Over My Head: DMR

[natedawg1604]

.... There are many brands. Do you have any recommendations for a brand?
....

Yup, I always use the the "official" rtl sdr store.

 

[Ensnared]

New Realm

Yes, a modified 2042 would work just fine for apps such as DSD+. I believe you would need a second receiver (a RTL-SDR would do, I think) if you were actually going to follow the trunking.

You can look up on the net to find out how to put a discriminator tap on a 2042, or you could have someone like G&G do it for you.

Mike

I am trying to wrap my head around this. So, you need one dongle for the DSD+ and another receiver?

I am rather confused here. I suppose one is for following the trunking? I am not smart enough to "modify" anything that requires soldering or most electronic endeavors. I once smoke a scanner when I attempted to open up the back and play. You are dealing with an electronic monobrow here.

 

[ka3jjz]

Yes, you would need 2 'receivers' for trunking - one to supply data from the control channel (in a standard Motorola system, the one that has the horrible motorboating sound on it), and one to follow the conversation.

What is a discriminator output? Just read the first section of this from our online glossary

Discriminator output - The RadioReference Wiki

And as for G&G - many RR members have had good success with Gerry, who runs it...

Home Page

Mike

 

[slicerwizard]

I am trying to wrap my head around this. So, you need one dongle for the DSD+ and another receiver?

I am rather confused here. I suppose one is for following the trunking?

With DSD+, one dongle is for monitoring/following the control/rest channel and a second one is used for following voice calls. If you want to analyze/monitor a DMR trunking system, two dongles is the way to go.

The dongles are also great for spotting and receiving RF activity anywhere from ~50 MHz to over 1 GHz, so they'll keep you busy for a while.

 

[Ensnared]

Search Function

It sounds like you're relying too much on ULS. FCC data has very limited utility, especially for private LMR systems. And no, the ULS frequency ID number tells you nothing, there is no data field in ULS which would provide LCN order.

To find comprehensive data on local DMR systems, you must "manually" search the entire UHF business band by (for example) running an analog band search in NFM mode and documenting frequencies with a loud annoying motorboat sound - they are VERY hard to miss if the DMR signal is somewhat strong. It's actually pretty simple once you get familiar with the process. Many also find it helpful to get a few $20 RTL dongles, because you can use DSD+ to automatically determine the LCN pair of a DMR frequency, along with system type, System ID etc. If a particular DMR frequency is active (or at least broadcasts regular idle messages), DSD+ will quickly spit out all relevant system parameters in very short order. Moreover, DSD+ will tell you IF the frequency is DMR, and if so, whether it's Conventional DMR, Capacity Plus or Connect Plus. Also, it detects & decodes Nexedge, IDAS, D-Star, ProVoice and of course P-25.

Also, RTL dongles allow you to use SDR#, which providers a great spectrum analyzer view over 2.4 MHz of spectrum, which can also assist with identifying DMR freqs.

Yes, I do intend to purchase a pair of dongles; however, I attempted to search the UHF band as suggested

Consequently, I found three frequencies. Two of these frequencies sounded like DMR. Two of these were on the list of Baylor Frequencies for the associated call sign, but it looks like there are two sites. One is on Bagby and the other is on top of Robinson tower off IH35. The 3rd transmission occurred on 461.475; however, the tone was noticeably lower than the sound of DMR.

I narrowed my search to the frequency range on the following call sign for Baylor operations and PD, WQMM459. Hence, I found two frequencies that fit the DMR sound, 461.10 and 452.4375. The louder of the two was 461.10. It was also the most frequently used of the two. It should be noted that the scanner rested on 452.4375 much longer than 461.10.

I will figure this out. In time, I will order Dongles.

 

[caltech831]

Trunked DMR

Can confirm TRBO Tier II Trunking system. I do not have the code plug of the radios (yet) but once I am able to download one ill see what the system is running and get the code info to y'all for scanning.