In message <[email protected]>, dated Tue, 7 Oct 2008, Gert Gremmen <[email protected]> writes:
>It's a typical example of international frequency regulators (ISO/ERC) >failing. Who the heck decided it was a good idea of allocating the 2.4 >GHz band (ISM frequency) to Wireless LAN's ? Of course the actual >decision was made by the standardization committee that wrote IEEE (!!) >802-b/g (any family?)to make sue of a licencse free band) I don't think those bodies are responsible (or not entirely). Frequency allocations are agreed internationally by ITU (but are not necessarily agreed on a world-wide basis, but by regions). > but this by lack of a suitable "free frequency". Or at least they were >thinking that a LAN would never approach a MicroWave oven. Good luck >that these devices operate on a rectified AC power without any >capacitance, so they switch off every half period, They have full-wave rectifiers, so it's the 2.45 GHz that switches off when the rectifier output voltage is too low, but the mains current doesn't switch off. On the other hand, the switching-off creates a comb of sidebands around the oscillation frequency at frequency separations equal to the mains supply frequency and its harmonics. So it's difficult indeed to avoid the emissions by selecting a particular carrier frequency (or frequencies) within the band for LAN use. > during which the LAN has the time to transfer some data. > >Many GHZ go unused currently, reserved to some non-operating system or >defense applications that may or may not be used one day. > >Take for example the 2900-3100 Mhz band could have been allocated at >the time to short range devices in a similar way as 2400-2483.5 has >been allocated today. But regulation agencies are always too late in >recognizing the market... Like the US Senate, the maxim is 'with all deliberate speed'. The decisions have to take in very many interests and be as 'future-proof' as possible. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Either we are causing global warming, in which case we may be able to stop it, or natural variation is causing it, and we probably can't stop it. You choose! John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
