HamSphere is a software Amateur Radio simulator that allows licensed radio amateurs and unlicensed enthusiasts to communicate with one another using a simulated ionosphere. It was designed by Kelly Lindman, a radio amateur with callsign 5B4AIT.
The system allows realistic worldwide connections between amateur radio operators as well as radio enthusiasts. In general it is similar to other VoIP applications (such as Skype), but with the unique addition of characteristics such as channel selection by tuning, modulation, noise effects and shortwave propagation simulation.
Before using the system it is necessary for a radio amateur's callsign to be validated. The HamSphere system relies on different amateur online callbooks for verification before his or her callsign is added to the list of validated users.
The system may be used without a verified radio amateur license and has a callsign generator providing unique unofficial HamSphere callsigns. The unlicensed user is required to pass a small exam before getting access to the system.
The software is written to run on Microsoft Windows, Apple or Linux using Java. There is another edition of the software running on Apple mobile devices (iPhone, iPod touch, and iPad), and is available as beta on request.
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Operators using the HamSphere software can operate it in two modes:
The HamSphere software has two modulation types:
The mathematical algorithm for the wave propagation is based on a stochastic model and pre recorded signal envelope. Multipath propagation is achieved by inducing multiple simulated electromagnetic paths digitally thus producing signal fading and audio distortion.
Signals are received and converted into audible form by using a product detector mixing the local oscillator signal with the received signal, very similar to Software-defined radio. The digital artifact of the decoded audio signal is later filtered with a 17-order FIR filter with a bandwidth of 2.8 kHz.