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NATURN
                              Trunking in South Africa
 

 

 


TRUNKING

 

 


5 Oct07: Been busy over the passed few week with new digital radios in the form of the type :P25 .

This has been a very interesting time to test the mixed mode operation and in my mind is the way of the future .When comparing what these radios are capable of , the D-Star functionality regarding voice is somewhat lacking.

 

We have very few ham activity on the digital audio modes in S.A .

Listen to an audio test: Analog /Digital C4FM test

 

On the left is the HT1250 and on the right is the ASRTO Saber III.

 

I have my own yahoo group relating to the Astro radio parameters , by invitation only .

 

 

 

Brief History : Public Trunking

 

South Africa brought trunking to the public sector in and around 1993.

 

Two major players invested in the networks .

 

Q-Trunk owned and maintained to this day by the state owned telecoms company called Telkom SA.Q-Trunk website

 

Fleetcall at the timed was owned and maintained by the State Railways offspring called Transtel.http://www.fleetcall.co.za/

 

The third regional operator only rolled out in KZN region , this being One2One

 

The frequency allocation was the 254-000 Mhz starting block at 12,5 khz with an offset of 8Mhz(Mobile Tx at 262-000.)

 

The block allocation was intermediate where the total of 432 channels were sub-divided into rows and colums .A-R across and 1-24 down )

 

Click on this link to see how the channels are defined in order to allow greater separation between the channels which allow for better spectral usage.

South African 250_Mhz Tunking_block.xls

 

Systems:

Q-Trunk : Marconi RNC and TSC’s where the RF hardware was locally produced Q&D transmitter/Receivers .Use mpt1343 numbering scheme .Q-Trunk offers the ACT NOW Voting which is extremely effective and allows the on-the-move mobiles to keep in the best RSSI and BER from the control channels .

Fleetcall : Fylde TSC and Key RF hardware .MPT1327 numbering scheme. Fleetcall seem to use voting more for load sharing in busy urban areas.

One2One :Nokia Controllers with Key and other RF .

 

Having worked in the environment each system had its own unique advantages.

 

Current Systems : Q-Trunk and Fleetcall still operate but One2One folded where the equipment was bought by Fleetcall/Transnet.

 

Systems are slowly being deployed in small confined areas such as the petrochemical companies but non in the way of private commercial ventures to superceded the old community repeaters .Our railways are currently using a UHF system BASE TX :455-000 that superceded the old allocation for the C-450 mobile telephone system. Their system is well used together with PSTN and PABX connections.

 

Trunking AFFSK : The data one hears on the Control Channel (CC ) and traffic channel (TC ) is 1200 bps 1200 hz and 1800 hz making up the binary 1’sm and 0’s .

Here are some explanations to the control channel and voice messages

Trunking\Control_Channel.WAV (App 1 min of downlink contol data on the given CC)

Trunking\Control.txt

Trunking\Voice_call_TC.WAV

Trunking\Simple_Voice_call.txt (note the BCAST Act now vote message)

Trunking\Simple_Voice_call_a.txt (Simple voice call setup over CC )

 

 

Future :I would like to see our government force the original Sabre migration from owners who have more than one community repeater on a site , over to a trunked system in order to make better use of the channels .Currently there are no private radio trunking systems in the greater KZN region.

 

I have in the past looked at a single channelled site linked into our current UHF system and that interest has been renewed.

I have read of other countries looking at a similar venture for disaster type scenarios in the field of emergency communications .This type of system together with its rich data/status messaging could be vital in disaster recovery exercises .

 

Our country does not have a variety of trunked systems and the growth has been somewhat stunted with the advanced cellular rollout .

 

Amateur Project: I have been trying to get a TSC in order to run an experiment for my own interest on perhaps UHF . (So if you have one such as a Zetron 827 of Fylde TSC – I would appreciate any donations towards this idea. )

 

A great idea could be that of some of the now redundant One2One allocation possibly being used for amateur experimental purposes.

Perhaps those that use trunking commercially could use simplex into their respective area repeaters .

At the moment these frequencies have been idle for some years now and they could be very interesting .

For mobile communications the 250 Mhz band works very well as it is not uhf and seems better than the amateur VHF allocation .

 

MPT 1327 /LTR and other trunking could be beneficial to the South African market but unfortunately some of the radio companies are less informed so they are hesitant to approach any form of trunking .

 

 

 

 

 

 

 

 

HARC Club Bulletin Schedule
7.055MHz 07h45 GMT +2 Sundays


 

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