Virginia State Police

[redburgundy]

That's great but please post these results so Uniden can track. UPMan has a format he would like.

Have you checked you have the appropriate service groups turned on?

OK, I've posted there also. But clearly this is an unrelated problem. Just about all the Service types are turned on, including Custom 1 for the conventional channel entries.

 

[JamesO]

I have changed from NFM to FM for the STARS band manually for the moment. Will need to monitor and switch back and some point for comparison.

Here is an interesting observation I have just noticed with STARS on HOLD for TG 67 is that when there is no voice traffic I am only showing 2 bars on the signal level display, however, when I do have voice traffic for STARS the signal level will jump to 4-5 bars.

It is almost like the control channel is lower in power than the voice channels?

I will get my AOR 5000 with my SDU fired up here at some sort to see if I can see what the signal levels are doing on the STARS system.

At the moment I have my 396XT on the FFX 800 MHz trunked system with the VSP Channel 2, on hold so I can compare TG activity and see if I am missing any traffic.

For the moment the 536HP is doing pretty well, I am sometimes missing the first few sentances of traffic that I am picking up on the FFX 800 MHz trunked Patch of VSP STARS.

Just a few interesting observations.

 

[DogT]

I've been hearing FX1, FX2, Cul1, Cul2, and then recently DOC Ops, and even heard some Radmaint today. But I'm listening to 6 sites.

 

[JamesO]

I find it hard to believe you are "actually" listening to 6 STARS sites, but depending on your location, this could be possible.

What you need to do is go through and hold on each site and see if you actually get signal bars and LNK & DAT displayed. Locked out everything other than Division 7 State Police for my area. The STARS network has too many sites and too many Talk Groups so you have to be careful as you may miss a lot of traffic.

As I say, the more you try to monitor, the more you miss! This is why many times I have multiple scanners running with subsets of what I want to monitor. Even when monitoring only a single STARS Talk Group and single control channel, I sometimes miss the first few words while the scanner locks on and decodes the Talk Group.

I have no idea what is going on here in Fairfax with the STARS tower, I need to compare the control channel level to the voice channels.

Just because you think an RF technician knows what they are doing when setting up a site or system, does not mean it is in fact working properly!

So it would be interesting to see if other STARS users are seeing a big variation in the control channel level as compared to voice channels.

I think I may have to get my HP1E set up and start looking at the Fairfax STARS transmitter site a bit more closely.

 

[redburgundy]

For what its worth, listening to STARS on my PSR-500, Culp 2 and FFX 2 always come up on 152.7275 MHz. That frequency is licensed to Mt. Weather but not to the Fairfax and Arlington sites.

JamesO, are you sure you're receiving the Fairfax site?

 

[JamesO]

No question I am listening to and have programmed the Fairfax site, 152.2025 MHz and this frequency is only reused in Henrico and Bedford counties.

What I am seeing is the Fairfax control channel is much lower than the voice channels. I see this is a problem and not by design, however, I need to compared closely a lot of other trunked systems to see how they are "typically" set up and configured.

If you can compare the STARS control channel levels to the voice channels that you can receiver it would be useful to see what is happening with other STARS sites are a comparison. I do not manage any trunked systems, but if I was managing them, I would attempt to run the control channel approximately 1.5-3 dB higher than the voice channels. The easy way to do this is hold on an high activity Talk Group and watch the signal level on the control channel then see what the level is once voice traffic is active.

What happens in the field guys get STUPID stuck in their head. I have been dealing with RF "systems" for over 20 years and dB's are very EASYto loose and HARD to get back. It still amazes me how the system techs still miss the big picture ALL the time.

Maybe someone is checking relative levels in a combiner and not looking at relative levels OTA??

What I am also finding is the nulls at 152 MHz are tough to deal with if you have fringe or marginal signal. I was sitting in traffic with my 396XT and had a decent signal, rolled forward about 3 feet and totally lost the control channel.

So for anyone monitoring STARS, please lets compare the control channel relative level to a voice channel level while locked on an active Talk Group. Please post the site(s) and number of S bars for the control channel and the voice channels.

I personally think the Fairfax site has a low control channel, but we will see?

 

[DogT]

Well, I've held on all 6 sites and I get a different SID on the control channel which mostly aligns with what RR says. I hold long enough to see it show up. Sometimes I get a carrier, but no SID, so I figure that is bogus, but if the carrier is always there and the SID blinking I figure it's real. Mind you, I'm just about line of sight for Fork Mt, Apple Orchard although it's a long way away and PW county and my antenna is fairly high, I'm not using a stick off the back of the radio. I don't know if this forum does image codes but here's the direct link to what I see http://i251.photobucket.com/albums/gg287/DogTi/other/996sid_zps8000c2ea.jpg

Dave

 

[JamesO]

Well, I've held on all 6 sites and I get a different SID on the control channel which mostly aligns with what RR says. I hold long enough to see it show up. Sometimes I get a carrier, but no SID, so I figure that is bogus, but if the carrier is always there and the SID blinking I figure it's real. Mind you, I'm just about line of sight for Fork Mt, Apple Orchard although it's a long way away and PW county and my antenna is fairly high, I'm not using a stick off the back of the radio. I don't know if this forum does image codes but here's the direct link to what I see http://i251.photobucket.com/albums/gg287/DogTi/other/996sid_zps8000c2ea.jpgDave

Dave,

Thanks for your feedback.

There are 2 separate things that need to be done to verify control channel vs voice channel level.

If you hold on the control channel you will see the site specific data/ID, however, you will not hear any voice comms. Although this is a good start, the radio will need to lock on the control channel, which may take a moment depending on the signal level. Once locked on the control channel you will then see the system specific data/ID.

Then the next think you want to do is find an active Talk Group for the site/system you are able to monitor, then hold on that specific talk group. What the S meter/bars carefully and once the voice comms drop, the radio will then drop back to the control channel. If you signal is very strong, you may need to turn on the attenuator or use an antenna on the radio to reduce the signal level a bit.

What I am trying to find out is if all the STARS sites have control channels that are much lower in level than the voice channels, do the control channels equal the voice channels or are the control channels slightly higher in level than the voice channels.

I am seeing a "problem" with the Fairfax site at this moment when the control channel is lower in level than the voice channels. I have to get some other equipment together to compare or get a reasonable idea of how many dB difference the levels are, but for now it is relative as compared to each other using the radio S meter.

The other major issue with STARS and a VHF trunked system is the frequency wave length and marginal or fringe level signals. The nulls for VHF appear to be about 12-18 inches apart. I spent some time in front of my house this evening monitoring the Fairfax STARS control channel. I could hold my 396XT locked on a Talk Group that was not active and if I only moved the radio horizontally between 12-14 inches I would fully drop the control channel. Move the scanner back to the original position, then control channel will reacquire.

So overall not sure the scanner has any specific issues with STARS yet, however, STARS the way some of the site transmit levels are set and the wavelength of VHF for use on a trunk system are all kind of a perfect storm.

I also assume that since VSP as originally on 159 MHx, the reused many of their original antennas and because of the up to 10 MHz difference in control channel vs voice channel frequency, there may be some antenna gain roll off issues that maybe the STARS radio techs have not taken into consideration when balancing out and setting RF levels at the transmitter sites?

Again, I see this time and time again when radio techs "think" they understand what they are doing but fail to see the much larger "system" picture?

 

[John]

I modified the Band Defaults for 150.8000 to FM and the STARS Ft Lewis site went from basically not working to working fine so far.

John

 

[JamesO]

Band default did not appear to do much for me, I will try turning it on and off some more.

I am starting to thing there may be a band step/frequency rounding issue. 2.5 kHz is missing in MANY places! Missed in some software and in some of the firmware,

 

[DogT]

James,

I need to work on how the receiver works on the digital modes. It's unclear to me how it finds a voice channel. I notice that when I hold, say on Hogback, there are 7 frequencies and only one of them is the control. That's the one I get the SID on. As I scroll past the 7 freqs, I go into the ID 'channels'. I'm not clear how to find the voice channels, much less their RSSI on the 996XT. I've only been into this 996XT for a week or so.

BTW, I've been to Hogback, I worked for the USPIS as a engineer until '05 and they had a P25 repeater there. As I remember they were just using Simulcast, no trunking, but totally encrypted with Astro HH and 110W Astro mobiles, UHF. Also been to Apple Orchard, same deal. I don't know what they've been doing since, I left and never looked back. I was never involved in any trunking systems.

Dave

 

[RF23]

James,

I need to work on how the receiver works on the digital modes. It's unclear to me how it finds a voice channel. I notice that when I hold, say on Hogback, there are 7 frequencies and only one of them is the control. That's the one I get the SID on. As I scroll past the 7 freqs, I go into the ID 'channels'. I'm not clear how to find the voice channels, much less their RSSI on the 996XT. I've only been into this 996XT for a week or so.

BTW, I've been to Hogback, I worked for the USPIS as a engineer until '05 and they had a P25 repeater there. As I remember they were just using Simulcast, no trunking, but totally encrypted with Astro HH and 110W Astro mobiles, UHF. Also been to Apple Orchard, same deal. I don't know what they've been doing since, I left and never looked back. I was never involved in any trunking systems.

Dave

My understanding is that the scanner sets on the Control Channel (CC) and does not scan the other channels because the CC tells it what frequency to go to. It may scan the channels once to find the control channel however. Therefore, you only need the CC or any frequency that could be the control channel and that is all.

The order of the talk groups and frequencies are not important either in a trunked system in scanning speed.

Most P25 trunked systems are "Explicit" and they broadcast their band-plans (if needed) so the big band-plan table does not need to be filled in in Sentinel, in fact if you do fill it in the radio will ignore it and only use what the CC sends to it.

Hopefully, others can jump in and correct any of this if I am wrong.

 

[JamesO]

Holding on a Voice Channel can be accomplished in 3 ways that I can immediately think of.

When there is no voice traffic the scanner will stay idle on the Control Channel (assuming you have only the single trunk system configured into a scan list). Once a Talk Group becomes active, then the scanner is instructed to tune to "x frequency" Voice Channel. If your display is set correctly, you can see the operating frequency of the channel the scanner is tuned/changes to.

Then you just look for the relative difference in the Control Channel signal level vs each Voice Channel signal level. I assume on most systems, the signal levels should be the same between Control and Voice channels. If you have a strong signal, you may need to use a different, less efficient antenna or turn the attenuator on each for the Control Channel and for the Talk Group you plan on holding on. This may be a bit tricky as it is unclear how the attenuator works on a trunked system, is it set "globally" for "x" trunk system or is is set on a per frequency or Talk Group? I think the attenuator would to be set for the Control Channel and the specific Talk Group? This way you have consistent results.

Then you watch the signal level as the scanner toggles between the Control Channel and Voice Channels when their is activity. I would also choose an active Talk Group to hold on. Not fun on a low usage talk group or a quiet time of the day trying to wait for a Talk Group to come active. You might be able to set up a single trunk group in a scan list, then put the scanner on Search rather than Scan and this should allow the scanner to follow any and all traffic on the trunk system, but I find this can be hard if there is a lot of traffic to really watch the relative levels especially if you want to move the antenna/radio around or do other testing.
1. When there is voice traffic on a channel in a system you are interested in, just push Hold and the scanner will "hold" on that specific Talk Group or be waiting for that specific Talk Group to become active again and then jump to that operational frequency.

2. Just push Hold while scanning and then use the rotary knob to step through frequencies and Talk Groups. Note this can be time consuming depending on what you have programmed into the current scan list. All locked out/avoided Talk Groups and Frequencies as well as operational Talk Groups and Frequencies will need to be stepped through. Once you find the talk group you want, just let the scanner sit on the Talk Group. When there is voice traffic on the specific Talk Group, the scanner will be instructed to tune to the frequency to follow the Talk Group. What the scanner does is once the specific hold Talk Group goes quiet, the scanner goes back and hangs on the Control Channel until it picks up the data stream for the specified Talk Group again and then continually repeats the process.

3. Assign a Tag to the Talk Group, this allows direct keypad entry to access the Talk Group. Probably the simplest way to access any Talk Group or Frequency. But you have to learn how to configure channel tags and use them.

My expectation in on most trunked systems the Control Channel and Voice Channels are at least the same level, possibly the Control Channel is slightly higher in level than the Voice Channels, however, I do not know if the S meter on the scanner is linear enough to be able to differential between 1-3 dB toward the upper part of the scale? But I have not tested yet also how many dB difference there is between the Fairfax STARS Control Channel and Voice Channels at my location. I also will want to perform some cluster measurements to verify the Control Channel is just not low in the 1 spot my antenna is located at.

I have a few different radios, so I want to perform similar tests around my house to see what the data shows. But the initial thing I am finding, at least with the Fairfax STARS Control Channel is the level is pretty low relative to the Voice Channels on the same system/tower/antenna.

 

[John]

That's essentially how it works.

The scanner and other radios listen to the control channel. When a radio wants to talk it requests a channel from the system controller. The group of radios known as a 'talkgroup' is assigned a channel number which is broadcast over the control channel. All radios that are part of that group then tune off the control channel and tune to the new channel number that was announced. So if you are scanning for this talkgroup your scanner will change to a new frequency and should then decode the voice conversation. When the conversation is finished the scanner will tune back to the control channel and wait for the next talkgroup it is programmed to scan.

The frequency it switches to is determined by a band plan. All the control channel sends is to use channel number xxx. The band plan tells the scanner and other radios how to calculate the actual frequency for that channel number. The way this is done is different depending on what kind of trunking system you are listening to.

So there are two basic parts of listening to a trunked system. Decoding the control channel so your radio knows when and where to go to listen to voice. The other main part is finding the right frequency to tune to based on this decoded information and then being able to actually understand the voice signal which in some cases means being able to decode the digital voice signal.

My understanding is that the scanner sets on the Control Channel (CC) and does not scan the other channels because the CC tells it what frequency to go to. It may scan the channels once to find the control channel however. Therefore, you only need the CC or any frequency that could be the control channel and that is all.

The order of the talk groups and frequencies are not important either in a trunked system in scanning speed.

Most P25 trunked systems are "Explicit" and they broadcast their band-plans (if needed) so the big band-plan table does not need to be filled in in Sentinel, in fact if you do fill it in the radio will ignore it and only use what the CC sends to it.

Hopefully, others can jump in and correct any of this if I am wrong.

 

[DogT]

I sort of figured out how the P25 CAI STARS system worked from reading Mark's scanner manual, but it takes me about 3 or 4 readings to connect into my feeble brain. At the moment I'm unclear on what the APCO band plan is or means. Still trying to wrap my mind around the control channel concept, but mostly because I'm only used to standard repeaters. I'm assuming the band plan is in the same range as the CC which is in the 150MHz range and is somehow multiplexed in the 'repeater'?

There's a couple of things I can do. I have adjustable attenuators, plus a Moto R2005D to set up what the bars in the 996XT mean/dBm. I'll try just programming one control channel into the XT that I know is good, maybe the closest one and see if I can pull out what the XT is doing when it opens on a talkgroup. It's too confusing with 6 sites programmed in because I'll get say Fx1 on Hogback and a minute later it'll be on Independent Hill or Dumphries. I'll hear responses from the same talkgroup on multiple sites. The other thing I can do is use the TS2000's sub rx to tune the various channels, it has a fairly accurate 'S meter' that I have calibrated, not that it will be able to decode anything, but it certainly will hear the signals. I have 2 nearly equivalent antennas. one for each radio. Scanner is on a Larsen UHF/VHF and the TS2000 is on a UHF/VHF diy colinear, both above the roof.

I wonder if the scanner is smart enough that when it finds a control channel on a specific freq for a specific site that it only searches that freq next time it scans through that site? And if it doesn't find the CC it starts looking.

Anyone have an idea how long a site will stick with a specific freq for a CC or do they tend to move around now and then?

It'll be a good day to play, it's raining, but there are robins in the yard and the snow is melting, sure sign of spring.

Dave

 

[RF23]

That's essentially how it works.

The scanner and other radios listen to the control channel. When a radio wants to talk it requests a channel from the system controller. The group of radios known as a 'talkgroup' is assigned a channel number which is broadcast over the control channel. All radios that are part of that group then tune off the control channel and tune to the new channel number that was announced. So if you are scanning for this talkgroup your scanner will change to a new frequency and should then decode the voice conversation. When the conversation is finished the scanner will tune back to the control channel and wait for the next talkgroup it is programmed to scan.

The frequency it switches to is determined by a band plan. All the control channel sends is to use channel number xxx. The band plan tells the scanner and other radios how to calculate the actual frequency for that channel number. The way this is done is different depending on what kind of trunking system you are listening to.

So there are two basic parts of listening to a trunked system. Decoding the control channel so your radio knows when and where to go to listen to voice. The other main part is finding the right frequency to tune to based on this decoded information and then being able to actually understand the voice signal which in some cases means being able to decode the digital voice signal.

Thanks John for the additional information it helps!

The reason I added the last sentence to my reply about some uncertainly on my part is that in "Rebanding" we do have to make changes to the "BandPlan" and I was wondering why the needed changes are not just broadcast with the CC but now I see better how it works and the necessity of the changes in the BandPlan that is part of the radio's base instructions.

 

[DogT]

Just some information, I've checked the control channels vs what I'm seeing and it appears that I'm really not hearing Apple Orchard, or Dumphries. Those channels are actually Hogback and Fork Mt. Here's the signal strength on the ones I'm getting measured on the TS2000 switching between 2 antennas. It's amazing how much different antennas make. I was really wondering about Apple Orchard, it's a long way away and I can only hear the N4MW UHF/VHF beacons from there with a beam.

Mt Wx 152.8025 019eh-0123 Larsen +50 pole +50
Fairfax 152.2025 019eh-0117 Larsen s3 pole +20
Fork 152.7125 018eh-0107 Larsen +60 pole +60
Hogback 161.8875 019eh-0108 Larsen s3 pole s5
Independent Hill 152.5475 019eh-0118 Larsen +20 pole +50

Now to hone things down and listen to one site for a while. I have yet to check the bars meaning on the XT.

 

[redburgundy]

STARS Band Plan Table

Can anyone who is getting good reception of the STARS system confirm that the Band Plan table is populated (using Sentinel)?

 

[Dafe1er]

Can anyone who is getting good reception of the STARS system confirm that the Band Plan table is populated (using Sentinel)?

Give me a refresher on what you are asking for. I have STARS working 100% on the BCD436HP. It was programmed with Sentinel.

 

[JamesO]

Can anyone who is getting good reception of the STARS system confirm that the Band Plan table is populated (using Sentinel)?

You should be able to run Control Channel only without a bandplan modification, at least that is what I am doing with Fairfax at this moment and IF I can aquire a solid Control Channel, it appears that I have STARS working for at least VSP Division 7 where I am located.

BUT the stable and strong Control Channel where I am located is a BIG if.

I am also running my 396XT the same way.

I did find the the Butel Software for the x96XT did not have the 2.5 kHz step sizes for the band plan, I have sent Butel an email but have not heard anything specific about my concern.

I do think even Uniden may have to deal with the 2.5 kHz step size as well. My HP1 Extreme only has a 5 kHz step size for the band scope, no 2.5 kHz. The other issue is do the synthesizers in the HP1 a the newer x36HP step as small as 2.5 kHz?? I have no idea, hopefully they do and hopefully Uniden will correct any software that does not allow for 2.5 kHz step sizes.