I do like the "snapshot" idea but I see immediately that it is a "pay" option in VMWare after downloading the free Player. If it's available as a free option in VirtualBox I may try that route just for laughs.
SDR's vs. Hardware Scanners/Receivers
- Thread starter KC1UA
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br0adband
Member
VMware Player is just that: it's for "playing" or using virtual machines that already exist/have been created - that's the catch. You're supposed to pay for VMware Workstation to get the full-on main package that allows you to actually do installs, customize the hell out of things, and so on.
But... when using VMware Player, all it really requires to get up and running is a bare-bones .vmx file (the configuration file for a virtual machine using VMware software like Workstation, or Server, ESi, Player, etc). That little text file is all you require to "force" VMware Player to start up expecting to find an installation ISO or whatever to get it working, but it's somewhat more complicated than using VirtualBox since that's a true VM package complete.
And yes, VirtualBox actually is free as in free beer if you're into such beverages.
Ooops... said I wasn't gonna do that again, oh well.
But... when using VMware Player, all it really requires to get up and running is a bare-bones .vmx file (the configuration file for a virtual machine using VMware software like Workstation, or Server, ESi, Player, etc). That little text file is all you require to "force" VMware Player to start up expecting to find an installation ISO or whatever to get it working, but it's somewhat more complicated than using VirtualBox since that's a true VM package complete.
And yes, VirtualBox actually is free as in free beer if you're into such beverages.
Ooops... said I wasn't gonna do that again, oh well.
Well in the words of Butthead, "uh....beer kicks *** or something...."
I've used VirtualBox but it's been a long time. The more I think about it, it may be more conducive to this type of project. My only concern is what amount of horsepower I need to set up the virtual machine with in order to ensure gnuradio and/or op25 or whatever else I wind up trying out runs adequately enough. I do see that VirtualBox has the snapshot feature as well.
What the heck, why not introduce yet another piece of software into the mix. I just got a haircut and it's too short to tear the stuff out (right now).
I've used VirtualBox but it's been a long time. The more I think about it, it may be more conducive to this type of project. My only concern is what amount of horsepower I need to set up the virtual machine with in order to ensure gnuradio and/or op25 or whatever else I wind up trying out runs adequately enough. I do see that VirtualBox has the snapshot feature as well.
What the heck, why not introduce yet another piece of software into the mix. I just got a haircut and it's too short to tear the stuff out (right now).
Well it's been an interesting several hours. I took my wife out to dinner and had quite a few of the aformentioned beers in the process, which pretty much put the kibosh on any more tinkering today, but beforehand....
I installed the latest version of Kali Linux in a VirtualBox and was able to get one of my RTL dongles working with gqrx. The audio quality was horribly bad. When I did my last partitioned install of Ubuntu (before I blew the danged thing to hell) I had gqrx running with the same dongle with fairly good audio, although not as good as I hear when using it in Windows.
I ran gnuradio, and found some instructions for setting up a basic WBFM receiver. Of course in VirtualBox you have to ensure that you've made it possible to access USB devices, so after about an hour of frustration that dawned on me....and once I did so I had "something" happening. After finding another .grc file for a simple FM receiver I was not having a great deal of luck, but again "something" was going on.
Knowing nothing about gnuradio and how to set up the components in sequence I can envision myself doing some "reverse engineering" with existing .grc files that work, and learning what the individual components mean and do. I have already learned some of the basics of gnuradio and to ignore using hex value in lieu of my limited but adequate math skills for entering values in Hz, etc. I also learned how to link various components together after uttering numerous four letter nouns, verbs, and adjectives.
Now I wonder if because I'm hearing "something" and not what I want to hear when running gnuradio, if that's because running it in VirtualBox instead of in the "real" world is limiting me from using the true power of the computer. I have cranked up the virtual machine as much as I can without it giving me the finger, and it still doesn't work well.
I think my next mission will be to install Kali Linux in a partition on the hard drive so it has the full capability of the computer, and then trying again.
Bottom line? I did "something"...and learned "something" in the process. And I didn't throw the computer out the window. It should also be noted that I can number the amount of dropped F bombs in the single digits. Now THAT'S progress!
I installed the latest version of Kali Linux in a VirtualBox and was able to get one of my RTL dongles working with gqrx. The audio quality was horribly bad. When I did my last partitioned install of Ubuntu (before I blew the danged thing to hell) I had gqrx running with the same dongle with fairly good audio, although not as good as I hear when using it in Windows.
I ran gnuradio, and found some instructions for setting up a basic WBFM receiver. Of course in VirtualBox you have to ensure that you've made it possible to access USB devices, so after about an hour of frustration that dawned on me....and once I did so I had "something" happening. After finding another .grc file for a simple FM receiver I was not having a great deal of luck, but again "something" was going on.
Knowing nothing about gnuradio and how to set up the components in sequence I can envision myself doing some "reverse engineering" with existing .grc files that work, and learning what the individual components mean and do. I have already learned some of the basics of gnuradio and to ignore using hex value in lieu of my limited but adequate math skills for entering values in Hz, etc. I also learned how to link various components together after uttering numerous four letter nouns, verbs, and adjectives.
Now I wonder if because I'm hearing "something" and not what I want to hear when running gnuradio, if that's because running it in VirtualBox instead of in the "real" world is limiting me from using the true power of the computer. I have cranked up the virtual machine as much as I can without it giving me the finger, and it still doesn't work well.
I think my next mission will be to install Kali Linux in a partition on the hard drive so it has the full capability of the computer, and then trying again.
Bottom line? I did "something"...and learned "something" in the process. And I didn't throw the computer out the window. It should also be noted that I can number the amount of dropped F bombs in the single digits. Now THAT'S progress!
br0adband
Member
/me is laughing somewhat hard now...
Yeah, like I said, not everyone has good luck or success with virtual machines, a lot depends on the horsepower of the hardware, yes, but if you have a recent modern processor that has VT-x support (not absolutely required but it can make a relatively big difference) you should be able to do this without many issues. It's not perfect, and it does have some limitations (only able to use USB hardware is one of them).
I personally wouldn't recommend using Kali Linux - most everyone goes for that one nowdays because of what it has "built in" but it's technically not considered to be a daily-runner type OS for anyone: it has a very specific purpose overall (security auditing and penetration testing) but it is a Linux distro in the long run. It's just not the same thing as installing Ubuntu or some other Linux distro "from scratch" and then adding your own requirements in terms of packages and software.
The best part of virtual machines, at least to me? If you don't like them you can just select the necessary file(s) and delete it completely without a trace, no harm no foul and you sure won't "blow out" any other installs that may be on the same machine in a dual/triple/etc booting situation.
But I digress, I said I wasn't going to talk about VMs anymore so, that's that.
Yeah, like I said, not everyone has good luck or success with virtual machines, a lot depends on the horsepower of the hardware, yes, but if you have a recent modern processor that has VT-x support (not absolutely required but it can make a relatively big difference) you should be able to do this without many issues. It's not perfect, and it does have some limitations (only able to use USB hardware is one of them).
I personally wouldn't recommend using Kali Linux - most everyone goes for that one nowdays because of what it has "built in" but it's technically not considered to be a daily-runner type OS for anyone: it has a very specific purpose overall (security auditing and penetration testing) but it is a Linux distro in the long run. It's just not the same thing as installing Ubuntu or some other Linux distro "from scratch" and then adding your own requirements in terms of packages and software.
The best part of virtual machines, at least to me? If you don't like them you can just select the necessary file(s) and delete it completely without a trace, no harm no foul and you sure won't "blow out" any other installs that may be on the same machine in a dual/triple/etc booting situation.
But I digress, I said I wasn't going to talk about VMs anymore so, that's that.
I tried Kali on the suggestion of a few other folks, but not with any intention of continuing to use it, more so to see my equipment working on a PC with gnuradio. Well that was "kinda" the case, so for me it was a step in the right direction. I know this isn't going to happen overnight.
In all likelihood I'll go back to installing some version of Linux in a partition. I have either Ubuntu 13.10 or Linux Mint Cinammon 16 (both 64 bit versions) already burned to DVD for install. I used Linux Mint in the past during a prior Linux dabbling and I liked it.
I know your comments about VM's are tongue in cheek, but with the right platform I expect they are a viable option. I "think" that doing so in my case was causing some issues for me though. The processor I'm using on the test platform is an AMD Phenom X2 545 Processor 3 GHz so it's only a dual core. 4 GB of RAM on board but with a 32 bit install on Windows 7 Pro SP1 only 3 of that is being used of course.
So unless someone tells me to not do so I'll try Linux Mint 16 at some point....the AFC Championship is close to starting though, so my beloved Patriots will cause a delay in that event.
In all likelihood I'll go back to installing some version of Linux in a partition. I have either Ubuntu 13.10 or Linux Mint Cinammon 16 (both 64 bit versions) already burned to DVD for install. I used Linux Mint in the past during a prior Linux dabbling and I liked it.
I know your comments about VM's are tongue in cheek, but with the right platform I expect they are a viable option. I "think" that doing so in my case was causing some issues for me though. The processor I'm using on the test platform is an AMD Phenom X2 545 Processor 3 GHz so it's only a dual core. 4 GB of RAM on board but with a 32 bit install on Windows 7 Pro SP1 only 3 of that is being used of course.
So unless someone tells me to not do so I'll try Linux Mint 16 at some point....the AFC Championship is close to starting though, so my beloved Patriots will cause a delay in that event.
AZScanner
Member
Right, in theory. In practice, not so much. Let's set some expectations here.
#1: IF you know the key and IF the system you are trying to monitor uses DES-OFB then you could decrypt that information using the known key. To try to brute force it would take a very, VERY long time. Could be days, could be years it all depends on how quickly you can try each possible key. You'd also have to create an automated way to try all the possible keys, unless you REALLY want the process to take forever.
#2 None of the current variants/flavors of DSD can decrypt anything and OP25 decrypts only one of many possible encryption algoriythms that are valid/approved for use on P25 radio systems.
For example, the system I monitor here uses AES256. So #1 the brute force method needed to crack that would take a supercomputer many lifetimes to work (if you're lucky) and #2 even if I could get my hands on a valid key, OP25 doesn't decrypt AES-256 so the key would do me little good. They also change their keys regularly. I think I read somewhere that they change the keys every 30 days. So if I spent several years brute forcing a key and got lucky (as in winning the Powerball 100 times in a row lucky) that key would work for a whopping 30 days before they would change it and I'd have to start all over. Hardly worth the effort, especially when often times the interagency talkgroups on the local DTRS will relay enough information to know what the hot call was about a few minutes ago that moved to encrypted channel such and such.
Now, I suppose if I were some sort of drug kingpin it might be worth the time and money I'd need to invest in cracking decryption to hear when "the man" was coming to bust me. Otherwise, it's far too cost prohibitive, technically complex, and impractical to even attempt, let alone achieve. Last but not least, it's highly illegal - as in Federal Prison time - to decrypt an encrypted message of ANY kind that you are not the intended recipient of. So even if you could do it, you'd never be able to tell anyone. Gee, that sounds fun, doesn't it?
As much as I would LOVE (and I mean LOVE) to be able to decrypt the dozens of encrypted talkgroups we have on our DTRS it's barely theoretically possible and very much so impractical to implement. For starters, I'd have to begin by reverse engineering DSDPlus which is the only flavor of DSD that even works halfway decently on this system and there's no source code (and probably never will be). Then, assuming I could even do that, I'd then have to research the P25 protocol to find out where the encryption/decryption takes place so I'd know where to run the AES-256 encryption protocol on the raw frame data. Third, I would then have to take the theoretical weaknesses found by researchers a few years ago and create a practical (as in works in real life) application that could exploit the weaknesses. All that remains after all that would be to create a data table that would hold every possible permutation of AES encryption on the known plaintexts found by researchers so that I could compare them against the raw incoming data stream. Piece of cake, right? Anyone have a few petabytes of data storage lying around that I could borrow, not to mention at least one $100,000 plus database server that could search all that data in a reasonable amount of time? I checked my junkboxes and my closet and could only turn up an old barely functioning laptop and a couple of 40 gig hard drives. I suppose I could rent the servers and space from a cloud provider such as Amazon but I'm a few million dollars short of the funds needed to set up such a cloud solution. Anyone want to loan me (or better yet give me) millions of dollars so I can accomplish something highly illegal that I will then be able to share with no one? Yeah... I didn't think so.
In short, please forget about ever being able to monitor encrypted P25 comms (without a known key) with an SDR one day. It's simply never going to happen. Ever. It pains me to say it, believe me, but it's the absolute truth. What SDR does let you do is create solutions that no scanner could ever match.
For example: Imagine taking 10 RTL dongles and a few old computers you probably already have laying around, and creating an array of "scanners" that, for the same price as one or two digital scanners, would let you listen to every radio system in your area simultaneously. Newsrooms around the country have spent thousands of dollars each on their arrays of scanners in order to have that same capability. You can now have the exact same array of receivers they do for couple hundred bucks or less. Or perhaps you would like to monitor every un-encrypted talkgroup on every frequency of your local DTRS without missing a single call. This has already been done using a little bit of open source software and a HackRF board that cost $300. That's powerful. That is game changing. If that doesn't yet have Uniden and GRE/Whistler's attention, it should.
SDR is indeed the future of our hobby, but please let's drop the fantasy of cracking encryption with it. The only way that will ever happen is if #1 the software used to monitor the talkgroups allows you to feed it a decryption key and #2 if someone who knows what the key is tells you what it is. Otherwise forget it. I've spent many hours researching this very thing and have come to the conclusion that it's about as possible in reality as it would be to win the lottery every single time you play. Also, all this hinting around and postulating that we will one day break encryption just makes us look like "the bad guys" to the folks we love listening to. Let's not give them any more reason than they already have to take our hobby away.
-AZ
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AZ, I agree with all of your statements but I will be disappointed if this thread changes into an argument over encryption.
What got me going on it was as stated again (and again) was that while OP25 may be wonderful, very few people are ever going to get to the point where they can make it work. That simple statement is pretty much synonymous with yours regarding ever getting encryption to work. I also fear that continued discussions of that topic are detrimental to the future of the hobby.
On the topic of my endeavors, just getting LINUX to work sometimes is a nightmare. Yesterday I did a fresh install of LInux Mint 16 Cinammon 64 bit into a 200 GB partition on my "test" platform....and immediately I have issues with it. It takes about 2 minutes for my wireless keyboard and mouse to even become available so that I can log into the OS. That's unacceptable and is just one of numerous quirks that have made me ultimately throw up my hands and give up on Linux every time I've ever installed it.
Maybe it's just me, but when you can't even get basic equipment to run on an operating system, how in bloody hell you're supposed to get gnuradio and OP25 to do so escapes me.
What got me going on it was as stated again (and again) was that while OP25 may be wonderful, very few people are ever going to get to the point where they can make it work. That simple statement is pretty much synonymous with yours regarding ever getting encryption to work. I also fear that continued discussions of that topic are detrimental to the future of the hobby.
On the topic of my endeavors, just getting LINUX to work sometimes is a nightmare. Yesterday I did a fresh install of LInux Mint 16 Cinammon 64 bit into a 200 GB partition on my "test" platform....and immediately I have issues with it. It takes about 2 minutes for my wireless keyboard and mouse to even become available so that I can log into the OS. That's unacceptable and is just one of numerous quirks that have made me ultimately throw up my hands and give up on Linux every time I've ever installed it.
Maybe it's just me, but when you can't even get basic equipment to run on an operating system, how in bloody hell you're supposed to get gnuradio and OP25 to do so escapes me.
AZ, I agree with all of your statements but I will be disappointed if this thread changes into an argument over encryption.
What got me going on it was as stated again (and again) was that while OP25 may be wonderful, very few people are ever going to get to the point where they can make it work. That simple statement is pretty much synonymous with yours regarding ever getting encryption to work. I also fear that continued discussions of that topic are detrimental to the future of the hobby.
On the topic of my endeavors, just getting LINUX to work sometimes is a nightmare. Yesterday I did a fresh install of LInux Mint 16 Cinammon 64 bit into a 200 GB partition on my "test" platform....and immediately I have issues with it. It takes about 2 minutes for my wireless keyboard and mouse to even become available so that I can log into the OS. That's unacceptable and is just one of numerous quirks that have made me ultimately throw up my hands and give up on Linux every time I've ever installed it.
Maybe it's just me, but when you can't even get basic equipment to run on an operating system, how in bloody hell you're supposed to get gnuradio and OP25 to do so escapes me.
Yes, Linux at times can be a pain. But it gets better all the time (I've been using it since 1999).
I would head for something with a newer kernel. Newer kernels bring nice improvements to hardware functions. I would say try Arch if you are comfortable following the wiki for install (great docs) or try Manjaro and update to the newest kernel and it should be good.
The problem with Ubuntu*/Mint is it is tailored at a friendly stable keep new comers happy approach. That makes it depend on somewhat older kernels and the such to keep the problems at bay. You can update the kernel by probably jumping through some kind of hoop but in the end you still have outdated libraries and such.
Manajaro or Arch is more tailored to our inner geek (we love radio are we not geeks? lol). So you are the admin and you fix problems. Manjaro is more tested and not as bleeding edge as Arch, but close with the newer friendly type things. Arch at the core however.
Getting some sort of SDR sometime next month . I might embark on this journey at that time and see if my Linux experience might lend a hand.
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AZScanner
Member
Agreed. That was not my intent, so if anyone would like to argue about it with me, please start a new thread. I love a good debate.
What got me going on it was as stated again (and again) was that while OP25 may be wonderful, very few people are ever going to get to the point where they can make it work. That simple statement is pretty much synonymous with yours regarding ever getting encryption to work. I also fear that continued discussions of that topic are detrimental to the future of the hobby.
On the topic of my endeavors, just getting LINUX to work sometimes is a nightmare. Yesterday I did a fresh install of LInux Mint 16 Cinammon 64 bit into a 200 GB partition on my "test" platform....and immediately I have issues with it. It takes about 2 minutes for my wireless keyboard and mouse to even become available so that I can log into the OS. That's unacceptable and is just one of numerous quirks that have made me ultimately throw up my hands and give up on Linux every time I've ever installed it.
Maybe it's just me, but when you can't even get basic equipment to run on an operating system, how in bloody hell you're supposed to get gnuradio and OP25 to do so escapes me.
Agreed here as well. Linux is great but it's like ordering a car at a huge discount (or for free) and then having it arrive in pieces. If you don't know how to build a car yourself from a collection of parts then really all you have for your efforts is a collection of parts, no matter how cool the finished "car" is supposed to be. Some distros take it a bit further and all the basics are (supposedly) included and compiled for you, but to do anything more specialized (such as GNURadio and OP25) then you have to build those yourself from the readily available "parts", much like my hypothetical car in the above example. As you and I have both learned the hard way, it's really easy to F things up if you don't know precisely what you're doing. I too ended up going back to Windows. It may have it's problems and shortcomings but for the most part, you can download a Windows program and it will work - the program itself doesn't care what type of computer you have, and there's not 100 different versions of Windows 7 out there so it's pretty easy to write a program that can talk to Windows and work without a bunch of tweaking and recompiling things, unlike Linux.
I recommended Kali simply because, like other Linux distros the basics are pre-installed for you and so is GNURadio. That leaves only OP25 to worry about. The more stuff that's already built for me = less stuff I have a chance of screwing up by building it and/or installing it incorrectly. So any absolute noob's guide to OP25 should start with a fresh install of Kali Linux, I think. I would also recommend using a dedicated computer for the task so that you don't have to wipe your primary computer and start all over if something goes wrong (been there, done that, lost some important pics that I found out later were NOT backed up, bought the chewing-out from the wife for losing the pics of our kids and moved on).I'm one of those rare IT types that has literally a dozen computers in the house, so setting up a dedicated box is not a big deal for me - which makes me feel even dumber that I didn't follow my own advice lol - but most "normal" people don't own a bunch of computers. So chances are good that someone trying this for the first time will use the only computer available to them - their primary one - and end up REALLY sorry they ever tried this stuff if they lose their important files and documents in the process.
The other thing I think that people should prepare themselves for is after all that work, they may have built something that only works about as good as what they already had on Windows - or worse, it won't work at all. I actually got as far as getting the DSD plugin to run inside GNURadio on Ubuntu. It seemed like it wanted to work - I saw talkgroup info and other stuff flying by in the DSD window, but the speakers never uttered a peep, So much for that. I had something running in Windows already on another machine that worked far better. So I abandoned the idea of Linux and reinstalled Windows (which is lots of fun if you don't have the actual install disks that came with the computer - oh the joy of spending your day downloading drivers and rebooting a bunch of times... )
I'd love to see a noob's guide to OP25 though. If you put one together and would like a guinea pig to try it out, I'll break out an old laptop I have laying around and give it a whirl. Good luck!
-AZ
The other thing I think that people should prepare themselves for is after all that work, they may have built something that only works about as good as what they already had on Windows - or worse, it won't work at all. I actually got as far as getting the DSD plugin to run inside GNURadio on Ubuntu. It seemed like it wanted to work - I saw talkgroup info and other stuff flying by in the DSD window, but the speakers never uttered a peep, So much for that. I had something running in Windows already on another machine that worked far better. So I abandoned the idea of Linux and reinstalled Windows (which is lots of fun if you don't have the actual install disks that came with the computer - oh the joy of spending your day downloading drivers and rebooting a bunch of times... )
I'd love to see a noob's guide to OP25 though. If you put one together and would like a guinea pig to try it out, I'll break out an old laptop I have laying around and give it a whirl. Good luck!
-AZ
That's the problem with Linux and why I am typing on a Windows laptop.
I started back in the day when it could take days and even weeks to get XF86 even working (the GUI). it was fun for the sake of tinker when I was younger but it got old. Even today, there is way more in Windows and there is not any piece of software that makes me think it is better in any way compared to Windows. It is fun and watching the progress is awesome, but the returns on time invested are only in the form of the experience, never the wow.
Boatanchor
Member
- Joined
- Jul 17, 2011
- Messages
- 991
I'm a little confused.
The OP's thread title was "SDR's vs Hardware Scanner/Receivers"..
I was thinking that this was going to be a discussion about the merits, or lack thereof, of SDR over 'Hardware Defined' scanners etc, presumably in the scanners traditional domain of V/UHF monitoring. It seems it has morphed into a discussion about OP25 and Linux.
Yet, from an interested spectators perspective, it would appear that OP25 really has no practical advantage over the likes of DSD or DSDPlus as far as general monitoring is concerned. In effect OP25, as a receive decoder, been made obsolete by the myriad of other digital voice modes in use today.
Correct me if I'm wrong but with OP25, for most people at least, a significant investment in time (installing and learning Linux/GNU radio etc) will only produce a P25 Phase 1 decoding platform, that may or may not work as well as DSDPlus.
I realize that DSD and probably DSDPlus were written in Linux and then compiled back to a Windows format. That's fine. All credit to the authors, who are obviously very clever people/person's.
Instead of opening peoples eyes to the possibilities of what can be achieved with a minimum investment of one or two $10 RTL tuner cards, an existing Windows PC and a tiny pieces of software named DSDPlus and Unitrunker, this thread is just likely to scare people away from SDR.
Fact is, for home based monitoring at least, it is no longer necessary (or even advisable if you want to monitor other digital voice modes) to spend $600 on the latest and greatest digital scanner from Uniden or Whistler. With virtually no computer skills/knowledge, you can now set up a basic DTRS monitoring system for less than $25!
And has been mentioned, the possibility of monitoring several/many channels simultaneously, is something that traditional scanners will never be able to emulate.
If that doesn't get your juices flowing, then nothing will..
For me, RTL dongles, the FuncubeDonglePro+, SDRSharp and Unitrunker (amongst others) changed forever the way I do things around here.
Now I keenly await the arrival of Airspy and others
The OP's thread title was "SDR's vs Hardware Scanner/Receivers"..
I was thinking that this was going to be a discussion about the merits, or lack thereof, of SDR over 'Hardware Defined' scanners etc, presumably in the scanners traditional domain of V/UHF monitoring. It seems it has morphed into a discussion about OP25 and Linux.
Yet, from an interested spectators perspective, it would appear that OP25 really has no practical advantage over the likes of DSD or DSDPlus as far as general monitoring is concerned. In effect OP25, as a receive decoder, been made obsolete by the myriad of other digital voice modes in use today.
Correct me if I'm wrong but with OP25, for most people at least, a significant investment in time (installing and learning Linux/GNU radio etc) will only produce a P25 Phase 1 decoding platform, that may or may not work as well as DSDPlus.
I realize that DSD and probably DSDPlus were written in Linux and then compiled back to a Windows format. That's fine. All credit to the authors, who are obviously very clever people/person's.
Instead of opening peoples eyes to the possibilities of what can be achieved with a minimum investment of one or two $10 RTL tuner cards, an existing Windows PC and a tiny pieces of software named DSDPlus and Unitrunker, this thread is just likely to scare people away from SDR.
Fact is, for home based monitoring at least, it is no longer necessary (or even advisable if you want to monitor other digital voice modes) to spend $600 on the latest and greatest digital scanner from Uniden or Whistler. With virtually no computer skills/knowledge, you can now set up a basic DTRS monitoring system for less than $25!
And has been mentioned, the possibility of monitoring several/many channels simultaneously, is something that traditional scanners will never be able to emulate.
If that doesn't get your juices flowing, then nothing will..
For me, RTL dongles, the FuncubeDonglePro+, SDRSharp and Unitrunker (amongst others) changed forever the way I do things around here.
Now I keenly await the arrival of Airspy and others
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AZScanner
Member
And if that's not enough reason for anyone to take the RTL_SDR plunge, there's this: http://www.rtl-sdr.com/
Tons of neat and interesting projects listed on that site from RTL users all over the world. Many of them come with a detailed how-to if you're interested in trying them yourself! Very cool. If you're curious about the future of our hobby it truly doesn't get any more bleeding-edge than the projects listed on that site.
-AZ
Tons of neat and interesting projects listed on that site from RTL users all over the world. Many of them come with a detailed how-to if you're interested in trying them yourself! Very cool. If you're curious about the future of our hobby it truly doesn't get any more bleeding-edge than the projects listed on that site.
-AZ
KA1RBI
Member
Earlier I "promised" not to re-post any more messages from the op25-dev mail list, but simply could not resist this update from Scott.
Here is Scott's post, plus one of the four images he included (see below). BTW he's doing this using an RTL stick.
I've actually never run DSD+ - How well does DSD+ handle simulcast LSM?
Best
Max
Here is Scott's post, plus one of the four images he included (see below). BTW he's doing this using an RTL stick.
I've actually never run DSD+ - How well does DSD+ handle simulcast LSM?
Best
Max
Attachments
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KA1RBI
Member
"morphed" ?? I've read the OP several times, and cannot agree with your assertion. I counted no less than five references to OP25 / GR...
Regards
Max
The title of the thread was a poor choice on my part. Sorry.
Maybe it should have been more pertinent to the merits of hardware P25 decoding vs. software P25 decoding, pro's and con's of each, etc.
I think we've kinda stuck to that. I'll always own at least one scanner, but moving forward? It's going to be very very likely SDR's all the way for me.
If this thread "scares" anyone, my apologies. The very fact that we're having the conversation speaks volumes about the possibilities that exist or lay ahead.
And you can get your feet wet for $20 or so. That's truly what got me hooked. Now I'm looking at spending hundreds of bucks on the REALLY good ones.
Maybe it should have been more pertinent to the merits of hardware P25 decoding vs. software P25 decoding, pro's and con's of each, etc.
I think we've kinda stuck to that. I'll always own at least one scanner, but moving forward? It's going to be very very likely SDR's all the way for me.
If this thread "scares" anyone, my apologies. The very fact that we're having the conversation speaks volumes about the possibilities that exist or lay ahead.
And you can get your feet wet for $20 or so. That's truly what got me hooked. Now I'm looking at spending hundreds of bucks on the REALLY good ones.
For Boatanchor and others who may be confused about this thread's primary focus - it actually grew out of a very relevant point brought up by KA1RBI and others in the Uniden forums on RR discussing the new upcoming models and how well they will or will not handle the very problematic LSM simulcast systems many are trying to monitor.
KA1RBI made the valid point that doing this properly really needs a different approach to demodulation than the traditional FM discriminator based method. I've been speculating this to be the case for a very long time now and have had many related discussions pertaining to this here on RR with many other technically inclined and experienced individuals including KA1RBI himself in the past. Basically, for those who are having trouble grasping this concept, it is a bit like taking a full on gourmet three course meal and throwing it in a food processor and then expecting to be able to completely and accurately recreate the structure, texture, taste, and appearance of said meal with the goop that comes out of the food processor; no matter how good the gourmet chef is at the end who is getting the resulting goop to work with, it is pretty much impossible to do said recreation! Think of that approach as the analog of the traditional FM discriminator dealing with a LSM simulcast signal and then asking DSD or whatever to deal with the result. Think of the quadrature demodulator approach as roughly the analog of taking that three course meal and simply putting each dish in tupperware containers and shipping them under cold storage to the final chef/preparer/whatever. Now, if I understand what KA1RBI was trying to claim correctly, then it appears to me what he was saying and is still saying, as in his last post, is that the OP25 stuff can handle this the right way and is already proven to work. If I am reading and interpreting his posts and claims correctly, I think he is saying that OP25 can emulate in software a full on quadrature demodulator that will significantly outperform any traditional FM discriminator based solution like the DSD variants.
Now, I have to admit that I am EXTREMELY ignorant of GNU radio and OP25 though I did look into it some years ago and just came away completely confused; I have a good RF hardware background with experience in hardware based PI/4 DQPSK modulation and demodulation and have worked with hardware quadrature I/Q modulation and demodulation but the newer fully software based stuff is way over my head I am very ashamed to admit.
I have dabbled in Linux with much the same results as some above have outlined and I seem to have some sort of unfortunate brain damage that precludes any useful amount of programming prowess on my part that nowadays seems to be nearly ubiquitous among virtually all multicellular life forms on the planet except myself. I was never very good at DOS and UNIX made my head ache ("grup"...?!...seriously?...I mean, it sounds like something my stomach does after consuming two bowls of chili and three cups of coffee in rapid succession!) and I had some serious UNIX gurus who tried their best to crowbar that stuff into my all too reluctant and recalcitrant cranium. GUI OS was really a godsend for me in terms of using computers way back when (I cut my professional computing teeth on VAX mainframes using VT-100 and VT-220 terminals!).
Anyway, getting back to the OP25 discussion, pardon my admittedly poor ability to comprehend here, but, if OP25 is all software then how does it get the signal it needs to work with since as has been said, the discriminator output is simply insufficient? I THINK that it is intended to be used with the USRP and equivalent types of hardware platforms in such a manner that they provide real final raw or maybe partially filtered final downconverted IF signals for the OP25 software to work with...is this correct? Or maybe they yield true I and Q baseband components for OP25 to process...?
Pardon me for being dense and uncomprehending here but I guess that my salient questions are as follows:
1) Is OP25 the name for the piece of software or is it the nomenclature used to describe the entire open source hardware and software project geared towards P25 Phase 1 and Phase 2 transmission and reception?
2) Assuming it is just the software, what kind of hardware does it expect for the RF and IF stages and what kind of signal does it need to optimally work with? I see references to the dongles now so I guess it can now work with those cheaper alternatives to the USRP stuff or am I misinterpreting things here?
3) Assuming that the OP25 software contains a fully workable software equivalent of a true quadrature demodulator then I think that is the most significant difference between it and the DSD variants and NOT the encryption handling feature - is this correct? I think that is what KA1RBI was trying to point out in his posts above using those constellation diagrams/readout screenshots he included.
4) Ok, again, pardon my denseness, but where did those screenshots come from, by the way? Did they come from the OP25 software itself or some form of complex modulation analysis software and/or hardware (like a Vector Signal Analyzer)? If they came from the software in question, then I have to say that that right there is another significant difference between it and the DSD software - a truly useful real time graphical analysis GUI based desktop geared toward complex digital modulation analysis!! If that is true then that elicits a big WOW from me right there!
Scancapecod, personally, I applaud your starting this thread even if the name is maybe a little misleading (I think it should have been something like "OP25 approach versus hardware based scanners and other alternative SDR methods") because I, too, have been interested in what OP25 is all about but have been put off by the rather cryptic and arcane (to me, ok, to me - I admit I am mentally deficient here so don't get too fired up please;-)) Linux and open source software references. I guess I really need that "OP25 For Dummies" tutorial so keep up the good work!
And, just for the record, I seem to have some weird curse or bizzaro cosmic issue when it come to Yahoo groups...odd spacetime distortions seem to occur and pesky microsingularities open up in uncomfortable places about my person when I try and deal with them, cats and dogs living together and rocks raining down from heaven, you know, general apocalyptic annoyances like that so I tend to avoid them like the plague. Seem to have the same problem with those automated checkout machines in supermarkets and hardware stores too, interestingly...
Anyway, I still remain very much interested in learning more! KA1RBI, I have always respected your information and knowledge and do respect the OP25 project even if I just can't wrap my head around many of its aspects. My hardware technical background is good but the Linux and software stuff just isn't there so I get so frustrated that I can follow enough of what you say just up to the point where you throw in the Linux and software references and then I just end up frustrated. That is just me and I get it. My problem. But, you see, I NEED that truly all inclusive step by, agonizingly simplistic to you, step manual that Scancapecod is going after here! And I suspect many others do as well; if he is successful in creating one (or you or someone else in your group is) then that should really help garner more interest in your project! Also, I think you should simply and concisely point out the really important advantages of the program versus the DSD alternatives - the more powerful P25 LSM simulcast demodulation capabilities - and not obscure them with graphs and cryptic references that many non-technical folks simply will not get. I DO know very well what those constellation readouts were saying!! But I bet many on here were just left in the dark!
-Mike
KA1RBI made the valid point that doing this properly really needs a different approach to demodulation than the traditional FM discriminator based method. I've been speculating this to be the case for a very long time now and have had many related discussions pertaining to this here on RR with many other technically inclined and experienced individuals including KA1RBI himself in the past. Basically, for those who are having trouble grasping this concept, it is a bit like taking a full on gourmet three course meal and throwing it in a food processor and then expecting to be able to completely and accurately recreate the structure, texture, taste, and appearance of said meal with the goop that comes out of the food processor; no matter how good the gourmet chef is at the end who is getting the resulting goop to work with, it is pretty much impossible to do said recreation! Think of that approach as the analog of the traditional FM discriminator dealing with a LSM simulcast signal and then asking DSD or whatever to deal with the result. Think of the quadrature demodulator approach as roughly the analog of taking that three course meal and simply putting each dish in tupperware containers and shipping them under cold storage to the final chef/preparer/whatever. Now, if I understand what KA1RBI was trying to claim correctly, then it appears to me what he was saying and is still saying, as in his last post, is that the OP25 stuff can handle this the right way and is already proven to work. If I am reading and interpreting his posts and claims correctly, I think he is saying that OP25 can emulate in software a full on quadrature demodulator that will significantly outperform any traditional FM discriminator based solution like the DSD variants.
Now, I have to admit that I am EXTREMELY ignorant of GNU radio and OP25 though I did look into it some years ago and just came away completely confused; I have a good RF hardware background with experience in hardware based PI/4 DQPSK modulation and demodulation and have worked with hardware quadrature I/Q modulation and demodulation but the newer fully software based stuff is way over my head I am very ashamed to admit.
I have dabbled in Linux with much the same results as some above have outlined and I seem to have some sort of unfortunate brain damage that precludes any useful amount of programming prowess on my part that nowadays seems to be nearly ubiquitous among virtually all multicellular life forms on the planet except myself. I was never very good at DOS and UNIX made my head ache ("grup"...?!...seriously?...I mean, it sounds like something my stomach does after consuming two bowls of chili and three cups of coffee in rapid succession!) and I had some serious UNIX gurus who tried their best to crowbar that stuff into my all too reluctant and recalcitrant cranium. GUI OS was really a godsend for me in terms of using computers way back when (I cut my professional computing teeth on VAX mainframes using VT-100 and VT-220 terminals!).
Anyway, getting back to the OP25 discussion, pardon my admittedly poor ability to comprehend here, but, if OP25 is all software then how does it get the signal it needs to work with since as has been said, the discriminator output is simply insufficient? I THINK that it is intended to be used with the USRP and equivalent types of hardware platforms in such a manner that they provide real final raw or maybe partially filtered final downconverted IF signals for the OP25 software to work with...is this correct? Or maybe they yield true I and Q baseband components for OP25 to process...?
Pardon me for being dense and uncomprehending here but I guess that my salient questions are as follows:
1) Is OP25 the name for the piece of software or is it the nomenclature used to describe the entire open source hardware and software project geared towards P25 Phase 1 and Phase 2 transmission and reception?
2) Assuming it is just the software, what kind of hardware does it expect for the RF and IF stages and what kind of signal does it need to optimally work with? I see references to the dongles now so I guess it can now work with those cheaper alternatives to the USRP stuff or am I misinterpreting things here?
3) Assuming that the OP25 software contains a fully workable software equivalent of a true quadrature demodulator then I think that is the most significant difference between it and the DSD variants and NOT the encryption handling feature - is this correct? I think that is what KA1RBI was trying to point out in his posts above using those constellation diagrams/readout screenshots he included.
4) Ok, again, pardon my denseness, but where did those screenshots come from, by the way? Did they come from the OP25 software itself or some form of complex modulation analysis software and/or hardware (like a Vector Signal Analyzer)? If they came from the software in question, then I have to say that that right there is another significant difference between it and the DSD software - a truly useful real time graphical analysis GUI based desktop geared toward complex digital modulation analysis!! If that is true then that elicits a big WOW from me right there!
Scancapecod, personally, I applaud your starting this thread even if the name is maybe a little misleading (I think it should have been something like "OP25 approach versus hardware based scanners and other alternative SDR methods") because I, too, have been interested in what OP25 is all about but have been put off by the rather cryptic and arcane (to me, ok, to me - I admit I am mentally deficient here so don't get too fired up please;-)) Linux and open source software references. I guess I really need that "OP25 For Dummies" tutorial so keep up the good work!
And, just for the record, I seem to have some weird curse or bizzaro cosmic issue when it come to Yahoo groups...odd spacetime distortions seem to occur and pesky microsingularities open up in uncomfortable places about my person when I try and deal with them, cats and dogs living together and rocks raining down from heaven, you know, general apocalyptic annoyances like that so I tend to avoid them like the plague. Seem to have the same problem with those automated checkout machines in supermarkets and hardware stores too, interestingly...
Anyway, I still remain very much interested in learning more! KA1RBI, I have always respected your information and knowledge and do respect the OP25 project even if I just can't wrap my head around many of its aspects. My hardware technical background is good but the Linux and software stuff just isn't there so I get so frustrated that I can follow enough of what you say just up to the point where you throw in the Linux and software references and then I just end up frustrated. That is just me and I get it. My problem. But, you see, I NEED that truly all inclusive step by, agonizingly simplistic to you, step manual that Scancapecod is going after here! And I suspect many others do as well; if he is successful in creating one (or you or someone else in your group is) then that should really help garner more interest in your project! Also, I think you should simply and concisely point out the really important advantages of the program versus the DSD alternatives - the more powerful P25 LSM simulcast demodulation capabilities - and not obscure them with graphs and cryptic references that many non-technical folks simply will not get. I DO know very well what those constellation readouts were saying!! But I bet many on here were just left in the dark!
-Mike
Last edited:
KA1RBI
Member
Hi Mike
Thanks for your interest in OP25. I'll try to answer all your questions below, let me know if I've missed anything
Scott (whose constellation diagram is posted above) was using a $20 RTL USB stick.
IMHO there are stupid questions and stupid questioners but this is NOT an example of that
OP25 refers both to the project and to the software
It can work with "conventional" SDR products such as USRP, hackrf, etc. as well as the USB dongles. It can also work with any scanner, but you have to tap the scanner in a different place (IF), not the usual disc. tap. If the tapped IF is low enough (it can be downconverted using simple circuitry) the result can be processed via a soundcard. The project refers to this mode as "audio IF".
The most simple way of inputting the data into a sound card is just as a passband signal at the IF rate. For soundcards a nominal value of 24 KHz is used in OP25. This signal is fed either to the left or the right channel digitized by the soundcard, at a sampling rate of 96 KHz. (Two separate, independent channels may thus be digitized using a sound card). This digitized signal consists of a real-valued set of samples and since the sampling rate in this case exceeds the Nyquist rate, we know by definition that it contains all of the information in the original analog IF signal (and then some). It is striaghtforward to convert this real-valued signal into a complex I/Q signal by
- setting the "I" channel to be simply a copy of the original signal
- setting the "Q" channel to zeros.
That is, the signal is "converted" from a real passband signal into a complex I/Q signal by simply zero-stuffing into the "Q" channel. Once this is done we shift the signal to zero IF by injecting a software LO at the negative of the IF frequency (-24 KC is used in this example), and we apply the result to a low-pass filter centered at zero Hz with a bandwidth of +/- 6.25 KHz (sometimes 7.5 KHz is used to provide a bit of slop to cater to accumulated frequency errors)... The resulting complex signal is for all practical purposes equivalent to one that would have been obtained via direct hardware complex I/Q sampling. There are other examples of this as well. For example the TVRX daughterboard uses a low IF and synthesizes the complex I/Q information via software. Also, there are two different tuners used in the RTL, only one of which utilizes a zero IF.
Note that in GNU Radio the term "quadrature demoduation" refers to the software equivalent of the discriminator method of FM demodulation. That is, if we fed the signal into quadrature_demod_cf() and then attempted to decode the resulting output we would have the same distorted and corrupted signal and would have all the same problems as if we were banging our head against the brick wall of trying to decode LSM/CQPSK as FSK4/C4FM...
As far as the distinguishing features of OP25 , LSM may be it for some, others might say it was the crypto capability, still others might cite the fact that the source code for the entire project is published under the GPL V3.
The constellation plot comes from the OP25 software itself. For a complete list of features including many screenshots, please see the signal scope page which is at SignalScopePage
We are painfully aware that the install process is not as easy as it should be, and there are changes pending to improve this further.
And it seems yah00 has been making life difficult for themselves as well. Time will tell, but you are certainly NOT the only one who would want this issue to be much improved!
Best
Max
Thanks for your interest in OP25. I'll try to answer all your questions below, let me know if I've missed anything
Scott (whose constellation diagram is posted above) was using a $20 RTL USB stick.
IMHO there are stupid questions and stupid questioners but this is NOT an example of that
OP25 refers both to the project and to the software
It can work with "conventional" SDR products such as USRP, hackrf, etc. as well as the USB dongles. It can also work with any scanner, but you have to tap the scanner in a different place (IF), not the usual disc. tap. If the tapped IF is low enough (it can be downconverted using simple circuitry) the result can be processed via a soundcard. The project refers to this mode as "audio IF".
The most simple way of inputting the data into a sound card is just as a passband signal at the IF rate. For soundcards a nominal value of 24 KHz is used in OP25. This signal is fed either to the left or the right channel digitized by the soundcard, at a sampling rate of 96 KHz. (Two separate, independent channels may thus be digitized using a sound card). This digitized signal consists of a real-valued set of samples and since the sampling rate in this case exceeds the Nyquist rate, we know by definition that it contains all of the information in the original analog IF signal (and then some). It is striaghtforward to convert this real-valued signal into a complex I/Q signal by
- setting the "I" channel to be simply a copy of the original signal
- setting the "Q" channel to zeros.
That is, the signal is "converted" from a real passband signal into a complex I/Q signal by simply zero-stuffing into the "Q" channel. Once this is done we shift the signal to zero IF by injecting a software LO at the negative of the IF frequency (-24 KC is used in this example), and we apply the result to a low-pass filter centered at zero Hz with a bandwidth of +/- 6.25 KHz (sometimes 7.5 KHz is used to provide a bit of slop to cater to accumulated frequency errors)... The resulting complex signal is for all practical purposes equivalent to one that would have been obtained via direct hardware complex I/Q sampling. There are other examples of this as well. For example the TVRX daughterboard uses a low IF and synthesizes the complex I/Q information via software. Also, there are two different tuners used in the RTL, only one of which utilizes a zero IF.
Note that in GNU Radio the term "quadrature demoduation" refers to the software equivalent of the discriminator method of FM demodulation. That is, if we fed the signal into quadrature_demod_cf() and then attempted to decode the resulting output we would have the same distorted and corrupted signal and would have all the same problems as if we were banging our head against the brick wall of trying to decode LSM/CQPSK as FSK4/C4FM...
As far as the distinguishing features of OP25 , LSM may be it for some, others might say it was the crypto capability, still others might cite the fact that the source code for the entire project is published under the GPL V3.
The constellation plot comes from the OP25 software itself. For a complete list of features including many screenshots, please see the signal scope page which is at SignalScopePage
We are painfully aware that the install process is not as easy as it should be, and there are changes pending to improve this further.
And it seems yah00 has been making life difficult for themselves as well. Time will tell, but you are certainly NOT the only one who would want this issue to be much improved!
Best
Max
AZScanner
Member
Hi Max,
If you want a real world example, check out my feed. It's kinda hit and miss, much like any other digital scanner to date on this system, but it does seem to handle LSM better than it's predecessor DSD.
I am curious about OP25 based on Scott's report that LSM is working for him. Can it be run on Windows? I'm really not interested in fighting with Linux again, but if it can be made to work with GNURadio for Windows, I might have a go with that to see if it works better on my local DTRS than DSD+ does.
Thanks for sharing this info with us and also for taking the time to answer all of our noob questions about it.
-AZ
KA1RBI
Member
Since the 1990's my New York State vanity plate [any further questions?]
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