Tipp City NXDN48/IDAS trunked system

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mtindor

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FCC license WQZE933 was issued to Tipp City in 4/2017. A construction notification has recently been submitted to the FCC, by Tipp City, regarding the buildout of this.

Looks like it will be an NXDN48 trunked system (either NEXEDGE48 or IDAS). Might be centralized (a 24/7 control channel) or decentralized (no control channel).

At any rate, those of you in the Tipp City area with the capability of sleuthing out NXDN systems might want to take a look at the frequencies on this license:

453.35
453.500
453.7375
460.025
460.175


If you happen to find this sytem online and can get details regarding it, please submit that information to the database at https://www.radioreference.com/apps/submit/?ctid=2094

Thanks

Mike
 

AE8I

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I am in the Tipp City area and have been trying to monitor this system, but without success, using two RTL-SDRs, SDR# and DSD+. There is no continuous data channel, but 453.350 and 460.025 both have short data bursts about every five seconds, apparently 24/7. DSD+ will simply not respond when I feed it either channel with the short bursts. As a basic test of my setup, DSD+ will respond to nearby DMR and P25 control channels.

This system appears to be neither a Type-C (dedicated control channel) nor Type-D (no control channel) system, at least as I've found commonly described in looking around the Web.

Whether a typical Type-C or Type-D system or not, if anyone has experience monitoring, via SDRs, a similar NXDN system with multiple channel intermittent data bursts, I would appreciate any suggestions that might help me get up and running.
 

TRNcommLLC

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I know Type-D data beacon will not show anything on DSD+.

I have tested it myself and the only time I have seen data in Type-D is when it was being used for voice or data.
 

AE8I

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So it may be possible to monitor the system, at least to some extent, by feeding each potential voice channel to a different instance of DSD+?
 

mtindor

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So it may be possible to monitor the system, at least to some extent, by feeding each potential voice channel to a different instance of DSD+?

You could do that, or you could use the feature in DSD+ that I have never used (and thus can't describe) whereby you just give it a list of frequencies to scan through and it'll scan and stop on them as they become active.

I can't remember if Type-D trunked systems have channel numbers or not. I know Type-C systems do. If Type-D systems do, then when there is voice activity on one of the frequencies DSDPlus would show the channel number. And as long as you ascertain the channel numbers associated with each frequency, it woudl be trivial to set DSDPlus up to scan the system (with two devices of course) or program it in a Whistler scanner that does NXDN.

On a Type-C system, there is a control channel. And on a Type-C system, each frequency that is part of a site has the same RAN and its own unique channel number. If you have the RAN and the ch.1 <-->frequency pairings, you can scan it with DSDplus using two devices.

If you had a Whistler scanner, you could presumably just throw the frequencies into an NXDN system configuration in the scanner without even knowing channel numbers or anything, since Whistlers do not rely upon the control channel to trunk. Despite Whistler scanners not using the control channel for trunking, they seem to do pretty well at following conversations anyway.

I haven't personally monitored any Type D systems that I can remember.

NOTE: DSDPlus + SDRSharp might yield better results if:

a. you make sure "Filter Audio" is unchecked in SDR#
b. make sure your audio levels from SDR# to DSDPlus are decent but not clipping
c. make sure you set a bandwidth in SDR# of about 4000 for NXDN48/IDAS
d. use the -fn option in DSDPlus to force only detection of nexedge48/idas.

If you can't decode any beacon databursts using that kind of setup, I guess DSDPlus isn't equipped to copy those. I don't have any nearby to test myself or I would.

Mike
 

AE8I

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Thanks to both of you for the replies.

I'll download the latest suite plug-in for the SDR# Frequency Manager and see if I can enable the scanning function, thereby negating the need for multiple instances. I'll also implement the other tweaks you recommended, Mike.

I've given thought to purchase of an NXDN capable scanner such as the Whistler TRX-2, but at the moment I am still opting for this much less costly alternative. At some point though, I suppose frustration may trump my frugalness.

I'll follow up here with whatever successes or failures I experience as I have more time this week to work on this further.
 

AE8I

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I'll follow up here with whatever successes or failures I experience as I have more time this week to work on this further.

Since well before my last post, I've noted no RF activity on this system, other than on the two previously discussed data burst frequencies. This is based on my monitoring of all system frequencies using a BCT15, where I've assumed that NXDN transmissions would be heard as some sort of white noise. The regular data bursts are easily heard on the BCT15.

I have also observed the SDR# FFT display for significant periods in the last few days and noted only data burst activity.

Therefore, it appears the system is not yet fully operational, or at this time it is used rather infrequently by Tipp City personnel. I'll continue to monitor the system for other than data beacon transmissions, and if so, try to decode them with my RTL-SDRs, SDR# and DSD+.
 
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