Confused Over Analog Vs Digital Freq's & P25

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Robert11

Confused Over Analog Vs Digital Freq's & P25

#1 Post by Robert11 » 28 Aug 2007 12:03

Hi,

I found on the wiki: "APCO-25 Stations In Our Listening Area", the link to being:

http://www.scancapecod.us/wiki/index.ph ... Listening_
Area

Would like to get this right:

Am I correct in that the frequencies that show with a control chancel (CC) are
Trunked, and therefore one would enter it into my Butel software for the 996 under: "Motorola Type 2 / P25
Correct ?

My understanding is that these frequencies are all digital in nature
Correct ?

And, for all the other frequencies that don't seem to have a CC associated with them, I would just enter them under: "Conventional"
Correct ?

Not sure what these are actually, though.
Are they part analog and part digital, somehow ? How ?

If anyone could clarify this a bit (no pun) for me, would be most appreciative.

BTW: Any of either type in the immediate metro-Boston area ?
If so, which type ?

Much thanks for the help with my dumb questions; appreciate it.
Bob

edmfox25

#2 Post by edmfox25 » 28 Aug 2007 13:19

Hope this answers some of your questions..

Unless stated otehrwise I have always operated on the assumption that unless it's stated that a system is a TYPE 2 P25 system then it's an analog trunked system. For instance the MSP system is Motorola TYPE 2 system, if you have a newer scanner then you can just program the CC. If not you would need to do both the CC and the voice channels.

With a trunk system there are no PL or DPL tones to program regardless of analog or digital operation.

In Mass ther more popular trunk systems are Worcester (EDACS wide), MSP (TYPE-2) MASSPORT (TYPE-2), CAMBRIDGE (TYPE 2)...all are what I consider to be analog. The only APCO 25 trunked systems that I know of in New England are NASHUA NH..TYPE 2/ APCO 25 and Connecticut State Police TYPE 2 APCO 25 and State Of Rhode Island TYPE 2 APCO 25. All you would need to program are the CC and the desired talk groups.

Hope this helps.

Robert11

From OP

#3 Post by Robert11 » 28 Aug 2007 14:33

Hi,

Much thanks,
Bob

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#4 Post by ScanBoston » 28 Aug 2007 15:10

Ed is correct but a side note there are P25 talkgroups on some of these trunks including the MSP. However all of these you enter into your scanner as Type2 analog systems. The main difference is if the Control Channel itself is Analog than the system is analog.

Robert11

From OP: A Bit More

#5 Post by Robert11 » 28 Aug 2007 17:12

Hi again guys,

I'm a retired engineer, and am still pretty good with differential equations and celestial mechanics, but, boy, I'll tell you, a lot of this stuff just throws me.
I think the problem, for me at least, is a definitive definition terminology of how these frequencies would, or are, shown and designated in the various data bases.

My old assumption that if it said "P25" or "APCO P25" and was trunked and therefore had a CC, that it would absolutely go under:
"MOT Type 2 / P25" was wrong I guess.

For it to go under "MOT Type 2 / P25" it would definitively would have to say:
either:
- Project 25, and I guess also be trunked.
- or, TYPE 2 P25

True ?

So, P25 does not automatically mean Project 25.
Correct ?

Do I have this more or less all correct now ?
---------------

I can't help but feel that many other scannerists probably have an incorrect, or at least an incomplete, understanding of this. Many like me, until I started to think a bit more about it, probably don't even realize they have it wrong.
Or, of course, it can be just my old age catching up, admittedly, and quite possibly.

If one of you experts ever has some time, it would really be great to come up with a "white paper" listing all the possible terminology, and the possible permutations in one place for all of us mental defectives.
There really are quite a few.

Particularly, the possible frequency /system label designations that one is likely to come across in the various databases, and under what type of System they should be entered under.
e.g.:

P25
TYPE 2 P25
APCO 25 trunked systems
MOT Type 2 / P25

Regards and thanks for putting up with me,
Bob

edmfox25

P 25/ Trunked

#6 Post by edmfox25 » 28 Aug 2007 18:09

Bob,

P25 or APCO 25 is the digital transmission mode of the signal. You will see that APCO 25 or P25 signals can be found in the VHF mode as is the case with NH STATE POLICE. They are APCO 25 non-trunked VHF. Or Mansfield,MA PD APCO-25 UHF narrow band. Or CT SP 800mhz, TYPE 2 APCO 25 trunked system. Same for the city of Nashua,NH or the State Of Rhode Island. Some
P25 signals can also be encrypted like West Warwick PD and maybe some PD's along the NH seacoast and most of the Federal freqs.

On the WIKI part of this web site you'll find the APCO 25 stations in the area and you will notice that the majority of these are non-trunked. I would refer to these as conventional radio systems using P25

I think it's just more of the scanner terminology they are lumping TYPE 2 and P25 under the same catagory because neither require a PL or DCS tone whether it's a trunked system or not. Depending on the scanner it's smart enough to know when it's a P25 signal vs. a conventional signal. However the scanner is not smart enough to decode a trunking system without programming it to do so.

P-25 means APCO 25.
Trunk means trunk and there are various trunk system types as I mentioned in the last post.
You will find TYPE 2 P25 systems.
You will also find P25 conventional freqs in the UHF and VHF band as mentioned above.

It's alot to take in but this site is great and for the most part very supportive and tolerant of people asking questions.

Not sure which scanner you have but to listen to anything that is P25 trunked or conventional system you would need one of the following:

UNIDEN 996 or 396 or 796, 785D w/ P25 card or a 285D w/P25 card.
RADIO SHACK..PRO 96 or PRO 2096

I'm sure some of the guys here will ellaborate more but hopefully this will get you going in the right direction.



Robert11 wrote:Hi again guys,

I'm a retired engineer, and am still pretty good with differential equations and celestial mechanics, but, boy, I'll tell you, a lot of this stuff just throws me.
I think the problem, for me at least, is a definitive definition terminology of how these frequencies would, or are, shown and designated in the various data bases.

My old assumption that if it said "P25" or "APCO P25" and was trunked and therefore had a CC, that it would absolutely go under:
"MOT Type 2 / P25" was wrong I guess.

For it to go under "MOT Type 2 / P25" it would definitively would have to say:
either:
- Project 25, and I guess also be trunked.
- or, TYPE 2 P25

True ?

So, P25 does not automatically mean Project 25.
Correct ?

Do I have this more or less all correct now ?
---------------

I can't help but feel that many other scannerists probably have an incorrect, or at least an incomplete, understanding of this. Many like me, until I started to think a bit more about it, probably don't even realize they have it wrong.
Or, of course, it can be just my old age catching up, admittedly, and quite possibly.

If one of you experts ever has some time, it would really be great to come up with a "white paper" listing all the possible terminology, and the possible permutations in one place for all of us mental defectives.
There really are quite a few.

Particularly, the possible frequency /system label designations that one is likely to come across in the various databases, and under what type of System they should be entered under.
e.g.:

P25
TYPE 2 P25
APCO 25 trunked systems
MOT Type 2 / P25

Regards and thanks for putting up with me,
Bob

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#7 Post by ScanBoston » 28 Aug 2007 18:53

Hi Robert it is a little confusing....

APCO P25 is just an approved digital transmission standard developed by Motorola and APCO. The idea was that it would help everyone go narrow-band in several phases but having a standard that would allow competition and interoperability. Inotherwords Motorola would license the technology to who others who could also make P25 radios.
So this really applies to all the conventional use of P25.

Then they decided to try and do the same thing with Digital Trunk systems. But to do this they also needed to come up with a standard. They decided that a P25 "approved Trunk system" Would have a 9600 baud digital control channel and all the Voice channels would be P25. Now we don't have any of these here yet. But they do exist around the country.

We have a few 3600 baud analog trunk systems that have P25 Voice channels on them along with analog channels.

So P25 does not mean trunked per say. But it can be used on a trunk or the whole trunk can be P25. If its being used on a conventional frequency, a repeater or as part of a mixed mode trunk they are just referring to a modulation type. If it's referring to a "P25Trunk" than its not only the modulation on the voice channels but also specifies the type of control channel. Again it's just trying nail down a standard for interoperability between systems and radios while conserving bandwidth.

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Pro-96 APCO-25 conventional??

#8 Post by rry4488 » 28 Aug 2007 18:59

Can a Pro-96 decode p25 conventional?
I thought it could decode p25 trunking only, not conventional
UNIDEN 996 or 396 or 796, 785D w/ P25 card or a 285D w/P25 card.
RADIO SHACK..PRO 96 or PRO 2096

edmfox25

#9 Post by edmfox25 » 28 Aug 2007 20:06

rry4488 wrote:Can a Pro-96 decode p25 conventional?
I thought it could decode p25 trunking only, not conventional

Well I listen to NHSP, Hanscom FD on my PRO-96 and neither of these are trunked but both are APCO-25 systems.

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#10 Post by Mark SNE Moderator » 28 Aug 2007 20:31

A "Conventional" frequency is one frequency that ONE agency or department operates on, like Barnstable Police on 855.2125. This is an analog (mode) conventional frequency which uses a DPL (digital private line tone) of 445. I know, there's that digital word again, but when I say DPL, it's the same thing as a PL tone, basically. The DPL does NOT make this a DIGITAL frequency. Understand?

A digital, or P-25, conventional FREQUENCY would be for example Pawtucket RI Police on 470.725. Digital frequencies do not use/have any tone associated with them, as digital modulation does not require one. This is the difference between an analog conventional and a digital or P-25 conventional frequency.

For trunking there are also the same 2 methods of modulation, analog and digital. Think the Mass State Police trunked system. Zone 4 for example uses up to 13 trunked (not conventional!) frequencies that are programmed as a Motorola type 2 system. No PL/DPL tones are used in a trunked system. The users of this system are identified with a unique talkgroup ID (Sandwich FD for example is 37744). Every mobile and portable radio in the Sandwich FD fleet has this unique Talkgroup (TG) ID programmed into it so that when they talk, the system will be able to identify them. Are ya with me so far?

Each "user" of a trunked system has their own TG ID. The Wiki section will show you who is who. This system currently operates in analog modulation, or mode. There is talk that sometime in the not too distant future that this system will convert from analog mode to P-25 digital mode. For scanning purposes if you have a digital equipped scanner all you need to do is program this type of trunked system as a type 2 Motorola. If this was a digital P-25 system then you would program it as a type 2 P-25 as per the scanner manual or programming software.

I hope this helps, Robert.
Mark,

Scan New England Moderator



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Robert11

Thank You From OP

#11 Post by Robert11 » 29 Aug 2007 08:06

Hello all,

Just want to say a quick thanks to everyone for helping clarify this for me.
Really helps a lot, and truly appreciate the time everyone took.
A lot clearer now.

Best regards,
Bob (Sudbury, MA; Uniden 996)

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#12 Post by IggyWFD » 08 Dec 2012 13:57

Sorry for jumping into the post late (by a few years) Looking at the Butel software, I have a choice between Mot Type II VHF & Mot Type II UHF. If I am programming a 396 (older version) that does accept digital, I have to have seperate systems for VHF freq or UHF freq, unless the are in the 800 digitals (exp, RI RISCON) and I correct?
(I am looking to put in Fed freqs, like ATF or ICE or non-FED NHSP)
John
BC IV, BC H/L, BC210, BC100, BC350A, BC100XLT, 996XT, 396t, 436, HP1

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#13 Post by cdgordon » 08 Dec 2012 17:00

Any conventional frequency (non trunked) can be mixed with any other conventional channels. It does not matter if they are analog or digital, use a PL or DPL, or are VHF-Lo, VHF-Hi, UHF, 700MHz 800MHz or 900MHz. They can be mixed in a single system.
Any Trunked system be it analog or digital, LTR, EDACS, SCAT, Motorola, or P25, is put into its own system. Keep in mind that some systems consist of multiple sites (CSP, MSP, RISCON, etc). These systems can have all the sites in one system.

chris

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