DMR Back to FM Possible

[pb_lonny]

In my area a few frequencies have gone what appears to be DMR, example audio here: Launceston Scanning Guy: Digital Audio on 493.225MHz

I don't own a DMR scanner (yet) but I have still kept these frequencies programmed in on the off chance they switch back for any reason. It has been over 9 months now.

Without knowing the specific model of radios they are using, do DMR radios also support normal FM? In areas where a switch to DMR has been made, has anybody seen them switch back or have any examples of FM being used on the same frequency as DMR?

I often run my scanner in search mode with it logging via my laptop, I have had a couple of examples where on one of the DMR frequencies it has logged CTCSS tones, this makes me think that some FM is still being used?

The reason for these questions is that I am working on updating the programming of my radio and will remove the DMR frequencies if they have little chance of carrying FM traffic.

 

[jonwienke]

You can program a channel in a DMR radio as digital or analog. But if you have digital capability, there's little reason to switch back. Doing so could be a violation of the channel license anyway.

I doubt the CTCSS tones are accurate. Digital uses all of the available audio spectrum when demodulated as FM, and depending on the bits being sent you can get spurious false positives on pretty much any tone. I have a pager tower near me, and even though I had a tone set on my frequently-used channels, it would still frequently break squelch on a regular basis. I got tired of the random bursts of static, so I reprogrammed the channels with a DCS code instead, which is far less likely to be randomly triggered by digital data.

Sounds like it's time to acquire a radio that can do DMR.

 

[troymail]

In my area a few frequencies have gone what appears to be DMR, example audio here: Launceston Scanning Guy: Digital Audio on 493.225MHz

I don't own a DMR scanner (yet) but I have still kept these frequencies programmed in on the off chance they switch back for any reason. It has been over 9 months now.

Without knowing the specific model of radios they are using, do DMR radios also support normal FM? In areas where a switch to DMR has been made, has anybody seen them switch back or have any examples of FM being used on the same frequency as DMR?

Scanners? Yes, certainly. Most real subscriber radios I believe can do both analog and digital

In areas where a switch to DMR has been made, has anybody seen them switch back or have any examples of FM being used on the same frequency as DMR?

Switch back? I've not seen any but there's always a possibility that a licensee found a reason to revert back. I think the new digital modes (DMR, NXDN, etc) are marketed to allow for "gradual" transition to digital - in other words allowing both analog and digital to be used. I know I've seen/heard both analog and digital on the same frequencies but I've never been sure if they are the same user/licensee or I just happened to be sitting in between two different licensed users - one using analog and the other digital. Having said that, in my area there is also a huge amount of "frequency reuse" - in some cases only separated by DMR color codes (and likely radio and talkgroup IDs that are designed not to overlap).

I often run my scanner in search mode with it logging via my laptop, I have had a couple of examples where on one of the DMR frequencies it has logged CTCSS tones, this makes me think that some FM is still being used?

Yes

The reason for these questions is that I am working on updating the programming of my radio and will remove the DMR frequencies if they have little chance of carrying FM traffic.

I'm constantly programming and reprogramming radios -- things routinely change around my location quiet a bit.

 

[sibbley]

I have one user in my area that is mixed mode. Sometimes operating analog with CTCSS and sometimes operating digital DMR.

 

[pb_lonny]

Thanks for the replies.

A DMR scanner is in the works, just hard to justify at the moment for a few frequencies only. I am continuously updating and changing my programming, this is going to be a major update / change of banks and adding some more users so I wanted to take the chance to remove them if they had little chance of carrying analogue audio again.

 

[pb_lonny]

I have one user in my area that is mixed mode. Sometimes operating analog with CTCSS and sometimes operating digital DMR.

This is what I wanted to know.

If you have two users with DMR radios and one is using FM and the other is in DMR mode, will the radio in DMR mode hear the FM audio?

 

[jonwienke]

No.

 

[pb_lonny]

So they would have to agree to change to FM before they switch off the DMR channel?

 

[jonwienke]

Yes.Or they would have to program the radios to scan the analog and DMR versions of the frequency into the radios.

But either way, it's something that would have to be planned and set up beforehand.

 

[pb_lonny]

Yes.Or they would have to program the radios to scan the analog and DMR versions of the frequency into the radios.

But either way, it's something that would have to be planned and set up beforehand.

Excellent, in that case I will remove them. I doubt they will ever switch back.

 

[reconrider8]

Our local pd actually did just that. They switched from analog to dmr then they did more work and they ended up switching back k to analog because they just couldn't get it like they were sold on how it was going to be

 

[INDY72]

If an DMR system is setup properly, then most users stay DMR as it gives so much more options. 2 Slots, multiple Color Codes, and multiple TGs per freq on conventional versus only one user at a time on analog conventional. An SMR with these multi mode setups has all kinds of options they can offer clients. I know of a couple of PDs that can run both, but now rarely uses analog except for interop purposes once they got all the bugs worked out on the DMR repeaters. And in the neighboring town, they run analog mainly, but use the DMR for special ops etc...

 

[natedawg1604]

It's also possible multiple unrelated entities are using the same frequency with totally different systems, presumably with each system located in a different city or county. In my area I'm seeing more and more instances of multiple systems on the same frequency in the Commercial UHF band (450-470), it's pretty annoying for scanner users...

 

[pb_lonny]

Thanks for the excellent replies, I have learnt a lot.

I have three frequencies in question, all are security staff at three separate sites for totally different businesses / groups.

 

[HudsonScannerGuy]

The BCD325P2 can do DMR now, and I heard Uniden EU released their version of the BCD436HP which can also do DMR (Paid upgrade)
I'd go with 325P2 or whatever the EU variant is because it may be cheaper, but upgrade was like 50 bucks US last I checked.

 

[slicerwizard]

I don't own a DMR scanner (yet) but I have still kept these frequencies programmed in on the off chance they switch back for any reason. It has been over 9 months now.

So why aren't you using a tapped scanner or a $20 dongle with DSD+?

For a guy who's so into RF sleuthing, you're really slow getting on the digital bandwagon.

 

[pb_lonny]

So why aren't you using a tapped scanner or a $20 dongle with DSD+?

For a guy who's so into RF sleuthing, you're really slow getting on the digital bandwagon.

Because that is too much like my work (IT) and I like my radios to be radios which I can carry around with me, not another computer I need to maintain...

 

[HudsonScannerGuy]

You can always get a DMR capable scanner.... (TRX 1/2, Uniden has some, and for when your at home a SDR would make perfect sense..)

 

[pb_lonny]

None of them are sold in Australian at the moment that support DMR. I was burnt many years ago with importing an overseas model.

 

[polkaroo]

Because that is too much like my work (IT) and I like my radios to be radios which I can carry around with me, not another computer I need to maintain...

I'd love to have DSD+ on a Pi built into an APX-style format and durability.