This is a post written by K0LAV (Paul), who is a local expert on commercial and amateur radio systems. He has graciously written this summary of digital amateur (FM) modes to clarify matters for prospective local operators.
Types of Digital radios that can or are being used with Amateur Radio
D-Star - (Digital Smart Technology for Amateur Radio). An amateur radio digital radio system (designed by the Japan Amateur Radio League) first introduced by ICOM in 2004. D-Star uses the GMSK transmission medium. D-Star provides both digital voice and high speed data modes. These systems can be IP linked for world- wide coverage. Currently there are at least 20 D-Star digital voice repeaters operating in Minnesota. There are 5 digital high-speed data stations operating in the Twin Cities. The voice repeaters are IP linked to a statewide “reflector” (master computer system) for operating statewide nets. A world wide IP linking system also exists that can be accessed by the Minnesota D-Star repeaters by connecting to other “reflectors” throughout the world.
Suppliers of D-Star equipment – ICOM, Kenwood has re-labeled some D-Star compatible radios but they have not been sold in the USA.
DMR - (Digital Mobile Radio) A dual time slot TDMA radio system designed for small business use that provides 2 independent talk channels within a 12.5 Khz radio channel. The Motorola TRBO DMR repeaters can be IP linked for additional coverage. 100s of world-wide IP linked TRBO amateur radio repeater systems currently are in operation, Twin Cities access to the world-wide DMR network is just being added.
Suppliers of DMR equipment – Motorola, Vertex/Standard, Hytera, Tait and Supura.
P-25 -(APCO Project 25) uses a modulation process called QPSK. P-25 is familiar in Minnesota as the ARMER 800 Mhz trunked public service radio system. Phase I P-25 uses C4FM (FDMA) modulation and provides one 12.5 Khz bandwidth signal per channel. The newer Phase II P-25 provides for two signals in a 12.5 khz radio channel using CQPSK (TDMA) and will replace Phase I in the future. Phase I and Phase II P-25 equipment is not compatible. There is one amateur radio P-25 repeater (using P-25 Phase 1) operating on the amateur radio frequencies in Mpls.
Suppliers of P-25 equipment – Motorola, Icom, Daniels Electronics, Tait and EF Johnson.
Yaesu - C4FM (Compatible 4 level Frequency Modulation). This system provides one 12.5 Khz wide signal (FMDA) and is very similar to P25 Phase I but with Yaesu’s special features added. Yaseu first announced this product in October of 2013.
Supplier of Yaesu equipment – Yaesu.
NOTES: 1) All of the above digital modes use the same proprietary DVSI “AMBE” vocoder to
encode/decode the speech to digital data.
2) GMSK (Gaussian Minimum Shift Keying) provides efficient use of spectrum
3) CDMA (Code Division Multiple Access) is a spread spectrum multiple access technique.
4) FDMA (Frequency Division Multiple Access) gives users an individual allocation of one or several frequency bands or channels
5) TDMA (Time Division Multiple Access) uses multiple time slots to provide two 6.25 Khz signals per radio channel.
Prepared by K0LAV Rev 10/12/14
No comments:
Post a Comment