| VLF - komunikacja z łodziami podwodnymi. |
SP5XMI pisze: polecam przeczytanie patentu numer 5038406, na przykład tutaj http://www.freepatentsonline.com/5038406.html to brzmi ciekawie "both receivers employ a Cesium filled atomic resonance filter (ARF) to separate the blue-green beam from any background light" wąskopasmowy filtr 'optyczny' ..."They are used regularly in Laser Imaging Detection and Ranging (LIDAR) and are being studied for their potential use in laser communication systems. Atomic line filters are superior to conventional dielectric optical filters such as interference filters and Lyot filters, but their greater complexity makes them practical only in background-limited detection, where a weak signal is detected while suppressing a strong background. Compared to etalons, another high-end optical filter, Faraday filters are significantly sturdier and may be six times cheaper at around US$15,000 per unit." No i dzięki kolegom i forum coś ciekawego się dowiedziałem :-) choć bardzo daleko od tematu ;-) bo już dalej od VLF jak niebiesko-zielony laser to chyba by ciężko było coś znaleźć w widmie. |