Hi, Saturdays 27 March 1999 took place at Muret (sub-prefecture of Haute Garonne department), near Toulouse, at the show for radio hams SARATECH, tests of high speed transmission via packet radio. For the first time in France F1BIU and F6FBB succeeded in transmitting digital information between two stations via packet radio with 76800 bauds on 1,2 GHz. Success was not guaranteed insofar as there developed separately radio and software data-processing having to be carried out by Victor F1BIU and Jean-Paul F6FBB, each one of their side. Briefly, the configuration was the following one: Jean-Paul F6FBB had prepared two computer Pentium 100 MHz with 16 MB of memory RAM, disc 200 MB, equip with HDLC SCC4 ATEPRA cards and G3RUH FSK modem with the addition of a adapter card by F1TE. Jean-Paul has already given on the "frpacket-sys diffusion list " the modifications necessary for the SCC4 card (for the use of modems providing RX and TX clocks). The operating system was Linux 2.0.36 (SuSE 6.0) on each PC (memory 16 MB) with modules AX25, ROSE and FPAC. Parameters EAX25 were MAXFRAME 63 and paclen 256. The packages were 16128 bytes. For the radio part, Victor F1BIU had assembled two sets of his kits TRX 1,2GHz. In fact, Victor had cable four of it partially. One can indeed cable on his printed circuit the TX and the RX or only one or both. If the both were cables, one can make only some connection in rotation (half duplex) by commutation emission and reception. On the other hand, if the TX and the RX be on separate cards, that will allow it to function in full duplex with the free choice of deviation from instantaneous frequency (variable according to the country). Two antennas's brought in by F6BVP in its luggage and have been contributed for the connection that will be only of a few meters between the two stations. The reception antennas were quarter wave 144 MHz. An oscilloscope displayed the clock RX of one of the receiving modems and the eye diagram. The first tests were carried out in half duplex. That made it possible to validate the operation of the connection package with transmission of frames tested with TCP/IP. The scrolling speed of the frames on the screen was impressive. For illustration of a little more alive high-speed transmission, it was decided to install on one of stations Netscape Navigator Web Browser and on the other station a Web server of pages with the image of the Internet site of F6FBB. But a problem emerged. Only one of the PC's was equipped with a CD/ROM. Drive, that's no problem with the installation of Apache (httpd) server installation, a connection can be made through the link at high speed. The transfer was complete in some minutes and the F6FBB CD was installed ! It will now be possible to connect to the server of F6FBB from the distant station by connecting with Netscape its good practice to see the speed display of data during the loading of images I made a note of speed of 5500 character per second. It was now decided to change, the configuration of the SCC4 card to full duplex (by changeing dynamic of only one parameter with sccparam), we noticed an accelerated speed until up to a point of 6500 character per second. The text and images JPG were displayed then more quickly on the screen. More quickly than a connection by modem on the Internet. One should be able to obtain rates of transfer even faster by optimizing the parameters of the TCP/IP. In its test preliminary Jean-Paul has indeed obtained different speeds according to the power of processor of PC. Speeds of 7000 to 7500 characters a second ... It should be noted that the Linux system is very well comprised since the cutting of several secondary links has disturbed nothing the unfolding of session, which take again when the link is restore. In addition, the design of SCC4 card involves the generation of a interrupt by character, be until 7500 interruption software by second, what constitute a load significant for the operating system. See F1BIU pages for high speed packet 1.2 GHz TRX with Linux at the following URL : http://www.ccr.jussieu.fr/physio/f6bvp/thd2.html 73 de Bernard Pidoux, F6BVP. Universite Pierre et Marie Curie - Paris 6 tel. +33(0)140-779-776
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