This section includes summaries of my radio projects and experiments. Amateur radio is a global technical and scientific community and these pages are my contribution. Some of these pages are simply overviews and how-to descriptions of fun projects and to show people what I am in to. I also include some of my notes to provide detailed descriptions of my experiments and their results. My notes are not research reports; I make them because they help keep me organized as I tweak variables while I run signal propagation and antenna analysis reports. My hope is that some of the projects inspire others to experiment.
The "QCX" is a 5W, single-band, high performance CW transceiver kit with WSPR beacon, and built-in alignment/test equipment.
End feds are a single wire, full length half wave single band or multi-band dipoles, operating without any radials. An end fed, antenna is still considered a dipole but its feed point is positioned at the end of a wire rather than the center.
WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. The program can decode signals with Signal to Noise ratios as low as -28 dB in a 2500 Hz bandwidth. Reception reports are automatically upload to a central database called WSPRnet, which maps and records the contacts.
KiwiSDR - Live streaming my software defined radio.
KiwiSDR is a software-defined radio (SDR) covering shortwave, the longwave & AM broadcast bands, various utility stations, and amateur radio transmissions, world-wide, in the spectrum from 10 kHz to 30 MHz. The KiwiSDR is a custom circuit board you connect to the BeagleBone Green or Black computer. You simply add an antenna, power supply and network connection. An HTML5-capable browser and internet connection will let you listen to a public KiwiSDR anywhere in the world. Up to four people can listen simultaneously to one radio — each listener tunes independently.
Note: This thing is seriously cool. You can tune in on any signal in the HF space and see all signals, all bands, and modes that my antenna picks up. Basically, I’m live streaming all data and voice signals picked up by my antenna. The Kiwi web interface allows you do do some wicked things. I like the TDoA algorithm which uses time difference of arrival with the receiver’s GPS to triangulate the location of any signal by working in concert with other public Kiwis…makes foxhunting numbers stations fun.
The QCX Transceiver contains a 200Hz audio analogue CW filter. Operating in CW, the CW audio filter is designed to produce a 700Hz signal. As such, the CW Tx/Rx frequency range in the transceiver is a 200Hz band around this reference frequency. This CW filter, however, limits Rx in WSPR mode, which covers a frequency range of 200Hz around a center frequency of 1,500Hz. This project note is a summary of the modification I made to the internal circuitry of the QCX transceiver, which allows me to receive in WSPR mode.
On March 27, 2019 I joined a discussion group at the CSU Mathematics Department. This presentation is a brief introduction to WSPR and some of the basics of sky wave propagation which served as a primer for the participants.