New to SDR, problems interfacing with Unitrunker

[CPAJ]

Hello,
I am an experienced scanner but new to SDR. I recently purchased a cheap SDR offline. The only writing on the actual usb is "DVB-T+DAB+FM" and "Digital Video Broadcasting USB2.0". The sdr on eBay is titled "NEW USB DVB-T & RTL-SDR Realtek RTL2832U & R820T DVB-T Tuner Receiver MCX Input" is here: NEW USB DVB-T & RTL-SDR Realtek RTL2832U & R820T DVB-T Tuner Receiver MCX Input .
It also states "The RTL2832U outputs 8-bit I/Q-samples, and the highest theoretically possible sample-rate is 3.2 MS/s, however, the highest sample-rate without lost samples that has been tested so far is 2.8 MS/s."

I have gotten the receiver to work with SDRsharp without difficulty using sharp's latest version. It tunes to FM or analog conventional frequencies as intended (with the exception of needing some slight tuning outside of the FM Broadcast band which I will elaborate on further below).

When I open up unitrunker is when I have the issues. I have tried a few combinations of settings to allow the Unitrunker to register the dongle. I have selected RTL2832 as receiver type and it will not feed back data. My intended purpose is to analyze P25 control channel data just as Unitrunker would do when using a discriminator tapped radio or other inline source. I do not need to actually use the SDR to decode or follow voice. I am trying to get a setup feeding the CC data to Unitrunker to analyze only like an inline source. Yes, I have selected to utilize the raw signal in the upper left column where you choose am/wfm/raw/etc.

Is the problem that my dongle does not have the required components that are compatible with Unitrunker? Am I mistaken in thinking that I do not need to set up a virtual; audio path since Unitrunker now incorporates RT2832?

It is also worth nothing that I have tried to get the sdr stick to work with SDRtrunker but it does not recognize it in that program, where as in SDRsharp the dongle shows. I believe that is because SDRtrunker is only configured to accept a few select SDR's at this time.

So that encompasses my first dilemma - getting the SDR, which registers in SDRsharp, to work along with Unitrunker to act as a signal radio to display CC information. If someone maybe has some screenshots or can describe the exact settings that should be selected when adding a new received to Unitrunker that would be great.

My second issue is minor but I need help. In SDRsharp the FM broadcast stations tune in just fine. When I go upwards to higher frequency bands the receiver is off by a few frequencies. Nothing drastic, but something that is actually transmitted on 500.000 might show as being on 500.175 on the program. This is a tuning issue and I have not found a way to tune these frequency errors in the program. This is important when locking into a control channel because Unitrunker knows the correct frequency that the CC is on but the SDRsharp program is showing a different freq. How do I correct/tune frequencies that I know are slightly off of their actual transmission frequency in SDRsharp?

Could the fact that the CC is drifting off the actual frequency in SDRsharp be the reason Unitrunker is not working? I do not believe this is the case because Unitrunker is indicating that it cannot get the configuration to even set up or recognize (I forget the exact error message warning the receiver setup gives but will provide it if this remains unresolved).

Finally, how do I set the audio threshold at unity to I do not hear the static on a conventional frequency until it is keyed up in the SDRsharp program?

Sorry for long post and thank you for any help.
-SDR Newbie

 

[br0adband]

As long as the Zadig drivers are installed properly meaning in Device Manager you'll see two entries like so:

and you can use something like SDR# to tune a frequency and it "works" then using Unitrunker to do what you want is relatively simple (given everything is working as just stated). Try these steps (and I'm doing them myself as I'm typing this to know it works for me based on past experience of doing this many times):

1) run Unitrunker

2) click the + button to create a new receiver (regardless of whether you have any already or not, for this example)

3) choose RTL2832

4) on the window that pops up (enlarge it a bit vertically so you can see more info at one time) we're going to change it to just 1 VCO so on the Info tab (should be displayed by default) click the VCOs section and adjust it to 1 VCO

5) set the Sample rate to 0.96 msps (that should be the default, you can change it if you really want to but since your intention is to monitor only the CC there's really no reason to change the default)

6) click the RTL Device section and select the one RTL device that should be visible as long as the Zadig drivers are installed properly and you've tested SDR# to make sure it can "see" the RTL stick and it's working - if it's not working or the drivers aren't installed properly then when you attempt to choose the device here there won't be anything listed - if that's the case you have to get the drivers installed properly and verify the device is visible to the OS and software first or Unitrunker will never be able to use it either

7) assuming everything in #6 is positive you should see the "Bulk-in; Interface (Interface 0): xxxxxxxx" info listed there in that section now (the x's represent a device ID and it may or may not be the same as mine hence me using x's)

8) in the Correction section you need to enter the ppm correction value for your stick - based on the info you provided you have one of the older "original" RTL-based sticks that use the R820T tuner chip (and not the newer improved R820T2) so that also means your stick will suffer from drift when it warms up to operating temperature. I can't tell you what the ppm is going to be but it typically can be anywhere from as low as 10 to as high as 80 so you're going to have to use SDR# to figure out what it is. If you don't already know what the ppm is - and I'm guessing you don't considering you mentioned that everything seems to be "off frequency" then here's the simplest manner I can suggest from another post I made to help someone else:

http://forums.radioreference.com/software-defined-radio/328894-sdr-problem.html#post2543335

Once you know the ppm for the stick (and if you have more than one stick they'll pretty much be different every single time so mark them with a marker or a piece of tape and write the ppm value on it so you're always aware of which one is which) then you can proceed but until then this isn't going to work well if at all - digital modes require much more precise tuning than analog broadcasts and if you're off-frequency by even a just 1 or 2 ppm (that stands for parts per million) it can totally wreck the decode of a digital signal completely.

9) Once you know the ppm input it as instructed and then check the Drift Correct box (this helps keep Unitrunker "on frequency") - newer RTL-based sticks using the R820T2 (the 2 means "second generation" basically) often will have an improved crystal oscillator which is temperature controlled and doesn't changed based on the heat of the stick whether it's cold or warm (the specs will list a TXCO or temperature controlled crystal oscillator) and the ppm is typically 1 or 2 literally meaning it's just off 0 itself. Your stick is not one of those so this ppm adjustment is incredibly important for proper operation and you're going to get nowhere until it's figured out and input as required.

10) Most everything else at defaults should be fine on the Info tab, you can check the Auto Gain box if you want, it's up to you.

11) Click the VCO tab at the bottom and the first thing I'd suggest is to go ahead and put in the CC frequency in the Park section.

12) Uncheck the following boxes:
- Analog
- Motorola
- EDACS48
- EDACS96
- MPT1327

and check the following boxes:
- P25
- APCO P25

This ensures that Untrunker is only going to be listening for P25 data and everything else gets ignored.

13) Adjust the volume on your speakers to a low point and then click the Play button and if everything has been done correctly up to this point you should get activity, you should be able to hear the typical 'growl' of the control channel data stream and in a few seconds (assuming you have a good signal strength as noted in the Health section (a measurement of the signal quality) a secondary Site window should pop up with the actual system data you're looking for and it should display talkgroup info scrolling by assuming it's an active system at that moment.

Now's the time to go back to the Receiver window and check off the Mute box to quiet that down since nobody gets much use from actually listening to a CC constantly.

I just followed those steps I laid out in that order and created a "new" receiver for my R820T stick tuned to 853.90000 MHz (a primary CC for a very large and very active system in my area for P25 Phase I comms) and it took about 30 seconds at most (not counting the time I was typing) to get that Site window popup and see activity so this should work in your case as well. Signal strength from the site/system you're hoping to monitor will play into this situation so again keep an eye on the Health section to see how it's going. The Site window will offer you a visual representation as well in the upper left hand corner - green means it's a good solid signal to work with, yellow is workable to a point and red is just not good at all so it could be an antenna issue at that point or perhaps you're in a dead spot area with low signal propagation as well but not specifically Unitrunker itself.

Hope this helps...

Also: Unitrunker can decode P25 Phase I and Phase II control channel data streams which can come in handy sometimes if you get Phase II systems in your area as those are growing in popularity over the "rather old" P25 Phase I systems nowadays.

 

[Dog]

Here is a link to the settings. At the bottom of the pages shows you how to find the correction ppm.
UniTrunker | Realtek RTL2832U

Finally, how do I set the audio threshold at unity to I do not hear the static on a conventional frequency until it is keyed up in the SDRsharp program?

I didn't see it in the previous post but I may have missed it. You can set the squelch in SDRSharp so you don't have to hear the static.

 

[br0adband]

Yeah, I neglected to cover the squelch question, but as just noted check the Squelch box and adjust as necessary - start at something like 75 and adjust down till you get no static at all and no lower. Different modes may require adjustment from time to time as well.

 

[CPAJ]

Thank you for all the replies, very informative.
Unfortunately, I am still having a problem getting Unitrunker to run the device. I followed all steps from your post and read the instructions article link posted here but whenever I complete setup and try to press play/run it attempts to for a millisecond and then the Run status switches right to "Stopped" and the status column states "Could not open!"
I have tried redoing my zadig config and am sure that is not the issue.
The stick is still working fine in sdrsharp and I have figured out my ppm correction rate and entered it as instructed.

Does anybody have any other suggestions or should I post screenshots?
Also, according to the seller, the item does definitely have the R820T (older) chip.

 

[SCPD]

Please post a screenshot of Zadig with the USB device selected.

 

[CPAJ]

Screenshots

Unitrunker, thank you for assisting. Here is the link to thezadig configuration window. It's asking if I was to reinstall my stick again so that leads me to believe it is already done if I am correct:

https://s1.postimg.org/emjk25ysv/zadig.jpg

Here is a screenshot showing that the dongle is correctly working in SDRsharp. In this example shot it is tuned to a local FM radio station without issues.

https://s28.postimg.org/3y9k5ucm5/image.jpg

The following two image links are the receiver setup configuration details as I try to add a new receiver per steps posted previously in thread (ppm is not the issue as that has been resolved):

https://s15.postimg.org/ds4fu2qtn/image.jpg

https://s31.postimg.org/5ug8kj3jf/image.jpg

Lastly ----- the last screenshot below shows the error message when I try to start/run unitrunker with the above settings:

https://s7.postimg.org/6ey3uvywb/image.jpg


*Any and all help is greatly appreciated. Sorry if this ends up being some simple overlooked error or a other problem on my part. Again, I am new to SDR so thank you for the patience. Have a great rest of your weekend and a good holiday tomorrow.

 

[Dog]

Thank you for all the replies, very informative.
Unfortunately, I am still having a problem getting Unitrunker to run the device. I followed all steps from your post and read the instructions article link posted here but whenever I complete setup and try to press play/run it attempts to for a millisecond and then the Run status switches right to "Stopped" and the status column states "Could not open!"
I have tried redoing my zadig config and am sure that is not the issue.
The stick is still working fine in sdrsharp and I have figured out my ppm correction rate and entered it as instructed.

Does anybody have any other suggestions or should I post screenshots?
Also, according to the seller, the item does definitely have the R820T (older) chip.

If it works with SDR Sharp the dongle and drivers are fine. Make sure anything that tries to use the dongle is closed. SDRSharp, SDRTrunker, etc.

 

[CPAJ]

I have tried it while making sure other programs such as sharp are closed. No luck.

 

[Dog]

I have tried it while making sure other programs such as sharp are closed. No luck.

In the Info tab next to RTL Device it shows RTL2838UHDIR:00000etc. It should show Bulk-in interface.

When you install the driver from ZaDig click optoins, show all devices, then select bulk in inrerface 0, then install or reinstall the driver.

 

[CPAJ]

In zadig, after selecting to list all options, I have tried to select both "HP True Vision HD (Interface 0)" and selecting the name of my dongle. I have tried to then install/reinstall both options.

I still face the same issue in unitrunker with the "Could not open!" status line.

 

[dave3825]

In the Info tab next to RTL Device it shows RTL2838UHDIR:00000etc. It should show Bulk-in interface.

When you install the driver from ZaDig click optoins, show all devices, then select bulk in inrerface 0, then install or reinstall the driver.

What is the difference between it saying bulk in interface 0 vs RTL2838UHDIR:00000etc ?

I ask because I have the same dongle and in my unitrunker, it says, RTL2838UHDIR:00000001 and my unitrunker works perfectly. It does not list bulk in at all. It also works perfect with Sdrsharp, Dennies sdrtrunk and HDsdr. I know a while back bulk in used to be displayed but no more. Not even in the device manager.

Just curious.

 

[Dog]

What is the difference between it saying bulk in interface 0 vs RTL2838UHDIR:00000etc ?

I ask because I have the same dongle and in my unitrunker, it says, RTL2838UHDIR:00000001 and my unitrunker works perfectly. It does not list bulk in at all. It also works perfect with Sdrsharp, Dennies sdrtrunk and HDsdr. I know a while back bulk in used to be displayed but no more. Not even in the device manager.

Just curious.

I must be out of the loop. As far as I know the hdir is the driver windows installs for the tv dongle. Which is why you use ZaDig to install modified drivers to use the dongle as a SDR.

However it looks like something has changed since I last dealt with that issue.If it works then it works and I am wrong. I apologize for any confusion.

 

[CPAJ]

OK - thanks for the input, people.
So the above poster confirmed that my dongle works in the configuration with unitrunker as I have it. I have followed all instructions. Their unit works with sharp but not trunk just as mine, but they get unitrunker to work. So it's not a broad unitrunker issue it has to be something undiscussed or unresolved on my end.

Can anyone look back over my updates and screen shots and help me get to the bottom of this? Thanks

 

[SCPD]

The differences have more to do with different versions of Windows than Zadig vs. the OEM DVB drivers.

 

[dave3825]

If it helps I am running win 7 64 bit and Unitrunker 1.0.32.27

 

[SCPD]

Can anyone look back over my updates and screen shots and help me get to the bottom of this? Thanks

Is the Realtek USB stick plugged directly into the host PC or a USB hub? Try a different USB port.

 

[pinkfish457]

This image https://s31.postimg.org/5ug8kj3jf/image.jpg shows you are using a frequency of 500.4857 Mhz. In a P25 system the second VCO "PARK" frequency should not show all 0's. Enter 500.000 as the second VCO park frequency, and see if it doesn't start running. You didn't post a pic of the second VCO, it should show VOICE, not SIGNAL.

 

[CPAJ]

Updates/Replies

Unitrunker - It is plugged directly into the computer. I tried a different port in the beginning but will try that again now that I have received more advice for settings.

Pinkfish - I will change this when I get home and update this evening.

Thank you all.

 

[CPAJ]

UPDATES

PINKFISH - I tried your advice.

Unitrunker - I also tried the top right "Pick A Site" option to load a system directly from my unitrunker known systems list, made sure I selected the active CC, and tried to run the program. It is still giving me the millisecond of trying to work then "Could not open". Have tried multiple ports, including the one that works inline with a pro651 for my intended purpose.

I do not understand what I am doing that has it inoperable. I have again tried to do my zadig. I have fixed my drift. I have tried all ports directly into the computer. I am able to monitor the CC with the Pro 651 but not the sdr. The SDR is able to work in sharp but not Unitrunker.

What in the world am I messing up? Anyone who can please help, speak up, it's frustrating because I know the program has great use I just cannot get my config to work.