“We said, why is it that complicated? It’s just to enable packet data, that’s it. And so we made a command to enable packet data and then our modem gets this command and it enables packet data. And that’s everything.”

Another problem solved by the board, he said, is that some Tetra base stations are apt to ‘forget’ telemetry devices after 30 minutes if they do not transmit frequently. “We had this problem and we solved it with implementing in our Tetra stack to send a packet to the base station. So maybe we fixed some base station bugs! We recognized it, and it was half a day!”

TECHNOLOGY FOR BIGGER DMR SYSTEMS

Motorola Solutions is not at present offering DMR Tier 3 support in its MotoTrbo DMR product family but instead has two system enhancements for implementing larger digital systems – IP Site Connect, which allows the linking of up to 15 repeaters at one or more locations, and Capacity Plus, a single-site trunking capability.

On the company’s stand at PMRExpo, DMR Direct Mode operation and Capacity Plus repeater operation are being demonstrated to show visitors by Wolfgang Meier, whose normal job is providing hotline support for Motorola’s network of dealers in Germany.

“I think I think you have heard something about DMR”, he begins. “DMR has two timeslots, each with 30 milliseconds, but only with 12·5?kHz [channel]spacing. This repeater is able to work in analogue mode or in digital mode. It’s the same with the portables: unlike with Tetra radios, here you can select an analogue channel. So it is possible to have first your standard analogue system with the old radios – maybe it has to be on the same frequency, VHF or UHF. Then, one day you can buy all new radios and work with analogue. And then one day you can change them all to digital.”

Picking up a handful of handportables, he continues: “These two are calling a group call on the first timeslot. And now I’m opening a new call and I’m automatically on the second timeslot. With Capacity Plus you can stick up to six repeaters, a maximum of 12 slots, and you have an automatic rest channel. The radios which are next speaking will automatically be pushed on to the rest channel.”

Capacity Plus can link up to six MotoTrbo repeaters at a site, adding the ability to support as many as 1200 users.

Professional amateurs

Mr Meier adds that IP Site Connect has already received a full workout behind the scenes at the hands of Motorola’s amateur radio club, whose members interconnected as many as 20 DMR repeaters. “But for using all the features the system has, you have to have not more than 15”, he cautions.

Club members were also able to access the system remotely from home via their broadband Internet connection. If the remote stations know the address of the master station, the whole system can configure itself automatically, updating the list of radios that are in the network. “It’s a very simple system”, Mr Meier observes, approvingly.