Basic ARMER Simulcast Questions

[WD0AKZ]

I live in Oakdale and using a PRO-96 I listen to Washington County Simulcast on 853.7375: SY40F T0105 BEE07 Site 005 Site DB ID:5827 Site NAC: N/A Lat: N44.99917 Lon: W-92.96278. The tower is just North of 34st (HWY 5) off of Hadley and the top of the tower would be line of sight with my location if not for trees

On the Armer-Site-Map-2016-10-01.pdf it shows a lot of tower sights with ID’s as “Z-1:S-5-7”. What do these ID’s signify and which one corresponds to the tower listed above?

On RR looking at the System Frequencies Names I see 29 sites that are listed as Simulcast. All say “Site Location: Various Minnesota”, some have specific Lat/Lon locations and others are not so specific, but some also have “Site Location: Simulcast 2 towers; Downtown Minneapolis and Downtown St. Paul” (Minneapolis City Center for example), or “Site Location: Citation Cable/Lino/Bethel/Stacy” (Anoka Co. for example). So where specifically are these sites (towers?) and are the frequencies listed for this site all being transmitted from this site (tower)?

Using Pro96Com decode Control channel 853.7375 data stream I see:
Site Information > Adjacent Site Information:
Site ID SysID CH Frequency Related To
101(T0101) 40F 00-1477 860.23750 Minneapolis City Center Simulcast
102(T0102) 40F 00-0381 853.38750 Anoka Co Simulcast
103(T0103) 40F 00-0409 853.56250 Dakota Co Simulcast
106(T0106) 40F 00-0233 852.46250 Chisago - Isanti Simulcast
192(T015C) 40F 00-0597 854.73750 Rush City – Prison 092 (5C) Chisago
196(T0160) 40F 00-0307 852.92500 Lino Lakes – Prison 096 (60) Anoka
197(T0161) 40F 00-1285 859.03750 Oak Park Heights – Prison 097 (61) Washington
199(T0163) 40F 00-1357 859.48750 Stillwater – Prison 099 (63) Washington
203(T0203) 40F 00-0173 852.08750 Ramsey County Simulcast 003 (3) Ramsey
214(T020E) 40F 00-0513 854.21250 Plymouth - Statewide Temp 014 (E) Statewide
340(T0328) 40F 00-0067 851.42500 Goodhue Co. Simulcast 040 (28) Goodhue
Note that of the 11 Adjacent Sites only 6 are Simulcast sites so that says that non-simulcast sites can be linked with a simulcast site?
I thought simulcast meant for example that if a unit in Dakota Co. wanted to communicate with the Washington Co. TG 3750 (WA Fire N) it could go through the Dakota Co. system and the communication would be simulcast over both sites on the sub frequencies related to each site so each can hear. So if I was monitoring WA Fire N on Washington 853.2625 I would be switched to a sub frequency and hear it, or if monitoring WA Fire N on Dakota 853.5625 I would be switch to one of their subs and would hear it as well. So where (how) do the non-simulcast sites in the above list relate to being heard on the Washington Co. data stream?

I have one bank in the PRO-96 with Washington Co. CC and the Washington Co. TG’s I want. I also have these same TG’S in another bank with the Dakota Co. CC. On Dakota I only hear some of my Washington TG’s, it’s not like all of them that are being transmitted on Washington are also being transmitted (simulcast?) on Dakota.

With our ARMER system does “Simulcast” mean simultaneous transmission of the audio/data on -multiple- frequencies, on multiple tower sights? Or does it mean the audio/data on the –same- frequency, on multiple tower sights?

For a few years now I have been playing with a SDR DVB-T USB stick receiver, BCD396XT, and PRO-96. I never had any luck getting a good audio decode with the SDR, the BCD396XT was fair during the winter and very poor during the summer, and the PRO-96 was poor all the time. I recently pulled the PRO-96 off the shelf and did the VR4 adjustment, now I’m getting 70%-98% decoding and 99% clear audio on Washington Co. so I’ll see what it’s like come spring. Obviously my problem with the first two were more of a signal issue than a hardware, the PRO-96 was hardware. As for listening to the Washington Co., if the site referred to above (T0105) is the –only- source for the frequency my radio is receiving then most likely my summer decoding problem is due to multipath vs the radio(s) hardware and the natural capture effect of FM if multiple on frequency signals are present.

Tnx for any comments.
George

 

[ofd8001]

The Minnesota ARMER system is a very complex radio system to say the least. It consists of many sub-systems all working together provide a statewide radio network.

Some of these sub-systems are simulcast, particularly those in large communities with big buildings. A simulcast system consists of more than one transmitter tower with all of those towers transmitting on the same frequencies. Thus if you have a sub-system such as Hennepin East with 7 towers (guessing the number) all 7 of those towers use the same frequencies.

As best as I can decipher it the "Z-2 S-5-7" would mean "Zone 2", "Sub-system 5, tower site 7". A Zone is a large area that can "homogenize" the sub-systems included in that zone. There is a device called a Zone controller that does, among other things, make the appropriate connections when a user roams from his home sub-system into another sub-system.

The stuff you see on your scanner compared to the entries in the database, compared to the ARMER tower map use a different set of numbers to reference the same thing.

 

[WD0AKZ]

The Minnesota ARMER system is a very complex radio system to say the least. It consists of many sub-systems all working together provide a statewide radio network.

So using the Washington County Simulcast T0105 site I used in my post, how can I find out specifically:
Is the tower at Lat: N44.99917 Lon: W-92.96278 the only one or if there are others, how many and where.
Is the tower at the above location the one I'm receiving the Control Channel from?
If there are more than the one tower, what is the configuration they are used in, for example say 7 towers:

If I'm listening to a TG conversation between two units that has been handed off to 851.7125, are all 7 towers of this site simultaneously transmitting this conversation on 851.7125? Or is it more like a cell system where the only tower(s) involved are the ones required to support the units having the conversation and more towers my be added if other units join in as needed?

As I said in my posting, I'm really trying to understand what I'm listening to try and figure out why I have had such a problem decoding in the past and will probably again have next summer.

tnx
George

 

[ofd8001]

If you haven't already seen it, this page may be of interest. https://dps.mn.gov/divisions/ecn/programs/armer/Pages/current-status.aspx There is a link where you can download a tower map which shows tower locations. You can zoom in to the metro area and count the number of towers for Washington County. (I get about 12).

With simulcast, the talkgroup's conversation is simultaneously being carried on all sites/towers associated with that system. That's how they came up with "Simulcast". So yes, that 851.7125 frequency is transmitting on all of the sites/towers for Washington Simulcast.

Much different than a cell conversation.

I do not know of any way you can use your scanner to determine which specific site/tower of a simulcast system your scanner is receiving. Quite often a scanner is actually receiving transmissions from multiple sites. If you could get your hands on propagation maps (probably very hard to find), you might see which sites/towers cover your specific location.

Though I'm a Minneapolis native, I'm living in Louisville KY where we have a 13 site simulcast system. I know from seeing propagation maps for our system, at my house I'm "covered" by three sites.

You probably are having trouble decoding the signal because you are receiving transmissions from two (or more) sites/towers. The signal gets to your scanner a tad out of sync and your scanner is having trouble with figuring out what its hearing. Kind of, sort of, like three people around you talking at the same time and making out what they are saying.

There are some settings in your scanner you can tweak to get a degree of improvement. They are model dependent so I'd need to know what you are using.

Also some scanners seem to deal with this syndrome called "Simulcast Distortion" better than others. My older Uniden x96 scanners don't do simulcast very well. However my newer x36 scanners are quite good. I found this to be the case for both the Louisville system and in Minneapolis when we go to visit.

This is kind of a "down and dirty" explanation of how a simulcast sub-system for ARMER works. Because the ARMER system is very robust and complex, there can be some interesting twists and turns when you have users roaming, such as a Washington County officer going into an adjacent county. Yet another twist and turn can occur with the state patrol units who deal with areas involving multiple counties.

But a guy who can get his arms around the Minnesota system, can get his arms around anything.

 

[JT-112]

Don't forget that Radio Reference maps sites within licenses in the database.

Go to the ARMER home page.

Then click on a name, like "Minneapolis City Center Simulcast" (first entry in the list).

On that page, you'll then see at least one if not several FCC licenses, here there's just one: WPER943. Click on that.

Boom, there you go, sites on a map!

If there are multiple FCC licenses, you'll have do this for each license to build up an idea of where the transmitters are.

This isn't 100%, errors do creep in but it's very helpful to get an idea of where things are.

 

[WD0AKZ]

"With simulcast, the talkgroup's conversation is simultaneously being carried on all sites/towers associated with that system."

"Boom, there you go, sites on a map!
If there are multiple FCC licenses, you'll have do this for each license to build up an idea of where the transmitters are."

Thanks to all that responded both here and via PM.

I pulled up the Washington Co. Simulcast site and as suggested went through the 4 callsigns listed which gave me the Lat/Lon for 16 sites.... Wow!! 16 sites all simultaneously transmitting on the same frequency... no wonder the SDR DVB-T USB stick (for sure) and my other scanners have decoding issues. I'm going to dump all these sights into the map and see just how far they are from me.

tnx agn for the help
George

 

[WD0AKZ]

Ok, I plotted all 15 Sites (1 site has 2 licenses) in Mapsource and then measured Distance from me:

Sites
15 <= 19.0 miles (the furthest one out is 19.0 miles)
7 <= 9.2 miles
5 <= 5.8 miles
3 <= 2.8 miles (the closest one is 2.3 miles)

Well I sure can't blame the poor decoding on weak signal. It also explains why the varity of directional antennas I have built don't help either, I'm on the West side of the county and have close sites N,E,S of me. I can Run but I can't Hide!!

Maybe I'll have to build a RF tight Faraday Cage, put the scanner in there and use a dummy load as a antenna. ??

Either way, I'm still having Fun and that's what it's all about... Right?

tnx agn for all the help

George

 

[ofd8001]

Simulcast distortion happens because there is too much signal.

On my local system I can disconnect the antenna and hear it better in some places even if I'm not close to a tower. I've heard people use a bent papeclip for an antenna with good results. Definitely counterintuitive.

One thing to note. In the "old days" a county would be covered by one transmitter on a real high tower using lots of RF power. With that setup, one could receive a given county's transmitter a couple of counties away.

Simulcast systems use multiple towers of low height (several of yours are around 100') and lower transmit power (yours are at a most 22 watts). They are engineered so their radio footprint is pretty much limited to the jurisdiction's area. The result is that the frequencies can be re-used a little closer. Very helpful given the lack of radio spectrum.

 

[blue5011]

Use google earth to show a elevation profile. Maybe there is a hill between you and the site you are wanting to receive. I was trying to receive local over-the-air digital TV. Wasn't working, ran a elevation profile and found a significant hill between my home and the transmitter.

Also use "ARMER Freqs and Talkgroups" RR webpage to find the # of the site and click on it. This will bring up a description and also a google map. With this map you can find where the tower is for sure, w/ out having to resort to lat/ long co-ord.

 

[blue5011]

Maybe I'll have to build a RF tight Faraday Cage, put the scanner in there and use a dummy load as a antenna. ??

Well don't do like I did and install steel siding and a steel roof. Yes, the steel will last forever but I had to buy a WeBoost "cellphone extender" just to make a phone call...

I use a 996XT w/ a rubber-duck, inside the house, and still get 3-4 towers in my area (flat farm country). When I had an external antenna at 35 feet I was hearing 8-10 tower sites. I have seen many comments and complaints about reception in the Twin Cities, glad I can hear my local PD/ FD /EMS w/ few problems.

 

[WD0AKZ]

Also use "ARMER Freqs and Talkgroups" RR webpage to find the # of the site and click on it. This will bring up a description and also a google map. With this map you can find where the tower is for sure, w/ out having to resort to lat/ long co-ord.

Yup, I was doing that and then it was pointed out above to take it one step further to click on the callsign(s) listed on that page which opens up even more information. I was using the Lat/Lon to plot all the 15 towers on one map.

Well don't do like I did and install steel siding and a steel roof.

Too late on this one. Two years ago we moved to a apartment style co-op which is steel/aluminum clad. With the 800mhz RD antenna, moving the scanner 1" can be the make/break for decoding. After seeing how I am surrounded by the tower sites for Washington Co., the close proximity, and a nice big water about 3/4 mi due East of me, I'm probably getting hammered by front end overload and multi-path. I have experimented with 1/4wave Ground Plane, Dipole, Corner Reflecter, and finally a 800 WaveGuide Cantenna 35"x9" antenna. I just have too much signal coming from all directions.

George

 

[blue5011]

What software are you using for the "SDR DVB-T USB stick receiver"? I bought one and have tried using "sdrsharp". I get a good "waterfall picture" signal, but no audio.

 

[WD0AKZ]

What software are you using for the "SDR DVB-T USB stick receiver"? I bought one and have tried using "sdrsharp". I get a good "waterfall picture" signal, but no audio.

I was using UniTrunker and DSD+ with a single SDR Dongle and dual SDR's. I have not played with the SDR's for a few years now so I really can't say that the status is of the software I was using, but I would like to fire them up again this winter and see what's new.

Have Fun!

George

 

[JT-112]

The issue people with scanners have with ARMER is that the system transmits in a modulation called CQPSK.

Scanners receive C4FM.

These formats are similar, but not at all the same. When you try to listen to a CQPSK signal (e.g., transmitted from ARMER simulcast sites) with a C4FM receiver (e.g., all scanners), well, you already know the results aren't great.

Yes, some people get lucky and have better results, but really, it's just luck in where you are. No scanners work all that well, and especially when compared to Motorola/Harris/Thales/Kenwood gear that public safety uses. It's not a signal strength issue, or location issue. It's that scanners aren't set up for CPQSK.

If you want to learn more, there are many many many posts on RadioReference. Use the terms LSM, CQPSK and C4FM and you should see a lot of material to go through.

Note: some SDR software is going to work very well with CPQSK - I've lost track of the specific apps that do, but DSD+ (not DSD) I believe is one of them. You'll need lots of patience and time to muck around on your PC to have success though.

 

[smitty54017]

I purchased my scanner about a month ago, and my AMER reception has been spotty in New Richmond. The scanner shows it's receiving full signal and that the system is online, but there are days I receive absolutely NOTHING from any of the digital systems on the AMER system, and receive only St. Croix County, which is analog. On other days, it comes in like I'm sitting right next to the tower. A friend lives in Woodbury and has the same issue. It's like they're using different frequencies on some days. I've tried turning off my WiFi, etc., with no change.

 

[ofd8001]

I purchased my scanner about a month ago, and my AMER reception has been spotty in New Richmond. The scanner shows it's receiving full signal and that the system is online, but there are days I receive absolutely NOTHING from any of the digital systems on the AMER system, and receive only St. Croix County, which is analog. On other days, it comes in like I'm sitting right next to the tower. A friend lives in Woodbury and has the same issue. It's like they're using different frequencies on some days. I've tried turning off my WiFi, etc., with no change.

What model scanner are you using? Might be some things to try depending on what you have.

 

[WD0AKZ]

Scanners receive C4FM.

I'm not sure if the BCX396XT I had last year had QPSK available but the PRO-96 I have now does not. That being said, since I did the VR4 tweak last week this old PRO-96 has been sitting here on the desk humming along with 80%-98% decoding and about 99% in the clear audio, but the real show will be what happens to the decoding once spring/summer comes back.

I did put a discriminator tap in it last winter with plans to feed it to DSD+ but never got around to it. That's on the "To-Do" list for this winter. I just want to get that set up as a backup for this summer.

George

 

[smitty54017]

What model scanner are you using? Might be some things to try depending on what you have.

Uniden BCD996XT.

 

[ofd8001]

The x96 line of scanners does have difficult decoding simulcast systems. You'll see all bars on signal strength indicator. The problem is you are getting too much signal (receiving multiple towers) and your scanner is having trouble with decoding the multiple sets of data coming in.

There are things you can try that might lead to varying degrees of improvement:

Set Site Attenuator to On. (Reduces the sensitivity of the scanner for that site).

Also, from Mark's Easier to Read Manuals:

P25 Adjust Mode this is a hidden setting accessible only by turning off the radio and pressing Hold when you turn the scanner back on. This mode sets the algorithm for P25 decode.
Scroll to 'P25 Adjust Mode' and press E/yes.
Enter 3-15 and press E/yes to save and exit.

P25 Adjust Level this is a hidden setting accessible only by turning off the radio and pressing Hold when you turn the scanner back on. Sets the RSSI value below which the scanner will not attempt to make P25 fine tune adjustments. If the signal is too low, RX reliability is not high enough to make P25 adjustments correctly. The default value is 50. People have had better decoding with this value turned up.
Scroll to 'P25 Adjust Level' and press E/yes.
Enter 1-200 and press E/yes to save and exit.

The tricky part is that you have to spend a lot of time tinkering around to come up with the best possible combination of values. It is variable based on scanner and location of the scanner. No one size fits all. Both my son and I have 996XT scanners and listen to the same system. The values that work best for me are 13 (Mode) and 175 (Value), but his are 11 (Mode) and 150 (Value).

I think you'll probably gain some improvement by changing these.

 

[WD0AKZ]

The tricky part is that you have to spend a lot of time tinkering around to come up with the best possible combination of values.

I agree with this also. I tried various settings and the audio cleaned up a bit as well, but I never really got it nailed down, Seems like I'd get it dialed in pretty good and then a few days later find myself needing to readjust again.

My PRO-96 doesn't give signal strength but it does give the % of decoded packets when tuned to the Control Channel and that is always bouncing around but it does give me a better perspective as to any changes I make.

I wish the BCD396XT would have worked out for me because I really liked setting the back lighting colors for Talk Group types (Red for Fire, Blue for LE) so even from a distance I could see who it was. Of course the FreeSCAN software sure made access to the options easy to set up. The PRO-96 lets me adjust the screen backlight timeout but it would of been nice to allow the backlight to activate on audio/digital squelch break.

George