Is this the best that I can expect?

[MOGA]

Before the City of Atlanta switched over to their digital trunked radio earlier this spring, I had excellent reception of their police and fire system from both handheld and base scanners that I operated from home and car, using portable OEM antennas. The sudden cold turkey of going from being in the know to knowing jack after my conventional trunking machines fell silent has been painful. Finally, I’ve acquired a digital scanner (GRE PSR-500) and got it programmed with a few Atlanta Fire & Police talk groups to start, just to get off the ground. I’ve been very much looking forward to once again knowing what is going on in my immediate community and fired her up after a quick last minute check of the firmware settings (current).

After about eight hours of listening, I am, uhh, not very pleased with the resulting experience. The audio is usually choppy and drops out regularly. It seems like once it gets going, it’s okay sometimes. But I miss the very beginning of nearly every transmission, and occasionally the entire dispatch is unintelligible because of how much the signal drops out. An earlier analysis of the system yields a signal that varies from 99% to 68%, with most of the samples coming in at 80% plus, yet the reception isn’t stable at all. The experiences of users in the thread PSR-500 Audio Cutting Out chronicle nearly the exact symptoms that I have, especially this remark:

Watching the display on the 106 closely, the "T" appears when the audio cuts out, seeming to indicate that the radio is attempting to track the trunked system, even though it was already on a voice channel and decoding a programmed TG.

Earlier today, I was out walking with my dogs along a culvert near GA DoD that is completely devoid of trees or structures for several hundred yards to each side to see if it would eliminate the wildly fluctuating signal strength. The radio was in a holster that, in turn, is attached to my backpack. I monitor the radio output using ear buds. I thought that if it is multi path that causes the earlier performance issues from inside the house, that operating in a wide open environment would present an improvement of reception. After all, a 320' AGL tower looms in the foreground from which I suspect Atlanta Public Safety simulcasts. It’s probably less than two miles from my home and always has City and State vehicles parked in the lot. Even if that is not the case, I thought that there may be a chance to see improvement due to not having any intermod around from stuff inside and around the house. Alas, no dice. The signal was as shaky and choppy as before when I was inside.

I’ve also played around with the settings as others have suggested. I’ve disabled multicast and delays. Disabled all priorities. Tried to attenuate the signal thinking that perhaps the front end was experiencing fundamental overload. Attenuating the signal results in reception that is so degraded that the scanner doesn’t even recognize one is there most of the time. What to do?

So I’ve come to ask folks that monitor the city of Atlanta system if they have similar experiences and if they’ve been able to mitigate them. Before I buy external antennas and cable and worry about guying up a mast on the roof, I am curious to know if the problem is not my radio or reception as much as an issue with the Atlanta system setup.

Thanks for any and all suggestions.

In addition to recently acquiring a new P25 scanner, I also am the first time owner of a VHF/UHF HT, MW/SW/FM portable, and HF rig. I also got a tech ticket last weekend. So you folks will be seeing lots more of my SN as I learn more about radio comms. I’m pumped to be diving into the hobby fulltime and to have a community with which to share my enthusiasm.

-MOGA

 

[N8IAA]

Radio Shack 800Mhz antenna!! Turn the squelch all the way counter clockwise for trunking systems. As good as this radio is on 800Mhz, it does not have the sensitivity my 96 had. You definitely need a better antenna to hear systems. In Gwinnett, I use a stubby 400Mhz antenna from my Pro-99. Works great on that system. Congrats on the ticket
HTH,
Larry

 

[b7spectra]

By the looks of your location, I presume you are in Atlanta. As Larry said, get the RS 800Mhz antenna. Very good! Also, you may even want to think about a 3" stubby as well. I have used both a UHF and 800 MHz antenna on my old Pro96 and as well on my new 396XT when I have used it at Hartsfield (to monitor the PD) with great success.

An external antenna on the house should also get you much better results - just don't scrimp on the coax!

 

[MOGA]

I have a 1/4 wavelength 800 antenna that llooks exactly like this. It worked wonders for the analog TRS reception on my old scanners but doesn't perform well with the GRE hand held at all. Yet, for $20 I'll give the RS 800 whip a try. At 7" in length it's probably at least a 3/8 if not a 1/2 wavelength so there may be some improvement over the diminutive 800 that I have. If not, I can always use it on another scanning device. And yes, I am in Atlanta proper. Grid EM73tr.

A couple things I observed last night after playing around with the scanner some more.

1-The scanner performs much better when it is in my hand than when it sits by itself. It's almost as if the body is needed to complete a mirror.
2- The RSSI fluctuates all over the place when tuned in to ATL P25, ranging from 200s to 700s. It varies by the millisecond. Mind you that the signal is 2-300s without affixing an antenna to the BNC connector. Some of the audio that drops out is due to the wildly changing signal levels of the voice channel. Anything below about 350 or so won't even register as a signal on the display nor generate any output from the speaker.
3-The other part of the issue is RF muting. I was able to discern exactly when the channel data was muted using the GRE remote control software that comes with the scanner. It seems that the radio mutes itself some 30ms after the signal is lost, even if there is actually voice data being sent that the scanner has a hard time receiving. There is also a slight delay between the time that the scanner begins to output audio again after the signal is reacquired. Changing a couple of the P25 trunking parameters in the expert setting area did help moderately. Specifically the 96CC HD2 and the 96VC SQ TO settings. Increasing the amount of time that is required before the radio squelches due to time out definitely made an improvement. I also disabled SuperTrack and reduced the Noise Thresh. A strong, steady signal is probably all else that I'm missing.

I've been too busy today to perform experimentation with monitoring other P25 trunked systems in the area to compare that reception to that of Atlanta's system. Hopefully I'll get to that tomorrow. In the meantime, I'll try out the RS antenna suggestion and report back with my observations, either tomorrow or Monday.

 

[MTS2000des]

well, welcome to attempting to monitor simulcast 800MHz digital radios with scanners that aren't capable of proper decoding of LSM CQPSK modulation.
I'll bet if you program your PSR500 on the MARTA mixed mode 800 TRS you'll have excellent decoding of digital talkgroups- because MARTA uses a true C4FM carrier and doesn't simulcast. Same goes for any of the UHF 400MHz federalie stuff, no problems there either.

However without boring you with technical details, Motorola had to modify the way P25 CAI is transmitted when it is simulcasted, which being that 800MHz sucks to begin with an requires multiple transmit sites just to cover the desired areas, this modification makes most digital scanners useless and horrible at good, reliable decoding of recovered digital audio on such systems. The antenna tricks MAY or MAY NOT improve your situation, if you are equidistant from all sites on a simulcast digital system, your pretty much SOL.

This is why I gave up on using any digital scanner to monitor Cobb and Atlanta's Astro 25 trunked systems, they just plains suck and until some scanner manufacturer gets serious and builds a radio capable of demodulating LSM, this is what you have. Until then, when I'm away from work where I am issued a system radio (XTS2500), I use a Motorola XTS5000 programmed for conventional RX only and scan them conventionally. All personalities are set for CQPSK/LSM and because they are the "real deal", it works great. Downside is during the day when the school buses (on ATL) or water works (on Cobb) are on there, you have much undesired traffic. It's kind of a throwback to the golden days of scanning 800MHz (analog then) trunking systems. Nuisance delete is set on side button 1, and since the radio automatically mutes on control channels and encrypted carriers, no funny sounds come from it. All conventional personalities are set to digital carrier squelch, CQPSK, LSM enabled, and set to RX only (not capable of transmitting!).

Maybe one day soon the folks at GRE and Uniden will "feel our pain" as 800MHz digital simulcast is being shoved down our throats by the Motorola money sucking vacuum cleaner and thus, will release a DSP refresh or build a radio capable of properly decoding LSM. I'd be first to buy one, or two if they do.

BTW, welcome to ham radio. Been licensed since I was 9, my call from 1986-2007 was KB4TPP, 2007-present is N4XTS (yeah, I'm a batwing guy...a love/hate relationship!). also active on GMRS, call is WQJU329. Our organization, WC4RAV, has a UHF repeater on 440MHz in Marietta, WC4RAV/R on 443.45 PL 103.5Hz. Welcome to the hobby, communications grew from my hobby into a full time profession. Amateur radio has blessed me with lifelong friends, career paths, and technical resources galore. again, welcome.

 

[MOGA]

I haven't had a chance to sit down and make careful, repeatable observations after affixing the RS 800 MHz whip yet here are my preliminary findings:

The reception was exactly the same as before when I first affixed the new antenna: signal strength all over the map and spotty reception. Disappointment set in, but it wasn't too bad because I didn't have much expectation going into the test. I headed to the kitchen for something for the missus and sat the set on the counter. Returning to it a few minutes later, I decided to check the signal on the control channel by using the Analyze function. At first, it was around 64%, which is much lower than before. So I waited until another sample was taken; it was 70%. The signal got progressively higher with each sample until it was ringing solid 99s. After about ten of those in a row, I returned back to monitoring.

Just like that, the signal was solid and stable at five bars on ATL P25. No more fluctuating. I listened for about five more minutes without one call being dropped/chopped. It's as if the radio "calibrated" itself for the antenna during the analysis, but I don't know if the relationship between the two events is coincidental, casual, or correlated. I'm not going to make much of it until I can duplicate the observation using the stock GRE ducky first, then analyzing after going to the 800 RS. I will check back in either late tonight or tomorrow with the results.

N4XTS, thanks for the warm welcome and the discussion of Atlanta's radio system. I don't have the acumen to fully understand all that you've shared. I gather that the problem is with the decoding on the side of the radio, however. That is valuable knowledge in itself. Whether an external antenna is available will make little difference if the radio is not equal to the task of demodulating the incoming signal. It is this type of information that I hoped to receive when I posted a solicitation for help in the GA specific discussion area instead of the GRE sub-forum. This is even more reason to not get my hopes too high for a sustainable solution to the problems I've had via a vie the 800 ducky.

 

[MOGA]

Sadly, I've determined that the earlier report of improved reception was only a coincidence. The signal seems to be better on some days than others. Also, it seems that depending on who is calling, I may not be able to receive the entire transmission. Sometimes its loud and pretty steady and other times...well, by now I'm sure you can guess. I'm inclined to believe that the 4 watt hand helds that APD uses are the culprit. Also, some consoles give better reception than others. In general, I can hear GSP the best and Zone 3 APD the worst. Atlanta Fire and Zone 6 kinda fall some where in the middle.

Howsomever, the RS 800 whip is head and shoulders better than the 1/4 whip that I had and a solid improvement over the stock GRE stub. I got great reception from inside my vehicle during a trip to Midtown yesterday while using it. Reception was especially solid in the 75/85 interconnector up by 14th street. Also down by Edgewood in the Fourth Ward. Once I got near my AO, however, the signal was decidedly degraded. The contour just isn't too hot in my neighborhood I suppose.

Yep. I'm beginning to suspect that the problem is the location of my home. I intend to put up a 7 element Yagi for the 800 band when ever I can get a response from El Paso Communications, as well as a dual RS whip setup on the portable itself when away from home. Will have the latter setup in service some time next week. Also, got a Larsen 825 MHz mobile SMR-antenna inbound for my vehicle. 5/8 over 5/8 over 1/4. That should give me some solid reception of Atlanta's digital system while in the Mercury.

 

[MOGA]

Checking in to report that the Larson NMO antenna is a SOLID performer for me. It's mounted on a Larson mag mount on the top of my vehicle. I can only imagine how well it would perform if the mount was a permanent, through the roof type.

I am curious about something. Until today I thought the varying reception while monitoring Atlanta PD was due to atmospheric conditions or something similar. It seems like on certain days, it's great, then without warning on other days, it's like the system is transmitting from the next county over. But, while paying particular attention to the display while scanning, I began to notice that certain voice channels are clearer and stronger than others. It's obvious that when my TGRPs are on a particular subset of VCs, I'm golden. To test that theory, I did a search of the 850 band and was able to pick up the individual voice channels of Atlanta's system. Sure enough, the signal strengths vary widely. Some are a solid five bars, while others flicker 2-3. Finding an explanation for this observation has piqued my curiosity.

How does the P25 system determine which voice channel to assign during a convo? Is it at all dependent on where the origin caller is in the coverage area? Why does the control channel signal strength always solid but when the voice comes into play, it sometimes becomes degraded? Is a particular frequency statically assigned to a tower within the system? I'd appreciate some insight into the workings of a trunked P25 but if anyone can point me the direction of a resource that would help me to find the answers to the questions, I would be happy to do the research myself.

 

[MTS2000des]

Larsen antennas are some of the best antennas money can buy, I've had the same NMO-270/B dual band antenna on five different cars sine 1994...that should tell you something.

As far as frequency assignments, P25 trunking operates on the same load balancing principles of analog trunking. However, remember that Astro 25 (tm) from Motorola (what all the 800 digital systems are in this area) is not pure P25 standard trunking, there are proprietary features enabled. One of the system enhancements sold exclusively by Motorola is SmartZone OmniLink which allows multiple local systems, if you will, to tie into a larger network.

A good example of this is the State of Indiana's Hoosier Safe-T Smartzone system, which began it's genesis as Indianapolis/Marion county's analog 800 TRS back in 1991. Unlike Georgia who cannot seem to make this happen, in 1997, Indiana state government spearheaded a project to link the various 800MHz Motorola Smartnet trunking systems together for interoperable communications across jurisdictions, using then available Smartzone (analog) zone controllers and other components needed to complete the system. Hence Safe-T was born, it was recently upgraded to Smartzone 4 (mixed mode) OmniLink and pretty much every agency in Indiana is on it. For more on this system, read here:

IPSC: Home

Of course like everything around here, no one at the state level has accomplished anything like Safe-T here for mostly political and budgetary reasons. After spending close to a third of a billion dollars in the last 5 years (collectively), the city of Atlanta, DeKalb, Cobb, Gwinnett and Walton all bought Astro 25 and still aren't interconnected.

In the 1990's, Motorola pushed 800MHz Smartnet systems on all the localities who now are being told they must upgrade to digital (Astro 25) trunking system or face end of life support issues for their legacy analog systems. The big "everyone else is doing it pitch" and that "I" word gets thrown around and everyone whips out their SPLOST check books.

But the ISSI software (needed to connect various sites) and coordination of wide area ID's is not happening (power/control issues). Cobb county bought the Smartzone 6 controller for $600,000 of our money and isn't utilizing the capability because it's not connected the way it was supposed to be.

Right now various sites are SIMULCASTING talkgroups full time, why your reception may be better on some voice channels and not others. The way it is SUPPOSED to work on a Smartzone system is channels on each site are dynamically assigned when a subscriber radio affiliates in that sites' coverage are on a talkgroup, the system "sends" their traffic over there. When they leave the coverage area (or de-affiliate from that zone), that talkgroup is no longer "activated" on that site. This is what makes monitoring a large Smartzone (analog or digital) system challenging when zones and users overlap.

Let's say for discussion that the system was setup as a SZ Omnilink with roaming enabled. A Cobb officer gets in a chase and winds up in DeKalb. His radio will automatically switch to a stronger site as he leaves the coverage area and signal degrades. The Zone Controller then routes that Cobb TG over to the DeKalb site so he can continue to communicate. Anyone with a scanner parked on the DeKalb site scanning for TG's will find that CCPD PCT 3 and hear ALL the traffic on that TG, UNTIL the officer returns (and his radio is logs off that roaming site) and then the TG is silent in DeKalb.

Right now talkgroups are being simulcasted but roaming not enabled, so it makes scanning much easier. While it will be a plus for officers and responders when/if roaming is enabled as they will have seamless coverage metro wide, it is going to be a boon for scanner listeners. Of course this same promise was the selling point of those analog systems of the 1990's that never happened around here because of the "herding cats" issue. (Rocky Moore of FC 911 did a great presentation on the UASI project and used this term. I think it describes our situation well.)

I realize this is a long answer but I hope it helps.

 

[jim202]

Is there any chance that you have a poor or broken antenna connection inside your radio? Moving
the radio around, or putting pressure to one side of the whip antenna or another while receiving a
signal should show if there is a broken or loose connection.

Have you tried to listen to any other 800 system in the area? You need to prove that it is the radio
or the system before you get much more worked up about this.

Jim

 

[MOGA]

Jim, I'm not sure that you intended the nonconstructive tone that is carried in your post, but I would like to clearly reply that it is not the radio/antenna that's defective, nor am I worked up about anything. As I learn more about the PSR and the operating conditions of my area, I find more enjoyment in using the GRE gear. B7s suggestion for the RS 800 whip was the first step in the right direction. Understanding the expert settings and doing some experimentation in that area yielded more gains. Putting up a SMR on a mag mount for mobile scanning has completely met my expectations. So I'm getting there but still need some help in understanding the things I observe. There's always room for improvement, especially in the department of scanning while in the house. In the southeast corner, where my office is, it's particularly challenging to monitor several frequencies that I mentioned earlier. But it's all good. I'm not belly aching for instant gratification, but having fun while I delve deeper into a new hobby. Cut me some slack, will ya?

MTS, that was precisely the insight that I hoped to glean about the system. Thank you for taking the time to explain it, and I found it to be a interesting read and not long at all.

If not before, I'll check back in once I get the Yagi off the ground.

 

[ButchGone]

While I know this thread is aimed at getting the GRE working right, can anybody who uses Uniden stuff like the 396 or 396xt chime in on how they hear the Atlanta P25 system?
I have a 396t and while driving through Atlanta along 75/85 I had no problems hearing APD and AFD. Signal did get choppy in the same places along the freeway where cell towers made analog signals a little scratchy. But I also noticed I don't hear the system until I'm close to town. On the analog system I could hear APD/AFD well beyond city limits.
Does the ATL P25 system use lower power, or have they returned the antennas at the sites to favor a good signal within city limits?
Here in Chattanooga they are building out a regional P25 800/700 system to span from Calhoun, GA to beyond Knoxville and I wonder what we can expect once this goes on line in February-March?
Thanx,
BG..

 

[b7spectra]

I've used my 396XT in downtown and inside the perimeter and it seems to work excellent on the Atlanta system. A hell of a lot better than the Cobb system! Even my 996T received Atlanta quite well. You may just have to tweak the settings.

 

[jcanupp]

I have clearly received Atlanta and Dekalb on I-85, just north of the Mall of GA. Gwinnett has poor signal at my home, in Gwinnett. Hall is a little choppy and I've had the same luck with Cobb (I can hear them in Sandy Springs). I'm wondering, systems with both encrypted and non-encrypted groups (Hall and Gwinnett) have like a coincidental bug or quirk?

 

[rmiller818]

Here is my guess as I experience what you where talking about here in Cobb.

The signal fluctuates due to the multipath distortion, its kinda canceling the signal out. Since you live in the city itself, there are probably multiple repeaters near you causing the distortion.

The first thing that has helped me the most is to enable the attenuator but only on the system itself (NOT the global attenuator) That helps knock the signal being received from the more distant repeater sites so hopefully you are only hearing the closest site to you.

If the system attenuator is not enough, try the global attenuator. I use the global attenuator sometimes in Cobb like if I am parked under a cell tower, turned it on before and it was decoding the system perfect.

My last suggestion is to play with the squelch and you may need to adjust it everyday or several times a day. Sometimes I have it all the way open, other times in the middle etc.

Give those a try and see if any of that works.

 

[MOGA]

I've used my 396XT in downtown and inside the perimeter and it seems to work excellent on the Atlanta system. A hell of a lot better than the Cobb system! Even my 996T received Atlanta quite well. You may just have to tweak the settings.

I've just learned that a number of public safety call signs held by City of Atlanta transmit from the State of Georgia building at 2 Peachtree Street, downtown. I wonder if that's why I got a good, solid signal while on 75/85 and you report good signals while downtown. It could also explain why I have a signal at my home that fluctuates at best. From the Georgia building looking south-east, there are numerous elevation changes, highway exchanges, many, many buildings (Grady, State Capitol, GSU complex among others) and last but not least, Grant Park with its many trees, directly in the line of sight between that address and my AO, which spans about four miles by my estimate. The State Building is high at 44 stories but that's just way too many obstacles in the way to permit a good signal IMO.

While not conclusive, I think it fits in with my experiences with multipathic signal reception and the unscientific observation that the contour sucks in the vicinity of my home.

 

[rmiller818]

FCC Callsign KNNH557 Details

That link has a map with all the repeaters for the Atlanta system, as you can see there is more than one. That might give you a better idea about your reception.

Did you try the attenuator and squelch?

 

[MOGA]

Thanks for the suggestion rmiller818; I tried playing with SQ and ATT before I sought help from the board. See post #1. Attenuating the signal degrades reception to the point that the signal doesn't open squelch when it's fully open. I experimented with that again earlier today from home with the same results too.

I found that there are more than just the KNNH557 license associated with Atlanta Public Safety system. Namely seven others. Five of those seven broadcast from 2 peachtree location. So, with that established, let me make sure I understand how this works. When a call from the Atlanta PS system goes across the airwaves, it's broadcast simultaneously from every tower licensed for Public Safety to the City of Atlanta? If that's the case then I should be all set as I have tower 2 of the KNNH557 system in line of sight from my home. It's the tower that I mentioned in post 1. At the time I didn't know for certain that *CoA* uses it. I suppose that based on the reception that I experience I assumed that certain calls may go out from one tower or the other. If this is truly a broadcast system then I guess there isn't a whole lot more that I can do. But I don't understand how that is plausible. At any time there may be any number of APD transmissions going out over a myriad of frequencies in the 850-860 band, and that doesn't include the other users of the system, such as Atlanta Fire, Fulton County, several other municipalities, Water Authority, etc. Are all calls going out from every transmitter concurrently?

At least I now know the direction in which to point the yagi when I get it next week.

 

[rmiller818]

Yep, being a simulcast system, each repeater transmits the same traffic on the same frequency at the same time. So having 2 sites near you is the problem, as the waves are reaching you at a slightly different time.

 

[INDY72]

And this is a worse issue on scanners on P-25 TRS's... *From experience on the Marion County, IN MECA P-25, and the AWIN P-25..*. When you get a multipath issue, it causes interesting to say the least effects in what should be a steady signal. Digital by itself is not as great at distances as analog on reception as its far more sensitive. With "mixed mode legacy" systems the issue is just as bad as on a true P-25. *Experience with the SAFE-T, Palmetto 800, and VIPER.*.. If your able to attenuate out one of the competeing repeaters signal it will help a lot, though from your experimentation it sounds like your in the "middle" and attenuation kills all the signals too much. You may have better success with the Yagi external antenna as it is directional. Sometimes I have noticed that just a few feet is all that matters in scanner reception on P-25... For example, great signal in your living room, while the kitchen sucketh. Keep us informed as to how the yagi works out.