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Thread: VHF Digital P25

  1. #61
    MembersZone Subscriber sdff1520's Avatar
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    Well, yeah, lots of them. Statewide VHF networks in South Dakota, Wyoming, Nebraska and I think North Dakota is doing VHF P25 for their statewide network as well. Several local agency P25 single site conventional systems both VHF and UHF in SD as well.


  2. #62
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    Quote Originally Posted by koechler View Post

    I had an engineer explain it to me and you're right "constantly being logged in" was a nonsense statement. Just because its constantly listening to the control channel doesnt mean it causes the radio to consume more battery. The high battery consumption im comparison to other digital standards like NEXEDGE and DMR are due to other reasons. How long does the battery of your ICOM radio last?
    Again, you are confusing technology. While in some trunked systems it may be
    constantly listening to a control channel, that is not the case in conventional system. It is decoding constantly however when listening to a P25 channel, and like any computer, that causes drain on the battery. Better battery technology and larger capacity batteries have helped this.

    Battery on my F70 lasts two days, as does my 9011. YMMV depending on usage, monitoring, etc.

    Quote Originally Posted by koechler View Post

    I guess I should specify when I say that a P25 system is not suitable for the fire service. I believe that it is not suitable for rural fire departments. Because of the high frequency used for P25 you would need a lot more base stations to cover the same area plus the equipment costs a lot more. I do believe, however, that any digital trunked system has clear advantages in high traffic urban areas as long as the radios are being switched to analog on the fireground (background noise problems)
    Blanket statements often get people into trouble. P25 is not frequency dependent. You could use P25 on low band, if someone made the equipment. VHF, UHF, 700/800 mhz P25 equipment is quite common. The amount of base stations in an area for coverage issues is for the most part band dependent.

    We can agree about analog on the fireground, and the background noise issue may not even be an issue anymore with the newer vocoders. I like my fireground very very simple.

    Quote Originally Posted by koechler View Post
    LVFD301, when would you recommend a fire department to go P25 and when not?

    Thanks for your help.
    P25 has some advantages. There are many areas in my rural coverage area that our analog system is broken or even non-existent, where I can switch to P25 and get through very clearly. (Non-existent may still be there, but not clear enough to enable the CTCSS at the repeater) As we narrowband, I see real issues - as people are seeing as much as 3db loss in systems that narrowband. We are going to have to do something different - our existing 5 repeaters are not going to narrowband and give us the coverage we see now, nor what we need.

    NOTE, P25 travels just as far as analog. It is the recovery of intelligible communications
    at the fringe that is affected.

    P25 may or may not be the answer. Simulcasting with voting may. Adding to the console system and making each department responsible for their own repeater may be the answer. Luckily I don't have to make that call. A very long string with two cans may be the prefered method.


    http://paapco.org/Power%20Points/Nar...%2016%2009.ppt

    talks about the coverage loss in a powerpoint show.

    http://www.simulcastsolutions.com/PD..._vs_wb_F14.pdf

    Is a bit more ..shall we say.. Technical.

  3. #63
    MembersZone Subscriber LVFD301's Avatar
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    Oh, and Missouri is building out a semi-statewide P25 VHF trunked system. (Urban areas
    will be 800)

    Many other areas have looked at it, but the big issue is lack of channels. In the midwest and west there are a lot more channel possibilities than say New Joisey.

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    Thanks for all this valuable information guys! One last question: From my understanding TETRA has a theorical maximum possible range of 35 km in normal configuration and 72 km in AGA mode meaning that low band or VHF wouldnt really bring much of an advantage range-wise. Right? The max range of DMR is 150km. What about P25?

    http://forums.radioreference.com/mpt...nge-limit.html

  5. #65
    MembersZone Subscriber LVFD301's Avatar
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    Quote Originally Posted by koechler View Post
    Thanks for all this valuable information guys! One last question: From my understanding TETRA has a theorical maximum possible range of 35 km in normal configuration and 72 km in AGA mode meaning that low band or VHF wouldnt really bring much of an advantage range-wise. Right? The max range of DMR is 150km. What about P25?

    http://forums.radioreference.com/mpt...nge-limit.html
    Have you ever been to a perfect world?

    I have yet to make it to such a place.

    My point? Those figures are for a perfect world - and that has yet to be invented.

    TETRA is a cellular architecture.

    RF range depends on the power, antenna, terrain and desired reliability.
    This is true for all systems, TETRA has no advantage over any other technology implemented with the same power on the same band.

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    Quote Originally Posted by sdff1520 View Post
    Well, yeah, lots of them. Statewide VHF networks in South Dakota, Wyoming, Nebraska and I think North Dakota is doing VHF P25 for their statewide network as well. Several local agency P25 single site conventional systems both VHF and UHF in SD as well.
    So basically states with very few ppl/sq. mile which makes absolutely sense. Do you know if the fire departments will keep their own infrastructure as a backup of if they eventually will get rid of it and even alert with P25? Please correct me, but isnt it a huge risk factor to have a statewide digital trunking system that can collapse because of the server going down?

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    Quote Originally Posted by LVFD301 View Post
    There are many areas in my rural coverage area that our analog system is broken or even non-existent, where I can switch to P25 and get through very clearly.
    Are you keeping your analog infrastructure as a backup, for alerting or both?

  8. #68
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    Quote Originally Posted by koechler View Post
    So basically states with very few ppl/sq. mile which makes absolutely sense. Do you know if the fire departments will keep their own infrastructure as a backup of if they eventually will get rid of it and even alert with P25? Please correct me, but isnt it a huge risk factor to have a statewide digital trunking system that can collapse because of the server going down?
    Most local agencies still have some infrastructure of their own for alerting. The statewide system does not provide for that. Many local agencies use the state system as their primary means of communication, some use it on occasion and some don't use it at all. All state agencies use the system, all local fire departments, ambulances and law enforcement have radios that work on the system, federal agencies in the state use the state system as well and even transit buses etc...

    Not a huge concern with the 'server' going down. A properly designed wide area trunking system has lots of redundancy built in. There are two network controllers running simulatneously, should one fail the other takes over. The systems are designed to prevent signle point failure and things that could cause complete failure are built with redundancy. In the event the building housing the network controller and and associated hardware were destroyed the system is still operational in 'site trunking' mode. All tower sites can work on their own, independantly and continue to process traffic, the wide area coverage is lost, can no longer talk from one side of the state to the other, but communications among units in the fied is still possible even if the network controller is non-existent.

  9. #69
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    Quote Originally Posted by koechler View Post
    So basically states with very few ppl/sq. mile which makes absolutely sense. Do you know if the fire departments will keep their own infrastructure as a backup of if they eventually will get rid of it and even alert with P25? Please correct me, but isnt it a huge risk factor to have a statewide digital trunking system that can collapse because of the server going down?
    Risk factor? Remember, we are talking about properly designed systems. Systems that depend on a controller should have two. Controllers should be in different regions of the state, and they should both be running concurrently. Add to that regional capability and even site based capability. Simplex if nothing else. Actually more robust and redundant than most analog narrowband systems.

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    Quote Originally Posted by LVFD301 View Post
    Risk factor? Remember, we are talking about properly designed systems. Systems that depend on a controller should have two. Controllers should be in different regions of the state, and they should both be running concurrently. Add to that regional capability and even site based capability. Simplex if nothing else. Actually more robust and redundant than most analog narrowband systems.
    Thanks again! LVFD, what are your reasons for keeping the analog infrastructure if the P25 network has better coverage and is just as reliable? This way you are maintaining two infrastructures.

  11. #71
    MembersZone Subscriber LVFD301's Avatar
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    You are reading things into what I said. The infrastructure may be more reliable IN A PROPERLY DESIGNED SYSTEM. Therein lays much of the rub.

    Agencies often can not afford a properly designed system, nor in many cases do they want one - feeling they know better than the engineers.

    I don't know that in a proper system you would need to keep analog

    There is also an issue with dependability of P25 in high noise enviroments. It IS better than it was, but it is not ideal yet.

    To me - I feel like P25 as a standard has not gotten their yet. We brought out one standard, and are about to bring out another - different p25 standard. Although the standard calls for the new radios to be backward compatable, why did we even go there in the first place.

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    Quote Originally Posted by LVFD301 View Post
    To me - I feel like P25 as a standard has not gotten their yet. We brought out one standard, and are about to bring out another - different p25 standard. Although the standard calls for the new radios to be backward compatable, why did we even go there in the first place.
    I absolutely agree on that.

    You should read this very interesting report from the FCC:

    http://energycommerce.house.gov/docu...07.26.2010.pdf

  13. #73
    Forum Member nmfire's Avatar
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    No matter what you do, there is still no such thing as a P25 voice pager that we're all accustom to. There probably never will be either. If you need voice paging, you will have to keep some analog infrastructure to accomplish that. Consequently, that same analog infrastructure can also serve as a backup for when the trunking system $hits itself.
    Even the burger-flippers at McDonald's probably have some McWackers.

  14. #74
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    Quote Originally Posted by koechler View Post
    I absolutely agree on that.

    You should read this very interesting report from the FCC:

    http://energycommerce.house.gov/docu...07.26.2010.pdf
    Yeah, thats been kicking about for a few months now.

    It all comes back to what is interoperability. It has been touted for too long and too much as a hardware issue when it is NOT, or at least the major part of it is not.

    But the training and people issues don't make money....

  15. #75
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    Quote Originally Posted by koechler View Post
    I absolutely agree on that.

    You should read this very interesting report from the FCC:

    http://energycommerce.house.gov/docu...07.26.2010.pdf
    Nothing very interesting in that 4 page drivel. They are admitting that what they told everyone would be the gold standard, is only fake green paint on tin plated potmetal.
    Nice advertisement for Mother though.

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