Progress Report: Big Box O’ RF

May 27, 2015 | Amateur Radio, Arduino, My Projects, WSPR | By: Mark VandeWettering

Previously, I wrote about a project I called the Big Box O’ RF. I’ve shifted goals a bit, and done some experimentation, and have changed some of my goals and approach.

First of all, I’ve changed the goal a bit. Instead of being a piece of test equipment, I’m actually more interested in using it to implement a beacon transmitter. It’s been quite some time since I have done any QRSS (slow speed Morse) or WSPR (Weak Signal Propagation Reporter) but I still find it to be a pretty interesting thing to do. What I’ve wanted to have for a while was a dedicated beacon transmitter that didn’t require the cooperation of my laptop and FT-817 to send out a modest signal. It seems to me that this totally doable mostly with parts I have on hand.


  • Output power between 250mw and 500mw
  • Controlled by an inexpensive microcontroller. While the Arduino would be an obvious choice, the Teensy LC or Teensy 3.1 are as easy to program, and offer some interesting improvements for similar cost.
  • Able to integrate multiple methods to keep accurate type of time. Initial prototype will probably use the Ultimate GPS I’ve been playing with. Alternatives include clock boards based upon the DS1307 or DS3231, or synchronization via Wifi/SNTP (almost certainly using the ESP8266).
  • Able to support multiple modes: at least WSPR, DFCW, and Slow Feld.
  • LCD panel to display information. Text based interface supplied via USB, allowing you to change message, frequency, timing, etc…
  • RF generated by my AD9850 module.

I’ve been tinkering with most of the modules independently, making sure I can interface with each of them. They all seem to work fairly well. As soon as I find an appropriate box, I’ll start getting them put together. I’ve built a harmonic filter for 30m (where I plan to do most of my operation). I need to work on the amplifier chain, as well as a little transmatch (I don’t want to dedicate one of my antenna tuners to this operation either).

More to come soon.


Comment from W4SDR
Time 5/27/2015 at 12:11 pm

Your system will be so cheap, and consume so little power, it could run off of solar/battery power. Which means you could afford to deploy it where the noise floor is lowest, and get some fantastic WSPR logs. Of course, the pleasure police are everywhere these days, but even they might not notice a little black box suspended between 15 meters of magnet wire high up in the pines…