The Motorola MTP700 was one of the first portable Tetra radios for the dutch emergency services. As in many cases also now there were quite some remarks after the radios had been purchased. It’s partially about ‘Special Coverage Locations’.
Special coverage locations
This term is used for locations in the Netherlands with insufficient coverage of the Tetra network ‘C2000’. These could be buildings with lots of concrete with rebars, tunnels, garages, etc. For emergency services it was a major hickup when finding out their radios had quit service in a large apartment building. Government, task forces, independent experts and many others were looking at each other and the summary was that nobody had ever told the network had to provide indoor coverage. Knowing this a long list with locations with insufficient coverage was created. To improve coverage on those locations, plans were made.
Gateway and DMO-repeater
One option to improve networkcoverage was the use of a so called ‘gateway’. This means the mobile radio in the vehicle would act as wormhole between DMO and TMO. All communication of the DMO talkgroup would be forwarded to network mode TMO and vice versa. The Motorola MTP700 offered the ability to connect to a gateway, but the mobile devices which had been built into the vehicles weren’t offering this option.
Another complaint was the low coverage of DMO. In cellars or larger buildings the use of DMO proved to be a challenge. In a matter of speaking the signal quality wasn’t better or worse than when using analog devices. But everyone was used to reconstruct the necessary information from a garbled signal. But digital communication devices had their limitations regarding this. The digital radio reconstructs the signal with mathematical error correction. But if the received dataflow gets too bad, the radio can’t reconstruct the information anymore and the radio provides either some robot voice or nothing at all. But luckily enough there was a DMO repeater. This mode turns a portable or mobile radio into a stand alone repeater by sending the received signal at a different time slot. By this everybody would be able to turn the own vehicle into a repeater. Except in the Netherlands: the mobile radios as well as the MTP700 portables weren’t able to handle DMO repeater mode.
Wet feet
As time passed on, another strange behavior of the Motorola MTP700 showed up. The radio didn’t like water at all. As soon as a drop of water came near by the radio, the audio quality became worse. and within a very short time the radio produced a Donald Duck like sound. Although the portable should be splash proof, this was very weird. Especially because the issue disappeared after an afternoon at the heating. So unlikely there was water in the housing of the radio. But it’s likely that water accumulated on the membrane covering the speaker, causing completely garbled audio. Luckily enough the police is never on the street when it rains… And also the fire brigade is never in contact with any water…
So then…
Currently most of the old equipment has been replaced (multiple times). Network coverage has improved a lot and also the terms ‘gateway’ and ‘DMO repeater’ are artifacts from the past. Special coverage locations still exist. Some are quite obvious: in a subterranean garage the Tetra network doesn’t exist. But at those location also the analog network would have quited. Other locations got improved (indoor) coverage after general improvement of the network or after installing an ‘indoor repeater’. Multiple larger buildings like hospitals have an indoor Tetra network as an extension of the C2000 network.