Archive for the ‘Test equipment’ Category.

Mini CW Keyer / QRSS beacon V1.1

I designed dedicated PCB for the CW keyer. The project is very similar to the version made on prototyping board.

keyer pcb

Here are the updates:

Continue reading ‘Mini CW Keyer / QRSS beacon V1.1’ »

Prototyping with PLL ADF4351

ADF4351 is very interesting PLL chip with many features. Here is prototyping board to start playing around with this interesting chip.


Continue reading ‘Prototyping with PLL ADF4351’ »

MODEM, parrot, CAT, …

Full bunch of wires is hanging from each HAM station and PC connected to the station: CAT, audio, each via dedicated interface for isolation or level shifting. Additional mess is with parrots or digital interfaces for digital mode. I wanted simple solution, which can be conected to PC via single USB cable.

I was looking for simple audio CODEC and found WM8731. To have enough processing power for some simple DSP audio I chose cortex M4F microcontroller. There is also micro-SD on the board for audio recording and playback, two mini-DIN connectors with YAESU pinout and galvanic isolation for USB. I stareted this project few months ago. I will add posts when I will make progress with module programming.


The PCB is 80x45mm.

Here is schematic: modem

And PCB layout: lingva


Stay tuned for further progress reports.


The software will be published on git.

Dummy load

I was looking for dummy load on ebay for HF testing. All dummy loads were too expensive. Then I found bag of thick film resistors. Unfortunately they were 820 ohm, which is not optimal for 50 ohm load, but close enough. Then I constructed two PCBs.

The construction is simple…

000 001 002 003 004 005 006 007


At the end I would like to put everything into oil bath to make it more suitable for high power testing.

The small SMA connectior is for measuring via the 1:10 voltage divider.

Here’s altium PCB for the two boards: dummyload (31.10.2014 21-23-06)