www.AMARAD.org mise à jour août 2012

Association des Marins Radios
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TECHNIQUE V I E / R
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Exemple de Récepteur interfaçable sur PC 0,01 à 3300 Mhz tous modes Modéle ICOM PCR1500
WR-G33EM Marine Receiver The WiNRADiO WR-G33EM is a high-performance receiver specially developed for marine applications. It covers the HF frequency range to 30 MHz, and contains a number of decoding facilities including HF Fax, NAVTEX, DSC and TELEX, as well as classical AM, SSB and CW radio modes. A GPS option is also available which integrates the receiver with a high-resolution global mapping facility.
The receiver comes in a small enclosure which connects to an IBM-compatible PC (desktop or laptop) via the supplied USB cable. An external antenna connects to the receiver. Frequency range 9kHz to 30MHz AM, LSB, USB, DSB, CW conventional modes DSC, HF Fax, NAVTEX, TELEX marine modes High sensitivity Excellent dynamic range Real-time spectrum analyzer Spot-on tuning in 1Hz steps Continuously variable bandwidth Automatic scheduling, recording and playback GPS option
Software Defined Radio The WR-G33EM is the first Software Defined Radio specifically designed for marine applications. A Software Defined Radio (SDR) is one where most of the radio signal processing is performed in software, using digital signal processing methods, rather than using traditional hardware parts, resistors, capacitors, diodes, etc. The received signal is digitized early in the signal processing chain, and any further processing, demodulation and decoding of the digitized signal is then performed entirely in software.
Signal émis sur la fréquence 2187,5 kzh en test par un navire. Il est interessant de visionner la forme de ce signal en utilisant SKYSWEEPER un analyseur dont vous pouvez voir la description réalisée par LUXORION sur son excellent site web.
SKYSWEEPER This is a signal analyzer and multi-mode decoder developed in Finland using an original graphic user interface, and powerful DSP functions. To not be intimidated by all its windows and functions, as soon as you launch the unregistered version, the system suggests you to run the built-in demo. Accept its proposal, because it will show you some 27 scenarii explaining each function of the program and the many decoders able to translate in clear text or image many "strange" sounds that you can hear on HF or VHF bands. The main screen is (off-)centered around the "Configuration Editor" window, in which the user selects and set the required functions (Analysis, Generic decoders, DSP filters, signal generator, RX/TX, etc). Each function calls new windows that pop up on the screen (IQ Constellation, Signal View, Eye diagram, signal statistics, 2 bit Analyzer, 3D-FFT, Spectrogram, Chat box for mode decoding, etc). SkySweeper Pro provides a high resolution phase analyzer (HFFT) up to 262144 point FFT with a frequency resolution up to 0.04 Hz able to detect any fast periodic signal or a weak signal lost in the noise. It provides a signal power/amplitude analyzer, FIR filters and different synchronization methods to decode less common modulations like DGPS, MPT-1327 or POCSAG. SkySweeper Pro is able to determine automatically the signal speed, to lock automatically to the signal, to remove RFI or AC hum from a signal, and to translate most coded messages transmitted on the air. A clock correction for SSTV is also provided in system settings. It decodes CW (speed between 10-80 WPM, tone between 300-2700 Hz), VHF packet (AX.25) or ACARS transmission, SSTV (in Scottie1, 2, DX and Martin M1, M2 modes), SYNOP, etc (this latter weather report is even translated in plain English) and many digital modes (Hellschreiber, PACTOR, SITOR-A/B, PSK31, PAM, 240 lpm HF Fax, etc) without problem. Fonts displayed in decoders are also well readable (Courier 10 or so). About limitations, I decoded successfully a CW message up to 60 WPM, SSTV and many other modulations when the signal was loud and clear. However a CW signal slower than 10 WPM is not correctly read and a CQ 30 dB stronger than the noise but associated to "shadow pulses" as strong as 24 dB like during an Aurora or EME traffic cannot be decoded. A weak SSTV signal is not clear either. A DSP helped a little (lowpass, bandpass, modifying pitch, decreasing noise, etc) but didn't permit to get the signal out. But don't worry, many other amateurs products can't extract such noisy signals either. If you want to read audio files stored on disk, SkySweeper does only supports .WAV in mono, 8 or 16 bits/sample and a sampling rate of 11025, 22050 or 44100 samples/s. Knowing that many files are saved in 8192 samples/sec or in stereo, these limitations should be lowered. Several modes work also in transmission connecting the PC serial port (or parallel) to the radio and using the Chat Box interface to work in CW, SSTV, RTTY, PSK31, Hell, MFSK16, PSK63, PSK125, QPSK31 or 4MFSK16. You can even receive and transmit over the Internet providing the correct IP address. In the next release of the program, the publisher, Mikko Huttunen, will try to change the minimum CW speed to 1 WPM, support more SSTV modulation modes, and audio formats like .MP3, maybe .RA. What is my final impression ? We cannot compare such a software with a hardware decoder like Klingenfuss' Wavecom for example that is practically able to decode anything. SkySweeper remains a software, and like all its competitors it is limited by the performance of its algorithms rather than by the hardware, in this case limited to the sound card. However, globally, with so many features gathered in an user-friendly interface it is one of my favorite programs to decode common modulations but not under too noisy conditions or too weak signals, what happens sometimes. The program provides an online manual describing each field while a tutorial is under development. SkySweeper runs on all Windows 32-bit platforms equipped with a sound card. A demo is available. It comes in three versions, the lastest (Professional v5.x) providing additional generic decoders and analyzers. The entry-level version 3.x Standard should already satisfy most amateurs and listeners. All versions can be upgraded.
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