Eight myths about DMR (MOTOTRBO).
· DMR is not compatible with analogue.
Simply not true, Motorola has a number of solutions which allow analogue and MOTOTRBO radio to interoperate and, in some cases, use the same system.
MOTOTRBO radios have the ability to scan an analogue and digital channel for activity – this ensures the radio user does not miss any calls on either system.
MOTOTRBO repeaters can be configured to operate in Dynamic Mixed Mode (DMM) which allows the repeater to switch between analogue and digital, depending on what signal has been received.
A number of Motorola Application Partners have easy to use solutions which allow the interconnection of almost any communication system, to a MOTOTRBO system. See the Application Partner link above.
· Switching to DMR is difficult to implement.
Since the MOTOTRBO radios and repeaters support dual mode (analogue and digital) operation, the process of migrating customers from a purely analogue system, to a purely MOTOTRBO system, is uncomplicated.
The rollover to digital can be implemented in phases and can be completed with virtually no disruption to communications.
Also, since MOTOTRBO uses existing PMR frequencies, no new spectrum licences are required (only a change to the ITU modulation code) and the existing RF infrastructure (i.e. filtering and antennas) can be reused.
· Switching to DMR will increase coverage.
Although the Forward Error Correction in MOTOTRBO radios, will increase the readability of received transmissions in weak signal conditions, there will be no improvement in coverage compared to analogue.
· Switching to DMR will eliminate or suppress interference.
DMR is not the magic bullet. If you are experiencing (or are perhaps causing) interference in analogue mode, you will still have interference (intermodulation) in digital mode.
The only thing that will change is the symptom: interference in digital mode sounds different to interference in analogue mode.
· You can have multiple repeaters on the same frequency pair (just use different colour codes).
DMR is not the magic bullet. The inability of operating two repeaters on the same frequency has nothing to do with DMR but is rather down to plain physics of RF.
If two repeaters have overlapping coverage, they should use different frequencies. If there is a small amount of overlap, and the area where the overlap occurs is of little consequence (i.e. on a mountaintop where few/no users go), then the two sites can be segregated by colour code.
Remember that in the area where the radio will either miss calls or produce garbled audio, if it receives two signals at the same time (a.k.a. doubling).
At least one manufacturer produces DMR infrastructure, which apparently supports simulcast operation but this is beyond the scope of this Blog.
· DMR is owned by Motorola.
DMR is a standard produced by ETSI. Motorola, along with a number of other companies (who also produce DMR equipment) were contributors to the standard but Motorola does not own the standard. MOTOTRBO is DMR but that is as far as it goes.
The manufacturers of DMR equipment however, have agreed to use the ABME2+ vocoder algorithm from DVSI Inc. - ABME2+ is licensed by DVSI Inc.
· Setting up a MOTOTRBO system is complicated.
No, setting up a MOTOTRBO system is just as difficult as setting up an analogue system. There is the MOTOTRBO System Planner; Motorola Solutions training and (of course) this Blog and my YouTube channel.
· DMR requires specialist test equipment.
Not entirely true, your existing analogue Communications Analyser can still be used to test MOTOTRBO radios. The radios have a built-in Test Mode, which allow you to perform all the necessary tests in analogue mode on predefined frequencies.
For details about the radios’ RF Test Mode, refer to the relevant Basic Service Manual.
Similarly, your existing power/SWR meter can still be used to check antennas – simply put the radio into Test Mode and check the forward and reflected power there. The power or SWR can also be checked while the radio is in digital mode, however some meters will only show half the true power because of the TDMA transmission. Some power meters will give erroneous readings (needle will jump around) and therefore the antenna should be checked in analogue mode.