{{unreferenced, date=July 2013 The Schematic diagram over the HamSphere system

HamSphere is a subscription-based internet service that simulates

amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communic ...

communication using

VoIP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...

connections over the Internet. The simulator allows licensed radio amateurs and unlicensed enthusiasts to communicate with one another using a simulated

ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an ...

. It was designed by Kelly Lindman, a radio amateur with

call sign In broadcasting and radio communications, a call sign (also known as a call name or call letters—and historically as a call signal—or abbreviated as a call) is a unique identifier for a transmitter station. A call sign can be formally assigne ...

5B4AIT. The system allows realistic worldwide connections between amateur radio operators as well as radio enthusiasts. In general, it is similar to other

applications (such as

Skype Skype () is a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for VoIP-based videotelephony, videoconferencing and voice calls. It also has instant messaging, file transfer, deb ...

), 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 call sign to be validated. The HamSphere system relies on different amateur online callbooks for verification before his or her call sign 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 software is written to run on Microsoft Windows, Apple OS X or Linux using

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

. Also available are mobile editions of the software running on Apple mobile devices (iPhone, iPod touch, and iPad) available from the Apple App Store, and on Android devices from the Google Play Store. The software is available for download as a free trial but requires a yearly subscription after the free trial expires.

Uses

Operators using the HamSphere software can operate it in two modes: *Simulation mode. This is the unique feature of HamSphere allowing the user to maintain connections under natural realistic conditions. Signals may vary and interference is present giving the user the impression that he or she is using a real shortwave

transceiver In radio communication, a transceiver is an electronic device which is a combination of a radio ''trans''mitter and a re''ceiver'', hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. The ...

. *Simulation off mode. This mode entails connection to other operators with the reliability of VoIP (noise-free) while maintaining the other typical characteristics of radio communication.

Operating modes

The HamSphere software has two modulation types: *

Double-sideband suppressed-carrier transmission Double-sideband suppressed-carrier transmission (DSB-SC) is transmission in which frequencies produced by amplitude modulation (AM) are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest pra ...

or DSB is the default mode of operation where the operator uses speech audio/phone. *

Continuous wave A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency, typically a sine wave, that for mathematical analysis is considered to be of infinite duration. It may refer to e.g. a laser or particle ...

or CW where the operator utilizes a built-in

Morse Code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of ...

keyer.

Propagation model

The mathematical algorithm for the wave propagation is based on a

stochastic Stochastic (, ) refers to the property of being well described by a random probability distribution. Although stochasticity and randomness are distinct in that the former refers to a modeling approach and the latter refers to phenomena themselv ...

model and pre recorded signal envelope.

Multipath propagation In radio communication, multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting, ionospheric reflection and refraction, and reflec ...

is achieved by inducing multiple simulated electromagnetic paths digitally thus producing signal

fading In wireless communications, fading is variation of the attenuation of a signal with various variables. These variables include time, geographical position, and radio frequency. Fading is often modeled as a random process. A fading channel is a ...

and audio distortion.

Detector and Filters

Signals are received and converted into audible form by using a

product detector A product detector is a type of demodulator used for AM and SSB signals. Rather than converting the envelope of the signal into the decoded waveform like an envelope detector, the product detector takes the product of the modulated signal and ...

mixing the

local oscillator In electronics, a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal. This frequency conversion process, also called heterodyning, produces the sum and difference frequencies from the frequenc ...

signal with the received signal, very similar to

Software-defined radio Software-defined radio (SDR) is a radio communication system where components that have been traditionally implemented in analog hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by me ...

. The

digital artifact Digital artifact in information science, is any undesired or unintended alteration in data introduced in a digital process by an involved technique and/or technology. Digital artifact can be of any content types including text, audio, video, ...

of the decoded audio signal is later filtered with a 17-order

FIR filter In signal processing, a finite impulse response (FIR) filter is a filter whose impulse response (or response to any finite length input) is of ''finite'' duration, because it settles to zero in finite time. This is in contrast to infinite impulse ...

with a bandwidth of 2.8 kHz.

References

* The HamSphere help file, from v 3.0.3.2 of the softwar
Short User Manual HamSphere

External links