oakland trunk Switching to Rebanded System tomorrow

[officer_415]

Nothing on any of these patches either. 2043, 2044, 2045 for Broadway EDACS system.

They don't seem to be patching anymore. BFO 1 uses Patrol 1, and BFO 2 uses Patrol 5. I haven't heard anything on Patrol 2 or 4 for a while. Patrol 3 is still car-to-car.

If Patrol 5 is down, it's probably because there are no EDACS radios affiliated with the talkgroup. Traffic seems to be simulcast on EDACS on an as-needed basis.

 

[cozmo]

mlangeveld You bring good luck. As of 10:30 PM Patrol 5 / BFO 2 is back up, but it has a bunch of static like a weak signal or something.

 

[naparish]

I picked up a P-106 so I can monitor the Oakland P25 traffic, and used the ARC software trial package and the RR database to program in the Oakland P25 and EDACS systems. When I was testing it last night, I noticed that I was getting traffic on the EDACS Patrol 5 TG that did not appear to be duplicated on the P25 system. Any clues as to what's going on (either with my scanner or with the systems)?

-- Neal

 

[Retired911Guy]

!!!!

NEW OAK P25 CONTROL CHL SITE 101 !!!!

EDIT: From Pro96com

FileVersion:6
-TowerInfo
#This section is here for information only. With the exception
#of the Call Sign(s), This data is not Read back into the program at all.
System ID : 136
System Name :
WACN : 92556
Tower Number (Decimal): 101
Tower Number (Hex) : T0101
Tower Description : (null)
Control Capabilities : Voice,Registration
Call Sign(s) :
Timestamp : Mon Sep 5 16:27:11 2011

-Tables
#Format: Table ID,Base Freq,Spacing,Input Offset,Assumed/Confirmed,BandWidth,Slots
00,851.01250,0.01250,-45.00000,"Confirmed",0.00625,1

-Frequencies
#Format: Channel,Usage,Frequency(/Slot),Input Frequency(/Slot),Hit Count
"00-0062","c",851.78750,806.78750,0
"00-0196","vp",853.46250,808.46250,0 <------WOW Changing FAST 2 mins later V Freq added !!! <--EDIT
"00-0260","vp",854.26250,809.26250,0 <-------Just Added 17:06 PST <--EDIT
-Neighbors
#Format: TowerID,TowerIDHex,System ID,Channel,Frequency,Tower Name
202,"T0202",136,"00-0226",853.83750,""
303,"T0303",136,"00-0088",852.11250,""

EDIT: 16:56 PST Serv 1 & 2 Patched to 65507 on Above V Chl according to Pro96com, However hear no audio on wildcard search, maybe techs testing control channel to see if it's reporting correctly.

Dave

 

[inigo88]

Haha I just got into Berkeley two hours ago, and found 851.7875 - Site 1-001, SysID: 136, WACN: 92556, NAC: A40. I was about to say that's gotta be some kind of record, then I found this thread.

I have some initial observations:

- I have listened to the control channel and voice channels in conventional analog mode, and it is like nothing I've ever heard before. It is definitely NOT the P25 our scanners were designed for (C4FM modulation). I am almost positive it is CQPSK modulation, P25 LSM.

- I am listening from Berkeley, almost directly inside the system's service area. The EDACS control channel comes booming in (haven't set up the rebanded systems yet). And yet my PSR-500 cannot keep a lock on the control channel (the T icon fluctuates on and off) despite a full signal strength meter. I am listening in wildcard talkgroup search mode and I *CAN* understand conversations, but they are broken and sporadic. Some are perfectly clear, some are completely garbled.

- These are exactly the symptoms I have read to expect from a CQPSK LSM system. Sorry to be the bearer of bad news, but until scanner manufacturers get their crap together that means you can expect poor performance from everything (save for maybe the latest HP-1 or PSR800, I'm not sure about those) even from within the city of Oakland itself! Since LSM uses multiple simulcasting towers on the same frequency, one possible remedy is to single out one tower with an 800 MHz yagi antenna and block out the rest (i.e the rooftop of 1111 Broadway would be an easy solution). Therefore site 2-002 is actually a "simulcast zone" (in Smartzone speak) - a conglomeration of multiple towers simulcasting on the same control channel frequency.

- I can offer one potential saving grace: The control channel for site 1-001 is operating in regular C4FM mode... NOT CQPSK / P25 LSM (according to my highly trained ears at least ). So they may be considering ditching LSM for a multi-site C4FM solution (or at least comparing performance from both system types)... For our sake I hope they do!!!

I'm on my phone at the moment, but tomorrow I'll try and find a CQPSK audio sample to compare with what I'm hearing.

 

[inigo88]

Well I can't find anything specifically stating it is LSM, but I can say the following about Site 2-002...

It is not this: http://kb9ukd.com/digital/astro96k.wav
(Motorola P25 C4FM control channel)

It is not this: http://www.w2sjw.com/sounds/800_Harris_IP-P25_Control.mp3
(Harris P25-IP control channel - I believe this is what Site 1-001 is)

It is VERY similar to this: http://www.w2sjw.com/sounds/700_Moto_P25_Control.mp3

I believe the two former use C4FM modulation while the latter uses CQPSK.

Please correct me if I'm wrong.

 

[norcaljpa]

Site 2 is a simulcast cell using LSM. Sites 1 and 3 are standalone (commonly referred to as repeater sites).

 

[inigo88]

Thank you for confirming LSM on site 2. For what it's worth, now that I know what to listen for, all the EBRCS control channels I've been able to find (sys ID: 1F1) are LSM as well.

 

[kma371]

Thank you for confirming LSM on site 2. For what it's worth, now that I know what to listen for, all the EBRCS control channels I've been able to find (sys ID: 1F1) are LSM as well.

And for those of us non- techno guys, LSM stands for?


Sent from my iPhone 4 using Tapatalk

 

[inigo88]

And for those of us non- techno guys, LSM stands for?


Sent from my iPhone 4 using Tapatalk

LSM = Linear Simulcast Modulation. Actually the technical name for it is CQPSK (Compatible Quadrature Phase Shift Keying). (I think there are some subtle differences but LSM ~ equals CQPSK.)

Apparently CQPSK handles multi-path receive better from simulcasting transmitters on the same frequency, and I think it has become an option on newer P25 (9600 bps) systems. However digital simulcast systems can be built just fine without using LSM, for instance the MERA (3600 bps Smartzone) East Zone "site" 1 uses ~10 Tx sites all simulcasting in C4FM modulation with no problems, it was just probably more difficult to set up to minimize tower coverage overlap and multi-pathing.

On a different subject, I fired up unitrunker on the Oakland EDACS Site 1 today, and confirmed the OPD service patch. Service 1 (12-026) and Service 2 (12-027) are being patched to talkgroup 15-155. The patch talkgroups are temporary so they shift around a little bit, but the trend seems to be that they stay in the 15-xxx range, along with Housing Authority PD and Piedmont PD.

 

[Retired911Guy]

Just talked to an engineer at GRE and he was very surprised that the OAK P25 site 101 was putting out a control CHL that was the GRE 500-600 models could not decode.

Gave him the Freqs and considering their USA HQ is in Central San Mateo CO, he said he would program up a 600 and monitor and try and figure out what it is, and if a firmware upgrade "could" (is the BIG word here) fix the problem.

God, I love it when you can just call the scanner company and ask for an engineer!!!

Dave

 

[jlanfn]

I can't access my Unitrunker right now, but I wouldn't be surprised if those site numbers are wrong. There should be a RFSS number in addition to the site number. I will try to verify later tonight.

I've noticed that many of the newer P25 systems in the Bay Area in the database put the RFSS number as the first digit in the site number, which is wrong.

 

[WayneH]

I can't access my Unitrunker right now, but I wouldn't be surprised if those site numbers are wrong. There should be a RFSS number in addition to the site number. I will try to verify later tonight.

I doubt they are. When entering them in to the database (1-001, 2-002, 3-003) it makes it look screwy so I can understand them being wrong. If there are others that are wrong why not update them yourself?


The system name is wrong too. Piedmont does not partly own and run the system with Oakland so its name shouldn't be in there.

 

[inigo88]

I doubt they are. When entering them in to the database (1-001, 2-002, 3-003) it makes it look screwy so I can understand them being wrong. If there are others that are wrong why not update them yourself?

The system name is wrong too. Piedmont does not partly own and run the system with Oakland so its name shouldn't be in there.

I don't think Piedmont's name should be in there either. The fact that they are subscribers doesn't mean they take part in administering or maintaining the system.

I can't access my Unitrunker right now, but I wouldn't be surprised if those site numbers are wrong. There should be a RFSS number in addition to the site number. I will try to verify later tonight.

The RFSS'es (haha) are correct. Site 1 is 101, or 1-001 (depending on your preferred RFSS/site P25 format), site 2 is 2-002, site 3 is 3-003. The former format is a Motorola system format "ZSS" ("Zone"/RFSS being first, then the site number), the latter is the RR database format (R-SSS, R=RFSS, S=Site).

Just talked to an engineer at GRE and he was very surprised that the OAK P25 site 101 was putting out a control CHL that was the GRE 500-600 models could not decode.

Dave, the LSM site is site 2-002 (not 1-001 as you stated in your post). Site 2-002 is using a CQPSK variant called Linear Simulcast Modulation (LSM), that are scanners are compatible with, but don't handle well because they're optimized for C4FM modulation. Please invite him to monitor site 2-002, I would love to hear his conclusions. Also tell him we want a PSR-500/600 firmware upgrade!

The LSM issue is several years old. Do a search for "P25 LSM" or "Linear Simulcast Modulation" in these forums and you'll find a lot of threads about this exact same issue from other states. We've just been lucky to avoid it in Northern California until now because there have been no P25 simulcast trunking systems up here.

Norcaljpa was extremely helpful in confirming the above, thanks again sir. For future reference for everyone else reading, both the LSM control channel and voice data in analog mode sound extremely different from their standard well known P25/C4FM counterparts. Try comparing the control channels from Oakland's site 2-002 vs site 1-001 and you will see what I'm talking about (or see several threads up, when I compared the links to the two audio recordings). Armed with this new information, it will be a lot easier to determine whether P25 sites are single-site or simulcast in the future.

 

[norcaljpa]

Armed with this new information, it will be a lot easier to determine whether P25 sites are single-site or simulcast in the future.

You can also usually make very well educated guesses based on FCC licenses and coverage area (or no guessing needed if you have someone kind enough to post it all online like EBRCSA, but I digress). If you have the same frequency at multiple locations with at least one neighbor within a dozen miles or so, it's a good bed that there's simulcasting going on, regardless of band (no getting around the value of C).

Either way, neither a scanner or subscriber much cares whether its on a simulcast or repeater site, as long as it's in range and there aren't any phasing issues.

 

[inigo88]

You can also usually make very well educated guesses based on FCC licenses and coverage area (or no guessing needed if you have someone kind enough to post it all online like EBRCSA, but I digress). If you have the same frequency at multiple locations with at least one neighbor within a dozen miles or so, it's a good bed that there's simulcasting going on, regardless of band (no getting around the value of C).

Either way, neither a scanner or subscriber much cares whether its on a simulcast or repeater site, as long as it's in range and there aren't any phasing issues.

Do you know the actual locations of the LSM simulcast transmitters in site 202? Based on the license info i have been strongly suspecting 202 is a simulcast of both APL (1111 Broadway) and Seneca, is that correct? If so that would explain our reception problems, because we're listening from the north bay outside the intended coverage area, and we're receiving the APL signal sooner than the same signal from Seneca and getting multipathing/out of phase destructive interference? Also it's clear that site 101 is a single "repeater site" at Gwin (Grizzly Peak), but do you know if site 303 will be a repeater site at station 25, and if so is it currently online? The control channel is announcing neighbor messages indicating that site 303 control channel is 852.1125, and that same frequency is the only freq licensed to the station 25/chabot site. I know Smartzone Quantar Intellirepeaters had an option called "voice over control channel", where you could have a single frequency IR site - is site 303 going to be the P25 equivalent, or are more frequencies going to be added?

Thanks a lot.

 

[norcaljpa]

Keeping in mind that I'm not an engineer...

That you're outside the coverage area by itself shouldn't matter. Multipath can be an issue. Even assuming that the transport delays are set exactly right and the RF is leaving the transmitter at each site at exactly the same time, you still have "flight time" to consider. For example, Broadway and Seneca are about 7 miles apart. That amounts to just under 40us as the RF flies. In a perfect universe, if you were equadistant from both sites, you would be in perfect phase. Anywhere else and one site is going to reach you sonner than another. Coversely, if you are exactly on the opposite side of one site from the other, you would get the full 40us delay. P25 is supposed to be tolerant of delays up to about 50us, so in theory this is in tolerance. This is by the way why LSM/CQPSK is used for simulcast - it stabilizes in each symbol state much more quickly than C4FM. There's some good reading on this topic available online.

In the real world, even with perfect phasing you're almost never going to have 0% BER. If a voice channel goes over the BER threshold you lose audio, but if this happens on a control channel the radio goes out of range and has to start the registration and affiliatiion process all over. I see the latter as being the biggest issue Oakland is dealing with now, since it's a longer service disruption than just losing voice frames.

If so that would explain our reception problems, because we're listening from the north bay outside the intended coverage area, and we're receiving the APL signal sooner than the same signal from Seneca and getting multipathing/out of phase destructive interference?

 

[Retired911Guy]

HighJacked this Quote posted by Inigo 2 days ago

Officers are complaining about dead spots on a daily basis. If you listen to an OPD talkgroup long enough you're bound to hear one. From last night:

Officer to dispatch: "I've been trying to call you for the last five minutes but couldn't get through. The entire (didn't catch the neighborhood name) is dead on these radios."
Dispatch: " *sigh* I'll add it to the radio log."

The problems are definitely not limited to the way our scanners are handling LSM.

The neighborhood must have been somewhere N or NW of Broadway, So, what did the techs do??

Changed the Control channel back to 851.1750 (CHL-1on the list) from 853.8375 (CHL 5 on the list) where it has been for the last month or so.

To bad for us in Marin, that was the best V CHL that that we could pickup (of only 2-3 of them all) (that's why we think the antenna for 851.1750 pointed N or NW cuz we get it well in Marin, but then OAK is obviously not try to cover Marin. So Martin, Forget what Inigo and I said at our little meeting the other day about trying to listen to 851.1750!!

Dave

 

[inigo88]

FWIW, I drove the whole 580 corridor about 3 weeks ago, and at some point I should have gotten some sort of line of site with or been near enough to the fire station near Chabot, yet I picked up no hint of the Site 303 (3-003) control channel on 852.1125. It's therefore my theory that site 303 is programmed into the zone controller as a single (non-simulcast) fill-in site, but still hasn't been hooked up yet. That would explain why the system is announcing it as a neighbor CC but there is no control channel to be heard.

 

[WayneH]

That would explain why the system is announcing it as a neighbor CC but there is no control channel to be heard.

Pro96Com should tell you if it's offline or not.