Houston P25 Simulcast Multipath Distortion

[bubbatex]

I'm located just beyond southeast Houston and monitor Houston Police and Fire on the Houston General Government Services Simulcast site of TxWarn P25. Like many others who have posted here, I'm experiencing severe multipath distortion in my reception. I'd estimate less than 20% of the transmissions are "clear," and even when I travel closer into the city, this does not improve much.

Note that when the system was first introduced in May 2013, I was unable to even receive much traffic because the signal was too weak on the stock broadband scanner antenna. By replacing the antenna with an 800 MHz one, I now get up to four bars of reception, but the multipath distortion is still a big issue.

It seems strange to me that the city would have implemented a simulcast system with multiple transmitters using the same frequency, since the target audience for this P25 Phase 1 site consists of interests such as news media, wrecker drivers, scanner enthusiasts, etc. who use off-the-shelf scanning equipment that does not deal with multipath distortion very well. Does anyone know if the city has plans to replace or add a system that is more scanner-friendly?

 

[loumaag]

You didn't say what scanner you were using but let me comment a bit about my experience just for information. I am outside the city limits of Houston also, put me in the Clay Rd and Fry Rd (WNW Harris Co) area and this is what I have experienced.

I have absolutely no success in using a Pro96 scanner to monitor HPD (I don't listen to HFD normally). The radio just cannot handle any multi path distortion at all. My everyday scanner at the house for HPD is a BC796D, it seems to do a fine job with almost any antenna (not outside) I use on it for that purpose. I also have used my Home Patrol 1 and a BC396T for doing so. In fact the 369T is my primary mobile scanner, mounted in the truck. This radio (the 396) does have some difficulty with distortion as I am mobile and moving around; however, overall I figure it is getting about 90% of transmissions with no distortion and of the remaining 10% I am usually able to figure out what was said by what surrounded the missed part.

With all that said, I don't normally monitor HPD on a regular basis, only when I am aware of some reason to or I am mobile and going into the city. As for them adding any capacity or systems for scanner users, don't count on it at all. The MA channels they established are dual purpose, for other agencies to have a channel they can use to contact HPD/HFD using FDMA and for other folks to monitor (wreckers, hobbyists, etc.) The fact that the capability is on the already established General Services site (which covers everything is was designed to cover) is pretty indicative that no further expansion is going to happen. As to what newer migrating agencies (such as League City, etc.) will be doing, we have to wait and see, but I suspect you will see them making decisions now and migration to start soon.

 

[bubbatex]

Multipath Distortion Follow-up

Hi Lou,

Thanks for the response and also thanks for all of your informative posts on the general Houston P25 thread -- they really helped all of us understand the new system and get over the initial shock of the transition.

I intentionally did not mention my scanner because I didn't want this thread to devolve into a discussion about the merits of scanner X vs scanner Y and when is scanner X going to be improved, etc. But since you asked, I'm using a Uniden BCD396XT with the latest firmware update applied. In the past I've been able to monitor the TxWarn P25 Phase I system just fine on the transmitters located in League City, Texas City, Baytown (new), and even when I'm up in Huntsville in Walker County, and this was using the the stock Uniden broadband antenna. There are very few distortion issues on these sites, even with just one bar of reception. The only difference I can see between these sites and the Houston P25 site is that these sites are not simulcast, i.e. they each operate on their own independent set of frequencies.

Another big difference I see between Houston P25 and the other P25 sites is that the reception strength on the Houston P25 system varies wildly. I'm watching it right now jump between 0 bars and 4 bars. Also, some of the voice frequencies on the site come in weaker than others. So for example, one SE Dispatch transmission on one frequency might be somewhat clear, then a subsequent SE Dispatch transmission on a different voice frequency will have a much lower signal and be much more distorted.

Last week I took my scanner a few miles closer to the Houston P25 transmitter, to work in SE Houston (Clear Lake), and though reception strength did improve, most of the transmissions were still distorted. As mentioned, switching to an 800 MHz antenna allowed me to go from about one garbled transmission received every 2-3 minutes, to receiving what I assume is most of the transmissions, but still with most of them distorted. There are also only a few spots in my home where I can now get tolerable reception - most spots just don't work. I found a suggestion from UPMan to set the squelch threshold to 0, but that didn't really help and seemed to slow the overall scan of the system (it would hold onto terminated transmission frequencies longer, which I guess is to be expected.)

I wonder if it would be possible for Houston to broadcast its traffic on the existing, outlying TxWarn P25 sites (e.g. League City, Baytown, Texas City). I seems this would benefit everyone, and there would not be the cost involved of creating a new site and paying for additional frequencies. I don't completely understand the technical details though and whether this is even possible. (In fact, that raises the question of why they did not take advantage of these existing sites to begin with).

I really feel for the people who depend on these comms for a living (wreckers, media etc.) and have to deal with all the problems this new system has introduced.

As far as your comment about other agencies moving to P25, I'm seeing a steady trickle. I'm now receiving a lot of Harris County SO and Texas DPS traffic on the "generic" P25 sites, and Metro PD has been on the Texas City site for quite a while. (That to me is really strange, given that I would not expect Metro PD to be anywhere close to Texas City.) Thankfully, most of the municipalities in my area are still on the analog TxWarn sites, and I receive these just fine. (Though kind of funny, I remember cussing their transition back in the late 1980s and 1990s from UHF.)

Regards,
Steve

 

[JoeyC]

It seems strange to me that the city would have implemented a simulcast system with multiple transmitters using the same frequency, since the target audience for this P25 Phase 1 site consists of interests such as news media, wrecker drivers, scanner enthusiasts, etc. who use off-the-shelf scanning equipment that does not deal with multipath distortion very well. Does anyone know if the city has plans to replace or add a system that is more scanner-friendly?

You only have 1 post to your credit so I think you are a bit confused about who the target audience is for the (any) system. I can't imagine anyone replacing a system because scanners do not receive them well when they cost many millions of dollars in the first place to implement. The key point, is does the system work for its intended users?

 

[bubbatex]

Joey

Joey,

Since I see you're in San Diego, let me help you out a little with the new Houston P25 system. If you do a little research, you'll find this article entitled "Houston Police and Fire P25" on the Radio Reference Wiki, stating the purpose of the Houston General Government Services Simulcast RFSS (see Houston Police and Fire P25 - The RadioReference Wiki).

The article states, "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."

One of the primary purposes of this system was to allow interests who use off-the-shelf scanners in their line of work, such as media, wrecker drivers, etc., to access communication on the system. So your statement "I can't imagine anyone replacing a system because scanners do not receive them well" misses the mark a little. And to answer your question, "does the system work for its intended users", the answer is no, not very well and not at this point in time.

 

[loumaag]

...
One of the primary purposes of this system was to allow interests who use off-the-shelf scanners in their line of work, such as media, wrecker drivers, etc., to access communication on the system. So your statement "I can't imagine anyone replacing a system because scanners do not receive them well" misses the mark a little. And to answer your question, "does the system work for its intended users", the answer is no, not very well and not at this point in time.

No and no. The addition of simulcasting the dispatch channels on the General Services site (at the bottom priority BTW) was done to assist those interests mentioned in the Wiki article and to allow mutual aid. The actual system works quite well so your last comment is completely off the mark. The actual system is Phase 2 and despite some ill informed reporting, there are almost no problems with it. The simulcast on Phase 1, that which you are listening to, is not part of the actual system used by the agencies at all. We have someone else in the area that can speak to this but I would not be surprised if the system got busy that an HPD dispatch MA TG could not be "bumped" by a sanitation truck trying to call it's base.

 

[vstream02]

Working loud and clear in Pasadena, I get an "ooh" moment when i hear westside or northwest those were hard on the old system to hear.

 

[bubbatex]

No and no. The addition of simulcasting the dispatch channels on the General Services site (at the bottom priority BTW) was done to assist those interests mentioned in the Wiki article and to allow mutual aid. The actual system works quite well so your last comment is completely off the mark. The actual system is Phase 2 and despite some ill informed reporting, there are almost no problems with it. The simulcast on Phase 1, that which you are listening to, is not part of the actual system used by the agencies at all. We have someone else in the area that can speak to this but I would not be surprised if the system got busy that an HPD dispatch MA TG could not be "bumped" by a sanitation truck trying to call it's base.

Lou,

All of my comments are directed at the General Services Phase 1 simulcast. I can't monitor the Phase 2 site because my scanner is not capable, so I have no comment on it. As described, the General Services Phase 1 simulcast is not working for me in League City with the stated equipment, and I've seen other posts mentioning the same problems.

Regards,
Steve

 

[teknishun]

Hi Lou,

I wonder if it would be possible for Houston to broadcast its traffic on the existing, outlying TxWarn P25 sites (e.g. League City, Baytown, Texas City). I seems this would benefit everyone, and there would not be the cost involved of creating a new site and paying for additional frequencies. I don't completely understand the technical details though and whether this is even possible. (In fact, that raises the question of why they did not take advantage of these existing sites to begin with).

I really feel for the people who depend on these comms for a living (wreckers, media etc.) and have to deal with all the problems this new system has introduced.

Just as a side note: Using UniTrunker I am monitoring the Santa Fe P25 site on Ginger Road and am surprised to find that 90-percent of the traffic from that site is HPD SpOpDisp TG 30080.
There is some HPD SE Disp TG 30020 but not very much. There are 3 or 4 other things
there too occasionally.

Why would HPD Special Ops be operating so heavily on that particular location? I did not think the
Santa Fe tower was one of the simulcast sites. Besides, on a simulcast site I can hear
all the TG that are listed in the HPD P25 Wiki.

From my indoor monitoring location in Alvin using the rubber duck antenna on the PSR-800, the
Santa Fe control channel is a bit "iffy" - it jumps all over from green to red to yellow, etc.

I may create a new scanlist on the PSR-800 and see what the voice traffic sounds like.

teknishun KF5OPQ

 

[KevinC]

Just as a side note: Using UniTrunker I am monitoring the Santa Fe P25 site on Ginger Road and am surprised to find that 90-percent of the traffic from that site is HPD SpOpDisp TG 30080.
There is some HPD SE Disp TG 30020 but not very much. There are 3 or 4 other things
there too occasionally.

Why would HPD Special Ops be operating so heavily on that particular location? I did not think the
Santa Fe tower was one of the simulcast sites. Besides, on a simulcast site I can hear
all the TG that are listed in the HPD P25 Wiki.

From my indoor monitoring location in Alvin using the rubber duck antenna on the PSR-800, the
Santa Fe control channel is a bit "iffy" - it jumps all over from green to red to yellow, etc.

I may create a new scanlist on the PSR-800 and see what the voice traffic sounds like.

teknishun KF5OPQ

All it takes is one radio affiliated to Ginger and you will hear all traffic on that TG. I would bet someone with a take home radio lives in the area and keeps their radio on...but this is just a guess.