GB7SU
The Southampton UHF DMR Repeater
Output: 439.4500 MHz, Input: 430.4500 MHz (DVU 36) Colour Code 8
IO90GW

GB7SU is currently operating from a temporary location in West Southampton, having operated previously from a site close to Dock Gate 10.
The long-term plan is to collocate GB7SU with the other Southampton repeaters to make DMR (Digital Mobile Radio) available to a wider amateur population.

The repeater is a Motorola DR3000 and the antenna is a 4-stack dipole array configured to give onmi-directional coverage.
   
In order to have access to the DMR network, a user ID is required. This ID is programmed into your DMR radio and is unique to you and can be cross-referenced to your callsign.

The DMR ID is obtainable from https://www.radioid.net/ just sign up and an ID will be issued. You will need a pdf copy of your licence which you can download from Ofcom if you don't already have a pdf version.

Ofcom can be found here https://www.ofcom.org.uk/manage-your-licence/radiocommunication-licences/online-licensing-service

DMR is a TDMA system - TDMA is Time Division Multiple Access. Basically, it's a digital system that has two time slots, allowing two concurrent conversations to take place on the same frequency.
This is easier to understand by viewing this diagram:
Analogue shown on the left is a constant carrier that we are all very familiar with when using for example an FM transceiver. With TDMA to the right, the time slots can be seen, there are two time slots each of 30ms, all in the same 12.5 KHz bandwidth of a standard FM transmission.

GB7SU is connected via the Internet to the Phoenix DMR network. This network consists of over 60 repeaters around the UK and many more around the world.

Your DMR radio will have what is known as talk groups, think of these as say, sub channels operating on the repeater. These talk groups are split across the two time slots. The different talk groups are for different functions, one for worldwide calling, one for European calling, one for UK calling then there are regional ones and others for general chat.

Below is a chart showing a list of talk groups and the time slot these talk groups are used on.

Those shown in green are permanently enabled talk groups. This means that if you transmit on say talk group 235 (UK wide calling) then your call will be heard on all the other Phoenix UK repeaters.

Those shown in orange are known as User Activated talk groups. This means that it is only active when you make a transmission on that talk group. If you transmit on talk group 82 and someone on another repeater transmits on talk group 82, those two repeaters are now linked together. They will continue to be linked until there is 15 minutes of no activity.

To initiate a contact, you may first go to one of the calling talk groups, this could be 235, the UK Wide calling talk group & announce for example 'G9XYZ monitoring talk group 235 for any calls'.

Once you have a reply, you can QSY to one of the appropriate User Activated talk groups, say 82 to continue the conversation.
Talk Group 9 is not linked to any other repeaters and is used for local chat. This would normally be on Time Slot 2.
Talk Group 810 (on Time Slot 2) is the Regional South West group. This is linked to GB7AV (Aylesbury), GB7BD (Bristol), GB7BK (Reading), GB7CT (Tring), GB7FI (Shipham), GB7KM (Cotswold Airport) & GB7TC (Swindon). Any transmissions on this Talk Group will be heard over all these repeaters.

Talk Group 9990 is 'Echo Server', this is good for testing your audio or the quality of your signal into the repeater. If you talk on this talk group, the server will repeat your transmission back to you immediately after you stop transmitting.

A full list of talk groups can be found here: http://www.dmr-uk.net/index.php/layout/

To see who has been active on GB7SU, take a look here: http://www.opendmr.net/monitor.php?filter=rpt&rptid=235136

A useful site to see what activity there is on the Phoenix network is here: http://phoenix-e.opendmr.net/# this lists all the UK repeaters and live activity, showing who is active on which repeaters & talk groups and also which talk groups are linked.

There are a selection of DMR radios available from the commercial models produced by Motorola or Hytera to those aimed at the amateur market from the likes of Anytone, TYT, Alinco, Wouxun etc.

Some dealers offer the radio fully programmed with all the UK repeaters (analogue & digital), simplex frequencies and a selection of other frequencies. It is advisable to have the programming cable & software too which allows you to insert your DMR ID & to make any specific changes/additions you may wish to do.

Personally, I find the Anytone D878 to be a super little radio, good quality sound, long lasting battery, a host of useful features and includes digital monitor mode which allows you to monitor all activity on a selected frequency, regardless of which talk group or time slot is in use.

The repeater keeper for GB7SU is Richard G4WFR, who can be contacted at gb7su@radio8.co.uk