Multiple RTL-SDRs Question

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snowbranch
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Multiple RTL-SDRs Question

Post by snowbranch » Thu Jan 09, 2020 7:40 pm

I've only recently taken up SDR and HAM so I apologize in advance for my ignorance.

I recently acquired 2 of the rtl-sdr dongles. I have a very basic question which I did not see answered here or even via Google. I installed both dongles (Windows 10, used zadig.exe on both) and when I try them separately on SDR# I successfully see frequencies and can hear local FM stations, etc. But when I have them both plugged in simultaneously, I don't see a way to select them individually, nor is there a hint that both are in use. For the input, the only relevant option is the same that is always there, RTL-SDR (USB).

Does this mean:

1. Despite having 2 dongles, only one is active in SDR#? (How to determine which?)
2. Does SDR# automatically combine the reception power of the two devices to enhance the signal reception?
3. Is there supposed to be a way to select them individually, but I don't see it? (And, alternatively, to manually combine them?)
4. Something else?

I have verified that both dongles are doing their thing. While I failed miserably with Unitrunker 1.x, I got a hold of Unitrunker 2.x and in a fraction of the time I spent trying to get Unitrunker 1.x and DSDplus to work, successfully tuned into my local P25 LEO dispatch network, using each dongle. (Uni 2.x is like a tiny miracle!)

I see many comments here and on the web about the benefits of having two dongles, even in SDR#. I'm trying to figure out whether or not I'm already enjoying them or need to take extra steps to get them to play nicely together within SDR#.

Thanks in advance,
snowbranch

rtlsdrblog
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Re: Multiple RTL-SDRs Question

Post by rtlsdrblog » Fri Jan 10, 2020 3:01 am

You can select them individually. With two plugged in, go into the configure menu in SDR# (the cog icon next to the play button), and then you can select the individual device.

You can't combine the two together for better reception (unless you do something much more complex with coherency, see our KerberosSDR for info on that)

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Re: Multiple RTL-SDRs Question

Post by Username » Fri Jan 10, 2020 5:27 pm

You can change the serial number --> https://rtl1090.com/installation-manual-2/ --> eeprom

snowbranch
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Re: Multiple RTL-SDRs Question

Post by snowbranch » Fri Jan 10, 2020 8:01 pm

Thanks rtlsdrblog. I had been looking in the place you check the source but not the cog icon. I can see them both, there.

I'm interested to know what kinds of things I can do with multiple rtl-sdrs beyond following trunked channels. Should be a fun journey!

Thanks for knocking my easy question out of the park!

snowbranch
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Joined: Thu Jan 09, 2020 2:50 pm

Re: Multiple RTL-SDRs Question

Post by snowbranch » Fri Jan 17, 2020 2:03 am

Well, maybe I broke one or more of them or maybe I didn't. I ended up with 3, because I wanted to use 2 with unitrunker (2.x; I had this working before purchasing the 3rd) and use the 3rd simultaneously on SDR#. With as much hassle as I had trying to figure out which radio was which when I only had 2, I figured with 3 I may as well try to change the serial numbers using eeprom as mentioned above.

Unfortunately, I could not find clear instructions on how exactly someone RUNS eeprom. Many forum posts and Google reference linux, and I'm on Win 10. They also seem to imply that there is some installed software for the dongles, such that I need only open up a command line and append the eeprom line. But I can find no such software.

So, I ended up checking out the GUI created by Joanne, referenced here: https://www.rtl-sdr.com/tag/rtltool/

This seemed to do what I needed. Unfortunately, it seemed that I did not do something properly as 2 of the 3 rtl-sdrs have little stars next to them. Only the third, most recent one does not have a star. I cannot re-open the other dongles. I suspect that I was supposed to click on 'close dongle' after changing them, but not understanding the significance, I merely hit 'exit' after changing each one. But I don't know if that is the case. This is just more information to help me solve the problem.

And what is the problem?

Well, on SDR# it now lists 5-6 separate devices, 2-3 of which if you click them say 'this device is no longer available.' By going through them individually, I do find 3 unique devices which successfully receive a signal, which I find encouraging. However, in Unitrunker, 6 devices are listed, but only 1 of them seems to work at a time. And here is the real kicker--all 6 devices have unique serial numbers, none of which are the ones that I set in the GUI.

I tried removing all the devices and then deleting all drivers/etc to try to start over 'fresh.' But I get the same results--2 of the 3 dongles cannot be opened in Joanne's GUI, all 3 work in SDR# but there are between 2-3 phantom dongles depending on its mood, and only one device at a time works in Unitrunker (you need 2 to hear anything!)

How can I get back on track here?

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Re: Multiple RTL-SDRs Question

Post by Username » Fri Jan 17, 2020 10:08 am

which software did you use?

snowbranch
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Re: Multiple RTL-SDRs Question

Post by snowbranch » Fri Jan 17, 2020 1:53 pm

The GUI created by Joanne, referenced here: https://www.rtl-sdr.com/tag/rtltool/

RtlTool.exe

snowbranch
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Re: Multiple RTL-SDRs Question

Post by snowbranch » Sat Feb 08, 2020 9:04 pm

I've made progress on this and want to share what I did so others who have similar issues may find a way forward.

First of all, as a correction to the above, you don't actually need 2 radios to use unitrunker 2.x, but it may be advised.

More to the point, I ended up contacting Joanne directly. She was extremely helpful in helping to isolate a big part of the problem. Essentially, no matter what changes I was making to the devices by uninstalling, reinstalling, etc, the registry entries were holding me back. Once I deleted the registry entries and then went through the process again, it was easier to discover that my best solution was to use eeprom to reset each device to their default settings, and then move on from there.

However, while this knocked some of the 'ghost' dongles off, it still remained that when I loaded unitrunker 2.x, multiple dongles were displayed beyond what I actually had plugged in, and Windows Device manager showed 2 devices for each one plugged in.

I found my solution hinted in this thread here:

https://forums.radioreference.com/threa ... rt.400469/

"You have a phantom third RTL device because you probably installed the driver with zadig to the bulk-in interface. You want to actually install the driver to the RTL2838UHIDIR (Composite Parent) device."

Combined with something said in the Unitrunker 2x group that explained that these devices, from the POV of the computer, have two separate USB components; thus the advice to install the drivers to bulk interface 0, and not bulk interface 1. However, using the radioreference tip, I enabled zadig to show composite devices and I saw that my RTL2838UHIDIR devices were showing default generic USB drivers, and not WinUSB ones. I installed WinUSB to each of the RTL2838UHIDIR devices (plugged in, one at a time), and all of the ghost dongles completely disappeared, leaving just the three distinct RTL2838UHIDIR devices.

Not sure where the problems started, exactly. I was trying to change the serial numbers of the devices but I think I was trying to write to one or more of the 'ghost' dongles, got confused, or at anyrate, got to the point where the devices wouldn't respond correctly and consistently anywhere.

I don't know if there are downsides to installing the drivers to the composite (RTL2838UHIDIR) rather than bulk interface 0, but so far in the places where I am concerned (SDR# and Unitrunker 2x), the radios appear to all be working as designed.

Thanks all for help. And good luck.

SB

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