DSDPlus What do the NXDN codes mean?

[ryanbytes]

The entity I'm listening to has two frequencies but they aren't trunked. On one frequency I have everything decoding perfectly. On the other I hear data that may or may not be NXDN as well. I'm hoping somebody could shine light on the codes next to voice packets in the screenshot I attached so I can look deeper into my setup or write off the data bursts as something other than voice. Thanks!

 

[racingfan360]

The e: xxxxxx indicates [voice] decoding errors.
CS Voice indicates Conventional Subscriber, so the signal is either Simplex or input to a Repeater. I'll take a guess the signal is too weak hence the errors.
Contrast with the first set of decodes which show CB - Conventional Base ie Repeater output - I'd guess that's a much stronger signal to you, hence no errors.
So when you say 'two frequencies' are you actually just trying to listen to both the input and output of the same repeater, and if so, why not just stick with the repeater output?

 

[LimaZulu]

Channels are actually trunked. You can tell that by RAN=1 and CB which indicates that the transmission is part of a trunked system. You are listening just one of the voice channels. Look for some more that are RAN=1 to be able to discover the whole system. Non-trunked (or conventional, as they are called) usually transmit RAN=0 and there will be no CB.
CS in your second reception means that you are hearing one of the trunk subscribers directly. In other words - you are hearing the receive frequency of the base. Obviously the signal isn't strong because there are a lot of errors. What you want is to minimize the amount of "e:.....". Just like in your first reception.

 

[racingfan360]

Yet the OP says they're not trunked....

Channels are actually trunked. You can tell that by RAN=1 and CB which indicates that the transmission is part of a trunked system.

Trunked would be TB not CB, not sure where you are getting that conclusion from. And I've monitored plenty of Conventional systems with RAN=1.

Non-trunked (or conventional, as they are called) usually transmit RAN=0 and there will be no CB.

I think you're getting confused, on both of those points.

CS in your second reception means that you are hearing one of the trunk subscribers directly.

Would be TS not CS. And without further info to confirm what the OP is tuned to, in theory it could simply be a simplex [conventional] channel, direct reception of a conventional subscriber.

 

[ryanbytes]

I'm listening to the Wabash City PD with 158.775 being what I think is the main dispatch repeater, this decodes perfectly. 154.710 is the frequency that has the occasional transmissions that aren't decoded. I thought I might be listening to an input but tossed that idea when I heard both sides of the conversation occasionally as though it was a repeater output. I haven't been able to contact anyone at the department or the company that takes care of their system to get more info on how things are set up so I'm pretty much in the dark. But it's good to know that the e:xxxxx codes from DSDPlus are just general decode errors and not indicators of something I'm missing with the system operation.

 

[AM909]

Knowing nothing about that system, and just looking at the license, it appears that there are two different, separate, systems.

There is a narrowband analog repeater that transmits on 154.8675 (the repeater "output"), repeating (30) mobiles and a control station that transmit on 159.0375 (the repeater "input"). The mobiles are also licensed for simplex "talk-around" on 154.8675.

There is also a single-channel NXDN digital voice repeater that transmits on 158.7750 (the repeater "output"), repeating (50) mobiles and a control stations that transmit on 154.7100 (the repeater "input"). The mobiles are also licensed for simplex "talk-around" on 158.7750.

 

[ryanbytes]

Ahhhhhhh ok! I've never heard anything on 154.8675 but I'll keep it in my receivers. The input offset for 158.775 isn't something I'm used to on VHF so that threw me. If the dispatch center is using a radio to get into the system instead of some sort of landline option that would explain hearing them occasionally on 154.710 as well.

Thanks so much!

 

[AM909]

@ryanbytes : They may have both a wired-remote/microwave/internet? setup as well as a VHF radio-based control station. I don't remember enough about the technicalities of licensing to know if they would have to separately license an FB (I'd guess not).

The 4.065 MHz offset between input and output on high-band is not unusual, as there really is no "usual" like UHF's 5 MHz – channel selection has more to do with interference reduction, duplex performance, etc.

They may have abandoned the analog system or keep it licensed and mothballed "just in case". I hear there's a lot of that out there on high-band, and some attempt to shake loose some of those abandoned channels for use by entities that want/need them.

 

[LimaZulu]

Yet the OP says they're not trunked....


Trunked would be TB not CB, not sure where you are getting that conclusion from. And I've monitored plenty of Conventional systems with RAN=1.


I think you're getting confused, on both of those points.


Would be TS not CS. And without further info to confirm what the OP is tuned to, in theory it could simply be a simplex [conventional] channel, direct reception of a conventional subscriber.

Yep, my bad, sorry! I was looking at the DSD window just to be sure that I am not going to mess things up, but that's exactly what happened. Didn't realize that I was looking at the window while I was listening a conversational channel at that moment

 

[ryanbytes]

@ryanbytes : They may have both a wired-remote/microwave/internet? setup as well as a VHF radio-based control station. I don't remember enough about the technicalities of licensing to know if they would have to separately license an FB (I'd guess not).

The 4.065 MHz offset between input and output on high-band is not unusual, as there really is no "usual" like UHF's 5 MHz – channel selection has more to do with interference reduction, duplex performance, etc.

They may have abandoned the analog system or keep it licensed and mothballed "just in case". I hear there's a lot of that out there on high-band, and some attempt to shake loose some of those abandoned channels for use by entities that want/need them.

Good to know about the offset stuff. I had no idea it wasn't like UHF. Thanks so much!