| • Science | • People | • Locations | • Timeline |
The 33 centimeter band has a somewhat short history, being one of the newest amateur radio bands.
In 1985, the Federal Communications Commission allocated the frequency band between 902 and 928 MHz to ISM (Industrial, Scientific, and Medical) devices. In that proceeding, the band was also allocated to the Amateur Radio Service on a secondary basis meaning amateurs could use the band as long as they accepted interference from and did not cause interference to primary users.
In the mid 1990s, many cordless phone manufacturers started producing phones that used the lower and upper ends of the 33 centimeter band for communication between the handset and base. These phones, which are regulated by Part 15 of the FCC's regulations, have made amateur use of the upper and lower end of the 33 centimeter band somewhat tricky due to the amount of these phones being used by the general population. Part 15 devices, by law, have to accept interference from any licensed radio service with which they share frequencies.
Today, the 33 centimeter band is rapidly becoming popular with many UHF enthusiasts. Currently, it is used by amateurs for a variety of purposes.
Amateurs who are involved in contesting use home-made or commercially available transverters to operate CWA continuous wave (CW is an electromagnetic wave of constant amplitude and frequency. An early method of radio transmission was continuous wave and consisted of an unmodulated carrier wave; unlike modulated modes, it has no information (in the communicati and SSB on the lower end of the band, usually just above 903 MHz. Depending on the contest, a contact made on the 33 centimeter band can get the contester more points than if the contact was made on another band.
Curiously no amateur radio equipment manufacturer has ever made an FMFM redirects here, for alternate uses, see Fm Frequency modulation (FM) is the encoding of information in either analogue or digital form into a carrier wave by variation of its instantaneous frequency in accordance with an input signal. This is typically radio for the 33 centimeter band. Amateurs who wish to build a repeaterIn telecommunication, the term repeater has the following meanings: #An analog device that amplifies an input signal regardless of its nature (analog or digital). A digital device that amplifies, reshapes, retimes, or performs a combination of any of thes and those who wish to use that repeater must do so using commercial equipment designed for use in the mid-800 MHz and mid-900 MHz range.
For many years, repeaters on the 33 centimeter band used a split of -12 MHz with inputs between 906 and 909 MHz and outputs between 918 and 921 MHz. Today, many new repeaters are using a split of -25 MHz with inputs between 902 and 903 MHz and outputs between 927 and 928 MHz. The reason behind this is that the selection of equipment that can be modified for a -12 MHz split is mainly limited to commercial repeaters and data radios which tend to be older, more expensive, harder to maintain, harder to find parts for, and very time consuming to modify.
With the explosion in popularity of Nextel phones with a push to talkPush to talk commonly abbreviated as PTT, is a method of conversing on half-duplex communication lines, by pushing a button in order to send, allowing voice communication to be transmitted from you, and releasing to let voice communication be received. feature, the marketplace has seen a flood of newer 800 and 900 MHz commercial mobile radios that are designed to the following specifications:
The receivers on many of these modern 800 MHz radios can be easily modified to receive higher than 870 MHz, to about 904 MHz with good sensitivityThe sensitivity of an electronic device, e. a communications system receiver, or detection device, e. PIN diode, is the minimum input signal required to produce a specified output signal having a specified signal-to-noise ratio, or other specified criteri. In addition, the transmitters on many of the aforementioned 900 MHz radios can be easily modified to transmit lower than 935 MHz, to about 926 MHz with acceptable power output. With this in mind, many amateurs have opted to set up repeaters with -25 MHz splits using modified 800 MHz radios as receivers and modified 900 MHz radios as transmitters.