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FCC mode for 5.8 GHz control and 2.4 Ghz video - solution inside

Discussion in 'Standard' started by Adrian Cable, Apr 2, 2018.

  1. Adrian Cable

    Jan 14, 2018
    Likes Received:
    San Francisco, CA
    For a long time we have had Magic Power and similar which increase the power of the 2.4 GHz video channel, but not the 5.8 GHz control channel, to FCC levels worldwide. Here is my solution to increase both 2.4 GHz and 5.8 GHz to FCC levels. I developed it for the Phantom 3 4K but it will work on the Standard just as well. It requires you to use Litchi instead of DJI GO.

    This patch is also useful if you are in the US, because (1) it increases the 2.4GHz drone power output from 25 dBm to 27 dBm, (2) without this patch, when using Litchi, the 5.8 GHz control channel still runs at CE power levels even if you are in an FCC zone, and (3) optionally it can start the RC and drone in channel 13, which is unused in the US, thus reducing wi-fi congestion. (DJI GO sends the drone a command when the home point is set to set the 5.8 GHz control channel power depending on GPS location - Litchi does not do this. The RC always starts in "world safe" regulatory mode i.e. CE, so with Litchi you will never get full control signal power even in the US.)

    Note that right now, if you are outside the US, you need to use Litchi. DJI GO will, I think, reset (at least) the 5.8 GHz control power to CE levels if you are in CE. Litchi will not do this. (If anyone in CE wants to check if DJI GO does in fact work, please let me know - I am in the US so cannot test it.)

    The instructions here assume you already know how to get FTP/Telnet access into the drone. That has been covered extensively elsewhere so no need to repeat it here. I also assume you are familiar with Linux. This process works - but I take no responsibility for bricked drones.

    Please transfer all files to your drone in binary mode, to avoid issues with line break translation.

    Step 0 - decide whether you want to use channel 13

    Channel 13 is unused in the US, and some devices may not support connecting to it. My iPhone works fine. I don't know about other devices.

    By default the files provided lock the RC to channel 13. Make sure your mobile device can connect to Wi-Fi networks on channel 13. If you want to skip the channel 13 lock, I tell you how below.

    Step 1 - return the drone firmware to stock

    This step is needed if you have ever used Magic Power or similar - you will need to get rid of it. I think Magic Power has an uninstall option (not sure first-hand as I have never used it), or you can revert the firmware from within the DJI GO app. (hold down "3 lines" icon in top right of screen for 10 seconds, then release, then select firmware.)

    Step 2 - enable telnet access on the drone and RC

    Covered extensively elsewhere (including username/password for FTP). Can most easily be done by editing /sbin/djiled.sh on both the RC and the drone, and adding this line after #!/bin/sh:

    telnetd -l /bin/ash &

    Once this is done on both RC and drone, restart both RC and drone, and ensure the RC is connected to the drone (green LED on RC).

    Step 3 - patch files on RC

    Make sure your PC is connected to the RC's Phantom3_xxxxxx wi-fi AP. Then:

    1. Telnet to the RC (
    2. Copy the file /sbin/chansel to /sbin/chansel_old
    3. Transfer the file rc/chansel from the attached maxpower.zip file to /sbin/chansel on the RC
    4. Make sure file permissions include execute, i.e. chmod a+x /sbin/chansel
    5. If you do not want to lock to channel 13, comment out the last line in /sbin/chansel using vi (i.e. change the line starting sed... to #sed...)
    6. Run: sync

    Step 4 - patch files on drone

    1. Telnet to the drone (
    2. Copy the file drone/djiled.sh from the attached maxpower.zip file to /sbin/djiled.sh on the drone
    3. Check permissions: chmod a+x /sbin/djiled.sh
    4. Copy the file drone/fcc58.sh from the attached maxpower.zip file to /sbin/fcc58.sh on the drone
    5. Check permissions: chmod a+x /sbin/fcc58.sh
    6. Copy the file drone/dji5b.bin from the attached maxpower.zip file to /root/dji5b.bin on the drone
    7. Run: sync

    Step 5 - restart hardware

    1. Power off drone, then RC.
    2. Power on RC, then drone.
    3. Run Litchi. Enjoy increased video and control range.

    Technical details

    To increase the 2.4 GHz downlink power, regulatory domain on both drone and RC are set to VE (Venezuela) which allows FCC power levels and also channel 13. Power is set to 27 dBm on the RC (same as FCC standard), and 27 dBm on the drone (increased from 25 dBm on FCC). This is similar to Magic Power etc.

    To increase the 5.8 GHz uplink power, the patched drone sends a network packet to apsrv on the RC shortly after connecting to the RC to instruct it to change the control power domain to FCC. This packet was captured during DJI GO's home point set procedure, which if the home point lies in the US, sends the command to the RC to increase the control channel power. This approach is new.

    Before and after power meter measurement pics are also attached. (You can ignore my amplifier set-up - the power meter is plugged into the RC antenna outputs.)



    5.8G before.JPG 5.8G after.JPG 2.4G before.JPG 2.4G after.JPG

    Attached Files:

    #1 Adrian Cable, Apr 2, 2018
    Last edited: Apr 2, 2018
    Rohanm likes this.
  2. Devilion

    Jun 28, 2018
    Likes Received:
    anyone can confirm this work ???
  3. Rohanm

    Dec 30, 2017
    Likes Received:
    Don't want to tweak mine as already achieving almost 5.85 km one way - would be interested in hearing from others though who have yet to try a modification to find out how well this performs
  4. Devilion

    Jun 28, 2018
    Likes Received:
    Is this the same as Magic Power ????
  5. Rohanm

    Dec 30, 2017
    Likes Received:
    Magic Power doesn't enhance the 5.8ghz signal - would be interested in trying this mod out should enhancement be possible
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