Is P25 Phase I here to stay or will it be replaced entirely by Phase II?

[afbailey]

After being an avid Broadcastify listener for a while now, I'm considering buying my first scanner. I live in the SF Bay Area, and my regional pulbic safety radio system is on P25 Phase I. I'm looking at scanners that are Phase I only. My question is whether or not Phase I systems will be around for some time yet, or if Phase I is just a stepping stone to Phase II, in which case I'll regret not buying a Phase II capable scanner within a few years.

I don't know anything about the technical details of either system and so I don't know if my question makes any sense at all from a technical perspective. I am interested to hear from those who DO know those technical details.

 

[MTS2000des]

Phase 2 (TDMA) is a logical path for P25 systems to go to. I am not in your area, but I manage a Motorola trunking system for a large agency. Out of staging, all talkgroups are capable of TDMA, but we initially went live in what is known as Dual Dynamic Mode (DDM) which allows a slow migration to TDMA as subscribers are replaced with newer ones. Old legacy Phase 1 equipment is now 10-15 or more years old, and as it's replaced with newer TDMA variants, more and more of our DDM talkgroups operate in Phase 2. Not sure if this is the case in your area (local scannists may know) but this is typically how P25 systems are deployed as of the last decade.

If you're spending money, buying a Phase 2 capable scanner is a safe bet. You also need to know if the desired system is using Linear Simulcast Modulation (LSM). Only the Uniden SDS series do a spectacular job of solid reception. Scanners based on older designs may or may not work well depending on the system(s) one desires to monitor, and may require a lot of tinkering with DSP settings and antenna placement to get good reception.

The folks in the California subforum will be able to guide you and I suggest you ask the locals.

 

[fredva]

As far as I know, the decision to stay Phase 1 or go to Phase 2 is made by the owners of the system based on their needs. Phase 2 provides more radio capacity than Phase 1 for the same number of licensed frequencies, so busy systems - or systems that might expect to be busy during a major incident - have an incentive to step up to Phase 2. But the timing will vary from one jurisdiction to another. Phase 1 and Phase 2 are both industry standards; neither are mandates.

What I would do if I was you would be to go to the California forum on Radio Reference and search for info on the systems you are interested in monitoring, and see if there has been any discussion of the systems going to Phase 2. A lot of times, if a jurisdiction awards a contract to upgrade a system, somebody will post about it in the forum to alert other scanner owners. And if you don't find info, you can ask a question.

 

[fredva]

MTS2000des brings up a good point: When purchasing a digital scanner, you need to know more than just whether the radio system is Phase 1 or Phase 2 - you should also find out if it is simulcast (LSM) or not and buy the appropriate equipment.

 

[kj6psg]

And Phase 2's modulation is designed for simulcast performance, so expect to see a lot more simulcasting as older systems migrate to Phase 2.

Within FCC jurisdiction, the topic of "6.25 kHz equivalent" (6.25 kHz FDMA, 12.5 kHz 2-slot TDMA, or less commonly 25 kHz 4-slot TDMA) narrowbanding gets thrown around quite a bit. New equipment needs to support "6.25 kHz equivalent" spectral efficiency, although deadlines for moving 700 MHz to 6.25e has been eliminated. Having to replace a five to ten year old trunked system because of changing regulations would have pissed off a lot of agencies. As far as I know, all new trunking equipment being sold know is either Phase 2 or Phase 2 capable.

Phase 2 doesn't affect any conventional usage (direct between radios, or non-trunking repeaters). Phase 3 is supposed to address that shortcoming. Phase 2 trunked systems also have a configurable capability to fall back to Phase 1 on a per-talkgroup basis if interoperability with Phase 1 subscribers is needed, but it reduces system capacity. Since Phase 1 equipment is getting increasingly uncommon, pretty much every Phase 2 system is operating in Phase 2 (though RRDB is often incorrect about the Phase in use.)

Scanners always lag well behind subscriber radios; we should have had software defined IFs by the time LSM became a thing, because it's necessary to decode the modulation. The ADC chips are getting cheaper, more available, and more specialized to the task at hand, which is why we're seeing SDR penetrating the scanner market now. Sticking with Phase 1 or non-LSM radios at this point is a waste of money. As more and more trunked systems deploy, spectral efficiency becomes significant, and regulators become less willing to approve Phase 1 use.

 

[iMONITOR]

After COVID I don't think there's going to be a lot of money available to fund new projects of any kind unless it's necessary.

 

[a417]

After COVID I don't think there's going to be a lot of money available to fund new projects of any kind unless it's necessary.

disagree, on many levels...but anyways for the OPs question, at one time 640k RAM was all you ever needed...

 

[hiegtx]

After COVID I don't think there's going to be a lot of money available to fund new projects of any kind unless it's necessary.

You may well be right. Here locally (Dallas, TX), the city and county agreed to build a new P25 Phase II system. This decision came out a couple of years ago, and the system was supposed to be operational this fall. However, they are well behind schedule, not even starting, as far as I see, on building or acquiring the sites necessary for the simulcast (many of them will be on existing towers, but in certain areas, a new site will have to be built for coverage). Dallas took somewhere in the $35 to $40 million dollar range hit from last October's tornado that went through the northern part of the city. Their application for FEMA assistance was denied, as not meeting requirements for funding. The governor is appealing that, but who knows.

Plus, a significant part of the city budget comes from sales tax revenue, which has also taken a dive during the pandemic. That affects the state as well, both on sales tax, as well as revenues from oil & gas production, which have declined both due to drops in the oil price, as well as lesser demand as people are driving less. Adding that loss of revenue to the toll of replacing damaged assets has lead the city to scramble and see where budget cuts can be made, even to the point of cutting back expenditures for public safety agencies.

After being an avid Broadcastify listener for a while now, I'm considering buying my first scanner. I live in the SF Bay Area, and my regional pulbic safety radio system is on P25 Phase I. I'm looking at scanners that are Phase I only. My question is whether or not Phase I systems will be around for some time yet, or if Phase I is just a stepping stone to Phase II, in which case I'll regret not buying a Phase II capable scanner within a few years.

I don't know anything about the technical details of either system and so I don't know if my question makes any sense at all from a technical perspective. I am interested to hear from those who DO know those technical details.

As others have mentioned, P25 is here to stay. In my area, all the new systems recently activated are Phase II, and most of the ones that have been P25 Phase I are on a path to upgrade as well.

For those that live in a rural area, they may not have to deal with Phase II systems yet, and possibly no trunked systems of any kind. But if you occasionally travel, and take your scanner, it's pretty much a certainty that you will encounter a Phase II system if your travels take you to or through one of the larger urban areas. Other than a few analog scanners, such as the BC125AT (which also is incapable of handling even an analog trunked system), both Uniden and Whistler are concentrating on Phase II capable units. Of course, there is a considerable market of used (but good condition) Phase I only scanners, but only buy one of those if you are confident that you will not need Phase II capability in the near future.

 

[fredva]

pretty much every Phase 2 system is operating in Phase 2

The Ohio MARCS system went online within the last five years. It is Phase 2 capable, but operates in Phase 1. Phase 1 scanners can still receive it. The Tennessee statewide system has a mixture of Phase 1 and Phase 2 talkgroups. So while it is pretty common for recent, Phase 2 systems to operate in Phase 2, there are at least some notable exceptions.

 

[iMONITOR]

disagree, on many levels...but anyways for the OPs question, at one time 640k RAM was all you ever needed...

I'm not saying no one will outgrow Phase 1, but if it's not necessary why spend the money? Remember who controls the cash and what it's spent on? Goveners, Mayors?

 

[hiegtx]

The Ohio MARCS system went online within the last five years. It is Phase 2 capable, but operates in Phase 1. Phase 1 scanners can still receive it. The Tennessee statewide system has a mixture of Phase 1 and Phase 2 talkgroups. So while it is pretty common for recent, Phase 2 systems to operate in Phase 2, there are at least some notable exceptions.

That's true in my area as well. One sizable semi-regional system, FWRRS, is P25 Phase II capable, though the majority of users, for now, are using Phase I

I'm not saying no one will outgrow Phase 1, but if it's not necessary why spend the money? Remember who controls the cash and what it's spent on? Goveners, Mayors?

That's true as well. Especially in times of tight budgets, in some cases due to the pandemic.

However, for the aforementioned system, FWRRS, one group of cities on a specific later are going to upgrade to Phase II. A large part of the reason for that is that the largest city in their county will be joining the system (and paying the cost of the Phase II upgrade), as well as their county agencies. The move to Phase II will give them additional voice channels using the same number of frequencies.

 

[Project25_MASTR]

P25 Phase 1 will always be around. Mainly because P25 Phase 2 is trunked application only (no conventional use). Now something to keep in mind, there are limitations to P25. For example, a P25 control channel can only actively handle 36 groups at once...therefore you can't have a system with more than 36 channels per site.

Another thing to consider, migrating to Phase 2 isn't an immediate need for everyone and may not be practical for fully built out systems, especially where sites are operating at the manufacturers maximum capacity. For example, (@MTS2000des please correct me if my numbers are off) if my memory recalls as of Astro 25 7.18, a simulcast site can have no more than 24 talk paths and non-simulcast site can have no more than 28 in terms of Motorola systems. So going Phase 2 in those cases may actually mean there are resources which are now unusable without adding controllers to utilize those resources as a secondary layer. I can actually think of two counties in Texas that built simulcast to Motorola's resource limits (at the time of construction) and had to be layered to provide additional coverage.

 

[GTR8000]

P25 Phase 1 will always be around. Mainly because P25 Phase 2 is trunked application only (no conventional use). Now something to keep in mind, there are limitations to P25. For example, a P25 control channel can only actively handle 36 groups at once...therefore you can't have a system with more than 36 channels per site.

Another thing to consider, migrating to Phase 2 isn't an immediate need for everyone and may not be practical for fully built out systems, especially where sites are operating at the manufacturers maximum capacity. For example, (@MTS2000des please correct me if my numbers are off) if my memory recalls as of Astro 25 7.18, a simulcast site can have no more than 24 talk paths and non-simulcast site can have no more than 28 in terms of Motorola systems. So going Phase 2 in those cases may actually mean there are resources which are now unusable without adding controllers to utilize those resources as a secondary layer. I can actually think of two counties in Texas that built simulcast to Motorola's resource limits (at the time of construction) and had to be layered to provide additional coverage.

The 36 max simultaneous calls is only when they are all implicit calls; on systems that use explicit signaling, that number is reduced.

As of ASTRO 25 7.17:
36 maximum simultaneous implicit calls
28 channels per ASR
30 channels per IP simulcast site (19 repeaters max at a full TDMA site (1 control + 18 voice = 36 max calls))

 

[radiopro52]

Here in Alabama we have a statewide P25 Phase II system that I think was first put online eight years ago. Many areas still only use Phase I, even some of the bigger cities like Birmingham and Huntsville. The system is nearly, if not completely, built out by now so I doubt they'll be spending any money on future upgrades anytime soon especially with current events. If they're planning to make the entire system Phase II they're certainly in no hurry to do it.

 

[bob550]

I will admit that I have no knowledge of the technical advantages of Phase 2 vs Phase 1 systems. However, as an observer, it would seem logical that if Phase 2 had a significant advantage over Phase 1 for the user agencies, they'd have migrated long ago. Without researching every P25 system in the country, I'd have to say that many haven't done so. That said, the choice to purchase or not purchase a Phase 2 capable scanner should be an easy one, as most produced today have that capability. There are also many available on the used market as well if that's the route you wish to take.

 

[Project25_MASTR]

The 36 max simultaneous calls is only when they are all implicit calls; on systems that use explicit signaling, that number is reduced.

As of ASTRO 25 7.17:
36 maximum simultaneous implicit calls
28 channels per ASR
30 channels per IP simulcast site (19 repeaters max at a full TDMA site (1 control + 18 voice = 36 max calls))

Thank you for the correction. There have been some updates which I was not up-to-date on.

 

[gmclam]

If money is no object, then purchase the latest and greatest model with all the bells and whistles. If money is tight, consider buying something used that will "just get you by" to monitor the Phase I system you want to hear.

Although northern California has been either analog or Phase I for a few years now, I travel up north often where Phase II is in wide use. When I started to look at what's available that's Phase II capable, I was quite disappointed.

The Sacramento P25 system has been on the air for many months, and it became clear to me that the bigger issue by far isn't whether I get a Phase II capable receiver, but one that can handle a multi-site system. There's really only 2 choices presently available; Uniden SDS-100/200 models or an "SDR solution" (actually the SDS models employ SDR). If you're always monitoring next to a PC, then SDR would be a cheap solution (and handle Phase II and other systems as well). If you need to be mobile, the SDS seems to be the only choice.

Regardless of what is purchased and placed into use today, some aspect will become obsolete tomorrow; yet today's model will work in some manner (even if only monitoring ATC). It's a moving target and you'll likely never be 100% future-proof.

 

[afbailey]

Very interesting responses! An update: so, I went to the Bay Area forum as some suggested, and found this which indicates that the system I'm most interested in might be switching over to Phase II as soon as next month. So, I guess that's that!

 

[GTR8000]

I will admit that I have no knowledge of the technical advantages of Phase 2 vs Phase 1 systems. However, as an observer, it would seem logical that if Phase 2 had a significant advantage over Phase 1 for the user agencies, they'd have migrated long ago. Without researching every P25 system in the country, I'd have to say that many haven't done so.

The most significant advantage of Phase II is that TDMA doubles your voice channel capacity without having to license additional frequencies, or purchase additional repeaters. There are also some technical advantages, such as the ability for the radios to receive messages while they are transmitting (preemption), which is not possible with FDMA. That works because the radio is transmitting in extremely short, quick bursts, and while it's briefly dekeyed it listens for signaling on the other time slot. The radio can be told to stop transmitting for various reasons, including preemption by the dispatcher or an emergency transmission, or because the radio has gone out of range.

The choice between Phase I and Phase II often comes down to money, and requires a cost analysis to be done to determine the best route. Albany's main simulcast cell has 18 channels, which means 18 physical repeaters per site because it's an FDMA system. If the system were TDMA, that same cell would require only 10 repeaters (1 control + 9 voice = 18 talkpaths) per site. There are obvious costs savings right there, even with factoring in the cost of having the TDMA option in each repeater. Less space taken up in each shelter, less heat output with one less rack of repeaters, less power draw from all the equipment, etc.

Of course the subscriber radios have to be factored in also. It obviously costs more to have the TDMA option added to each radio, and with an FDMA-only system you can get away with using older radios that were never capable of TDMA (Motorola XTS/XTL, for example). This is important if you are migrating from an older trunked system, such as Albany did with the SmartZone system.

 

[btt]

The Sacramento P25 system has been on the air for many months, and it became clear to me that the bigger issue by far isn't whether I get a Phase II capable receiver, but one that can handle a multi-site system. There's really only 2 choices presently available; Uniden SDS-100/200 models or an "SDR solution" (actually the SDS models employ SDR). If you're always monitoring next to a PC, then SDR would be a cheap solution (and handle Phase II and other systems as well). If you need to be mobile, the SDS seems to be the only choice.

I would like to add the BlueTail Technologies P25RX to that list. It operates stand-alone and is shown to work in multi-site LSM systems.