How is a NXDN system configured

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Notarola
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How is a NXDN system configured

Post by Notarola » Mon Aug 07, 2017 7:07 pm

Being new to NXDN and not being familiar with it I thought this might be a good place to ask basic questions.

There is a bit of NXDN near me but its commercial traffic on a 4800 baud system. There is also some NXDN in the rail yard and the right of way maintenance. There is currently no need for me to have to worry about supporting it. However I would like to have a better understanding of the systems. Amy links to .pdfs or other technical documents would be nice.

To start I have read some info on FDMA and have a ok grasp on the fundamentals. A technical question do you know how many sub bands are used in NXDN also what the actual subband center freq? IE carrier freq - 750hz, - 1500hz etc. Obviously the baud rates would affect the number of subbands and spacing.

To start I assume simplex and conventional repeater operation is programmed similar to DMR but thats as far as I have gone. Trunking is going to be another matter so Ill save those questions for another post.
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Re: How is a NXDN system configured

Post by kb1kvd » Tue Aug 08, 2017 10:54 am

NXDN is setup in 4 level FSK with 4 subbands it's +1050Hz, +350Hz, -350Hz,-1050Hz of center freq at 4800 baud. The programming of NXDN is a lot like P25 conventional, instead of NAC's it's RAN's. RAN is radio access number which in NXDN there are 63 RAN's. Talkgroups are setup similar to P25 with 65000 talkgroups available. One of the links that I can recommend is http://nxdnradio.com/ which is an amateur radio group who has developed NXDN for amateur radio. I'm affiliated with the Massachusetts group who developed the system in New England. Most railroads who are using NXDN are primarly using for non mainline use, such as yards, mow crews, and mechanical forces.
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Re: How is a NXDN system configured

Post by Notarola » Tue Aug 08, 2017 5:53 pm

Thanks for the rail info that matches what I have heard active.

Next is how is a trunked system configured. I know they use a syskey of sorts but again thats the limit of my experience.
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Re: How is a NXDN system configured

Post by kb1kvd » Wed Aug 09, 2017 2:33 pm

That's my next step is to figure out the trunking side since we have an ambulance company who is running multi site. It's going to be one of those rainy day projects at work where I get a couple of FR-5000's running on the bench to play with trunking in nxdn.
10% of the people cause 90% of the problem and 90% of them are within a mile of your location.

If it wasn't for jerks and idiots life would be pretty dull.
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Re: How is a NXDN system configured

Post by Notarola » Wed Aug 09, 2017 4:16 pm

I assume trunked access works identically to other trunked systems. A unit logs into the CC and then idles untill the TG is active. I hope to get a more detailed understanding of the exact method used.

The link you provided gives some good info on the data structure. The NXDN Specification Overview Level 1 provides a lot of what I was interested in. I wonder if Level 2 or higher is available
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Re: How is a NXDN system configured

Post by kb1kvd » Thu Aug 10, 2017 2:43 pm

That's my understanding of the system, I was asking our contact within Icom about those features back a last christmas. If you check out NXDN official website there's even more information http://www.nxdn-forum.com/ . The NXDN forum is a group of two way radio manufacturers and test equipment manufacturers and they have some of the detailed white papers up there. It's a good read if you want a tech school level of understanding of the protocol.
10% of the people cause 90% of the problem and 90% of them are within a mile of your location.

If it wasn't for jerks and idiots life would be pretty dull.
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Re: How is a NXDN system configured

Post by Notarola » Thu Aug 10, 2017 4:09 pm

Thanks yes the tech level is what I am interested in. Actual unit programming will be next but from what I have seen its just a matter of site, freq(s), TG. SID of 000 looks like it will let you populate fields for learning etc.
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Re: How is a NXDN system configured

Post by kb1kvd » Thu Aug 10, 2017 4:41 pm

There's a video on youtube that was posted talking about NXDN. The video was posted by one of our club members and was put on by another friend who's a radio maintainer for amtrak out of Providence,RI. The presentation was done at a amateur radio convention here in Massachusetts a couple of years ago.

Part 1: https://www.youtube.com/watch?v=u6Yi24xbPvo

Part 2: https://www.youtube.com/watch?v=Mktn70kQDMA
10% of the people cause 90% of the problem and 90% of them are within a mile of your location.

If it wasn't for jerks and idiots life would be pretty dull.
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