Help with 2 RTLSDR on 1 PC scanning 2 Frequencies

[SCPD]

Hi all, Total noob here looking for some advice on running dual rtlsdr dongles on 1 PC & listening to 2 separate frequencies at once. I will try explain best I can.

I was using unitrunker to listen to local police on AP25 Digital but they have just gone encrypted so that's now useless, What I'm currently doing is using 2 rtlsdr dongles & listening to 2 separate frequencies for local fire department (both rural analogue frequencies) by creating 2 voice receivers with unitrunker (1 receiver for each rtlsdr device) & playing both receivers at the same time so I can monitor both frequencies at the same time thru pc speakers.

Now here's my dilemma, Is it somehow possible either with unitrunker or another sdr program to be able to set 1 of the 2 frequencies i'm tuned too as a Priority channel so that they both don't overlap thru pc speakers if both frequencies happen to broadcast at the same time? I tried messing with the 'rank' function of unitrunker but doesn't seem to work across multiple voice receivers (only for multiple VCO's on 1 receiver) & the 2 frequencies are further than 3mhz apart so can't use 1 dongle (I don't think).

I would like the software to work like my old-school analogue scanner where I could scan multiple stored frequencies & have 1 channel set as priority so it detects any broadcast & locks onto it, then returns to scanning once broadcast finished?

I've also thought about some sort of PC Audio program that could possibly 'auto mute' a Virtual Cable 2 if it detects any sound via Virtual Cable 1 (if that makes any sense?). That way I could output 1 frequency to Virtual Cable 1 & the 2nd frequency to Virtual Cable 2 via unitrunker & when sound is detected on Virtual Cable 1 the software will detect & mute Virtual Cable 2 as to stop overlapping voices thru the pc speakers.

I have tried googling & reading many threads but finding little information & not sure if i'm just missing something simple I could do or If I have no option but to manually mute each receiver when the other is broadcasting.

Any help, ideas or some direction on what I could do to accomplish this would be greatly appreciated.
Thank you RR community.

 

[KevinC]

I moved your thread to the SDR forum for better visibility.

 

[br0adband]

The short sweet answer at least from me is "No, I don't think that's currently possible." Now for the reason(s) why:

Since you did specify you're looking at monitor analog transmissions specifically (as well as other useful info so good for you doing that), just two of 'em, then I have to ask are they frequencies or channels that are in use on a trunked system and I ask that because Unitrunker is a trunking system decoder and it's not technically something that you'd use to monitor traditional analog frequencies in a non-trunked manner. I'm not even sure it's possible to use Unitrunker in that respect but perhaps Rick aka Unitrunker himself will chime in.

The issue with SDR hardware and software at this point in development - any device, and any software - is that it's not as easy to use as a traditional analog or even a digital capable handheld or base scanner. The hardware is, definitely, because the hardware is basically just a tuner pulling in radio signals, but the real magic comes from what's done with the signals by the software.

Unfortunately, nobody has yet just created an analog or digital "front end" for SDR devices (of any kind) that allows you to basically use the hardware like it was an analog or digital scanner. I wish I was a "programmer extraordinaire" because I would more than likely have created such a thing by now but I'm not, and sadly nobody else has either. Perhaps someone at some point will make this type of front end interface a reality and throw in all the features and ease of use that a "simple" scanner interface has to offer.

Sure, there are a lot of SDR applications out there, and some even provide the ability to "scan" frequencies hopping from one to another in whatever database the application is capable of using. SDR# is arguably the most well supported SDR application in terms of extending the functionality using plugins, and there are several of those available that make it a pretty nice interface (which is what it is, essentially). I use SDR# myself with my RTL sticks, and I use the very popular and very awesome Frequency Manager+Scanner by Jeff Knapp and while it's got a freakin' ton of capabilities it doesn't offer any type of traditional Priority feature during the scanning process that it's able to make happen.

Now, I could be off about some aspects but so far in my own research and testing the only Priority option I've ever seen in any SDR related software is with Unitrunker, and that's designed for trunked system decoding, so unless it's capable of purely analog monitoring (and it very well could be depending on how a system is set up, hopefully Rick might chime in here on this) on a single or multiple frequency basis then I'm not sure that anything else exists out there for doing that.

It does seem pretty frustrating sometimes that things we take for granted as "so easy to do" with a traditional analog or digital scanner is apparently very difficult to do with SDR so far but that could always change with a new release of some new application that could take the SDR world by storm, certainly.

As for the multiple virtual audio cable solution, something like that might actually work in a real-time sense but you just never know: an active audio signal on one source could potentially be used for such purposes to "trip" a mute on another audio signal source and then unmute when the priority one has no activity, sure, but I have no clue where you'd find such a thing. It would more than likely end up being a custom piece of software someone would have to crank out, not impossible but more improbable than anything else.

Anyway, I'll be keeping an eye on this thread just in case some solution presents itself that might prove useful to others so good luck with it, welcome to RadioReference, and happy new year.

 

[slicerwizard]

Two analog channels? One dongle, SDR# and a scanning plugin, no?

The OP didn't say he actually needed priority scanning.

 

[br0adband]

The OP didn't say he actually needed priority scanning.

He/she didn't? Then what did this portion ask for (with the actual relevant component highlighted)?

I would like the software to work like my old-school analogue scanner where I could scan multiple stored frequencies & have 1 channel set as priority so it detects any broadcast & locks onto it, then returns to scanning once broadcast finished?

Now call me silly or whatever but I read that and interpret it to say: "I'd like to be able to monitor two frequencies using an RTL stick and SDR software: one of the frequencies can be marked/set/tagged as a priority frequency/channel so that even if a transmission is being received on the other frequency the software will switch the tuner back to the priority channel/frequency for monitoring, and when the priority channel/frequency has no more activity, it'll switch back to the second channel/frequency if there's activity or go back to scanning both of them for activity."

Because the OP stated he/she just wanted two frequencies monitored in this manner with one of them being marked/set/tagged as a priority it's obviously quite simple to do with traditional scanners as all of us are well aware - that's a basic function of pretty much any programmable scanner made since oh, 1982 or something around that time, but with SDR software it's still somewhat of a sticking point.

At some point I figure we'll see some SDR scanner application or an improved plugin for current applications that does add this particular aspect, but so far none that I'm aware of - even using some of the awesome plugins - doesn't provide that functionality.

 

[Voyager]

Based on this:

Now here's my dilemma, Is it somehow possible either with unitrunker or another sdr program to be able to set 1 of the 2 frequencies i'm tuned too as a Priority channel so that they both don't overlap thru pc speakers if both frequencies happen to broadcast at the same time?

He says he really doesn't want a priority - just the ability to not hear both audios at the same time.

So, I can see why there is confusion in what he really wants. He says he wants a priority, but goes on to explain the reason which does not require a priority channel. Then he goes on to describe priority.

All in all, very unclear. But I can see wiz's interpretation (and yours too, br0adband).

I'm surprised none of the scanning plugins support priority - especially if it's within the window of the display where it can do so without sampling which interrupts the current signal.

 

[br0adband]

True, true, always two points of view on most anything, I didn't read it that way but I can see how someone would so I hope slicerwizard doesn't think I was railing him there.

And yeah, as I stated above it is somewhat frustrating that there really is not workable "software defined scanner" application which basically can make an SDR hardware device work exactly like a modern handheld/base/mobile scanner but I keep hoping.

I truly do wish I that I had spent more time on the software development side of things in my career and now somewhat early retirement - I'm a hardware geek primarily and haven't written a program (in BASIC, no less) since the early 1980s so at this point in the game I wouldn't even consider trying to get involved with SDR application development at this point.

One of my all-time fave software applications for use with scanners was this one (this is just one possible view configuration):

When I had my BC246T I used that for programming it as well as controlling it from that interface directly and I absolutely loved it. Still have that program backed up in several locations but I'm happy to see the website for it is still up and running, the author created a version for the BCD396T as well and that's still available too:

Scannerbase Extended Info

But I would actually pay hard currency if someone were to create an SDR application with that type of main/primary interface that just uses an SDR device - like our beloved RTL sticks which are nearly perfect for just such a purpose - and leave all the rest of the typical SDR type stuff (the spectrum display, the waterfall, all the "knobs" for various config alterations and so on) "behind the scenes" of the interface and basically turn an RTL stick or some other SDR device into a plain old "traditional" scanner.

We've got plenty of SDR apps and more cool stuff being created all the time, but sometimes I just long for the simple days with that kind of interface and the ability to make it function exactly like an actual physical scanner in all the respects that matter but also be capable of so much more. Imagine such an application that had it all built in:

- trunk tracking ability with 2 SDR devices (one signal, one voice)
- digital format decoding (aka DSD+ working as a potential plugin, perhaps? A dsdplus.dll? )
- all the obvious features and functionality of computer controlled monitoring and then some
- benefits I can't even imagine at this moment for the future

That would be pretty awesome, at least I think so.

 

[slicerwizard]

That's a crappy interface for an SDR. All that screen space wasted on those fixed buttons...

A decent interface would show you all of the systems you're scanning and the banks within them and let you quickly enable/disable system or banks, or hold on any channel or talkgroup, even if the system they're in isn't currently enabled. It would also maintain a list of the channels and talkgroups you'd recently tuned to or held on. Then there's metadata like PTT counts, group sizes, ... And there would definitely be a spectrum display to show you stuff like how you're using way too much gain, etc. And so on and so on. It wouldn't emulate a dumb scanner.

 

[Voyager]

We've got plenty of SDR apps and more cool stuff being created all the time, but sometimes I just long for the simple days with that kind of interface and the ability to make it function exactly like an actual physical scanner in all the respects that matter but also be capable of so much more. Imagine such an application that had it all built in:

- trunk tracking ability with 2 SDR devices (one signal, one voice)
- digital format decoding (aka DSD+ working as a potential plugin, perhaps? A dsdplus.dll? )
- all the obvious features and functionality of computer controlled monitoring and then some
- benefits I can't even imagine at this moment for the future

That would be pretty awesome, at least I think so.

SDR# comes close, but the pieces don't talk to each other.

It has:
DSD+ Plugin
CTCSS decoder with squelch
CDCSS decoder with squelch
Several scanning programs
Recording

What is missing is:
* The ability of the scanning plugins to use the CTCSS/CDCSS squelch plugins for un-muting audio. (it's one or the other, but not both)

* The ability to select which frequencies in the scanning plugins are control channels so you don't get hung up on those.

* NAC decoding

But, SDR# with DSD+ and Unitrunker with the above finishes would make for one heck of a scanner program. A nice GUI would round off the human interface (one that looks like an actual scanner).

 

[br0adband]

And yet a "dumb scanner" ends up being a pretty useful thing considering that's what we've all been using for decades until someone realized the "cheap USB TV tuners" and SDR could be so much more. Sometimes some of us just want to listen in and not have to have some overly complex tool to get the job done.

I think I made it pretty clear with that post above that what I'd like to have isn't basically anything you just described: we already have multiple SDR apps that provide such functionality and they all basically work pretty much the same with the same types of informational displays, what I'm interested is something that is very narrow profile in nature and gives the end user exactly what you said it wouldn't, an emulated scanner interface with the expected functionality without having to have an actual physical scanner.

Least that's what I want, apparently you and some other folk require something vastly more complex - and so do I in some situations - but that's fine, each of us has different requirements and wants for our monitoring hobby. For me personally my "Holy Grail" would be one single application that can use one single tuner like an actual physical scanner has 'cause modern ones don't have two VFOs and get the job done whether I want to monitor a conventional system, a trunked system, analog, digital, or any mixture of any of those. And note I am specifically talking about scanners, not Ham radios with dual VFO capability across multiple bands, not in the same window (i.e. 2M/440 operation) and that means those plain old vanilla "dumb scanners" are still doing more with just one tuner than current SDR software is.

As for the functionality well, since it would be my own programming (meaning the frequencies, TGIDs, RIDs, etc) to make the application work I'd already know what systems I'm scanning, the concept of banks is ancient nowadays, the quick key aspect gives me one touch access to enable/disable systems at will, the concept of holding on a channel or a talkgroup in a system that isn't enabled seems a bit baffling - if it's not enabled, how the hell would it work in first place?.

That application when used with my BC246T years ago does maintain a list of activity and what's been monitored, hit counts, dates/times of first/last activity, etc. As for a spectrum display it wouldn't be needed (but could be there if so desired and enabled at will) since I'd already know the best settings for a given system or even down to the best settings for the given SDR device I'm using. You can see other aspects of it on the preview page:

http://www.scannerbase.com/bc246t_advanced_virtual_control_software/

I think it would emulate a plain old vanilla "dumb scanner" pretty damned well, but that's just me.

Anyway, sorry for running this thread off-topic this much.

 

[Voyager]

I think I made it pretty clear with that post above that what I'd like to have isn't basically anything you just described: we already have multiple SDR apps that provide such functionality and they all basically work pretty much the same with the same types of informational displays, what I'm interested is something that is very narrow profile in nature and gives the end user exactly what you said it wouldn't, an emulated scanner interface with the expected functionality without having to have an actual physical scanner.

Did you miss the part about "A nice GUI would round off the human interface (one that looks like an actual scanner)."? I'm thinking a GUI like ProScan gives. Sorta like the above, but polished.

And I thought that the concept was to basically have a program that makes an SDR function like a current radio scanner. That isn't what you want?

 

[br0adband]

Did you miss the part about "A nice GUI would round off the human interface (one that looks like an actual scanner)."? I'm thinking a GUI like ProScan gives. Sorta like the above, but polished.

And I thought that the concept was to basically have a program that makes an SDR function like a current radio scanner. That isn't what you want?

I was typing that long post when you made yours, I didn't see your post till after I'd made mine, but my post I just made was kinda sorta pointed at slicerwizard and not you.

Never used ProScan so I have no idea what it looks like; the interface for the AVC application I'm talking about is what a scanner actually looks like: it's basically taking the physical interface of the BC246T and translating that to an onscreen interface.

So you (Voyager) and I are on the same page, actually, that's exactly what I want, yep.

Maybe someday it'll happen, I'm pretty sure on that.

ps
Just looked at ProScan's screenshots, so yeah, something like that but that AVC software was doing that type of interface over a decade ago so it was pretty far ahead of the curve thanks to Uniden providing total computer control of the BC246T and BCD396T when they were released.

Maybe the developer of ProScan needs to work on the next big thing: ProScanSDR

 

[Voyager]

Maybe the mods can break these posts (7 to current) into a new thread. I think it deserves that.
EDIT: I asked the mods to do that.

As for ProScan...
ProScan

I think just about anyone would agree those really look nice!

ProScan really is just remote control of existing platforms. They would have to add, well, basically everything I mentioned in post 9. That may be a lot of work based on the fact that so many of the plugins exist and work well - especially like DSD+. I'm not sure many would want to put a commercial venture in that kind of spotlight. I'm sure the reason DSD+ still exists is the lack of deep pockets to go after. I'm also sure ProScan's pockets are deeper and more attractive to certain licensees who may have axes to grind over their IP and its, ummmm, travels.

Now, a platform that simply uses DSD+ and Unitrunker as a plugin - or better yet just talks to those programs? They have zero issues with liability, I would think.

 

[SCPD]

Thankyou all for the detailed explanations, As I'm fairly new to the rtlsdr scene I was having trouble trying to explain what I was looking for & if I was using correct terms so I'm sorry for any confusion.

Br0adband basically nailed exactly what I was trying to explain in this previous post -

Now call me silly or whatever but I read that and interpret it to say: "I'd like to be able to monitor two frequencies using an RTL stick and SDR software: one of the frequencies can be marked/set/tagged as a priority frequency/channel so that even if a transmission is being received on the other frequency the software will switch the tuner back to the priority channel/frequency for monitoring, and when the priority channel/frequency has no more activity, it'll switch back to the second channel/frequency if there's activity or go back to scanning both of them for activity."

I also understand it's probably pointless using Unitrunker to monitor analogue frequencies but for some reason it's just easy for me & works, Sometimes I have issues with sdrsharp freezing up or just using a lot of resources on the pc it's setup on but Unitrunker rarely has a problem.
If I have any frequency I want to monitor I find it easy to just create new voice receiver & punch in the details & hit play & save the profile, I do have a few other digital trunked frequencies I monitor sometimes so it works good with dsd+.

I really need to spend more time reading up & learning to use sdrsharp with various plugins as I mostly just use it for browsing/finding local frequencies as I'm in a rural area so there's limited or seriously outdated information on the net about local frequencies.

I'm slowly picking things up as I go along

 

[br0adband]

Protip: SDR# is not the only SDR software out there.

SDR-Console aka SDR-Radio is another fantastic application, very well supported and offering a ton of possibility but it doesn't have a massive plugin-based extension system like SDR# does. It's also a bit more complex in terms of functionality but it is considered to be (at least by myself and several other people around here) as an incredible piece of software. SDR# gets all the press because it's quick and easy to "install" and get functional but again it's not the only game in town. SDR-Console/Radio, HDSDR, CubicSDR, and several others exist so it doesn't hurt to grab 'em all and play with 'em to get your feet wet that much faster and learn a variety of methods for monitoring.

And yes, SDR-Console/Radio does have a memory system but it won't "scan" in the traditional sense, no. That's where SDR# gets more use and discussion because there are those plugins like the one I mentioned (arguably the most popular one for that application) and people find it somewhat easier to use - it more of a framework to start with and then add functionality with the plugins as each individual requires in their own monitoring setups.

You'll get there, it just takes research, time, and experience.

 

[slicerwizard]

As for the functionality well, since it would be my own programming (meaning the frequencies, TGIDs, RIDs, etc) to make the application work I'd already know what systems I'm scanning, the concept of banks is ancient nowadays, the quick key aspect gives me one touch access to enable/disable systems at will

Ah yes, having to remember numbers to turn systems on and off in a computer program - that's so cutting edge...

the concept of holding on a channel or a talkgroup in a system that isn't enabled seems a bit baffling - if it's not enabled, how the hell would it work in first place?.

Genuinely sorry for introducing advanced concepts that are baffling to you.

 

[Voyager]

SDR-Console aka SDR-Radio is another fantastic application

SDR-Console is advertised as being free.

I've heard claims (that I've never personally followed up on) that SDR-Console works for a while, but then stops working unless payment is made. Do you know if that is true?

 

[br0adband]

It's technically a commercial piece of software as I understand it, but the developer offers it for non-commercial aka home/hobbyist use for free. The way it works is it includes a license file that does expire after a certain amount of time on a certain date but the reason for that - with respect to the home/hobbyist version - is because the developer releases updates for it so, when he does a new version or update it's expected that you'll install that and the license extends with the updated version. There's more info here:

Here's a version 2 Licence

(and for the record the most current license which you can use expires on July 1, 2016 - my currently used one would have expired on January 7th, a few days from now, but I just added the new key and I'm good to go for the next ~6 months now)

I've been using it without issues for 2+ years now, never had a single issue with it not working because of some license issue and I do update it whenever new builds are released. There is a chance - ain't there always? - that the developer might decide to make it a pay-for-play application later this year, but again that's a non-issue for me: considering all that his application is capable of (which is quite considerable) I think it'll be worth what he might ask for it. I have no idea how much that might be and I don't suspect it'll end up being some crazy pricing but even so, I'd more than likely pay for it if it does become that type of application.

v3 should be coming soon with some new features and functionality so that's something to look forward to as well.

 

[Voyager]

Thanks for the clarification. That sounds like forced updates. Can you imagine if Uniden tried something like that what the response would be?

I'm also not crazy about the prospect that I may install SW that may have an as-yet-undisclosed purchase price. A term comes to mind, but I'm not going to "go there".

 

[br0adband]

Well there's 6 months of use till the current license expires (on top of the 2+ years I've been using it free by design), free of any monetary cost, take it or leave it, and it could continue being free to hobbyists which has traditionally been the idea as stated there on the licensing info page - it's not that tough to figure out.

I'm sure as hell not going to pass it up because it's an incredibly useful piece of software.