Java program to decode DMR

[nycap]

Originally Posted by IanWraith

Hi



You need to tune to the frequency that is transmitted from the tower.

A simplex channel is one where the radios transmit on a single frequency directly to each other usually over a small area.

This is the case for the system i am trying to monitor. I know there is one fixed control point but im sure there are some mobile repeaters. There is only one frequency used (at least officially).

[Mike_G_D]

Originally Posted by nycap

Right. the positive line of the sheilded cable is in contact with the 10k resistor before the cap. the negative is grounded where the cap is grounded. problem is i didnt use the 2.2nf cap becuase i couldnt find one. i used the smallest cap i could find (a .01uf) and i was thinking this might not lower the leaky if signal hence the programs failure to sync/decode.

Thanks.

Ahhh! Ok, I didn't know you were talking about a SHUNT cap! Yes, that is for a completely different purpose - it's there to shunt high frequency "gunk" from the discriminator (or the PC) to ground and keep such signals from interfering with correct operation of the PC sound card and radio discriminator. I don't think it's really terribly necessary in most cases as the sound cards are usually pretty well filtered from high frequency signals and the discriminator usually doesn't have an issue with such signals - at least in my experience. Still, it actually IS good practice to use a high frequency shunt filter cap in such a system as long as it is the right value - low enough to attenuate the high frequency noise but not so low so as to attenuate the desired audio frequency range. What might be a problem in your case, then, is that the lower value cap you are using is actually passing too much low frequency audio to ground - I would completely remove that 0.01uF shunt cap and see what you get. It won't kill you to not have it installed.

-Mike

[Unitrunker]

Originally Posted by Mike_G_D

Ahhh! Ok, I didn't know you were talking about a SHUNT cap! Yes, that is for a completely different purpose - it's there to shunt high frequency "gunk" from the discriminator (or the PC) to ground and keep such signals from interfering with correct operation of the PC sound card and radio discriminator. I don't think it's really terribly necessary in most cases as the sound cards are usually pretty well filtered from high frequency signals and the discriminator usually doesn't have an issue with such signals - at least in my experience.

Vintage Uniden models leak lots of IF (around 900 khz). The shunt cap is of benefit to external slicer circuits. It's usually not needed on computer audio inputs.

[Mike_G_D]

Originally Posted by Unitrunker

Vintage Uniden models leak lots of IF (around 900 khz). The shunt cap is of benefit to external slicer circuits. It's usually not needed on computer audio inputs.

Ok, that makes sense. Anyway, I really think nycap should omit his shunt cap and then see if his levels improve - I think they will. There still may be other problems, of course, but that should help.

-Mike

[Forts]

This was posted on another forum and I thought I would share it here... A DMRDecode user in Texas came across a system which he believes is now using RAS. He says this shows up before every transmission:

FID=16 11000010000010010010000100000000000000000000000000 00000000000000

I haven't come across any systems using the new security features yet in my area, so I really can't say what it is he may have found.

[IanWraith]

Hi Forts
Cheers for that. It will be interesting to see if that starts to appear more often in other systems.

Regards

Ian

[gvodvarka]

I see the same thing here also 1100000…... ect I also see this:
CACH : TACT Ch 1 Continuation fragment of LC
Slot Type : Colour Code 13 CSBK
Capacity Plus CSBK : CSBKO=62
Activity Update : LCN 4 is the Rest Channel
11000100000000000000000000000000000000000000000000 00000000000000

[AZScanner]

This may or may not already have been posted (my apologies if it has) but when I run this program I get an error that says something to the effect of "Cannot find the main class, exiting". Anyone else run into that and if so, how did you fix it?

Thanks,
-AZ

[kubaval]

Hello Ian, I have got a question about my technical problem.
I can not recived simplex data with DMR JAVA program.
User in our city have not a repeater. Can you help me???
Thank you. Bye, James

[IanWraith]

Hello James

I'm afraid that at the moment DMRDecode doesn't support simplex DMR.

Sorry

Ian

[AZScanner]

Hi Ian,

Any chance you could post an answer to my question? I'm sure I'm doing something stupid - to me Java is something I pour into a mug and drink in the morning. But I'd really like to give your program a try.

Thank you,
-AZ

[Forts]

Originally Posted by AZScanner

Hi Ian,

Any chance you could post an answer to my question? I'm sure I'm doing something stupid - to me Java is something I pour into a mug and drink in the morning. But I'd really like to give your program a try.

Thank you,
-AZ

I've never seen that one. What OS and Java version are you using?

[AZScanner]

Originally Posted by Forts

I've never seen that one. What OS and Java version are you using?

It's a windows 7 box. I have no idea what version of Java. I can check it later on and let you know. I'll try updating or reinstalling it to see if that helps.

-AZ

[Forts]

That could be your problem. Ian updated the Java requirements a few months back.

[MikeOxlong]

You can usually type java -version to see what's installed.

[AZScanner]

OK guys, now I'm getting annoyed by this thing.

I downloaded the latest version of the program here: https://github.com/IanWraith/DMRDecode/downloads

I copied it to a folder on my hard drive called DMRDecode.

I updated Java to version 6 Update 17.

I double click the Jar file in the folder.

I get the following error from something called the Java Virtual Machine Launcher: Could not find the main class:com.dmr.DMRDecode. Program will exit.

Obviously I'm doing something wrong as it works for everyone else but me... the question is what??

Thanks for the help, guys
-AZ

[Forts]

I'm running Oracle Java version 7 on my machines. Maybe give that a try?

Download Free Java Software

[AZScanner]

Well why the heck didn't my Java updater thing update to version 7? I literally just ran the update a little while ago. Oh well,downloading now I'll let you know if it worked. Thanks for the info.

-AZ

Edit: That was it, now it runs! Thank you!

[nycap]

Originally Posted by IanWraith

Hi



You need to tune to the frequency that is transmitted from the tower.

A simplex channel is one where the radios transmit on a single frequency directly to each other usually over a small area. There are a small number of such setups here in the UK but the vast majority of systems use a repeater.

Regards

Ian

I just want to thank you. Hats off to you for such an awsome program. After putting in the 2.2nf cap in its been working very well.

After monitoring for a while now i have some new questions;

(1) what is the "logical link"; and (2) why is it that sometimes i hear the digital signal but nothing happens in the decoder?

Thanks again.

[IanWraith]

Hello Nycap

Firstly glad you like the program. As for your questions ..

1) The word "logical link" I must admit I don't know. I have followed the wording used in the official ETSI specs without fully understanding parts of it.

2) There are many reasons for this. Sometimes the signal is so strong it is distorting in your scanner and sometimes there are reflections in the signal which really mess up the demodulation of the bits.

Sorry I can't help more.

Regards

Ian