In this section, I describe my past and current projects. Note that activities related to (RF) experiments and maintenance, calibration, repair, etc. of instruments and gear is described under Activities.
- pa3gyf-gpib: GPIB Interface.
- pa3gyf-jinstrument: Software for controlling (for instance) GPIB and MIDI instruments.
- jdj-30v-2a: Lab Power Supply.
- pa3gyf-gpsdocxo: GPS-Disciplined Oven-Controlled Crystal Oscillator.
Archived projects are no longer being maintained and are included for historical reasons only. This typically implies that I no longer have the result(s) of the project, and have to rely mostly on memory and Google for their descriptions. This section may not be that relevant to you, to be completely honest.
Well, here’s the (incomplete) list:
- [jdj-fg-01] A sine/square function diy function generator: This was a DIY function generator with sine and square wave outputs (separate). I got it as a Christmas (?) present from my Dad. Must have been between 1975 and 1980, and he probably bought in the Belgian city of Kortrijk (really, best guess here). I built it, it worked, and I was really happy with it, and used it for many years. It was a Wien Bridge Oscillator in a mostly plastic bright-orange enclosure and an aluminum front. It was powered directly from mains 220V. What I remember vividly was the weird DC Offset for the square-wave signal. The signal went from -0.2V to +6.2V (guessing here), and it was impossible to set the DC Offset. It featured an amplitude control potentiometer, but as far as I remember, that control only worked for the sine wave. There was also a four-position switch for the (since-only?) amplitude range. In addition, there was a four-position frequency-range knob (200Hz/2kHz/20kHz/200kHz, I think, but maybe the highest range was just 20 kHz, I do not remember). I remember that I had to stick Al-foil manually on the interior of the orange plastic enclosure for reasons of shielding. If anyone knows what brand/model this was or could be, please contact me!
- A signal tracer: After I obtained a function generator (see above), I decided that I needed something called a signal tracer. I know for sure I built this project from a design described in an electronic magazine like Elektuur or Hobbit. The unit featured an audio chain with built-in speaker, a (VU/log) meter, and some kind of RF detection circuitry or probe, as well as a much-needed Volumen control. The unit generated an amazing amount of hum, and I haven’t used it that much actually…
- Memory Extension on a ZX Spectrum: I remember the amount of RAM on my ZX Spectrum was 16 KB, and by stacking RAM chips on existing one, it was possible to extend this to the full 64 KB (I think).
- Memory Extension on an Acorn Atom: I think I did the same memory-extension trick on my Acorn Atom. But mind you, the RAM on the Acorn Atom was just a few (2?) KB.
- A 300 bps modem: Not really a project of myself, but around 1985 I bought a 300 bps homebrew modem from my flat mate Rindert Nauta. I used it very often to dial in to the computer modem/terminal server.
- A Z-80 based micro-computer board: Pretty sure I worked quite some time on a Z-80 system by constructing a back plane and then mounting boards like ASIA, PIO on that back plane.
- External 5.25″ and 3.5″ disk drives for the Sinclair QL and/or the Amiga 500: I mounted the disk drives in a large enclosure with a switching power supply. It worked, but the noise was terrible.
- An Amiga-500 Audio/MIDI interface: One of my first “really thorough” projects. Only the MIDI interface worked well; the audio part (including Audio In) never really worked as the interface chip(s) on the Amiga constantly blew up.
- AMAS-MIDI: Spin-off from previous project? The PCB layout I found for it was marked JJ91. I remember having a nice box doing two times MIDI IN/THROUGH, a switch (for something) and 4x MIDI OUT (carrying the same data).
- A dip-meter: Battery-powered with multiple separate coils for frequency selection.
- A Morse Decoder: This was a Velleman kit (K2659), which I usually liked somewhat. But not this one: This kit never made it into on operational unit. Here’s all that’s left of it.
- A DCF-77-locked frequency counter: Another relatively thorough project. A basic frequency counter (not sure where I got it from) combined with a DCF-77 receiver. Since the receiver never really locked, this project was not really a success. The DCF-77 receiver is described on Rob’s Web: https://www.robkalmeijer.nl/techniek/electronica/electronicabladen/elektuur/1987/02/page46/index.html (in Dutch). I’m 100% sure this was the design I used (and I simply purchased the PCB). Unfortunately, I have not yet found the frequency-counter circuit. I’m pretty sure it was an existing design, maybe from Elektuur, with three different inputs: 10 MHz, 100 MHz and 1 GHz (the latter using a prescaler). [update 20210219]: The DCF-77 receiver was from the article “DCF Ontvanger 77.5 kHz” (right?) in “Elektuur HF Boek deel 1, pag. 70”. From the same book, the article “KG Frequentie-meter” provided the basis for the counter. And I did construct the PCBs myself…
- [pf0a+pa3gyf – pa-144-1kW] A 1kW 2m PA: A project I undertook with Frank van Vliet pf0a and others, but had to abandon in 1999. The aim was to build a 1kW [well, legal-limit] PA for 144 MHz using a by-then famous “Russian Tube”.
- A Stereo 100W Audio Amplifier: Meant for my guitar. From an Elektuur article, but I only found the PCB codes: 82089-1 and 82089-2.
I currently maintain the following projects:
pe1ckk+pa3gyf – lcg-asb44: An LCG Audio-Distribution box
A project I undertook (in 1996/1997) more or less by request from Hans PE1CKK from the Lighthouse Contest Group LCG. The (his) idea was to provide fine-grained control to two contest operators each with a (stereo) headset to select any combination of four input sources to their left or right headsets. I delivered the switch box, but despite warnings from Hans, the box did not perform very well in presence of strong RF fields, so Hans had to add massive RF suppression in order to make it work. But, as far as I know, the modified box has been operational in the LCG for some years. Unfortunately, I do not have a private version of the box nor pictures of the prototype, but I do maintain the project documentation for historical reasons.
[update 20210219] I actually found a picture containing the box (I think…) on the right-hand bench:
As stated, the unit was aimed for two operators; as clear from the picture, each operator manipulated the audio routing with a 4×2 matrix of digitast LED switches and the Left/Right volumes with two potentiometers above the routing matrix. As far as I remember, the 6.3mm jack plugs for the headsets were at the front of the unit.
Here are the schematics and PCB layouts for pa3gyf – lcg-asb44. I don’t remember which program I used to design the PCB (wasn’t it just named ‘pcb‘?), but the project directory is a hell of lot cleaner that a typical KiCad project. The enclosure was cut, bent and post-processed by Hans PE1CKK in less than an hour at his work.
For the record, below is an interesting detail from the main board PCB design:
Other, yet undocumented projects
- A 144 MHz Transverter Switch Box.
- An HF transmitter/receiver.
- A 6m transverter.
- Another 6m transverter.
- A 70cm transverter.
- A 23cm transverter (Hans, PE1CKK?).
- Another 23cm transverter (DB6NT).
- A DB6NT 23cm Low Noise Amplifier (LNA).
- A 3cm transverter (DB6NT).
Currently, I am considering picking up the following projects:
- A GPIB to Ethernet converter with proper Service Request support.
- A monitor module for the MSIB bus on an HP-70000 MMS.
- 100 MHz and 1 GHz Reference Signals from a 10 MHz Reference Signal with proper lock support.