TRX-1 DMR audio

[ka3nxn]

Having an issue with Buckingham, Co VA. They went DMR and when I pick them up on my scanner I get a lot of echoing and very distorted audio. Every once in a while I do get clear audio. The signal that comes from the tower is full scale so I don't think it's a signal reception issue. Any ideas?

 

[DMR_Conventional_Scanner]

I have two possibilities I can think of for now:

1. Well, are you standing right next to the tower? Because that can overload the radio and cause it to struggle to decode the audio.
2. (Less likely, as you said, "Every once in a while I do get clear audio.") DMR encryption can cause a chopped-up, bouncing pitch voice type of sound. (Best I can describe it.) Here's an example: http://www.w2sjw.com/sounds/DMR_128_Enc.mp3

Hopes this helps... or at least a little.

 

[Ubbe]

I get a lot of echoing and very distorted audio.

That's very common when a new DMR system are setup. Users have two radios too close to each other, often the same user trying to monitor how his transmission sounds, and you get feedback and with a delay from the DSP audio processing that creates echo.

There will be locations where the coverage are bad and creates a lot of bit errors and distorsion. Sometimes it's just the radios audio processing that needs different settings of microphone levels and AGC and also noise reduction that always add distorsion so I always disable that in a radio to get a much clearer sound without artifacts and muffled audio.

/Ubbe

 

[ka3nxn]

I have two possibilities I can think of for now:

1. Well, are you standing right next to the tower? Because that can overload the radio and cause it to struggle to decode the audio.
2. (Less likely, as you said, "Every once in a while I do get clear audio.") DMR encryption can cause a chopped-up, bouncing pitch voice type of sound. (Best I can describe it.) Here's an example: http://www.w2sjw.com/sounds/DMR_128_Enc.mp3

Hopes this helps... or at least a little.

I just listened to the audio in the link that you sent and that's exactly what I get. When this happens I do see that I am getting a full signal from the tower so that's why I'm puzzled.

 

[ka3nxn]

I have two possibilities I can think of for now:

1. Well, are you standing right next to the tower? Because that can overload the radio and cause it to struggle to decode the audio.
2. (Less likely, as you said, "Every once in a while I do get clear audio.") DMR encryption can cause a chopped-up, bouncing pitch voice type of sound. (Best I can describe it.) Here's an example: http://www.w2sjw.com/sounds/DMR_128_Enc.mp3

Hopes this helps... or at least a little.

Negative, I'm miles from the tower.

 

[Ubbe]

I just listened to the audio in the link that you sent and that's exactly what I get.

The link only have an audio example of an encrypted signal, no echo or distorsion. But maybe it can be difficult to tell the difference if you are not familiar with encrypted signals. Then in your case it can be some talkgroups that are in the clear and others are encrypted.

/Ubbe

 

[ka3nxn]

The link only have an audio example of an encrypted signal, no echo or distorsion. But maybe it can be difficult to tell the difference if you are not familiar with encrypted signals. Then in your case it can be some talkgroups that are in the clear and others are encrypted.

/Ubbe

The cops are the only ones using the new DMR. It's not encrypted because I do get good transmissions every once in a while.

 

[tvengr]

The cops are the only ones using the new DMR. It's not encrypted because I do get good transmissions every once in a while.

They can be using partial encryption (Sometimes yes, sometimes no). That shows as Mode Te (Lower case "e") in the database. If encrypted full time, the Mode will be TE (Upper case "E").

 

[tvengr]

Are you sure they are using DMR? The frequencies in Buckingham County are licensed for NFM and P25.

 

[ka3nxn]

Are you sure they are using DMR? The frequencies in Buckingham County are licensed for NFM and P25.

Yes, They made an official announcment a while back that they were switching to DMR. I also have inside infor that they are using DMR from one of their cooms folks. Like I said i sometime will get a perfectly good transmission.

 

[ka3nxn]

Yes, They made an official announcment a while back that they were switching to DMR. I also have inside infor that they are using DMR from one of their cooms folks. Like I said i sometime will get a perfectly good transmission.

Yes they are using DMR. If you look on RR and look at their SO dispatch it is listed as DMR.

 

[tvengr]

Please attach your CDAT archive file so we can take a look at it. Click on Attach files and open the file.

 

[tvengr]

In the license, I see the 151.31 MHz frequency is used on 4 different sites. The sites may all be transmitting at the same time (Simulcast). Yes, conventional frequencies can use simulcast sites also and you may be experiencing simulcast distortion. That will cause the intermittent garbled audio issues you are having. This wouldn't be the first time that an agency changes emission types without first seeking authorization from the FCC. The emissions listed in the FCC database often are not accurate. Take your radio near to one of the sites and see if the problem disappears. If you are close to a site, it will override the out of phase interference from the other sites. If the audio clears up, simulcast distortion is the problem.

2	N/A	GTOWER	45.7	51.8	166.0	4487 GLENMORE ROAD NEAR
3	N/A	GTOWER	24.4	24.4	397.2	3069 LAURAS LANE
4	N/A	LTOWER	45.7	45.7	311.5	578 WILLIS MOUNTAIN PLANT LANE NEAR
6	1300013	LTOWER	118.9	120.4	105.8	1268 Bremo Rd

 

[Ubbe]

When using VHF conventional it could also be that the dispatcher choose which site to transmit from and when the dispatcher switch from one site to another the OP are suddenly out of range. It could be a bit shaky using VHF for simulcast when the radio waves are 6 times longer and could probably make it equally more difficult for the discriminator to handle it. Are there actually any simulcast systems on VHF that works properly?

/Ubbe

 

[tvengr]

When using VHF conventional it could also be that the dispatcher choose which site to transmit from and when the dispatcher switch from one site to another the OP are suddenly out of range.

It is possible that the dispatcher could be switching sites. Usually, the database will show separate repeaters if that is the case.

 

[tvengr]

It could be a bit shaky using VHF for simulcast when the radio waves are 6 times longer and could probably make it equally more difficult for the discriminator to handle it. Are there actually any simulcast systems on VHF that works properly?

It seems to me that the same amount of delay would result in less of a phase difference with a VHF signal due to the longer wavelength. I would think that simulcast distortion is more of a problem on 700 and 800 MHz frequencies. I would appreciate any replies in reference to that.

 

[pallen444]

Do the wire trick put a pice of wire Between the plug and ground it to the antenna works great on my 1040 give it a try
you will like the boost.