How to improve NXDN scanning

[daredevil1]

I don't see how that would have anything to do with it dropping mid-conversation.

 

[sibbley]

I can confirm that deleting the control channel does not make the issue go away.

I agree.

 

[sibbley]

Would it make sense that the frequencies need to be entered in a specific order to allow the TRX-1 to follow conversations correctly on NXDN?

This makes some sense to me. I had been working on an LTR system and wasn't having much luck with LCN finder. I programmed into my TRX-2 and had a similar situation until I realized I had not set auto adjust home repeaters. Once I went in to the software and set that to yes all was well. Prior to using that setting I had dropped comms or no audio at all.

 

[troymail]

I can confirm that deleting the control channel does not make the issue go away.

...and for some systems, you do not want to do that. Several of us are seeing voice popping up on that same control channel.... If you don't have the control channel programmed, you'll miss those transmissions.

 

[sibbley]

I've posted 4 short videos on my website showing my issues with NXDN trunking. NXDN: DSD+ vs TRX-2 | Life n Liberty

Descriptions can be found under each vid.

 

[theTastyCat]

Hey all - dumb question, but how can I tell what the control channel is to remove it? Got my NXDN freqs from the link in the OP (thanks OP!); it's for the Sheriff's Office in Cheatham County, Tennessee.

 

[HOLEBILLY]

I have just one conventional NXDN freq programmed as conventional and the radio traffic still breaks up bad. I get full signal and Im about 8 miles from tower. It is really clear and clean voice until it breaks up. Just got to wonder if they got this right yet. I hardly ever get to hear both sides of conversations and its what I got the trx1 for, our county sheriff.

 

[theTastyCat]

Yeah, that's why I bought a scanner; wasn't really a point for me until now since local LE was NXDN. Hopefully they'll get it figured out soon - maybe these issues can be fixed with firmware?

 

[KD4YGG]

Notes on How to Improve NXDN Scanning

Have successfully decoded several NXDN4800 trunked systems programmed as trunked using the TRX-1 this past week. All systems were multi-site.


Please note I state "decoded", as the jury is still deliberating the term "trunk tracking" as it applies to this radio.


No success yet with the one NXDN9600 system I've tried.


Here are my observations. Your mileage may vary.


Channel Number / LCN Order:
Similar to EDACS and DMR, NXDN site frequencies MUST be programmed in proper order to allow the TRX-1 and TRX-2 scanner to decode properly.


Site RAN:
This is in HEX and NOT decimal.
If unsure, set to ANY


Do SET MODE to NXDN4800


Set DWELL to 2.0 seconds


Set COUNTRY to USA (for U.S.A. systems)


Site Thresholds:
Have had better decoding success with:
50% Low Threshold
95% High Threshold


For systems with a "control channel" frequency do NOT check the NXDN-D box


Use talkgroup delay of 2.0 seconds to allow replies.
This appears to help with "dropped transmissions".


Also, the systems I've monitored have CW identifiers, GPS AVL data, etc. This, plus the control channel, appears to cause the "S" indicator to constantly flicker. I've not observed that this has any negative affect on the systems I've monitored.


Posting for the benefit of other TRX-1 and TRX-2 users.
As stated, your mileage may vary - these observations are just based on my experiences.

 

[AggieCon]

Finidng the control channel

To identify the control channel (or continuous data channel):

Import all of the systems frequencies as conventional objects. Change the Mode to NFM and the DMode to Analog for each of the frequencies. Enable recording if you want to have a record of your test.

Load these to your scanner.

Go to browse objects on the scanner and monitor each of the frequencies with the squelch all the way down.

If you hear static, you are not on a NXDN-C control channel.

If you hear the digital buzz (boat engine, diesel purr, whatever you want to equate it to) continuously (i.e. longer than the length of a voice broadcast), you are on either the control channel or a data channel. Since those channels are not providing you with anything of interest, there is no reason to have them slow your scanner down or cause more substantial problems.

Keep in mind that a lot of the NXDN-C systems rotate control channels.

On another note: On the merit of having the system channels programed in the proper order, you can use a similar method to determine the channel rotation. Set your squelch to a reasonable level. Scan all of the analog frequencies, programmed as described above. Once you hear the digital buzz, take note of the frequency and "SKIP" it. Do this until you hear traffic on all of the frequencies. Then do it again (or twice more) to confirm you have the order right.

Overall, there seem to be substantial problems in this NXDN release relating to the digital decoding.

 

[AggieCon]

I've posted 4 short videos on my website showing my issues with NXDN trunking. NXDN: DSD+ vs TRX-2 | Life n Liberty

Descriptions can be found under each vid.

I love your URL. Thanks for posting those videos.

The scanner is showing full signal on a 125 watt system. DSD+ is doing just fine.

I am thinking that either the digital decoder is not properly decoding or the CPU is not recognizing the data as NXDN (due to bad software coding). I don't think there is much the user is going to be able to do fix this.

I think this is also why the control channels are tripping it up. Unlike a P25 or DMR control channel, it is not making sense of what it is receiving, so it doesn't know to ignore the frequency and move on. Likewise, it doesn't even know when it is on a voice call.

What a waste of everyone's time.

 

[theTastyCat]

Many thanks, Aggie - got three control channels identified and skipped. Trying again now! Hoping for better performance now. But basically what I'm gathering is that this initial NXDN release has serious firmware issues that will likely be cleared up in future releases - is that basically the idea?

YGG, thanks a lot for all those tips. I'm a ham as well but this is a *whole* new world; my knowledge of repeater operation really hasn't carried me very far into modern scanning! I'd like to try your tips as well, but I'm coming up dry as I'm now on my second day of TRX-2 ownership. I've looked in EZScan for where to set to NXDN4800, set thresholds, and the NXDN-D box. Would you mind sharing where I can find these? Also, I copied and pasted the freqs from the OP - would they be in the correct order from there?

Sorry for all the dumb questions - I am really looking forward to getting this running well!

 

[theTastyCat]

Hey, here's another dumb question; the local NXDN I'd like to monitor is part of a system that has 30 sites. I'd like have the freqs set up in three separate scanlists, each with just one of the three closets sites selected. How can I specify sites when importing freqs from the OP's site? Can't figure out how to choose once they're imported.

Thanks a lot!

 

[AggieCon]

Are you importing them into EZ Scan as trunked or conventional objects?

If you are creating them as trunked, create each site as a separate system. Create talkgroups and a wildcard for each system, and then assign the talkgroups & wildcard to the applicable scanlist (you will make a new scanlist for each system-site)

If you are doing it as conventional, just sort the frequencies into three different scanlists.

The order is system dependent; however, it is common to order in frequency order, so my website might list them in the right order. See the method described above to determine it on your own. Using SDR and a program like DSD+/FMP or SDR# can also be really useful.

The thresholds, etc. are found on the Trunked Radio Systems tab, under the Site Options tab. I'm not sure they really matter. If you set them wrong, the radio might ignore something you want to receive.

Check the control channels again in a day or two. Confirm that what you identified was actually control or data; also, make sure the control channel doesn't rotate through the system frequencies.

Feel free to email. Also, let us know which system you are trying to receive.

Your questions are not dumb at all. And the scanner marketed did not put out adequate documentation regarding NXDN. For example, the Windows Help file does not explain the NXDN settings for the site options tab.

 

[theTastyCat]

Aggie, I can't tell you how much I appreciate all your help as well as your unending patience! What little I have gotten this thing working is really exciting, and with the help of good people like you I think I'm getting closer and closer to it working full throttle.

The two systems I'm trying to monitor are Cheatham County, TN Sheriff's Office (NXDN, part of larger DHS system with 25 sites) and Metro Nashville PD (P25).

Per your recommendation and via your great link, I imported the freqs conventionally. Are you saying use the same frequencies in three different scanlists? Becuase I haven't figured out how to do that - in Conventional/Scanlists I've been able to change a freq to multiple scanlists, but the freqs don't appear in the new scanlists. Or, did you mean to split the freqs up into different scanlists? Sorry...the theory behind this, as well as how the different sites work (clearly different than the ham repeaters I'm used to!) is pretty fuzzy.

Tomorrow morning when my brain is working again I'll try to figure out the freq order.

THANK you!!

 

[theTastyCat]

Hey Aggie - trying to get my channels in the right order. I'm a bit confused; when I scan through and it stops on a digital purr, I hit SKIP and it immediately lands on another digital purr. If I hit SKIP as many times as I can, I can usually get through 4 or 5 channels before the signal drops (2-3 seconds). Is this the correct method? Alternatively, if I let it scan through, it always stops on 4 specific channels out of the 52.

So because I can keep hitting SKIP and it immediately lands on several more channels, that seems to indicate the system is transmitting on several channels at once...that can't be right...what am I missing?

Trying to continue to test but it's just gone dead...of course

Thanks again!

 

[theTastyCat]

I am sorry to have singlehandedly ruined this thread! Following up via e-mail instead.

 

[sparklehorse]

Hmm...reprogrammed and tried again...eventually it just goes dead. Reprogram and there's plenty of activity. Reading the manual - perhaps my SKIP key has been reprogrammed to Lockout instead...promise I didn't do that!

When you Skip a channel, it is essentially locked out until you go into the menu and tell the radio to release all skipped channels. They're not restored by a power cycle.

.

 

[theTastyCat]

Thanks Sparkle - just came to the same conclusion!

 

[AggieCon]

Howdy,

I assume this is the system you are after: ULS License - Public Safety Pool, Trunked License - WQBY325 - CHEATHAM, COUNTY OF - Frequencies Summary

As you mentioned, it has three different sites.

Think of a site as a ham repeater. If there are three sites, think of it like three repeaters but in different locations.

Now, with the trunked systems, each repeater location actually has multiple repeaters. The control channel tells the radio which input frequency to transmit on (i.e. which repeater to use); likewise, the control channel tells the receiving radios which repeater to listen to.

There are multiple sites (repeater locations) to increase the geographic area that is covered by the radio system.

Calls can be broadcast by 1, 2, or all sites simultaneously. The traffic might be identical on all sites, or there could be calls that are on some repeater sites but not the others.

If all of the traffic is identical on all of the sites, there is no benefit to monitoring more than the site that you can best receive. If there is something of interest on a different site but is not broadcast on your "home" site, then it might be useful to monitor more than one site.

When you did the channel order test, there are two possibilities:

1) The channels are actually the same exact frequency just duplicated in the scanner/EZ Scan. The basic Quick Import on Digital Frequency Search duplicates most trunked frequencies twice. The Advanced Quick Import will have an option to exclude the duplicate mobiles (once that feature of the website is complete).

2) You are picking up the same call on multiple sites. If the frequencies are indeed unique, then you are likely picking up the same exact call simulcast on more than one site.

If you go to the location tab of the FCC ULS license page, you can see which frequencies belong to each site.

The Station Classes are probably incorrectly done on this license. They should be either FB6/MO6 or FB8/MO8. This is the case with a lot of licenses. Since the licensing is sloppy, I err on providing duplicate data on my website rather than suppressing useful frequencies. I do not suppress mobiles (MO), because many MO frequencies are of interest. On the other hand, trunked system input frequencies are not terribly useful. But I can't suppress them if they aren't licensed properly.

Also, program 453.3625 separately. It looks like a talkaround/tac frequency for the county court or jail. It should be NXDN.

I would put each site into its own scanlist. There is a bug with EZ Scan. Sometimes they don't move scanlists correctly. If you go to the scanlist tab and open the scanlist setting, then close it again, sometimes that moves the frequency to where it is supposed to go.

As an example, here is how I would organize it (channel order is made up below):

Scanlist 10: CCSO ASHLND NXDN
460.275 Channel 1
460.3625 Channel 2
460.575 Channel 3

Scanlist 11: CCSO PLSNTV NXDN
453.4875 Channel 1
453.7375 Channel 2
460.6125 Channel 3

Scanlist 12: CCSO KNGSSP NXDN
453.6875 Channel 1
460.3375 Channel 2
460.625 Channel 3

Scanlist 13: CCSO Court/Jail
453.3625 CCSO Court?

All of these would have a Mode of NXDN, "any" NXDN RAN value, and 0 for talkgroup (any).