glSDR is a free program for the Android operating system designed and developed by Alex Lee Shing Cheung, an innovative application that lets to all amateurs radio and of radio listeners enthusiasts, through technology SDR (Software Defined Radio), to connect via the Internet to servers amateur radio to listen to radio stations all over the world. From the technological point of view, glSDR allows you to remotely control a radio SDR real, its operation is in relation to the hardware receiver placed online and developed within the Ghpsdr3-Alex Project, based on the SDR original software by John Melton G0ORX/N6LYT. The developer has also integrated the function to transmit in Voice mode, allowed after enabling the transmission with a User name and a Password when connecting to a secure server. Let’s explore this fascinating application to discover closely the characteristics and operating features. After downloading the program from the Google Play Store and verified that the installation is successful, staying connected to the Internet, launch the glSDR application from your Android device. Opening the application on the main screen are clearly visible, the server data and his operation status, the spectrum to warterfall in OpenGL ES 2.0 version, the tuned frequency, the signal status, the waveform in which peaks appear indicate the presence of radio activity, also, are manageable the zoom functions in the area of interest, the buttons to refine the search frequency, where the indicator represented by a vertical line brought into in alignment on a peak of the waveform goes to synchronize the radio station that is located at a certain frequency realizing the listening of the latter. If you open the application and screen is devoid of content, which means that you are not connected to any server or the server that we selected is not available, then you will see an error message telling you to try another server. Before being operational with glSDR you must be sure you are connected to a server, thus from the main menu to access to voice “Server”, here you will open a new window named “Select a Server” where we go to select a available server from the list, They will be given the IP number, the name of the server and the number of clients connected. It’s important to know that the first client that connects to a server is in Master mode, has control on the VFO, on the Bands, Frequencies and other functions of the SDR radio, the next client will be put in slave mode, and so others in this mode in which it is allowed only to listen and see the display spectrum cascade in passive mode. When the disconnects the Master client , the next client that is in Slave mode will become the new “Master” taking the control on all fuction of the SDR radio. It can happen that when connecting to a server in slave mode there is no audio output, it is likely that the bandwidth is exceeded due to many clients connected simultaneously. For a good setting glSDR explore the content within the main Menu, where we find the following functions: “Band” to select the band of interest to us on which we want to operate, available in 40, 30, 20, 17, 15, 12 and 10 meters, even in GEN and WWV, in addition, the Reset function; “Mode” to select the mode of transmission available in LSB (Lower Side Band), USB (Upper Side Band), DSB (Double Side Band), CWL (Continuous Wave Lower), CWU (Continuous Wave Upper), FMN (Frequency Modulation Narrow Band), AM (Amplitude Modulation), also in DIGV, SPEC, DIGL, SAM and DRM; “Filter” to select the filter can be set in the values of 5.0k, 4.4k, 3.8k, 2.9k, 2.7k, 2.4k, 2.1K, 1.8ke 1.0k; “Connection” to view, enter the IP number or Name of the server; “Receiver” to select the receiver among those listed, progressively marked by a numerical value; “AGC” to select the gain automatic voltage in mode: OFF, LONG, SLOW, MEDIUM and FAST; “DSP” to activate the digital signal processing in NR, ANF, NB, IQ Correction (you must activate Rx IQ correction only for servers connected to DSP-based hardware IQ, such as Softrock, UHFSDR, but not for the hardware in direct sampling, such as Perseus), and RX DC Block (this feature eliminates or reduces the central peak in some radio from the differential in the DC potential of the I and Q channels); GAIN” to set the gain value from 10 to 100; “FPS” to set the playback rate of the frames that make up the movement on the display; “Spectrum Average” to set the value of the spectrum of mediation, and as a filter FMN to 80KHz for listening to broadband in FM broadcasts; “Allow TX” to configure the transmission; “Button Move Spectrum” to enable the button to move the spectrum; “TX User Password” to enter the user name and password that enables the transmission; “MIC GAIN” to set the value of the microphone gain; “Master” to take over the master connection with authentication via username and password, generally recognized by the owner of the server; “About” for more information on your version of the application, and finally,”Quit” to exit the Menu. The glSDR application from the major operational capabilities on mobile devices is the result of a good job done by the author and his latest update is the version 48.
Source: glSDR / App Link: glSDR
Developer Link: Ghpsdr3-Alex Project