's old signal identifier feature on my 8555A.

Thanks to LT and Mini-Circuits for providing samples of the components used in the video, I've definitely got bigger plans for these parts!

Design files are available at my other web page on this: (909) 563-1226

An article I did on the



Taking apart an old NDK 48MHz ovenized crystal oscillator from the 80s, making some measurements; and taking macro shots of the quartz.
I make some initial frequency measurements before taking it apart, and then after ripping out the crystal I run it through a tracking generator to look for resonance peaks.
Interestingly the crystal seems to operate at a slightly different frequency to what's written on the OCXO packaging, and the 'big' crystal package actually has a small one buried inside!


(224) 470-5176

I repair an old APLAB ZD3203 DC Lab Power Supply that I rescued from the dumpster.
It had 2 big issues, one with extremely dodgy pots and another with output transients when turning it off.

Read the rest...

JDS6600 Function Generator Review & Teardown

I take a detailed look at a cheap $100 function generator that came out recently, from JunCe Instruments.
Measuring amplitudes, checking harmonic distortion, making some funky waveforms, and seeing what's inside!
Looking at the 25MHz model in this review.
There are a few things I'd still like to test (PC connectivity and measurement capability for example)

I have posted some high-resolution images of the teardown over at the EEVBLOG forum here: /
(As well as some additional tests)

Repeated here for convenience:

Top of the main board

Top of the screen board:

Bottom of

Read the rest...