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4,966 Posts
Finally got around to chasing this source of noise down, briefly mentioned here in this other thread.
Using updateDVB and the mohu TV tuner mentioned above, as seen by my OTA antenna system. Turns out it is EMI coming from the LED panel of a TV which is in the room just below the VHF yagi on the roof.
The end result of that noise source is a 2 dB degradation to the SNR on RF CH 5, 79 MHz here, from 21 dB SNR to ~ 19 dB SNR.
I guess that says something about the design of even these little TV tuner dongles these days, is pretty good.
As looking at that spectrum you would think the degradation would be a lot worse.



rtl2832 SDR probing with just the little 6" whip antenna they come with dangling near the offender.
qspectrumanalyzer program snapper. red line is peak hold from when the
offending TV was still on, yellow line is with the TV off.

98 Posts
It's been on the top of my wish list to my wife for about a year... ebay is full of them now at extremely attractive prices, even cheaper as diy assembly kits!

4,966 Posts
Put the NanoVNA to work for real yesterday.
The CBAND line on my C/Ku antenna crapped out last week. CBAND signals dead as a doornail for about a week.
With nice weather yesterday finally got around to sweeping the line with the nanoVNA using the Distance to Fault or TDR function.
It was Dead On pinpointing exactly where the issue was... two connectors with corrosion...
Replaced all 4 connectors there at the Grounding Block (2 for C, 2 for Ku), all good again.

Sweeping from inside the house towards the LNBs, with the LNBs connected but not powered obviously.
The LNBs are about 33m out.
Good Line (Ku Band) for comparison.

Bad Line (CBAND), see the fault at 4.5m? See how it's much higher than the LNB at the end of the line?
That's a reflection at the grounding block outside on the side of the house. Should not be any major blips there until the load is seen
at the end of the line. Load is the LNBs with no power applied in this case. But you could use an Open, Short,
or 75 ohm termination or even an antenna as the load.


98 Posts
NICE!! I'm enjoying my nano vna, but I haven't had time to explore the TDR functions yet... it sure works great for characterizing my various scanner and long wire antennas!

Premium Member
1,139 Posts
Tips for Setting Up an RTL-SDR Dongle as a Spectrum Analyzer

Pete Higgins had a tutorial for setting up an SDR dongle as a spectrum analyzer on the HighDefForum, which was very helpful to users not familiar with assembling a folder of open-source software, including me. His tutorial is no longer available because that forum folded. Pete isn't able to recreate that thread, so he suggested that I post any tips available from an archive which I didn't know existed.

This image showed in Pete's first post, but only if you were signed in:

Post by majortom:
2013-12-01, 08:55 PM

majortom said:
here is another option for viewing the raw rf spectrum without a 20,000 dollar spectrum analyser...
using one of them 10 dollar dvb-t dongles...

since it's in python it can be used in a Linux, Windows or Mac environment..
Due to the way it works...uses a sliding window while doing FFT in like 2Mhz chunks,
it's kinda slow doing a scan...But it could be useful in spotting whether your having
mutipath on..
at 10 bux for one of these dongles, first discussed in this thread I don't see how one could go wrong...
Post #9 by Pete Higgins, 04-04-2014, 04:07 PM

RTL2832U + R820T DVB-T USB Tuner Card Hints & Kinks 04-04-2014, 04:07 PM

A new version of RTLSDR Scanner was released on April 2nd. It can be found here:

Install 32 bit Microsoft Visual C++ for RTLSDR Scanner
I ran into a problem getting the RTLSDR Scanner software to work with Windows 7 following a fresh install. After countless reinstalls, I discovered that I needed to install the 32 bit version of “Microsoft Visual C++ Redistributable (x86) {vcredist_x86.exe}”. The software author actually suggested installing Microsoft Visual C++ but since all my Windows 7 computers are 64 bit I was installing the 64 bit version and that didn’t seem to work. Three computers with fresh installs of Windows 7 setup flawlessly by first installing the Microsoft Visual C++ Redistributable (x86). It can be downloaded @ no charge from Microsoft here:

To install SDR# for use with the RTL2832U + R820T DVB-T USB Tuner Card, go to the section titled “Important note for RTL-SDR users” and use the installation script provided in this section.
Unzip “” and double click on the “install.bat” file. I suggest moving the sdr-install folder and its 3 files to C:\. The SDR# application and all of its files will then be found @ C:\sdr-install\sdrsharp\. Apparently, these dongles require a lot more support than some of the other software defined radios. The stable release only contains 20 files and the release installed for my dongle has 32.

Post #12, by Pete Higgins, 11-06-2016, 04:04 PM

RTL/SDR Update

It’s been over two years since I started this thread and a lot has changed in the world of software defined radio.


In order to communicate with the RTL2832U + R820T2 dongle you need to install generic USB drivers. Zadig is a Windows application that does that. (Note; You need to download the correct version of Zadig for either Windows XP or Windows Vista & higher) The latest version of Zadig is 2.2.

In Zadig, go to Options and make sure “List All Devices” is checked.
Select “Bulk-In, Interface (Interface 0)”, “RTL2832UHIDIR” or “RTL2832U”, whichever shows up with your dongle plugged in.
Ensure that the driver on the right hand side of the green arrow is selected as WinUSB
Click the Replace or Reinstall Driver Button

Link to download Zadig:

Link to Zadig 2.0 - User Guide:


SDR# has an active spectrum analyzer display that displays a ~2 MHz portion of the spectrum which is limited by the bandwidth of the dongle (For example 88 MHz to 90 MHz). RTLSDR Scanner progressively scans from a user defined lower frequency limit up to a user defined upper frequency limit then stitches the entire scan range into a conventional spectrum analyzer display (For example 88 MHz to 108 MHz or 470 MHz to 700 MHz). It looks at each segment for 131 ms by default. RTLSDR Scanner has proven invaluable to be able to view the channels received at my location and their relative signal strengths. It is capable of loading two saved scans to compare the effect of different antenna configurations.

The author has traditionally used a script based install that from my experience was occasionally prone to failure. He recently released standalone versions of the application that while a little more involved to initially configure seem to be bulletproof and portable from one computer to another when configured.

Link to download RTLSDR-Scanner:

(Note; for 32 Bit version (i.e. XP, Win 7 & 10 32-Bit, etc.) scroll down the page)

1. Plug RTL2832U + R820T2’s dongle into a USB port or hub.
2. Run Zadig to install the WIN USB driver (If you’ve already installed SDR# this step isn’t necessary).
3. Download the RTLSDR-Scanner executable file.
4. Make a RTLSDR-Scanner directory & copy the RTLSDR-Scanner executable file to it.
5. Download & copy the RTLSDR libraries to the RTLSDR-Scanner directory.
6. Optionally, download & copy msvcr100.dll to the RTLSDR-Scanner directory.
7. For the 64-Bit RTLSDR-Scanner executable download & install Visual C++ Redistributable Packages for Visual Studio 2010 (x64) or 2013 (x64).

The latest standalone 64-bit release of “rtlsdr_scan-windows-64bit.exe” is v1.0.22497.10311 released on Sep 20, 2016

The latest standalone 32-bit release of “rtlsdr_scan-windows-32bit.exe” is v1.0.22180.60082 released on Jan 28, 2016

These are both Windows executable files that require additional support libraries to function.
I suggest creating a directory (folder) labeled “RTLSDR Scanner 32 Bit Stand Alone v1.0.22180.60082 Released on 28 Jan 2016” and copying “rtlsdr_scan-windows-32bit.exe” into it.
For the 64-Bit executable create a directory “RTLSDR Scanner 64 Bit Stand Alone v1.0.22497.10311 Released on 20 Sep 2016” and copy “rtlsdr_scan-windows-64bit.exe” into it.
The 64-Bit RTLSDR-Scanner executable requires you to install Visual C++ Redistributable Packages for Visual Studio 2010 (x64). or Visual C++ Redistributable Packages for Visual Studio 2013 (x64).

Both the 32-Bit and the 64-Bit versions require you to download the RTLSDR libraries and utilities from Osmocom named “RelWithDebInfo”.

Link to download RelWithDebInfo:

Download and unzip to a folder on your PC. It will create a directory named “rtl-sdr-release”. When you open that directory, you will see folders labeled x32 & x64. You need to copy the following files into the directory that contains the RTLSDR-Scanner executable file so it ends up looking like this:

pthreadVC2-w32.dll or pthreadVC2-w64.dll
rtlsdr_scan-windows-32bit.exe or rtlsdr_scan-windows-64bit.exe

Notice that except for “pthreadVC2-w32.dll” or “pthreadVC2-w64.dll” and the RTLSDR-Scanner executable all the RTLSDR library files have the same name but are different file sizes. You must copy the files from the correct x32 or x64 directory depending on which version of RTLSDR-Scanner you are setting up.


The correct version may already be on your system – or maybe not.

Both the 32 & 64-Bit versions of RTLSDR-Scanner require msvcr100.dll. Like the RTLSDR libraries, msvcr100.dll comes in 32 & 64-Bit versions. The 32 bit version is incompatible with the 64 bit one.

The 32-Bit version of msvcr100.dll is 756 KB (It comes with SDR# if you need it or can be found in the Windows 10 Professional Windows\SysWOW directory)

The 64-Bit version of msvcr100.dll is 810 KB (I just copied it from the Windows 10 Professional Windows\System32 directory)

To make your RTLSDR-Scanner setup portable, I recommend downloading the correct 32 or 64-Bit version and including it in the directory with the RTLSDR-Scanner executable file.

Many programs depend on msvcr100.dll and usually install it in their application directory, or C:\Windows\System32 and/or C:\Windows\SysWOW64. My 64-Bit Windows 7 & 10 Professional installations had the correct 64-Bit version installed. However, Windows 7 Home Premium 64-Bit and Windows 10 Home 64-Bit did not. Also, when I did a fresh install of Windows XP Media Center Edition the 32-Bit msvcr100.dll was not installed. Windows will first look in the application directory and then in all the directories in the path statement to find msvcr100.dll. If you overwrite a 32-Bit version with a 64-Bit version or vice-versa you may break other applications. That’s why I recommend including the appropriate msvcr100.dll file in the directory with the RTLSDR-Scanner executable file.

Finally, if your installing the 64-Bit RTLSDR-Scanner executable download & install Visual C++ Redistributable Packages for Visual Studio 2010 (x64) or 2013 (x64).

Link to download RTLSDR-Scanner & the Visual C++ Redistributable Packages:

I noticed that the Stand Alone versions take longer to load than the older versions installed by the script method. When I queried the author (Al) he replied “The stand alone application takes longer to start up as it extracts files to a temporary directory first when you run it. It's quite normal and nothing to be concerned about”.

I listed the dongle software that I experimented with here:

66 Posts
Thank you rabbit73.
And thank you Pete for introducing me to this RTL SDR. You were kind enough to sit with me on the phone and explain all the idiosyncrasies, how to install it and a lot more. I still use it almost everyday for my testing.

It really helps to see what changes I've made before I put my antennas all the way up on the mast. It's much easier to work on them at roof level before putting them way up.

435 Posts
I've bundled my channel_scan and channel_report scripts into a lightweight Docker container that works on both the Raspberry Pi and X86 computers. It comes with a pre-compiled version of hdhomerun_config that's been modified to only scan to channel 36 now that the FCC re-pack is done.

321 - 329 of 329 Posts