27 November 2016

Si5351 output waveforms

I finally managed to have myself some shack time this weekend and one of the curiosities I had was to check the output waveform of the Silicon Labs Si5351 I2C programmable VCXO. The chip is quite popular among homebrewers thanks to its low price, ease of use, the fact that it generates 3 independent outputs across a very wide bandwidth (8kHz to 160MHz) and that it offers lower phase noise than the cheap & cheerful AD9850/1 DDS modules.

Adafruit Si5351 module

By the way, there are also some versions of the Si5351 that have 8 independent outputs instead of 3, if you really need that many.

The test setup included an Arduino Duemilanove with the NT7S library, an Adafruit Si5351 module and a Tektronix 2225 oscilloscope. I used the middle output for the test (CLK1), which was terminated with a 75ohm load. Oscilloscope vertical scale is 0.1V/div and horizontal scale is adjusted depending on frequency.

First test, 100kHz output:

Si5351 output at 100kHz

Output looks like a clean square wave, with a nice rise time. Peak to peak amplitude is about 650mV into 75ohm, which puts the power output at 0.7mW (-1.5dBm).

30 October 2016

RedPitaya expands line-up with 7 StemLab models

Red Pitaya, the 21st century alternative to laboratory test instrumentation, have just replaced their single product with 7 new models called STEMlab.

The original Red Pitaya is a powerful piece of hardware that can act as a dual-channel oscilloscope or spectrum analyser, signal generator,  8-channel logic analyser, LCR meter, vector network analyser and much more. It has no problem working as a dual-RX dual-TX DDC/DUC HF+6m transceiver and there is even a project for a full featured final product in the works, called the Red Pitaya Hamlab.

It can do all these thanks to the fast 14-bit 125Msps dual-ADC, matching dual-DAC and powerful onboard FPGA, but mostly because there is a strong software development effort behind it. Most of the team was working on high-performance test instrumentation for particle accelerators before Red Pitaya, so they must know what they're doing.

Anyway, back to the new models: the first 3 of them use a more affordable version of the Red Pitaya original board, that has the 14-bit ADC replaced with a 10-bit one. They seem to be aimed at the educational enviroment where functionality and pricing is more important than performance. The naming scheme is intuitive, so here it goes:

Red Pitaya STEMlab 125-10 Starter Kit

24 July 2016

Onion Omega2 - $5 WiFi Linux computer

The Onion Omega2 is a miniature Linux computer with integrated storage and WiFi connectivity. It runs on Linux so it supports many programming languages such as C++, Python, PHP, nodeJS etc, plus there are apps you can install for different purposes.

The base Omega2 model costs just US$ 5 and comes with a 580MHz CPU, 64MB RAM, 16MB storage, b/g/n WiFi, 15 GPIO ports, 2x PWM, 2xUART pins and I2C, SPI and I2S interfaces.

14 July 2016

Baofeng UV-50X3 - new mobile radio

Baofeng just launched the UV-50X3 triband mobile radio and it looks like a jab, cross and left hook to the established japanese manufacturers who were caught dreaming about DMR, C4FM, D-STAR and other leprechauns.

Yes, the chinese manufacturers aren't creative, but they are really good at copying stuff and manufacturing it for a fraction of the price, so the resemblance to some japanese models shouldn't surprise you.

Or maybe the Yaesu FTM-350AR ?
Kenwood TM-d710 looks a bit similar, don't you think ?

27 June 2016

Yaesu FT-891 Operating Manual

The Yaesu FT-891 user manual has just been released and can be downloaded by clicking on the link below: