If you were to ask a dozen different amateurs what ham radio meant to them chances are you would get 12 different answers. Radio amateurs have discovered a richly rewarding high-tech hobby that has many different appeals to different people. Whether it is the ability to talk to local friends over the radio waves using a hand-held transceiver (HT), communicating digitally with packet radio to exchange personal messages or vital information in an emergency, talking to other hams anywhere in the world, or engaging in contests with other Radio Amateurs over the airwaves there is something for everyone. The section What Hams Do gets into more detail about these activities.
Saturday, July 21, 2012
What is Amateurs Radio??
If you were to ask a dozen different amateurs what ham radio meant to them chances are you would get 12 different answers. Radio amateurs have discovered a richly rewarding high-tech hobby that has many different appeals to different people. Whether it is the ability to talk to local friends over the radio waves using a hand-held transceiver (HT), communicating digitally with packet radio to exchange personal messages or vital information in an emergency, talking to other hams anywhere in the world, or engaging in contests with other Radio Amateurs over the airwaves there is something for everyone. The section What Hams Do gets into more detail about these activities.
Friday, January 21, 2011
Wednesday, May 12, 2010
Saturday, July 12, 2008
Radio horizon
In telecommunication, radio horizon is the locus of points at which direct rays from an antenna are tangential to the surface of the Earth. If the Earth were a perfect sphere and there were no atmospheric anomalies, the radio horizon would be a circle. To compute the radius of the circle drawn on the earth in such a case use the formula:
This is the geometric straight line of sight horizon. For an equivalent formula for an antenna height in metres and a radio horizon in kilometres would be
These formulas are approximations for the case that the height is much smaller than the earth radius. The precise formula is
where r is the earth radius and h the height.
The radio horizon of the transmitting and receiving antennas can be added together to increase the effective communication range.
Antenna heights above 1 million feet (1966 miles, or 3157 kilometres) will cover the entire hemisphere and not increase the radio horizon.
VHF and UHF radio signals will bend slightly toward the earth's surface. This bending effectively increases the radio horizon and therefore slightly increases the formula constant. The ARRL Antenna Book gives a constant of 1.415 for the feet/miles formula for weak signals during normal tropospheric conditions. This can usefully be approximated as:
In practice, radio wave propagation is affected by atmospheric conditions, ionospheric absorption, and the presence of obstructions, for example mountains or trees. The simple formula above gives a best-case approximation of the maximum propagation distance but is not sufficiently adequate for determining the quality of service at any location.
From Wikipedia, the free encyclopedia
Wednesday, December 26, 2007
BLOG DEDICATED TO MY HOBBY HAM RADIO
Its begin when i accidentlty read a books regarding radio. I still remember the tagline on one of the chepter 'In radio or wireless comunications, a transmitter converts data into electromagnatic (EM) waves intend for recovery by one or more receivers'. After finish its me really getting aquainted with ham radio.