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  • NEXEDGE vs. P25

    I believe that analog systems with two-tone alerting covers the needs of almost all rural fire departments but I've heard from some departments that they purchased analog capable NEXEDGE or DMR base stations and are slowly replacing their analog radios with analog capable NEXEDGE/DMR radios. Currently they are still operating in analog mode but this way, they say, they can switch to digital as soon as all the equipment is exchanged plus they are ready for super narrowband (6.25Khz...if this is ever going to happen...)

    Their reason for getting NEXEDGE and not P25 was the price. While P25 is partially funded by the government we have to realize that only 20% will come from the fed. Who is going to pay the rest? P25 is more complex and expensive plus you will need approximately 4 times more base stations because of it being operated in the 700Mhz band.

    The downside: Well, again...not funded by the feds plus they wont be interoperable with the public safety departments that are implementing P25. But what if nobody around you uses P25? Why did such an expensive (and actually old) technology become the standard? The answer is: Motorola.

    The marketing people at Motorola did a great job. They made everybody believe that P25 is for mission critical communication and that DMR (Mototrbo), NEXEDGE, dPME is for business critical communication. There is no logical technological reason for this. No sorry...there is one. This way Motorola can charge a super premium for so called mission critical equipment. The only reason why a P25 radio can cost multiple thousand dollars is because there is not enough competition. TETRA radios (P25 equivalent of Europe) in comparison cost as little as $350.

    Funny enough: After their own dealers started to sell Mototrbo systems to fire departments their mission critical vs. business critical didnt seem to hold up anymore. Google "mototrbo public safety" and click on the 2nd link!

    I like to say:"Never touch a running system!" and that's why I hope that most of you will stick with their analog systems (at least for alerting). But I'm also wondering how many of you are looking into P25 alternatives when going digital.

  • #2
    Personally I won't consider moving our FD to any sort of digital system until the vocoder background noise issues have been resolved to the point where digital audio works as well or better than analog in all expected environments. The only way I'd do that is if the FCC drags me kicking and screaming by mandating 6.25 kHz operation. Fortunately, it looks like the vocoder issues may be resolved before that happens, although it still remains to be seen.

    Prior to narrowbanding, I see absolutely no advantage to having fire service communications use digital modulation for voice traffic. We generally don't need encryption, which has traditionally been the only reason to move to digital.

    Post-narrowbanding, digital may gain some range advantage in some situations, particularly for single-site systems.

    As for what form of digital, you're correct in that there is no technical reason for a public safety agency to use P25 instead of DMR. However, there is an operational reason, and that is interoperability. P25 is the public safety interoperability standard for digital voice. Unfortunately the P25 standard has moved slower than the pace of technology, and now other digital alternatives are widely available that are less expensive. This isn't surprising, as building a consensus standard among a variety of manufacturers is an extremely painful and slow process. It's much easier and cheaper for each manufacturer to simply do their own thing and put a product to market.

    Agencies that deploy non-P25 systems do so at the risk of sacrificing interoperability. While we can currently fall back on analog as an interop solution, there may come a day (6.25 kHz) when that's no longer possible, and a digital voice standard for interoperability will become even more important.



    • #3
      6.25 khz narrowbanding? Wow, that's news to me...then again I'm used to operating under NTIA standards and not FCC with Civil Air Patrol, we've only had to switch from 25 khz wideband to 12.5 khz narrowbanding.

      Anyway, as a Communications Director on the Group level, i.e. multiple counties, I've come to know quite well the pros and cons of P25 over the past couple of years since we've been pushing our conversion adamantly, on the orders of our National Commander.

      P25 is good in that it offers better signal quality, and also gives a slight range boost in the mid-dropoff areas when compared to analog. This of course allows you to get out a bit farther if you're somewhat on the fringe of your repeater or whatnot. The problem though is once you're out of range, you're screwed, period. There is no faint signal that you can make out by opening the squelch like there is with analog. Either you hear the transmission, or you don't. It's digital, packet data. And if the radio can't get the data, it doesn't get the information it needs to convert it back into analog sound waves. I used it myself during one of SC's (rare) snowstorms last year when CAP was placed on alert. Couldn't get out on analog because of the weather, so had to flip over to digital. Cut through the noise great.

      The other problem with P25 though is that if you don't have a dual-mode radio, you won't hear digital traffic. Our main radio that we use, the EF Johnson 5317 mobile and its handheld version the 5100 series are dual-mode. This means that regardless of which mode you're in, analog or digital, as long as you're scanning or on the channel, you will hear transmissions on that channel, analog or digital.

      My problem now is that due to some radio reassignments all my equipment is analog. A Motorola MTS-2000 handheld (the basic version with no keypad and the small one-line channel display on the top) and a Vertex VX-4204 for my in-car radio (Although it does happen to have listed as a national VHF calling channel my county's fire paging freq. They're probably not aware it's the VTAC 3, heh). So whenever we do our weekly checks, I can only participate on analog days, Thursday and Sunday. On the digital day, Tuesday, I have to get a relay from someone operating on digital equipment...that or I'm usually out at the building myself and of course there's digital gear out there.


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