Linux SDR scanning advice

[ssilicon]

Hello everyone. I'm interested in expanding my scanning horizons. I have some experience with scanning with dedicated devices (ie scanners). However I want to explore the world of SDR scanning.

I am primarily a Linux user. I prefer Linux native software or native Linux builds of multi-platform software, but am willing to run something under WINE or Virtualbox if it's cool enough. I'm not really too much interested in rebooting into Windows (dual boot) to run scanning apps, as I tend to like to run them in the background while I do other things.

I have a good, roof mounted, wide band discone antenna available for my scanning needs (when not switched over for my ham use). Yes, I already have a quality antenna switch so that only the same radio I am transmitting from is connected to the antenna (and no other radios etc.).

Currently, I own a couple of RTL-SDR V4 devices which I have used successfully with SDRangel (well just one of them, but they are the same model). I bought 2 of them because it is my understanding that due to their rather limited ~2MHz bandwidth (not frequency range), you need at least 2 for trunk scanning. One of them to monitor control and the other to hop around where control dictates. Anyway, to use more than one receiver simultaneously like that, I would need to split my antenna feed into as many paths as I have receivers going. Due to my knowledge as a ham and other experience, I suspected that a crude Y type splitter might not provide great results. After researching a bit I came to understand that a device called a multi-coupler is what one would use. I've seen some out there on the web, with varying prices and frequency ranges capability. My discone has a receive range of 25MHz to 3GHz. While I suppose I could have an occasional or potential interest in scanning that wide, my main scanning interests lie around in ham, public safety etc. so VHF, UHF and 800MHz and so forth. I don't recall much going on in my area past the 800MHz stuff (but I know where to look to check on that ).

So what are some thoughts some of you SDR scanning veterans might have to offer? Should I just set one of my hand held trunk tracking scanners up on the desk with a whip antenna, as that is probably good enough to get the local 800MHz P25 system pulled in and then play conventional scanner with one of the RTL-SDRs I already own using the roof discone? Now that I write it out, that does seem like the more responsible, reasonable approaches. Or what might be a more compelling reason to look into a multi-coupler, or a wider bandwidth SDR like a HackRF (20MHz bw) or LimeSDR (60MHz bw).

What's some good scan software for me as a Linux guy? SDRangel is really cool, but it is not a scanner app. I am able to take my measly 2MHz bandwidth RTL-SDR and monitor a crap-ton of public safety type conventional FM stations centered around 155MHz all at once with it though! That's just cool. Anyway, what do you all think?

 

[JimmyJet727]

Definitely give sdrtrunk a try. Runs very well on Linux Mint.

GitHub - DSheirer/sdrtrunk: A cross-platform java application for decoding, monitoring, recording and streaming trunked mobile and related radio protocols using Software Defined Radios (SDR). Website:

A cross-platform java application for decoding, monitoring, recording and streaming trunked mobile and related radio protocols using Software Defined Radios (SDR). Website: - DSheirer/sdrtrunk

github.com

As for determining how many dongles are required, here is a very helpful tool. Just copy/paste the frequencies from your radio system of choice from the RR database.

SDR center frequency calculator

 

[ssilicon]

Thanks for your tips Jimmy. The calculator is convenient. Before I just examined my lowest freq and highest one, made sure they were less far apart than the max bandwidth and then divided by 2 and added it to the low freq to get my base freq. I'll look at sdrtrunk. It's one I've seen pop up on my wanderings already (along with a number of others).

What are some of you others using?

 

[bhall7]

Trunk Recorder (GitHub - TrunkRecorder/trunk-recorder: Records calls from a Trunked Radio System (P25 & SmartNet))
SDR++ (Release SDR++ Nightly Build (currently 1.2.1) · AlexandreRouma/SDRPlusPlus)

 

[cheap_ottawa_scanner]

I like to use the combination of SDR++ and DSD-FME (GitHub - lwvmobile/dsd-fme: Digital Speech Decoder - Florida Man Edition) for everyday monitoring with call recording (if you want to enable it). Performance wise it will do pretty good single sdr trunk tracking depending on system size etc.

For example I am using two dongles 24/7 right now to monitor two systems. Using the fact the SDR++ lets you add more radio VFO's means I can cover every single channel on both systems and then pipe them into DSD-FME and record every single decoded call.

A quality of life thing to do is to look at how to change the serial number on the sdr dongles so it becomes easier to organize using more than one at a time. rtl_eeprom or something similar is what I have used in the past (you really only need to do it once per dongle)

 

[ssilicon]

More good tips thanks. I have just been digging into SDRtrunk for the past couple hours. It seems quite good. I will take a hard look at SDR++ after I get a handle on what SDRtrunk is capable of.

Funny you mention about serial number. I ran rtl-test:

> rtl_test
Found 1 device(s):
  0:  RTLSDRBlog, Blog V4, SN: 00000001

Yeah... I'm sure my actual unique SN is 00000001! I appreciate the tip. And you were close, rtl-eeprom is the command to change it (among other things).

 

[ssilicon]

Greetings folks. Okay, so I have begun to play around a bit with SDRtrunk. I will look at SDR++ coming up in the future yet when I'm ready to dive into that one. For right now though, I would appreciate if someone with the specific answer could answer this more specific question for me: Does SDrtrunk, SDR++, or some other software allow a mode of operation where the software will scan more in the way that an actual hardware scanner does? What I mean by this is have a big list of frequencies to scan, which can span well beyond the scope of bandwidth of the SDR receiver, and the targeted frequency keeps being adjusted to the next entry in the list to scan. This would be in the same way scanners have been operating even well before SDR technology was involved. As of right now, I have dove into SDRangel and SDRtrunk. Both programs are really impressive from what I've seen so far, but seem to require that everything you want to scan all falls within the bandwidth of your SDR receiver or combined multiple receivers.

Now don't get me wrong, I think it's really cool to be able to keep track of several individual frequencies at the same time. But as cool as that is, and it is and has it's time and place, I think that is more accurately called monitoring. Is it not just possible to have software which rapidly, systematically, and in succession, focuses on one frequency at a time and not be concerned about having enough bandwidth to also pick up other frequency targets simultaneously? That's what I think is more appropriately called scanning. The only limit for an SDR to function this way would be it's effective frequency range. Bandwidth would only have to be wide enough to handle what would be needed for the expected signals to be processed; for example 50KHz for FM comms. Even if money is no object, I think one might be hard pressed to find gear which can literally listen to all possible frequencies of interest simultaneously. And believe me, cost does matter to me. Hehe.

Perhaps what I will call the scanning mode is supported in the software already mentioned here? If so, I just haven't discovered it yet. I have dug into the docs of SDRangel and SDRtrunk at a greater than casual level, but not yet microscopically. I don't mind really digging into documentation for specifics if I know the ore is there to mine, but it's hard to justify going full IRS audit level for answers that might not even be findable. That's where I hope the great community of RR is able to definitively point to what's worth deep diving into and save a brother some time and effort.

 

[RobDLG]

What I mean by this is have a big list of frequencies to scan, which can span well beyond the scope of bandwidth of the SDR receiver, and the targeted frequency keeps being adjusted to the next entry in the list to scan.

For conventional channels, RTLSDR-Airband will scan in this manner.

 

[merlin]

Not much advice here, I run a Debian platform and heve Airspy HF Discovery and have Noo Smart T with SDR sharper.
Both just simply run just like in Windows. I don't recall how I loaded the drivers, probably Zadig. it runs on Linux also.
You should have no problems with 'rtlsdr-Airband', I will try it.

 

[Enjoi19]

I don't recall how I loaded the drivers, probably Zadig. it runs on Linux also.

Zadiag is specifically for Windows.

Pretty well works out of the box on Linux. Some systems may need some permissions updated and drivers blocked.

 

[DC31]

For conventional channels, RTLSDR-Airband will scan in this manner.

Yes, RTLSDR_ airband does just what you describe. What you are talking about appears to be scanning ANALOG channels much like an analog scanner would. SdrTrunk and most of the others are focused more on digital/trunking system monitoring

 

[Enjoi19]

SdrTrunk and most of the others are focused more on digital/trunking system monitoring

Not at all - SDR Trunk does excellent analog, I use it for several areas, as well as Trunk-Recorder does it fairly well too, including on some SmartZone systems I monitor still.

 

[ssilicon]

Not at all - SDR Trunk does excellent analog, I use it for several areas, as well as Trunk-Recorder does it fairly well too, including on some SmartZone systems I monitor still.

Yes, it does excellent analog... as long as all the channels you want to scan fit within the (usually more limited than you would like) bandwidth of the SDR receivers(s) in use.

To scan a list of channels that do not fit nicely into that bandwidth, you basically have two solution directions to go:

1. Expand that bandwidth capability. Either by:
   1. Upgrading to an SDR which has all the bandwidth you require built right in.
      1. Can you even find one that meets the requirement?
      2. If you can find one, can you afford (or wish to afford) to purchase it?
      3. Is it so uncommon (likely due to its massive cost) that it is not adequately supported by enough software?
   2. Purchasing multiple cheaper SDRs and allowing the software to make use of the combined bandwidth of the several devices.
      1. An issue with this route though is the antenna situation.
         1. One antenna can be split to feed multiple receivers by use of a multi-coupler.
            1. Finding a multi-coupler which can pass all the bandwidth you require may likewise be too expensive or maybe even impossible to obtain at all.
         2. Provide each individual receiver it's own dedicated antenna. If you just want to use cheap, simple table-top telescopers, this might work; if you have the table space and you are satisfied enough with the performance level of the antennas. I'm not sure the performance would satisfy me, but I know I don't really want to burn up the space.
2. Or, find and use software which works more like a traditional dedicated scanner device.
   1. Bandwidth requirements are very modest, since only one frequency is processed (at a time). The bandwidth requirements would only be as big as needed to handle demodulating whatever type of signal used at the most demanding single frequency.
      1. Therefore, even a single cheap RTL-SDR can more than handle the job.
      2. Since only one receiver is needed, only one single antenna is needed; foregoing all the ugliness outlined above.

I have a very nice roof mounted wide band (meaning frequency range) antenna. I would love to leverage it's performance so a solution that allows me to use just one antenna is what I'm shooting for. Due to the issues outlined previously, this makes software which operates (or has a selectable mode of operation) more like a traditional dedicated scanner device probably the most attractive to me.

I really appreciate the feedback you people are providing. It looks like I will have to explore RTL-SDR Airband software. The name seems to imply it might specialize in air band. If so I hope it doesn't have limits which get in the way of non air band. Time will tell.

 

[ssilicon]

More good tips thanks. I have just been digging into SDRtrunk for the past couple hours. It seems quite good. I will take a hard look at SDR++ after I get a handle on what SDRtrunk is capable of.

Funny you mention about serial number. I ran rtl-test:

> rtl_test
Found 1 device(s):
  0:  RTLSDRBlog, Blog V4, SN: 00000001

Yeah... I'm sure my actual unique SN is 00000001! I appreciate the tip. And you were close, rtl-eeprom is the command to change it (among other things).

Correction:

It seems in linux that the commands are accessible either by the underscore (rtl_eeprom) or dash (rtl-eeprom) nomenclature. I'm not sure about Windows.

 

[WMaScanner]

Yes, it does excellent analog... as long as all the channels you want to scan fit within the (usually more limited than you would like) bandwidth of the SDR receivers(s) in use.

To scan a list of channels that do not fit nicely into that bandwidth, you basically have two solution directions to go:

1. Purchasing multiple cheaper SDRs and allowing the software to make use of the combined bandwidth of the several devices.
   1. An issue with this route though is the antenna situation.
      1. One antenna can be split to feed multiple receivers by use of a multi-coupler.
         1. Finding a multi-coupler which can pass all the bandwidth you require may likewise be too expensive or maybe even impossible to obtain at all.

I have a very nice roof mounted wide band (meaning frequency range) antenna. I would love to leverage it's performance so a solution that allows me to use just one antenna is what I'm shooting for. Due to the issues outlined previously, this makes software which operates (or has a selectable mode of operation) more like a traditional dedicated scanner device probably the most attractive to me.

I mangled your quote a bit, but I am in a similar situation to you but on Windows. Multicouplers are analog devices and do not have any limit on the "bandwidth" they can pass - they will have a frequency range they can pass through (although these are very wide), but there is no limit on the amount of 'data' they can pass through as it is analog. An active multicoupler output will be more or less the same as its input, if your antenna can get 460 MHz, your output will also get 460 MHz. Each output can use the same frequency range.

For my setup with similar goals as you, I have a Stridsberg Engineering MCA204MIL 4-output multicoupler that passes 25MHz to 1 GHz hooked up to the end of my discone coax and run SDRTrunk with a SDRPlay RSPDx-r2 (which works wonderfully) monitoring an 800mhz trunk, play around with a HackRF One to monitor other digital stuff (although I find its performance very poor, very poor frequency stability, very prone to overload from pagers etc) and two analog scanners to monitor the analog frequencies I scan through.

I'm considering getting an SDRPlay RSP1B to also use with SDRTrunk, it's only $140 at HRO and seems to have much the same performance as the RSPDx-R2 in the VHF and UHF range, and I can't really overstate how great the RSPDx-r2 has been, 10 MHz of bandwidth with very good filtering and sensitivity.

For your situation already having a good antenna on the roof a multicoupler and more SDRs or analog scanners is absolutely the way to go. Stridsberg is the go-to, there are some posts in the forum here about ways to build your own with higher performance for cheaper, but that was a bit above my level.

You'll see posts in the forum about Stridsberg being hard to get a hold of recently, I just bought the multicoupler last month, their communication wasn't great and it took a couple of weeks to get to me, but it did come and they were very nice and helpful on the phone when I did get a hold of them.

 

[ssilicon]

Hey WMA... Yeah I fully understand the bandwidth vs frequency range concepts. It's just that in radio lingo, the term band is often legitimately used to describe a range of frequencies. For example the amateur radio 2 meter band (USA) is from 144 Mhz to 148 MHz. And by extension, bandwidth is often used to describe how large the gap is between the lower and upper boundaries of that band (or range of frequencies). So what I mean by limits for the multi-couplers is what frquency ranges they can properly pass on to each of the attached antennas.

Take for example the brand you mentioned, Stridsberg. It looks like the highest frequency any of their models support is 1 GHz. I think a typical RTL-SDR can tune from 0.5 MHz to 1766 MHz, or 500 KHz to 1.766 GHz. My Diamond discone antenna has a usable receive frequency range (sometimes referred to as bandwidth) of 25 MHz to 3 GHz. And even though it might be less common than some other bands, there are things allocated spectrum up there that might be of interest to a scanner enthusiast. For example the 13 cm ham band has allocation in the 2.3-ish and 2.4-ish GHz frequencies. I haven't seen a multi-coupler yet that handles what a cheap RTL-SDR can tune less less alone what my antenna can offer. For you, with an antenna that tops out around 1 GHz those multi-couplers can meet the challenge and I agree that's probably a good fit for you. And truthfully, if I can decide to live without what's past 1 GHz, it might be a fit for me too. I appreciate the info. I'm not at decision phase yet though. Keep it coming!

 

[WMaScanner]

I also have a Diamond D130N and have heard that its real-world performance above 1GHz isn't really that good - it's definitely not as good at ADSB as a dedicated antenna - but more to the point I don't think there is virtually anything above 1Ghz of interest to the scanner listener. I've poked around the RRDB quite a bit just seeing what is out there and I have never seen anything above the 900Mhz band. There are those ham bands in the 1.2 and 2.3 GHz bands (and even up to the 1mm band at 250 Ghz!) but those are limited to hyper enthusiasts with specialized equipment and are not in common use. Those higher frequency bands are also quite short ranged, as well - there is a reason wifi is at 2.4 Ghz and not shortwave! Higher frequencies also suffer from significantly more fixed-line losses in coax, so the signal coming from your Diamond on the roof - which will be great in VHF and UHF - will be significantly attenuated by the time it gets down to your SDR. People who seriously track ADSB (which is really the only notable thing of "scanning" interest I would say above 1Ghz) will usually have a dedicated 1090Mhz antenna with an RTL-SDR running off of a Raspberry Pi right there with less of a foot of coax to minimize feedline losses.

Of course - if you are ever actively playing around with your radio stuff, and want to see what is out there above 1Ghz, you can just unplug your multicoupler and hook the antenna feedline right up to your SDR and see all there is to see - there is interesting stuff like satellites above 1Ghz, but that's not something you really "scan" like you would public safety frequencies, you would generally see when it is coming, and point a directional, tuned antenna at it, not a discone.

All that being said, it's a fascinating hobby, and an SDR and a discone on the roof is a great way to see the all kinds of different stuff out there, but I would definitely invest in a better SDR (SDRplay or Airspy - the RTL-SDRs are great for what they are, and the price, but the sensitivity, dynamic range, and resistance to interference leave something to be desired) and a multicoupler and get to work!

P.S. The Sigid Wiki is a great resource to see what is out there and ID new signals - you'll see there is not much above 1Ghz besides satellites

Signal Identification Wiki

This wiki is intended to help identify radio signals through example sounds and waterfall images. Most signals are received and recorded using a software defined radio such as the RTL-SDR, Airspy, SDRPlay, HackRF, BladeRF, Funcube Dongle, USRP and other devices.

www.sigidwiki.com

 

[DC31]

I really appreciate the feedback you people are providing. It looks like I will have to explore RTL-SDR Airband software. The name seems to imply it might specialize in air band. If so I hope it doesn't have limits which get in the way of non air band. Time will tell.

Please report back on your experiences here. Yes, the name is misleading.

 

[ssilicon]

I also have a Diamond D130N and have heard that its real-world performance above 1GHz isn't really that good - it's definitely not as good at ADSB as a dedicated antenna - but more to the point I don't think there is virtually anything above 1Ghz of interest to the scanner listener. I've poked around the RRDB quite a bit just seeing what is out there and I have never seen anything above the 900Mhz band. There are those ham bands in the 1.2 and 2.3 GHz bands (and even up to the 1mm band at 250 Ghz!) but those are limited to hyper enthusiasts with specialized equipment and are not in common use. Those higher frequency bands are also quite short ranged, as well - there is a reason wifi is at 2.4 Ghz and not shortwave! Higher frequencies also suffer from significantly more fixed-line losses in coax, so the signal coming from your Diamond on the roof - which will be great in VHF and UHF - will be significantly attenuated by the time it gets down to your SDR. People who seriously track ADSB (which is really the only notable thing of "scanning" interest I would say above 1Ghz) will usually have a dedicated 1090Mhz antenna with an RTL-SDR running off of a Raspberry Pi right there with less of a foot of coax to minimize feedline losses.

Of course - if you are ever actively playing around with your radio stuff, and want to see what is out there above 1Ghz, you can just unplug your multicoupler and hook the antenna feedline right up to your SDR and see all there is to see - there is interesting stuff like satellites above 1Ghz, but that's not something you really "scan" like you would public safety frequencies, you would generally see when it is coming, and point a directional, tuned antenna at it, not a discone.

All that being said, it's a fascinating hobby, and an SDR and a discone on the roof is a great way to see the all kinds of different stuff out there, but I would definitely invest in a better SDR (SDRplay or Airspy - the RTL-SDRs are great for what they are, and the price, but the sensitivity, dynamic range, and resistance to interference leave something to be desired) and a multicoupler and get to work!

P.S. The Sigid Wiki is a great resource to see what is out there and ID new signals - you'll see there is not much above 1Ghz besides satellites

Signal Identification Wiki

This wiki is intended to help identify radio signals through example sounds and waterfall images. Most signals are received and recorded using a software defined radio such as the RTL-SDR, Airspy, SDRPlay, HackRF, BladeRF, Funcube Dongle, USRP and other devices.

www.sigidwiki.com

Of course, nothing really ever is as good as a dedicated antenna. But I can't (or won't) justify many different dedicated antennas applicable to various areas of interest. For me, compromise antennas are where it's at because my house is only so big and for that matter so is my budget. Right now up on the roof I already have: an outdoor WiFi access point, a large VHF/UHF/FM TV antenna, and a Diamond D3000N discone. I plan to in some way or fashion, the specifics are not yet decided upon, also add some kind of HF antenna. For me, in my situation, that's going to be plenty. I wish I could just go hog wild but alas, reality. I'll also add that my discone has an N connector (thus the N in the model name). As I'm guessing you already know, based on the fact that you got a D130NJ instead of a D130J, PL259/S0239 connections aren't as friendly to frequencies above 2 meters. So my discone with N connector is connected to my N connector based Apha Delta antenna switch, via genuine Times Microwave LMR400 feedline.

The D3000N is just a somewhat upgraded D130NJ. I'm not sure where your (anecdotal?) evidence of poor performance is on the Diamond discones, but mine has worked very well for me thus far. In fairness though, I haven't personally had much to compare it to. What it has let me do is pretty good VHF/UHF ham transceiving and also some good scanning.

Crap, I have to run right now, but I'll pick up on this a bit later.

 

[WMaScanner]

I also have a full run of LMR400, it works well. I don't have a cite for it, but I have read in a couple different places that both of those discones aren't great above 1Ghz, I do believe the 3000 is better than the 130 at that though. It should be noted that most everything above 1Ghz is either very specialized or very short range, unlike HF, VHF and UHF which we are awash in...

Both of those discones will work great in VHF and UHF (and you'll be able to pick up more than you'd think in HF as well) and it sounds like you have the start of a great setup - my only point with all of this was to say don't let lack of above-GHz performance dissuade you from a good VHF/UHF multicoupler like the Stridsberg, because that would be the perfect complement to the D3000/LMR400 setup you already have if you want to add more receivers.