440 МГц жиілік бөлігі: Әуесқой радио және спутниктік байланыс үшін

Portion of radio spectrum allocated to amateur radio and amateur satellite use

The 70 centimeter or 440 MHz band is a portion of the UHF radio spectrum internationally allocated to amateur radio and amateur satellite use. The ITU amateur radio allocation is from 430 to 440 MHz; however, some countries, such as the United States, allocate hams 420 to 450 MHz. Depending on the country the band is shared with other radio services (in United States with government radar systems such as PAVE PAWS). and Trinidad and Tobago, the band ranges from 420 to 450 MHz with some geographical limitations. In Canada and Australia, the band is 430–450 MHz. In the UK, amateurs are allocated 430–440 MHz. By international treaty between the US and Canada, operation in the portion of the band from 420 to 430 MHz is prohibited north of Line A, which runs just south of the Canada–US border from Washington state to Maine, and east of Line C, which runs from northeast to southeast Alaska.

70 centimeter propagation characteristics lie midway between 2 meter and 33 centimeter (~900 MHz) bands. Above 200 MHz, as frequency increases, building penetration is reduced. Smaller obstacles may also block or reflect the signal. However, higher frequencies also present a lower noise floor, making it easier to overcome both natural and artificial interference, especially prevalent in urban environments.

Propagation considerations often take a back seat to channel availability or economic concerns in system planning. One practical concern when comparing the 70 centimeter band to the 2 meter band is that a quarter wavelength antenna is much less unwieldy at 70 centimeters than it is at 2 meters. Portable antennas for 2 meters are generally continuously loaded coil spring or "rubber duck" types, while on 70 centimeters they can be a full quarter wavelength. The difference can be as much as 8 dB. The primary advantage of 70 centimeters is that base station antennas of very significant gain (up to 11 dB or so) are practical while 6 dB is about the practical limit on 2m. The extra 5 dB of receive and transmit gain are often critical for long range communication, particularly for high power repeaters which can then concentrate all of their power and receive sensitivity at the horizon. The 70 centimeter amateur band also provides a wider spectrum than the 2 meter band (in the U. S., this is 30 MHz of spectrum, compared to only 4 MHz on the 2 meter band). and Switzerland, a portion of the 70 cm band overlaps with a secondary frequency allocation for the operation of Radio control models. In Germany, 33 frequencies were available for RC use, and in Switzerland, ten frequencies are available. These frequencies fall within the LPD433 band used by short range devices in Europe. In North America, licensed amateurs may conduct RC operations in the 70 cm band, but unlike similar operations in the 6 meter band, no specific frequencies have been set aside for RC use. American radio amateurs may use a maximum of one watt of radiated RF power, on any ham frequency authorized for data emissions, to control RC models. Canadian radio amateurs may use any amateur frequency above 30 MHz for the control of RC models. Plus or minus 5 MHz is a common repeater frequency offset in the 70 cm band.