1. #1
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    Default APCO P25 Question

    I have been reading up on APCO Project 25 systems and have a question on interoperability. If a P25 system were setup on 154MHz (local FD for example) how would it interoperate with an 800 MHz P25 system from another jurisdiction, such as State Police? Would the fire dispach center need to have a radio for the 800MHz system or is the data sent to the respective dispatch center for transmission on their system?
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    The two P25 systems in different bands (800 and VHF Hi) are NOT interoperable. The only way to get those two radios 800 and 150 to talk to each other is with the intervention of a dispatcher with access to both systems, or if the two systems are linked (many possible equipment solutions here) ie... whats transmitted on one system is also automatically transmitted on the other.

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    In other words...

    No 154Mhz radio is going to work on 800Mhz
    No 800Mhz radio is going to work on 154Mhz

    The only way to cross radio traffic from one band to another is with some kind of hardware. This can be a console patch or a dedicated cross-link controller, or one of these fancy new interoperability controllers. In any case, being P25 or not has no bearing on it. The hardware senses RX on the 154Mhz side and keys up the 800Mhz side, passing the audio through. Vis-Versa, the hardware senses RX on the 800Mhz side and keys up the 154Mhz side, passing the audio through. You could use P25, VSELP, DES, OpenSKY, LTR, Type II trunking on one side, and a radiating jelly donut on the other side. It doesn't matter.

    So what the hell is the point of P25? It is for IN BAND interoperability. The biggest use of this is for 800Mhz trunking systems. Previously, there were several proprietary standards and nothing worked together. Now, if everyone builds to P25 standards, everyone can talk to eachother. (P25 is a whole set of standards, not just digtal modulation). The digital modulation allows for integrated voice and data as well as the voice quality improvements when it is working properly.

    Now, as for making a single conventional repeater P25, there isn't much of a purpose. In fact, it inherently inhibits interoperability. There is nothing more interoperable than conventional analog voice. If you are conventional analog now, making it conventional digital only isolates you from everyone else. Plus, why would you want to buy a $3,000 portable radio when a $700 radio will do the job flawlessly? I mean, hello? DUH?

    This is the major hangup with a lot of grant funding. Some boneheads in the goverment (probably lobbied by Motorola) decided that P25 is the save-the-world solution to everything and totally overlooked the conventional aspect. They took it upon themselves to make rules such "any radio purchased with this grant money must be P25 complient." This is great for people with trunking systems. This is stupid, prohibitive, dangerous, and counter-productive for people with conventional analog systems.
    Last edited by nmfire; 03-27-2005 at 10:12 PM.
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    Thanks for the reply. I had the same thoughts about P25, but thought I was missing something. I came to this conclusion while researching interoperability issues for our Fire Act application. I can greatly improve my departments interoperability with other town departments and other jurisdictions, for less than $25,000. I could not see where spending truckloads of money on a P25 system would be an improvement.

    I found a list that states the advantages to P25:

    * Coordinate communications with other agencies and jurisdictions.
    -I can do that without P25.

    * Purchase radios and other equipment from more than one vendor.
    -We currently do this.

    * Upgrade or migrate systems without replacing all your equipment.
    -Been there, doing this now, and will do it again


    * Share resources with other organizations to control costs.
    -We do this with several items.


    My system is VHF analog voice using repeaters, and I do not see that ever changing.

    Looks like P25 is a more complicated and expensive way to do what we already do now.

    I am not suprised that the FCC has stated that digital radio is the mode of the future. Just look at the mess they are making with the broad band over powerlines issue (BPL).
    Last edited by KenNFD1219; 03-27-2005 at 11:49 PM.
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    Yea. It's asinine. If you currently have or were upgrading to a trunking system, it would make perfect sense for all the reasons those reasons. But, since you are just looking to improve your current conventional system, it is stupid.

    As far as I know, the FEDERAL Fire Act grants do not require P25. We got a Fire Act grant a few months ago for radios and P25 is no part of it.

    The town got a "homeland security" grant from the state. The state decided to make decisions for us as usual and said that any radio purchased with their grant money needed to be P25. This is how stupid it is... We use conventional analog UHF. A rugged kick *** UHF conventional analog radio costs about $800.00. They wanted us to buy a $3,000 P25 radio and just use it in analog mode. So we are supposed to buy a $3,000 product and just use $800.00 worth of features in it?? Yea, sure. I think not.

    Instead, we are going to use it on infrastructure that P25 has no effect on. Radio tower work, combiners, installation work, labor, misc parts, etc. Basicly all the stuff that isn't an actual transmitter or receiver.

    Typical state operation.
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    It's not exactly your states fault. The Feds have directed the states as to what can/cannnot be purchased using Homeland Security Funding. I will agree in many cases it makes no sense, but its a federal directive that the states are instructed to follow. Same thing happens here. In 2003 much analog non-p25 equipment was purchased using Homeland Security $$$, in 2004 we saw very little non-p25 equipment purchased, MOST was p25, extreme justification had to be given as to why non-p25 equipment was desired or needed. It is my suspicion that in 2005 it will be nearly impossible to use Homeland Security Funding to purchase non-p25 equipment.

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    Fortunately, the state one works out ok for us. An actual conventional analog radio (be it mobile, portable, or base) is actually the least expensive part of any system. Hell, a medium power continuous duty conventional repeater is only about $1500 now. The infrastructure around it is usually a big cost factor. For example, installing an antennas and feedline on a typical 200' tower can easily cost $10,000 in parts and labor. A transmitter combiner with circulators and a RX pre-amp could easily cost just as much. Rack mount systems, lighting protection, power supplis, backup power, etc is expensive. 7/8" coax cable is $3/ft!

    So, don't fret too much about the P25 requriement. If you can spend it on other radio related items, do so and save your regular budget for the actual radios.
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    With regard to your current analog repeaters never changing.... don't count on it. More and more manufacturers are turning to digital radios, especially as the bands are refarmed and narrowed. There may be a time when analog radios will be hard to find. None of this has any bearing, of course, on whether or not what you have works now, or not. It seems as if your system works well for your needs. The marketplace will be driven this direction, either through need, or through planned obselesence.

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    Of course, just like 20 years ago, people were still using punch cards instead of CAD computers.

    But, I don't envision our rural town going to digital in the next 10 years. It is not practical and we can't afford it.
    Even the burger-flippers at McDonald's probably have some McWackers.

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