DSDPlus Channel activity question

[radionut44]

New guy still learning FastLane:
When I monitor my local system with one dongle the channel activity screen never shows but 1 channel in use at a time, even when (because I am also monitoring with 2 scanners) I know at least one additional channel is in use. But if I input the control frequency for a nearby (and much busier system) into the Fmp24 window I may at times see 3 or more other channels active in addition to the bold channel that I am hearing. Why do I only see the bold channel being heard when I monitor the local system and know at least one other channel is active?

 

[merlin]

That is how the channel activity panel works. DSD only decodes 1 channel at a time but the channel panel will maintain what channels have been heard from a given system. Sort of works like a real radio where once an active radio (source) captures the system, any other channels are muted.
Probably the most informative panel is the activity log.
2 scanners on different frequencis. You could do similar with 2 dongles and running a second itteration of DSD, but still the same limitations
as watching a single system.
Screenshot is a bit how I have my displays. With the spectrum display, I can see if DSD has lost the control channel. works together with the audio spectrum. Most of what I use the event log pannel for, is I can see if a talk group is encrypted or not.
Hope this helps.

 

[radionut44]

I just verified: on the busy system while audio was being decoded from the bold channel, 3 more channel grants popped on the display. I did not expect the audio source to change, but I saw the additional activity. On the local system (also a P25 type 1) I never see more than the bold channel with audio being decoded, even when because of the 2 scanners I know another channel has come active, but no other channel Shows in the channel activity window.

 

[maus92]

New guy still learning FastLane:
When I monitor my local system with one dongle the channel activity screen never shows but 1 channel in use at a time, even when (because I am also monitoring with 2 scanners) I know at least one additional channel is in use. But if I input the control frequency for a nearby (and much busier system) into the Fmp24 window I may at times see 3 or more other channels active in addition to the bold channel that I am hearing. Why do I only see the bold channel being heard when I monitor the local system and know at least one other channel is active?

What is your local system, and what is the nearby busier system?

 

[radionut44]

Local is Kernersville NC P25, busier is Greensboro/Guilford county P25

 

[merlin]

I just verified: on the busy system while audio was being decoded from the bold channel, 3 more channel grants popped on the display. I did not expect the audio source to change, but I saw the additional activity. On the local system (also a P25 type 1) I never see more than the bold channel with audio being decoded, even when because of the 2 scanners I know another channel has come active, but no other channel Shows in the channel activity window.

This is still one system. Let it run a good while and all of the channel grants should show. What I see here is RID 42203 is being decoded. ( a single subscriber)
Targets 555, 2391, and 2077 are active but not being decoded.
This information is also reflected in the 1R log panel and saved to 1R logfile.
I think the confusion here is Kernsville and Greensboro/Guilford county are on a single system. Busier is just a lot more talk groups and activity.
Get a screenshot of your 1R event log panel, you will have a better idea of whats happening on the site.
At the very bottom of mine, it shows BEEOO.18B-1.1 NAC:180
This is the statewide ICAWIN site number 1.1. Network access =180
Following that are neighbor sites.
Above that, is all the talk groups (agencies) that are regestered on the site.
Like you, some are very busy, some rarely heard.
Other activity not decoded is affiliation requests grants/denials etc.

 

[radionut44]

Kernersville is BEE00.946 and is NOT part of Greensboro/Guilford!

 

[maus92]

I don't have a definitive answer for you, but there are differences between the two systems that *might* explain the behavior that you describe. The Kernersville system is a single transmit site aka "ASR", whereas the Greensboro/Guilford system consists of a multi-tower simulcast site and an ASR. The single sdr method of tracking a TRS is a bit of a kludge compared to a multi-sdr configuration that constantly monitors the control channel. The single sdr config relies on data encoded in a "sub-channel" of the currently tuned traffic channel, rather than the control channel. There is more comprehensive system data carried on the control channel. Perhaps the "subchannel" of the Kernersville site is not configured to carry data about other concurrent voice channel grants. I would need to dig into the TIA specification docs to understand if this could be the case.

 

[radionut44]

I have another dongle. I may venture into 2 dongle…I’m still learning from single dongle monitoring.

 

[merlin]

OK, IF Kersville is a separate site, it must have a separate control channel frequency.
You can create a .bat file for that frequency.
That will give you 2 .bat files. one for the Kernsville and one for the Greensboro/Guilford.
Select your choice then run 1R.bat.
I yet need to look into the database to see what you are dealing with.
Here is the full scoop for your Greensboro/Guilford system:

Greensboro / Guilford County Trunking System, Greensboro, North Carolina

Greensboro / Guilford County Trunking System Profile

www.radioreference.com

What is in the database for Kernsville:

Forsyth County, North Carolina (NC) Scanner Frequencies and Radio Frequency Reference

Scanner Frequencies and Radio Frequency Reference for Forsyth County, North Carolina (NC)

www.radioreference.com

More to sift through:

North Carolina VIPER Trunking System, Varies, North Carolina

North Carolina VIPER Trunking System Profile

www.radioreference.com

About 2 dongles. I tried to monitor both the local PS site and a UHF NXDN site and had problems with audio connections.
Easier just to have 2 separate sites and monitor one or the other.
There is a way to do it, but DSD documentation is not very clear on the subject.
BTW, It looks like you will need 3 .bat files to cover your needs, not counting neighbor counties you may be able to receive.

 

[radionut44]

Note it is Kernersville, not Kernsville. I was not trying to monitor both sites at the same time, only comparing that without changing anything except switching the control channel frequency of the Fmp24 window to the other system, when monitoring Greensboro the channel activity window often showed several frequencies at use at the same time ( and the TG for each), but when monitoring Kernersville the window only showed the frequency being decoded, when at least one other frequency had become active, as varied by being received on a scanner. I posted a screen shot of the Greensboro system showing this.

 

[brian]

Here's my guess:

With one receiver, DSD+ tunes it away from the control channel to a voice channel with activity. Therefore, you lose the data stream indicating channel grant information for other frequencies while tuned to the voice channel.

Some radio systems are configured to pass channel grant information over voice channels. This is done to support features like priority scan on subscriber radios. A subscriber is a single receiver too, and in scan mode it can find itself tuned to a voice channel being used by a lower priority talkgroup. The channel grant data being passed by the voice channel allows the radio to know when a higher priority talkroup becomes active on a different voice channel. The subscriber then abandons the lower priority talkgroup channel and switches to the higher priority talkgroup channel. It's essentially a limited control channel data stream carried on each active voice channel.

DSD+ is decoding that data on the voice channel too, for the system that's configured to carry it. It's continuing to show that data in the channel activity window while tuned to a voice channel. For the system that isn't configured to carry that data on the voice channel, you lose that information in the channel activity window.

This may be inaccurate, and some with far more detailed technical knowledge of how P25 systems are (or can be) configured can correct my assumptions. But it's my best guess based on your description.

 

[radionut44]

That makes sense. Now another question related to channel activity. How can I lock out voice decoding for a TG? I tried setting priority to 0 but it still decodes. I want to see the activity, but not hear it.

 

[merlin]

No matter. You can still monitor the 3 sites I posted above using 3 bat files.
I have seen all 5 of my systems voice channels active at one time but note,,,,,repeat,,,,note.
Talk groups (channels) are serviced on a first come//first served basis and the first user to grab the system is the one you hear.
When their call is done, 3 seconds later, the channel is released, and the next in line is the decoded users, IF they are still in a call state.
This is why you can miss a number of calls when the decoded users have the site.
NOW,,,with a single dongle, the only way you can change to another system is to close the event log then close FMP24.
Select the bat file for the system you wish to monitor and double click. Then double click '1R.BAT' and you are running.
Dont be surprised if you decode a call on the control channel. doesn't happen often, but can.
When the call is released, it is also possible to loose the control channel. DSD will search for it and may take another call to capture the control channel again.

 

[merlin]

That makes sense. Now another question related to channel activity. How can I lock out voice decoding for a TG? I tried setting priority to 0 but it still decodes. I want to see the activity, but not hear it.

That can't be done with DSD+.It is just the way P25 works.
I use DSD+ for site info to program like a Motorola XTS. With that, I can choose a talkgroup or several that are programmed into sets.
Say: city 1 PD dispatch, city 2 PD, city 1 FD, city 2 FD, into channel knob 1. County SO, county FD/EMS, knob #2. Etc.... to knob #16.
What they call a bandplan. 16 sets of various talkgroups.
DSD+ just does it differently like having only one knob position and decoding everything on a site or one single set.

 

[dave3825]

How can I lock out voice decoding for a TG? I tried setting priority to 0 but it still decodes. I want to see the activity, but not hear it.

If you do not want to hear the audio on a, or any tg, one way is to open the groups file in your DSDPlus directory and change Normal to L/O on the said tg's.

 

[cg]

Right click on an active TG in the activity window and first click makes that TG LOW, second click makes it L/O. Left click makes it HIGH, second click makes it HOLD.
Right click on the Pri(ority) column of an active TG and you increase the priority number, left click decreases the priority number. If you wish to use the priority, under the Control tab, click Monitoring Threshold and set where you wish. Lower the number, the higher the priority.

 

[DaveNF2G]

The easier way is to set the priority of the talkgroup very high, like above 90, then set the decode threshold to a lower value. DSDPlus will ignore any talkgroup with a priority number that is larger than the threshold.

 

[radionut44]

You guys have given me some valuable information. I have not seen any of that in any of the files. Did I miss some documentation about those settings and how to change them?

 

[cg]

You can hit the "?" key while in the Event Log window for a brief list of shortcuts.
You can create a Help file for each of the EXE files by running:
DSDPlus -h >DSDPlus_help.txt
FMP24 -h >FMP24_help.txt
FMPA -h >FMPA_help.txt