The two meter and seventy cm ham radio bands are the most popular of all of the ham radio bands and it is where most new hams start out. The two meter band is a VHF or very high frequency band and the seventy cm band is a UHF or Ultra high frequency band.
Upon obtaining an amateur radio license or "ticket" generally a hams first investment is in a dual-band hand held two way radio, frequently referred to as an HT or Handy talkie, a term which developed from the old term: walkie-talkie. Customarily the amateur radio operators second investment is in a mobile dual band UHF/VHF transceiver or "rig" which they mount in their vehicle or radio Shack. These two rigs have very similar functionality but the hand held battery-operated rig is usually limited to a maximum output power of about 5 watts. The mobile radio which is connected to the vehicles twelve Volt power supply, or if it used as a base station, to a transformer supplying 12 Volts DC and is capable of transmitting generally up to about 35 watts.
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UHF and VHF frequencies are line of sight. Depending on the power output and the location of the transmission aerial UHF and VHF transmissions are able to reach the visible horizon and maybe just a little beyond, but that is the limit. There is one notable exception to this rule which is Tropospheric ducting, where under very unusual and quite rare weather conditions VHF and UHF radio signals travel very much further than the horizon. amateur radio operators take advantage of this phenomena when it does occur by communicating with other hams over great distances.
A 5 Watt Handy-talkie will have an operative range "depending on the terrain and elevation" of roughly 3 miles. A mobile rig on full power with a good antenna in a good location will probably have a maximum range of fifteen to twenty miles under favorable conditions. To get over this limitation in range amateur radio operators make use of radio repeaters, which are frequently owned and operated by amateur radio clubs, but some are privately owned. These radio repeaters are automatic transceivers that listen or receive on one frequency and transmit on a different frequency, this is frequently referred to as "the split". The radio repeater takes the signal that it receives on the input frequency and instantaneously retransmits it on the output frequency using a lot more power, generally about a hundred Watts. In addition to the higher power most of these radio repeaters aerials are located on the top of very high towers or high buildings which actually increases it's range.
A ham's Handy talkie can be used to transmit on the repeater's input frequency and receive on the repeater's output frequency effectively increasing the range of the hand held rig to just beyond the horizon, maybe even as far as thirty or forty miles. Many radio repeater systems have several receiving aerials located throughout the repeater's coverage area but just one main transmitter. In this way a large city can be completely covered with a radio repeater system with hams being able to receive the radio repeater just about anywhere in the city and they are able to be received by the radio repeater or "hit the radio repeater" as it is generally referred to, again from almost anywhere in the city.
Recently some repeaters around the globe have been connected to the World wide web and can be linked to each other using the World-wide-web. For example an ham radio operator in Moscow Russia with an Handy-talkie can chat through their local repeater with a fellow amateur who is driving in their car in New York city United States.
Some radio repeater systems are continually linked to each other but most are linked as and when required by the user and the link is dropped at the end of the conversation.
Most amateur repeaters are open to all licensed ham radio operators at no cost. These radio repeaters do take money to buy, operate and maintain. They are usually funded by club membership dues and events held by the club like Hamfests. If a ham finds themselves using a radio repeater frequently then maybe they should really consider joining the club that owns the repeater and help to finance it.
Black Friday DEWALT DC970K-2 18-Volt Drill/Driver Kit 2011 Deals
Nov 19, 2011 13:47:16
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