ARLA/CLUSTER: Tecnologia TDMA para as bandas de amador?

[João Gonçalves Costa]

TDMA - A sigla TDMA vem do inglês Time Division Multiple Access , que quer dizer "Acesso Múltiplo por Divisão de Tempo". O TDMA é um sistema digital que funciona dividindo um canal de frequência em até seis intervalos de tempo distintos. Cada utilizador ocupa um espaço de tempo específico na transmissão, o que impede problemas de interferência.

Mais informações sobre a tecnologia TDMA em:
http://tinyurl.com/4blpw5q

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TDMA next development in amateur radio?
 
Time division multiple access (TDMA)* is a channel access method for shared medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. 

The users transmit in rapid succession, one after the other, each using his own time slot. This allows multiple stations to share the same radio frequency channel.

On Tuesday, March 15, the ARRL filed a Petition for Rulemaking and a Request for Temporary Waiver to authorize the use of single-time-slot Time Division Multiple Access (TDMA) emissions in the amateur radio bands at and above 50 MHz, wherever multiple-time-slot TDMA is authorized.

The ARRL - which called its Petition "very narrow in scope" - seeks to facilitate the use of and experimentation by radio amateurs with existing narrowband spectrum-efficient digital voice and data technology." Such technology is now in regular and increasing use in the private land mobile radio services, but its use in the Amateur Radio Service is now apparently unintentionally precluded by two specific Commission rules," the ARRL's Petition stated.

Radio amateurs are presently using a Motorola narrowband (12,5 kHz) digital land mobile system - commercially marketed as MotoTRBO and they ask to make it legal.

The use of TDMA digital emissions in certain frequency bands in the Amateur Service is on the increase, the ARRL noted. There are numerous narrowband UHF repeater facilities now operating that use multiple slot TDMA repeaters and single slot TDMA handheld digital transceivers, principally in the 70 cm band. These systems have been installed primarily in the western part of the US and in the New York City area, but also in several Midwestern states.

The South African Radio League (SARL) is currently studying the ARRL initiative in respect of the South African Radio regulations. Comments and input are invited to artoday  sarl.org.za