On Mon, Feb 8, 2010 at 11:08 PM, John Homer H Alvero <[email protected]> wrote: > On Mon, Feb 8, 2010 at 10:49 PM, fooler mail <[email protected]> wrote: >> On Thu, Feb 4, 2010 at 12:31 PM, Junix Gaspar <[email protected]> wrote: >>> >>> I wonder whats the proximity for a jammer... >> >> depends on the wattage and the height of its jamming device... >> >> the higher the wattage .. the longer its range... but you dont need to >> have a high wattage jamming device if you have a clear line of sight >> to your target... thats why external antennas such as cellsites, >> AM/FM/TV transmitter needs a higher structure... > > signal diminishes with distance, think of "free space loss". so yes, > distance is also a factor. the lower the MHZ, the more resilient it is > to LOS. 2.4ghz can penetrate more obstacle than 5.4. that is why > 900mhz systems are often dubbed as (non|near)-line-of-sight wireless.
hi, it only needs 1 watt of power for Apollo astronauts to communicate from the moon to earth... One of the biggest factors of reducing the range is the obstacles in the path of transmission... these obstacles absorb (eg. non-metallic objects) and reflect radio waves (eg. metallic objects).. another thing.. even if there are no obstacles at a longer distance.. you need a higher antenna because of earth's curvature .. this will give you a better line of sight... furthermore, regarding to low frequency versus high frequency... lower frequencies have a greater penetration power than to a higher frequencies for non-metallic object.. both degrade its signal based on the density of that non-metallic object... for a metallic object... although it reflects the signal for both high and low frequencies... if there is a hole in it.. higher frequencies can pass to that hole as long as its wavelength fits to that hole... higher frequencies have a shorter wavelength than lower frequencies... but longer wavelengths travel greater distance than a shorter wavelengths given on the same power output (watts)... fooler. _________________________________________________ Philippine Linux Users' Group (PLUG) Mailing List http://lists.linux.org.ph/mailman/listinfo/plug Searchable Archives: http://archives.free.net.ph
