racingfan360
Member
- Joined
- Dec 19, 2005
- Messages
- 1,190
So this one's really confused me....wonder if anyone else can shed some light:
At a recent event I was scanning several NXDN9600 and MotoTRBO users - they were all broadcast from approx the same location, all via (different) repeaters. Normally, with my laptop I find that I just need to set DSD running (dsd etc). If it machine guns, I know Ive got the setup wrong, and need to invert (dsd -xr etc). In my experience, its the scanner/souncard setup that determines if you need to invert...not the signal you listen to.
I'd been decoding several TRBO users ok. So I was really surprised when I heard some machine gunning against one specific freq. I initially assumed encryption. Upon further analysis I found the user of this freq was sometimes inverted (ie needed dsd -xr for clear speech), sometimes not (dsd was ok). Luckily I had a 2nd scanner and a mp3 recorder, so I was able to capture some raw discriminator traffic independently. Later i repeated the test...same results, so i think that rules out the scanner/laptop combo doing live decoding. I also found I needed to invert DMRDecode respectively when the signal went from invert to non invert. I am 99% sure this behaviour was apparent on one single TRBO user, across both TDMA channels (according to DMRDecode anyway).
Anyone else seen anything like this, or care to offer an explanation? I'm confused. I was almost thinking its like a basic form of privacy.....it's the first time I've seen 'Broadcast' listed in the Service Options btw in DMRDecode:
21:33:57 DMR Data Frame
CACH : TACT Ch 1 Last fragment of LC
Slot Type : Colour Code 1 Terminator with LC
Group Voice Channel User LC
Service Options : Non-emergency/Broadcast/No priority
Group Address : 16777215 Source Address : 1
21:33:52 DMR Data Frame
CACH : TACT AT=1 Ch 2 Continuation fragment of LC
Slot Type : Colour Code 1 Terminator with LC
Group Voice Channel User LC
Service Options : Non-emergency/Broadcast/No priority
Group Address : 16777215 Source Address : 1
TIA
Jim
At a recent event I was scanning several NXDN9600 and MotoTRBO users - they were all broadcast from approx the same location, all via (different) repeaters. Normally, with my laptop I find that I just need to set DSD running (dsd etc). If it machine guns, I know Ive got the setup wrong, and need to invert (dsd -xr etc). In my experience, its the scanner/souncard setup that determines if you need to invert...not the signal you listen to.
I'd been decoding several TRBO users ok. So I was really surprised when I heard some machine gunning against one specific freq. I initially assumed encryption. Upon further analysis I found the user of this freq was sometimes inverted (ie needed dsd -xr for clear speech), sometimes not (dsd was ok). Luckily I had a 2nd scanner and a mp3 recorder, so I was able to capture some raw discriminator traffic independently. Later i repeated the test...same results, so i think that rules out the scanner/laptop combo doing live decoding. I also found I needed to invert DMRDecode respectively when the signal went from invert to non invert. I am 99% sure this behaviour was apparent on one single TRBO user, across both TDMA channels (according to DMRDecode anyway).
Anyone else seen anything like this, or care to offer an explanation? I'm confused. I was almost thinking its like a basic form of privacy.....it's the first time I've seen 'Broadcast' listed in the Service Options btw in DMRDecode:
21:33:57 DMR Data Frame
CACH : TACT Ch 1 Last fragment of LC
Slot Type : Colour Code 1 Terminator with LC
Group Voice Channel User LC
Service Options : Non-emergency/Broadcast/No priority
Group Address : 16777215 Source Address : 1
21:33:52 DMR Data Frame
CACH : TACT AT=1 Ch 2 Continuation fragment of LC
Slot Type : Colour Code 1 Terminator with LC
Group Voice Channel User LC
Service Options : Non-emergency/Broadcast/No priority
Group Address : 16777215 Source Address : 1
TIA
Jim
