TxWARN Monitoring in Nacogdoches County – One SDR or Two?

[jasonreina]

I’m setting up an SDR receiver system to monitor TxWARN agencies in Nacogdoches County, TX. Since TxWARN is a P25 Phase II trunked system, I want to confirm the hardware requirements before I commit to a build.

I’m aware of the 3.2 MHz bandwidth limitation on a single RTL-SDR dongle. The Nacogdoches site has a total frequency spread of 4.3875 MHz, which on paper suggests that two dongles would be required to cover the entire site.

That said, I’ve also seen reports that it’s possible to monitor this site with only one RTL-SDR, depending on talkgroup activity and how the software handles control/voice hopping.

So my main questions are…

• For those running TxWARN in this region, is a dual-dongle setup mandatory in practice, or is single-dongle operation workable without significant traffic loss
• Have you run into site-specific challenges with Nacogdoches (e.g., control channel placement, simulcast distortion, or gaps caused by the frequency spread)?
• If you’ve tried both approaches, what was your real-world experience with coverage and missed calls?

Any insights from folks actively monitoring the Nacogdoches TxWARN site or one similar would be greatly appreciated. Below is a screenshot of the RR listing from Texas Wide Area Radio Network (TxWARN) Trunking System, Various, Texas.

 

[Enforcer52]

RTL-SDR dongles bandwidth is only 2.4Mhz (actually only around 2.2 in my experience) not 3.2Mhz. You will need two dongles to effectively cover the entire spectrum that Nacogdoches County uses. With one dongle you would miss calls on one end or the other of the spectrum depending on what the main control channel is.

When conditions are good and I turn my 18 element beam to Nacogdoches it takes two dongles to cover them. I use SDRTrunk for monitoring.

There is a Broadcastify feed for the county.

www.broadcastify.com/webPlayer/37196/web

 

[boatbod]

The answer for how "many dongles" depends on "what software". op25 can do the job with a single dongle if you are only interested in listening to one conversation at a time. If you are using SDRTrunk you'll need at least two dongles, or maybe a third if you take account that the receiver sensitivity rolls off at the edges of the receiver band.

 

[JimmyJet727]

Handy tool here. Copy/paste all the freqs from RRDB and click calculate...

SDR center frequency calculator