Why P25 phase II instead of DMR tier 3?

[GTR8000]

Actually, it's 2, 12.5khz talkpaths in one 25khz bandwidth

Actually, it's two logical channels within a single 12.5 kHz physical channel, hence the "T" (time) in TDMA.

 

[RRR]

You sure about that? I always thought it was 2 12.5 Khz talkpaths in one 12.5 kHz bandwidth...but I could be wrong.

Doh! You are right, Duh. I have Tetra on my mind, along with NXDN, and NXDN has favor because it is the only easily / affordably obtained digital format that can do 6.25, not that we will ever see that requirement in our lifetimes.

 

[speedway_navigator]

I started when we had low band and no hand held radios

I remember when I got on the San Diego SO as a reserve we had low band in our area, others were UHF. When I pulled the metal antenna out and extend it I thought 'I have not done this since I was 6 and had a CB portable". The antenna was long enough I thought they should have given us fencing lessons in the academy.
Like you said, before portables cops knew it was 1 on 1 and acted accordingly, your mind and wits were your best defense.

 

[TampaTyron]

The way we work through the systems is as follows:
-Are there any regulatory/interop requirements of specific solution being quoted?
-Who is paying, what is budget, what are the payor's technical requirements (like grants)?
(keep in mind that "P25 capable" for a grant is different than "must talk to Agency X on System Y with crypto Z for interop")
-What does the system actually need to do?
-What is purchasing/installation timeframe?
-What are the documentation requirements?

I have installed dozens of TRBO systems for public safety agencies. TRBO seems to do 90% of the functionality at 20% of the price.

But, if there are grants requiring P25, specialized interop needs that a patch cannot fill, extra rugged radios/accessories, AES256, simulcast, or extreme audio conditions..... then P25 may be a better fit.

Ok.....Here is your quote/bid. TT

 

[mmckenna]

-What is purchasing/installation timeframe?

So often overlooked by "internet/youtube experts" that will complain about a system they know nothing about. I've run into situations where it was "we need XYZ right NOW!". Often due to sudden failure, rapid change in needs, etc.
-or-
We need XYZ and this is the budget you must work within, no exceptions, don't ask, or we'll find someone who can".

It's easy to sit back in a recliner and Monday morning quarterback systems when people don't know the entire picture.

 

[speedway_navigator]

I remember one agency we worked with where the cops we heard to mutter "someone is going to die" because they thought the new system would fail when they found out bat wings had lost out.

 

[mmckenna]

I remember one agency we worked with where the cops we heard to mutter "someone is going to die" because they thought the new system would fail when they found out bat wings had lost out.

Yeah, got that when we switched our PD to Kenwood radios. They were the "worst radio EVER!!!!!". That was 10 years ago, guess what they are still using.

 

[DeoVindice]

But, if there are grants requiring P25, specialized interop needs that a patch cannot fill, extra rugged radios/accessories, AES256, simulcast, or extreme audio conditions..... then P25 may be a better fit.

This goes the other way, too. A lot of heavy industrial clients should be using mid-tier APX, Viking, or XL subs for some segments of their operations. XPRs don't hold up in processing plants or underground, and high-noise performance leaves a lot to be desired. At least the R7 improves on the last point.

Sure, it's more expensive, but so is downtime, injuries, and property damage caused by failed communication.

 

[CanesFan95]

But what's stop from making more solid, durable radios & better audio, higher encryption regardless of the digital mode?

 

[dickie757]

Cash cow. MotoTRBO [edit and DMR] wont fetch the dollars and grants that APX and P25 does. APX money pays my bills. On that note, I'm not entirely sure I'm OK with it.

 

[mmckenna]

But what's stop from making more solid, durable radios & better audio, higher encryption regardless of the digital mode?

Money.

The big companies that make radios used in public safety like the higher prices of the P25 gear. They could (and some do) make perfectly good DMR radios that would meet all the needs. But most agencies are buying with grant funds, or have at some point, or need to interop with other agencies that do, so they have to keep buying P25 radios.

DMR, NXDN, etc. are perfectly fine for an isolated agency that only needs that, and maybe analog for interop. Many do just fine that way.
But get into more urban areas, and P25 is king.
No agency is going to suddenly toss ALL their P25 gear just so they can buy all new stuff that does another digital mode.

in other words, that ship sailed a long time ago.

 

[CanesFan95]

So forgetting about the physical quality of a radio. Does P25 RF work better than DMR RF? Why is one considered "public safety grade" over the other?

Or do they purposely only make radios on one mode flimsier / less durable than another mode and the mode itself is arbitrary.

 

[mmckenna]

So forgetting about the physical quality of a radio. Does P25 RF work better than DMR RF?

No, not really.

Why is one considered "public safety grade" over the other?

The mode isn't really considered "public safety grade". It's just been adopted as the de facto standard that most agencies use. The feds have made it a requirement if federal grand funding is used to buy the radios. The idea is that they want as many agencies as possible to be able to interoperate.

Also, if you look at the NIFOG guide, the 700MHz interop frequencies are P25, not DMR.

The term "public safety grade" is usually used to describe the subscriber radios. Durability, knob size/spacing for gloves, water resistance, audio output, etc...

Or do they purposely only make radios on one mode flimsier / less durable than another mode and the mode itself is arbitrary.

You can buy whatever you want. I've got radios in use by a PD that would not be considered "public safety grade" and don't do P25, however they have lasted 10+ years under heavy use. You can absolutely buy cheap DMR radios. You can also buy higher end radios. Take a look at the Kenwood NX-5000 line. Will do several digital modes, including DMR. Durable radio. Will do P25 if it's ordered that way.

 

[GlobalNorth]

P25 Phase 1 and 2 = APCO

 

[Project25_MASTR]

Chicken and Egg scenario in most cases. The big push for a common radio standard for larger agencies really came after 9/11. Project 25 built on what was already established with Project 16 but forced on of P16's flaws...allowing each vendor to utilize their own trunking format, P25 fixed that in the sense that any manufacturer's P25 radio should work on any manufacturer's P25 system which is why companies like Airbus and Etherstack exist today as they don't manufacture subscribers. Anyway you slice it though many departments, especially larger ones, began migrating to P25 solutions before DMR products were even available.

 

[speedway_navigator]

We did a test around Grimes chapel TX with a fire dept that had VHF DMR and P25-1, the range on that day was about equal.

 

[speedway_navigator]

About 5 or 6 years ago I saw an article comparing prices of TETRA portables in the EU or UK to P25 portables here. I think the TETRAs were under 3 grand each.

I'm not smart enough to know the engineering behind 'public safety grade' radios vs commercial but I bet P-25 could be done less expensively. I've seen components soldered on pc boards when I took the Max+ class at CSS mindshare in September, I can't see much difference in the mfg process when the mechanics of assembly are taken into account.

The codec and RF chips needed for P25 might be more costly than DMR but the displays and knobs are probably similar cost.

 

[mmckenna]

I'm not smart enough to know the engineering behind 'public safety grade' radios vs commercial but I bet P-25 could be done less expensively. I've seen components soldered on pc boards when I took the Max+ class at CSS mindshare in September, I can't see much difference in the mfg process when the mechanics of assembly are taken into account.

Pretty sure, early on, the goal for P25 and it being the standard, was that it would drive the cost down.

Obviously that didn't work out very well.

Greed is a huge part of it. No company wants to disappoint shareholders, even if that means screwing first responders.

 

[mastr]

But what's stop from making more solid, durable radios & better audio, higher encryption regardless of the digital mode?

If there was a significant demand for "more solid, durable radios & better audio, higher encryption regardless of the digital mode" (at what would necessarily be a higher price) they would probably be on the market right now. IMHO, the "stop" is that the majority of DMR system users are willing to accept the features and price point of the radios currently offered.

 

[N4KVE]

The discussion so far is about the P25 mode vs the DMR mode. How about the ruggedness of the radio? How long would a XPR7550 last on a cop’s belt? One shift? It might last on Barney Fife’s belt, but not in the real world. Just turn the volume control on an APX6000, or 4000, & compare that to a XPR7550. That says it all. Any cops carry an APX900?