Houston Police and Fire P25
From The RadioReference Wiki
The Houston Police (HPD) and Houston Fire (HFD) departments have made the switch to digital TDMA technology.
In April and May of 2013 the Houston Fire department and then the Houston Police department abandoned the use of their respective legacy UHF analog conventional systems and moved to the TxWARN P25 system. This move, in addition to moving from an analog conventional system to a digital trunking system caused problems since HPD and HFD are using P25 Phase 2 technology.
The City of Houston recognized that this move would cause problems for various interest that monitor those agencies and as a partial aid to those interests, including the scanner hobbyist, the dispatch channels for HPD and the main dispatch channel as well as 4 regional channels for HFD are being simulcast on P25 Phase 1 talk groups, allowing for normal P25 trunking capable scanners to monitor those channels.
In addition to the move to P25 Phase 2 technology, both HPD and HFD are making extensive use of encryption on all tactical (Tac) and talk around (TAC) channels. The reasoning for this is not within the scope of this discussion; however, it should be noted that their decision to leave non Tac and TAC channel in the clear is to everyone's advantage.
This brings this discussion to the simulcast of the dispatch channels and regional channels (for HFD) in P25 Phase 1 technology and how that can be implemented in a normal P25 trunking scanner.
Specific Talk Groups
The HPD has identified 12 channels and HFD has 5 to rebroadcast in P25 Phase 1, they refer to these as Mutual Aid channels as any authorized user can access these to communicate with them:
- HPD -- These cover the basic 12 dispatch / common use channels they had on the legacy analog conventional system minus the old car to car channel (Channel 8) which is not available any longer
- TG 30180 - HPD North MA -- North Dispatch; also known as North Shepard
- TG 30181 - HPD NEast MA -- North East Dispatch; also know as Kingwood
- TG 30182 - HPD SEast MA -- South East Dispatch
- TG 30183 - HPD SWest MA -- South West Dispatch; also known as Beechnut
- TG 30184 - HPD Cntrl MA -- Central Dispatch
- TG 30185 - HPD SCtrl MA -- South Central Dispatch
- TG 30186 - HPD NWest MA -- North West Dispatch
- TG 30187 - HPD West MA -- West Dispatch; also known as Westside
- TG 30188 - HPD Sp Op MA -- Special Operations Dispatch; traffic dispatch; used to be Channel 7 on the legacy lineup
- TG 30189 - HPD Detct MA -- Detective Dispatch; hasn't been used for detectives for a long time; used to be Channel 10 on the legacy lineup
- TG 30190 - HPD CtyWd MA -- Citywide Dispatch; a common use dispatch monitored channel used for wide events
- TG 30191 - HPD AIrprtMA -- Airports Dispatch; common use for airports around the city
- HFD -- These cover the dispatch channel and four quadrant regional channels. The Tac channels that were previously used are no longer available, even as direct equivalents to the legacy analog conventional channels and all Tac channels are encrypted in any case.
- TG 40002 - HFD Disp MA -- Robot dispatcher, backed up by live dispatcher who can be contacted and occasionally calls individual units on this talk group
- TG 40018 - HFD NE RO MA -- North East Regional Operator - This and the following three channels are used for communication back to dispatch office on a regional basis. They have not, so far been used in working a fire; although, responding units occasionally will ask questions or receive direction on these.
- TG 40038 - HFD SE RO MA -- South East Regional Operator
- TG 40058 - HFD NW RO MA -- North West Regional Operator
- TG 40078 - HFD SW RO MA -- South West Regional Operator
- Other -- There is at least one more P25 Phase 1 channel available at this time, although of limited interest
- TG 45191 - Hou Parking1 -- Houston Parking Enforcement channel
To receive the above talk groups, a scanner must be programmed with the specific site 3-05 and, depending on your scanner's make up, as a separate system or bank.
|005 (5)||Houston General Government Services Simulcast||853.725000||854.012500||854.387500||854.462500||856.437500||856.737500||856.762500||857.262500|
In general, as stated above, the specific site needs to set up as a separate system in your scanner. It should not be combined with other sites as the traffic on that site is separate and distinct from other sites in the system. This system should really be considered as four layers or Radio Frequency Subsystems (RFSS) , even though there are only three layers enumerated. For programing purposes the following should be considered:
- Layer 1 - contains only P25 Phase 1 traffic for the regional area in and around metropolitan Houston and close in environs. This includes, but is not limited to Austin, Brazoria, Chambers, Ft Bend, Galveston, Harris, Liberty, Montgomery, Walker, Waller, and Washington counties.
- Layer 2 - contains only P25 Phase 1 traffic for the regions outside the areas covered by layer 1.
- Layer 3 - contains a mix of P25 Phase 1 and Phase 2 as follows:
- All layer 3 sites except 3-05 - carry only Phase 2 traffic for the City of Houston and some other smaller entities in and around the city; for example, the Memorial Villages which are in the clear but Phase 2 only. These entities also make extensive use of encryption on other than the dispatch channels and in some case (Bellaire for example) encrypt the dispatch channels also.
- Layer 3, site 5 - the Houston General Government Services Simulcast site. This site is used for the all City of Houston public works in addition to the simulcast of the HPD/HFD channels mentioned above.
Naturally, a lot of interest is in how to program this system for more than one agency. As such, in general you should consider it as three separate systems from a scanner programming standpoint.
- Layers 1 & 2 as one FDMA (Phase 1) system
- Layer 3 sites (except for 3-05) as one TDMA (Phase 2) only system
- Layer 3, site 05 as a mixed FDMA / TDMA system
Non HPD/HFD Phase 1 Only
Treating layers 1 and 2 as you would any other P25 system, considering overlap and who uses what sites, you would program your scanner as you would for any other P25 trunking system.
All Phase 2
If you are in possession of a GRE PSR800, you can program all the TDMA available channels in, using layer 3 sites remembering that different traffic is carried on site 3-05 than is carried on the rest of the layer 3 sites. In other words, if you happen to have a PSR800 and wanted to listen to HPD or HFD in TDMA, that traffic is not carried on site 3-05, but rather on the other sites under standard affiliation concepts with a preference given to sites 3-01 through 3-04, meaning sites 3-11 through 3-16 will only carry HPD/HFD traffic if an affiliated radio is completely out of range of the primary sites. That programing is not the subject of this article but this explanation is given to help understand what is carried where.
HPD/HFD Phase 1 Simulcast
As stated above, this is found using the listed talk groups and on the specified site (3-05). Interestingly enough, that site uses only 800 MHz frequencies. This means that even older scanners, capable of following a P25 9600 bps control channel, but not able to tune 700 MHz frequencies can be used to monitor these simulcast talk groups. Such scanners include Uniden BC796D and Radio Shack Pro-96 type scanners. Please note, this site is simulcast from seven different towers (at this time), so your scanner does have to deal with multi-path distortion.
Naturally, each scanner model or brand is programed differently so the following detailed steps for setting this up are in general and you will have to use this as a guide to setting your individual radio up:
- Program site 3-05 as a separate single site system
- Program only the talk groups you want to hear from the list above
- Since the P25 control channel is the same no matter what type of voice channel is being used (Phase 1 or 2) and you do not want your scanner chasing talk groups it cannot hear, the following two points are vital:
- Set the system up as Closed or ID Scan, depending on the brand of scanner
- Do not set a "wildcard" talk group up on the system
Almost any P25 trunking scanner can be used for this. Some handle multi-path distortion better than others, and how you adapt your scanner programing to fit this situation is up to you. However, so far it has been shown that the above works on radios as varied as a Uniden BC796D to the HP-2 and a Pro-96 to the PSR800. The key is to remember that monitoring the HPD/HFD Phase 1 simulcast transmissions needs to be considered as a separate operation from any other operation your scanner might be tasked with.
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