All things 900 Mhz

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The 33-centimeter or 900 MHz band is a portion of the UHF radio spectrum internationally allocated to amateur radio on a secondary basis. It ranges from 902 to 928 MHz It is primarily used for very local communications as opposed to bands lower in frequency. However, extremely high antennas with high gain have shown 33 centimeters can provide good long-range communications almost equal to systems on lower frequencies such as the 70-centimeter band. The band is also used by industrial, scientific, and medical (ISM) equipment, as well as low-powered unlicensed devices. Amateur stations must accept harmful interference caused by ISM users but may receive protection from unlicensed devices.

Today, the 33-centimeter band is rapidly becoming popular with many UHF enthusiasts. Currently, it is used by amateurs for a variety of purposes. FM repeaters Until recently, no amateur radio equipment manufacturer has ever made an FM repeater for the 33-centimeter band. But nevertheless, amateurs have adapted other equipment for use in this band. Amateurs who wish to build a repeater and those who wish to use that repeater must do so using modified commercial equipment designed for use in the mid-800 MHz and mid-900 MHz range. The bulk of modified commercial equipment is manufactured by two companies, Motorola and Kenwood.

In 2012, the first two-way 900 MHz radio made specifically for the Amateur Service was introduced by Alinco. The DJ-G29T is a dual band portable radio operating on the 222 MHz and 900 MHz bands and is fully programmable.

Amateur television Amateur television is a popular activity on the 33-centimeter band, and some manufacturers produced ATV equipment for this band. The first repeater to use the band, the NU6X/R (Amateur TV Network) on 923.25 MHz, was activated and used at the minute the FCC allowed amateur use of the band and featured in QST Magazine. The repeater moved to 919.25 MHz and call changed to W6ATN because AVM part 90 service at 927 MHz began operation as a primary user of the band.

CW and single sideband Amateurs who are involved in contesting use home-made or commercially available transverters to operate CW and SSB on the lower end of the band, either just above 903 MHz or just above 902 MHz. SSB/CW operations usually use horizontal polarization for most contacts. VHF/UHF contests are conducted by the ARRL several times each year to encourage operations across all ham bands. Contacts must be made in the simplex mode - that is, without using a repeater. Any mode (FM, SSB, CW) can be used. Contact scoring is higher for 33 cm than the lower bands (6m through 70 cm).

Amateurs who use local repeaters on the 33-centimeter band use commercial handheld or mobile 900 MHz radios. As shown above, these radios can transmit between 896 and 902 MHz and receive between 935 and 941 MHz. Getting many of these radios to transmit on the repeater's input frequency (between 902 and 903 MHz) and receive on the repeater's output frequency (between 927 and 928 MHz) usually requires very little or no circuit modification, depending on the choice of radio. For instance, the Motorola model GTX (mobile and handheld versions) do not require any hardware modifications at all. Using these commercial radios, however, has one handicap: flexibility. Unlike most other ham radio bands, in which one can tune to any frequency within an amateur band, modification of "Channelized" commercial radios maintains them in a channelized state. Therefore, once programmed, the frequencies they operate on cannot be changed at will without re-programming. However, since almost all FM radio equipment used on the 33 cm band amateur band was previously designed for and internally programmed for frequencies outside the 33 cm band edges, reprogramming is always necessary to get them working properly between 902-928 MHz after any physical modifications have been made. This includes the GTX.

Popular equipment used on the 33-centimeter band EF Johnson models 8615, 8640, 8644 and 8655 GE DTMX 9315B (TMX) Ericsson MDX GE Mastr II GE Mastr III MA/Com Orion Kenwood TK-480 / Kenwood TK-481 Kenwood TK-980 / Kenwood TK-981 Kenwood TK-931 Alinco DJ-G29T Motorola MaxTrac Motorola Spectra Motorola MSF 5000 Motorola GTX Motorola MTX Motorola MCS 2000 Motorola XTS 2500 Motorola XTS 1500 TAIT T800 Series "eXRS" 900 MHz FHSS Part 15 radios Downeast Microwave 902-144HP3 transverter

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Useful websites for more information.


Skyler, W0SKY Serious 33cm activity abounding in the Western portion of the United States Skyler F YouTube




Southern California 33cm Amateur Radio Group

GENERAL DISCLAIMER, this wiki site and the content are presented solely for informational/educational purposes only! If you chose to follow any link or procedure outlined herein, you do so at your own risk. All trademarks, trademark names, service mark names, trademark images and logos used on this wiki page are done so with an educational or informative intent. All trademarked names belong to the owner and no violation or infringement is intended. Note that the repeater operational rules vary from country to country. What is legal in one place may not be legal in your area. Check before you use 33cm. 73, Have fun, be thoughtful, help your fellow ham and most of all operate safe.