Baltimore County (Project 25)

System Information

• FCC Information
• The database entry for this system is here

Linear Simulcast Modulation

Baltimore County's new Motorola P25 7.x system employs an RF simulcast method known as Linear Simulcast Modulation. This technology supposedly enhances a subscriber radio's ability to overcome digital simulcast multipath distortion by shaping the digital packet waveforms using CQPSK (Compatible Quadrature Phase Shifting Key) modulation. Because of this, if the digital packets arrive at a subscriber radio from multiple transmitters out of sync, the radio is able to organize them and decode them without distortion.

Because scanners are not readily prepared to capture digital packets with these modified shapings, scanners have trouble decoding the packets. This can hold true not only for voice signals, but also control channel signals. This is why you may be in a solid coverage footprint area, but not receiving the system signals in a clear manner.

Baltimore County Fire Department talk group assignments

The Baltimore County Fire Department is divided into three battalions. The first battalion encompass the central and northern portions of the county, and is bordered to the west by Falls Road, and to the east by Harford Road. The second battalion is the west battalion and is all points west of Falls Road. The third battalion is the east battalion and is all points east of Harford Road. Each battalion is assigned two complete sets of fire ground talk groups, allowing each incident to have a primary operations talk group, an incident command talk group, seven expansion talk groups, and an announcement call talk group. As an incident with a battalion chief is dispatched, the operations for that incident are assigned to the TAC x2 talk group for that battalion. If the incident escalates and the need for multiple tactical and IMS talk groups are needed, "command net" is instituted and the incident commander will use the TAC x1 talk group, while the incident functions can expand to the TAC x3 thru TAC x9 talk groups. Typically, operations will remain on the TAC x2 talk group, eliminating the need for the people "in the trenches" to change their radio. The announcement call talk group (AC x0) allows commanders to use regroup logic to make transmissions over all the TAC talk groups assigned to that set.

Here is a sample for the first battalion's first set of fire ground talk groups. The Bxx is the position of the talk group in the portable radio. For example, the first talk group is located in ZONE B, and knob position 12.

• 9460 B12 AC 10 Announcement Call for TAC 11 thru TAC 19
• 9461 B11 TAC 11 Command NET talk group
• 9462 B3 TAC 12 Primary operations talk group
• 9463 B4 TAC 13 First expansion talk group
• 9464 B5 TAC 14 Second expansion talk group
• 9465 B6 TAC 15 Third expansion talk group
• 9466 B7 TAC 16 Fourth expansion talk group
• 9467 B8 TAC 17 Fifth expansion talk group
• 9468 B9 TAC 18 Sixth expansion talk group (typically used for EMS)
• 9469 B10 TAC 19 Ninth expansion talk group (typically used for HAZMAT)

• The first battalion is assigned AC 10 thru TAC 19 and AC 60 thru TAC 69.
• The second battalion is assigned AC 20 thru TAC 29 and AC 50 thru TAC 59.
• The third battalion is assigned AC 30 thru TAC 39 and AC 40 thru TAC 49. These are non-wide-area talk groups that will only work on the south system.
• There are two sets of spares, AC 70 thru TAC 79 and AC 80 thru TAC 89.
• There are two sets of non-wide-area talk groups for the north system, AC 110 thru TAC 119 and AC 120 thru TAC 129. These are currently not regularly assigned, and are reportedly for site trunking and failsoft conditions.

Multi-Zone

The UPGRADED Baltimore County system is a two-zone system. The reason for this is because you can only effectively simulcast from a certain number of towers before timing sync is degraded.

Your scanner (and the RRDB) refer to these zones as "sites." While typically a "site" is referring to a single tower site/transceiver location, in this case, a "site" is a group of tower sites all transmitting the same EXACT signal (known as simulcasting). With the old system, all 9 tower sites always transmitted the same exact signal -- it was a total simulcast --- therefore, scanners and radios only see the system as one "site."

With the upgraded system, there will be two "sites" or "zones" to cover the county, because, with the addition of other tower site locations, there are too many towers to have a total simulcast. The reason is very technical and beyond the scope of this post.

The main "zone" or "site" covers the majority of the county. The tower sites simulcasting the signal of this zone are as follows:

1. Towson (Fire Station #1)
2. Woodlawn (county highways shop on Windsor Mill Rd)
3. Hunt Valley (on Warren Rd east of I83)
4. Cub Hill (on the grounds of Hickey School for Boys)
5. Kingsville (Belair Rd at Harford County line)
6. Allender (Eastern Sanitary Landfill on Days Cove Rd)
7. Essex (rooftop site at CCBC Essex mid-rise building)
8. Northpoint (Precinct 12)
9. Sparrows Point (Fire Station #57)
10. Halethorpe (county highways shop on Brady Ave near Washington Bl and I695)
11. Catonsville (northwest corner of Rt. 40 & Rolling Rd)
12. Red Run (New Towne High School in Owings Mills)
13. Arcadia (Arcadia Volunteer Fire Company carnival grounds)
14. MEMA (Camp Fretterd military reservation in Reisterstown)
15. Jacksonville (Jacksonville Elementary School)

The following sites will cover the extreme northern end of the county, comprising the second "site" or zone:

1. Maryland Line (Rt. 439 just east of I83)
2. Hereford (state highways yard on Mt. Carmel Rd just east of I83)
3. Spookhill (at the city water facility on Prettyboy Reservoir)

It seems clear at this point that, because of the large footprint covered by the south site, it will carry most traffic on the system. It is unclear exactly how much of the traffic will be carried on the north site. It is likely that there will be a few talk groups "forced" onto the north site at all times, while most talk groups will only be carried on the north site based on registration/affiliation. What this means is that, as a radio enters the footprint of the north site, it will register with the site's controller, identifying the talk group with which is it affiliated, causing the site to begin carrying that talk group. If no radio is registered/affiliated with the north site for a specific talk group, that talk group will not be carried by the site. This is significant for scanner users because a scanner cannot register, therefore, some talk groups may be silent on this zone.

To add to the fun, there are a handful of talk groups that are ONLY for the north site. These talk groups appear to be reserved for a condition called "site trunking." Site trunking is a fallback function that occurs when a remote site (such as the north site) loses contact with the system controller, causing wide area calls (calls over multiple sites) to fail. If this were to occur, users on the "detached" site would revert to talk groups specific to that site, allowing users to continue to communicate within the footprint of the site. Dispatchers may also continue to connect with the site via some sort of RF link or back-up microwave path.

Object Oriented Programming

If you own the Pro-106, Pro-197, PSR500, or PSR600 scanner, you have some options as to how you want to monitor the system:

1. If you will only ever monitor from within the footprint of the main (south) site, you may chose to ONLY enter the south system frequencies (remember, you only ever have to enter the control channel frequencies). You may miss calls that only occur on the north site, but these calls should be rare.
2. If you move between the coverage footprints of the two sites, you may chose to set your scanner to "ROAM." Is this mode, your scanner will evaluate the strengths of the signals of the control channels from both sites and chose the strongest signal to lock on to. If the signal strength drops below a set threshold, your scanner will automatically evaluate the signal strength of the other site's control channel, and, if it is stronger, will switch to that site. Remember, if your scanner locks onto the north site, calls specific to the south site will be missed.
3. If you are within reception of both sites, and want to ensure that you hear all calls, you can set your scanner to "STAT" or stationary mode. In this mode, your scanner will sample the control channels of both sites for brief amounts of time, almost like scanning two different systems, but referring to the same list of talk groups IDs.

If you chose option 2 or 3 above, you need to enter in all control channel frequencies (8 total) and select the appropriate multi-site mode.

Thanks to ocguard in this thread for this information

Object Oriented Software Example Screens

• These screens should be used as a starting point. You may need to play around with other settings to make it work in your situation. This is particularly true of utilizing the attenuator to cut signal overload issues. Both the North and South site frequencies are shown. To view the full image, simply click on it.

ARC500 Screens

• For those screens that show more than one TSYS, look at the bottom 4 entries

• 

  TSYS and Frequencies

• 

  Expert Settings Screen 1

• 

  Expert Settings Screen 2

• 

  Global Expert Settings

• 

  Global Misc Settings

Win500 and PSREdit500 Screens

• 

  PSREdit500 screen

• 

  Win500 screen

PSR-800 Bandplan Tables

CH-LO	CH-HI	OFFSET	BASE FREQ	STEP	SLOTS
0	4095	0	851.00625	6.25	FDMA
4096	8191	4096	762.00625	6.25	FDMA
8192	12287	8192	851.01250	12.5	TDMA 2
12288	16383	12288	762.00625	12.5	TDMA 2

Unidentified Talkgroups

• as of Nov 25 2011
• 9433
• 9618 (Police, heard units dispatched at PCT 9/11 border. However, RIDs coming up are all special units, generally in the 22509XX range.)
• 9622 (Police, possibly warrants TF/ ETT/ SOD)
• 9629
• 9630
• 9647 (Police unknown, partial encryption)
• 9648
• 9652 (Police, probably investigative based on recorded conversation. All units spoken of and locations identified are in PCT 1, so this may be 301 or similar.)
• 9656
• 9657
• 9665
• 9668
• 9670
• 9866
• 9869
• 9870
• 9871
• 9872
• 9873
• 9874
• 9876
• 9877
• 9880
• 9884

Unit Ids

About 115 radio IDs seen so far (using Pro96Com)

---

RIDs identified using PSR-800: Labels include home channel (Precinct-based units and all dispatch radios) and any special tags for quick-reading clarity (MED 4 instead of M4, SHER S24 instead of S24), organized by sequential numeric RID. BCoFD and PD units use vehicle-specific portable radios.

• 15004 P7 COC DISP
• 15005 P8 PAR DISP
• 15006 P6 TOW DISP
• 15008 P2 WOO DISP
• 15009 P3 FRA DISP
• 15010 P1 WIL DISP
• 15011 P9 WHM DISP
• 15012 P11 ESS DISP
• 15014 P12 NOR DISP
• 15017 A3 ADO ADO
• 15018 FD TAC OPER
• 15019 F1 MAIN DISP
• 15020 F1 MAIN DISP
• 15023 F4 WEST OPER
• 30000 C221 EMRC
• 30001 C224 EMRC Med-224
• 2240347 PD AIR N80?CP
• 2240351 P1 PRECINCT 1
• 2240352 P2 PRECINCT 2
• 2240377 P1 CAU 7110
• 2243060 ENG 261
• 2243079 ENG 13
• 2243109 ENG 464
• 2243134 AMB 335
• 2243143 ENG 19
• 2243157 EMS 3
• 2243158 EMS 2
• 2243164 MED 13
• 2243168 ENG 10
• 2243169 MED 3
• 2243176 ENG 16
• 2243177 ENG 6
• 2243185 ENG 5
• 2243211 TRK 18
• 2243213 MED 4
• 2243220 MED 18
• 2243227 TRK 297
• 2243245 AMB 415
• 2243249 AMB 356
• 2243257 SQD 523
• 2243277 MED 2
• 2243306 ENG 18
• 2250007 P1 110
• 2250008 P1 111
• 2250009 P1 113
• 2250010 P1 114
• 2250011 P1 115
• 2250012 P1 116
• 2250013 P1 117
• 2250014 P1 125
• 2250015 P1 127 (D)
• 2250016 P1 129
• 2250017 P1 130
• 2250028 P1 172
• 2250033 P1 181
• 2250034 P1 182
• 2250037 P1 185
• 2250040 P1 127? (D)
• 2250045 P2 210
• 2250046 P2 212
• 2250047 P2 213
• 2250048 P2 214
• 2250050 P2 216
• 2250051 P2 225
• 2250053 P2 227
• 2250054 P2 228
• 2250055 P2 229
• 2250056 P2 230
• 2250063 P2 240
• 2250064 P2 241
• 2250066 P2 243
• 2250067 P2 244
• 2250069 P2 246
• 2250120 P4 PRECINCT 4
• 2250130 P3 328
• 2250158 P6 625
• 2250159 P6 626
• 2250161 P6 629
• 2250191 P6 629
• 2250213 P8 813
• 2250215 P8 825
• 2250216 P8 826
• 2250217 P8 827
• 2250218 P8 828
• 2250230 P8 PRECINCT 8
• 2250237 P9 911
• 2250239 P9 914
• 2250240 P9 915
• 2250241 P9 916
• 2250242 P9 PRECINCT 9
• 2250243 P9 PRECINCT 9 (P9 has 2 radios)
• 2250244 P9 925
• 2250245 P9 926
• 2250247 P9 928
• 2250248 P9 930
• 2250267 P11 1110
• 2250268 P11 1111
• 2250270 P11 1113
• 2250272 P11 1115
• 2250273 P11 1116
• 2250274 P11 1125
• 2250280 P11 1131
• 2250283 P11 1142
• 2250313 P12 1211
• 2250314 P12 1212
• 2250315 P12 1213
• 2250318 P12 1225
• 2250323 P12 1241
• 2250324 P12 1243
• 2250326 P12 1245
• 2250347 P12 1229
• 2250356 TEU 1409
• 2250357 TEU/CRASH 1410
• 2250366 TEU 1416
• 2250371 TEU 1441
• 2250373 TEU 1440
• 2250393 TEU 1466
• 2250394 TEU 1467
• 2250396 TEU 1469
• 2250506 PD AIR N80?CP
• 2250743 P8 825
• 2250745 MCU 1972
• 2250832 K9 1528
• 2250834 K9 1526
• 2250836 K9 1529
• 2250845 NARC N10
• 2250848 NARC N13
• 2250860 NARC N27
• 2250895 NARC N214
• 2251002 CRIMELAB 2041
• 2251006 CRIMELAB 2045
• 2251035 P1 CAU 7110
• 2251040 P1 CAU 7115
• 2251041 P1 CAU 7116 (D)
• 2251045 P2 CAU 7123
• 2251068 P6 CAU 7164
• 2251087 P9 CAU 7190
• 2251088 P9 CAU 7194
• 2251089 P9 CAU 7195
• 2251106 P1 CAU 7116 (D)
• 2251190 P12 PRECINCT 12
• 2251282 P1 112
• 2251283 P1 126
• 2251284 P1 128
• 2251291 P3 326
• 2251297 P6 611
• 2251298 P6 627
• 2251306 P8 811
• 2251307 P8 812
• 2251310 P9 912
• 2251311 P9 929
• 2251315 P11 1145
• 2251316 P12 1209
• 2253021 BSH 342
• 2253030 RHB 155
• 2253031 RHB 154
• 2253052 ENG 302
• 2253175 MED 13
• 2253182 EMS 8
• 2253183 ENG 2
• 2253184 EMS 6
• 2253192 TRK 5
• 2253235 ENG 5
• 2253241 BSH 5
• 2253245 AU 248
• 2253309 UTL 357
• 2253320 ENG 41
• 2253397 ENG 18
• 2253404 DIVISION 4 (Unsure if actual unit or temp ID- BCoFD has Battalion Chiefs, not heard as Divison Chiefs)
• 2253529 DIVISION 3 (Same as above)
• 2253579 MED 13
• 2253660 UTL 319
• 2253665 RHB 155
• 2253666 AMB 203
• 2253706 MED 4
• 2253745 ENG 5
• 2256018 SHER S132
• 2256050 SHER S21
• 2256066 SHER S24
• 2256075 SHER S41
• 2260462 BCFD TRK 20