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Thread: Find Out Existing RF Signals (Cell/Mobile/Pager etc) In Your Area

  1. #1
    Captain abcd567's Avatar
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    Find Out Existing RF Signals (Cell/Mobile/Pager etc) In Your Area

    The space around ADS-B antenna contain not only 1090 MHz signals, but also lot of other signals at different frequencies. The closer the frequency of a signal to 1090 MHz, your ADS-B antenna picks it stronger. For example if there are three signals of equal strength, one at 144 MHz, 2nd at 850 MHz and 3rd at 950 MHz, the ADS-B antenna will pick 950 MHz one the strongest, 850 MHz one a bit less stronger, and 144 MHz one much fainter.

    As the Cell/Mobile/Pager signals exist in the range 850 MHz to 1200 MHz, these are picked strongly by ADS-B antenna and this mixture is fed to the receiver, overloading its front end tuner. To overcome this situation, a hardware called “Filter” is used. As its name shows, it filters out unwanted signals and passes a narrow band of frequency say 1075 MHz to 1150 MHz, blocking most Cell/Mobile/Pager signals from reaching the receiver.

    In order to determine if a filter is needed or not, it is necessary to scan frequencies in the range 800 MHz to 1200 MHz. If the scan shows very few and weak interfering signals, adding a filter will not give any appreciable improvement. On the other hand if the scan shows a lot of strong interfering frequencies, adding a filter will give substantial improvement in ADS-B 1090 MHz reception.

    Software developers have developed softwares which use (DVB-T+ADS-B Antenna) to perform this scan. There are following two ways it can be done. Please click the options below to see the details.


    OPTION-1:
    DVB-T is plugged into Raspberry Pi (or is plugged into a Desktop/Laptop running Linux Debian/Ubuntu)

    OPTION-2:
    DVB-T is plugged into a Windows Computer - Using GUI rtlpan.exe.

    OPTION-3:
    DVB-T is plugged into a Windows Computer - Using Command Line.

    Last edited by abcd567; 2017-11-12 at 04:16.

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    Captain abcd567's Avatar
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    OPTION-1:
    DVB-T plugged into Raspberry Pi.

    This method uses software tool rtl_power which is part of software package rtl-sdr.

    Credits:
    Kyle Keen (keenerd): For rtl_power and heatmap.py
    Oliver Jowett (obj): For guide how to use rtl_power and heatmap.py


    STEP-1 of 6:
    Install required packages (rtl-sdr and python-imaging), and get the python script (heatmap.py) to create image scan.png from scanned data stored in file scan.csv

    Code:
    sudo apt-get install rtl-sdr
    sudo apt-get install python-imaging
    sudo wget https://raw.githubusercontent.com/ke...map/heatmap.py
    sudo chmod +x heatmap.py

    STEP-2 of 6:
    Free the DVB-T Dongle which is in use by a decoder like dump1090, or dump1090-mutability, or dump1090-fa.
    Code:
    sudo systemctl stop dump1090
    sudo systemctl stop dump1090-mutability
    sudo systemctl stop dump1090-fa
    STEP-3 of 6:
    Once DVB-T Dongle has been made free, run following test
    Code:
    sudo rtl_power -f 800M:1200M:100k -i 30 -c 50% -e 30m -g 30 -F 9 >scan.csv

    The above command will generate following output.
    Code:
    Number of frequency hops: 286
    Dongle bandwidth: 2797202Hz
    Downsampling by: 1x
    Cropping by: 50.00%
    Total FFT bins: 9152
    Logged FFT bins: 4576
    FFT bin size: 87412.56Hz
    Buffer size: 16384 bytes (2.93ms)
    Reporting every 30 seconds
    Found 1 device(s):
      0:  Realtek, RTL2832U, SN: 00001003
    
    Using device 0: Generic RTL2832U
    Detached kernel driver
    Found Rafael Micro R820T tuner
    Tuner gain set to 29.70 dB.
    Exact sample rate is: 2797202.148434 Hz
    [R82XX] PLL not locked!

    Wait for 30 minutes for scan to finish.
    When scan is finished, it will say "Exiting.... Canceled by user".
    Scan will create a file "scan.csv" in current folder and save scan data in it.

    This will produce a very wide image (4000 pixels!) that shows spectrum power from 800MHz - 1.2GHz.
    If you want a narrower image, increase “100k” above to something larger, it controls the bandwidth that corresponds to one pixel on the x axis.
    -i controls the integration interval (time for one pixel on the y axis)
    -e is the total runtime, longer gives you a taller image.


    STEP-4 of 6:
    Don't forget to Reboot Pi so that system is restored to normal, and data feeding is restored.
    Code:
    sudo reboot

    STEP-5 of 6:
    Create an image "scan.png" in current folder from data stored in file "scan.csv"
    Code:
    ./heatmap.py scan.csv scan.png
    This will produce a very wide image (4000 pixels!) that shows spectrum power from 800MHz - 1.2GHz.


    STEP-6 of 6:
    Copy the image "scan.png" from Pi to your Win/Mac Computer. To copy a file from Pi, you will need to install on your Win/Mac computer an SCP software. Some popular free of cost software are FileZilla (win and mac) or WinSCP (win) or CyberDuck (win and mac).



    Example of Scan of Existing RF Signals by rtl-power

    The original image is very wide (4000 pixel), but displayed in this forum smaller (874 pixel). As a result details are not clear.




    Three 500 pixel wide cut-outs from above 4000 pixel wide image. These cutouts show details better.





    Last edited by abcd567; 2017-11-08 at 07:37.

  3. #3
    Captain abcd567's Avatar
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    OPTION-2:
    DVB-T plugged into Windows Computer - Using GUI rtlpan.exe


    Important: If you want to plug in your DVB-T Dongle into Windows Computer, you should install its driver Zadig.

    STEP 1 of 7:
    Create a new folder of a name of your choice and at a location of your choice. For this guide, I will use new folder name "RF Scan", location inside "Download" Folder.

    STEP 2 of 7:
    Download RelWithDebInfo.zip from here:
    Download Link: http://osmocom.org/attachments/downl...ithDebInfo.zip

    Web Page: https://osmocom.org/projects/sdr/wiki/rtl-sdr
    (scroll down to bottom of page to find download link)


    STEP 3 of 7:
    Un-zip RelWithDebInfo.zip. It will create a folder RelWithDebInfo and inside this folder another folder rtl-sdr-release which contains several files and 2 folders named x32 and x64 . Copy ALL files of folder x32 into newly created folder RF Scan.

    STEP 4 of 7:
    Download rtlplan.exe from the site given below, and save it inside the folder RF Scan
    https://sourceforge.net/projects/guiforrtlpower/





    STEP 5 of 7:
    Double-click rtlpan.exe to start the software.

    STEP 6 of 7:
    In the rtlpan window, make settings as follows (see screenshot below)
    start freq: 800Mhz (800000000)
    end freq: 1200Mhz (1200000000)
    step: 100kHz
    Gain: 49.6



    STEP 7 of 7:
    Press "START" Button. The scan will start and the scan image will start building gradually. Wait for about 15 to 30 minutes for scan image to build to sufficient height. Click "STOP" button to stop the scan. In addition to scan image, a file scan.csv will be generated inside folder "RF Scan"




    Last edited by abcd567; 2017-11-12 at 17:44.

  4. #4
    Captain abcd567's Avatar
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    OPTION-3:
    DVB-T plugged into Windows Computer - Using Command Line


    Important: If you want to plug in your DVB-T Dongle into Windows Computer, you should install its driver Zadig from http://zadig.akeo.ie/


    STEP 1 of 7:
    Download Python Installation File python-2.7.14.msi from the site given below, and install it on your computer
    https://www.python.org/downloads/

    STEP 2 of 7:
    Download Python Imaging Library Installation File Pillow-4.3.0.win32-py2.7.exe from the site given below, and install it on your computer
    https://pypi.python.org/pypi/Pillow/4.3.0

    IMPORTANT NOTE: Pillow and PIL are not compatible. If you have already installed PIL, first uninstall it, and then install Pillow




    STEP 3 of 7:
    Create a new folder of a name of your choice and at a location of your choice. For this guide, I will use new folder name "RF Scan", location inside "Download" Folder.

    STEP 4 of 7:
    Download RelWithDebInfo.zip from here:
    Download Link: http://osmocom.org/attachments/downl...ithDebInfo.zip

    Web Page: https://osmocom.org/projects/sdr/wiki/rtl-sdr
    (scroll down to bottom of page to find download link)

    Un-zip RelWithDebInfo.zip. It will create a folder RelWithDebInfo and inside this folder another folder rtl-sdr-release which contains several files and 2 folders named x32 and x64. Open folder x32




    Copy following 3 files of folder x32 into newly created folder RF Scan.
    (1) libusb-1.0.dll
    (2) rtl_power.exe
    (3) rtlsdr.dll





    STEP 5 of 7:
    Download file heatmap·py by Right-Clicking on the link below, and choosing "Save Link As..."
    Move the downloaded file heatmap·py into folder RF Scan.

    https://raw.githubusercontent.com/ke...map/heatmap.py



    STEP 6 of 7:
    Make sure no program is using DVB-T Dongle. Stop any such program to free DVB-T.

    Open Command console by typing cmd in search. Once the Command Console is open, do following:

    Code:
    # First CD to folder RF Scan
    #Once in folder RF Scan, give following command
    rtl_power -f 800M:1200M:100k -i 30 -c 50% -e 30m -g 30 -F 9 > scan.csv

    The above command will generate following output.




    Wait for 30 minutes for scan to finish.
    When scan is finished, it will say "Exiting.... Canceled by user".
    Scan will create a file "scan.csv" in current folder and save scan data in it.

    This will produce a very wide image (4000 pixels!) that shows spectrum power from 800MHz - 1.2GHz.

    If you want a narrower image, increase “100k” above to something larger, it controls the bandwidth that corresponds to one pixel on the x axis.
    -i controls the integration interval (time for one pixel on the y axis)
    -e is the total runtime, longer gives you a taller image.




    STEP-7 of 7:
    Create an image "scan.png" in current folder from data stored in file "scan.csv"
    Open Command console by typing cmd in search. Once the Command Console is open, do following:

    Code:
    # First CD to folder RF Scan
    #Once in folder RF Scan, give following command
    heatmap.py scan.csv scan.png
    The above command will generate following output.



    This will produce a very wide image (4000 pixels!) that shows spectrum power from 800MHz - 1.2GHz.


    Example of Scan of Existing RF Signals by rtl-power




    This image is very wide (4000 pixel), but displayed smaller. As a result details are not clear.
    Click over it to see bigger size.


    Three 500 pixel wide cut-outs from above 4000 pixel wide image. These cutouts show details better.







    Last edited by abcd567; 2017-11-12 at 17:43.

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