Quote from: Neil White on Today at 05:47:08 am
How do the newer digital two way radio technologies such as Motorola MotoTrbo or Kenwood Nexedge compare to traditional analog two way radio systems for production communications? Are there any significant factors that need to be considered when designing systems that use these type of products?
Don't know. Maybe Henry Cohen will chime in.
I've been summoned . . .
There's two aspects I've found when looking at using DMR (digital [land] mobile radio) in production environments; first as a stand alone communications platform and second, if being interfaced to a hardwired PL system.
As a stand alone platform the biggest considerations are:
- Audio quality; slightly less pleasant than analog but generally fine. In high SPL environments however, TDMA codecs tend to get overwhelmed and intelligibility can suffer greatly.
- TDMA (Motorola Trbo and Vertex) vs. FDMA (kenwood & Icom); we all know what happens when a TDMA GSM phone is transmitting on the control channel when too close to RFI susceptible audio devices. FDMA also has the advantage of being true 6.25kHz voice channels in simplex mode without the need for the repeater, versus analog's and TDMA simplex's 12.5k.
- DMR bases and repeaters have some built-in or easily added option card capabilities for IP back bone connectivity to multiple sites, remote control & monitoring and voting. But this comes at higher base price for the DMR repeaters over analog.
- Analog maintains a price advantage for a similarly durable portable radio.
- DMR in digital mode can offer better battery life per charge.
- Higher tier analog radios can be found in compact models whereas all the current DMR offerings remain at the traditional size and weight.
- At the service fringe, analog will be noisier but can remain intelligible. Digital may remain completely clear a bit further, but will suddenly cut out completely or be unintelligible; it's not a graceful degradation.
- DMR offers immunity from casual evesdropping and many of the radio models offer some level of encryption.
When interfacing DMR repeaters or bases to a PL system, things can get interesting.
- Some DMR repeaters, when in digital mode, have no A/D - D/A for getting analog 4-wire audio in and out; you must purchase a separate dispatch console interface.
- There's inherent latencies in the A/D and D/A which could cause echoing or other anomalies with the interfacing.
- DMR radios in constant transmit seem to need greater cooling capacity and/or can't be set to the same power levels as analog. Not a major issue unless building multi-channel systems with transmitter combiner(s).
I've come to the conclusion that unless there is a feature or features specifically offered by digital radios that one would regularly use, it's not worth changing over one's inventory. That said, the fact that FDMA radios can be true 6.25kHz/voice channel in simplex, the spectral efficiency aspect is not insignificant these days.
