KiwiSDR antenna switch extension [and BeagleBone Black/Green GPIOs]



  • Hi Martin,

    the LF-GP is also based on the PGA-103+ amplifier circuit. Currently it has a 6 meters long whip starting 2 meters over ground level. It's located 170 meters from my house to get away from the worst noise around the house.The PGA-103+ amplifier is preceded by a 3 MHz low-pass filter. Noticed to-night that it overloads the Kiwi, so will probably shorten the whip. It is always a balance between day-time sensitivity and night-time overload. 


    Mauritz / SM2BYC

  • edited September 2017
    Hi Mauritz,

    All good.

    BTW if you have back to back input protection diodes connected across the amplifier input (as I show in the diagram) you may find they add to your IMD. I've had to connect them in series across the supply rail so that they are reverse biased, with the antenna connected to the junction of the diodes and the capacitor to the PGA input.

    Also don't run the PGA without a load (or the attenuator network) on the output, as they tend to blow up if they don't see a 50 Ohm load (or something close) on the input :-(

    I must update the diagrams to show this correctly.

    Send me a private email if you wish to discuss further.


    Martin - G8JNJ
  • Hi Martin,

    yes, PGA-103+ are sensitive devices, I have killed a number of these. For the moment I have the protection diodes connected as on your WEB pages. I also had an idea to connect these to supply rails for lower IMD but could not find any information in the data sheet about maximum input voltage only about maximum input power. So to be safe I just left them over the input.


    Mauritz / SM2BYC
  • Hi Mauritz
    Hi Martin

    I experience the problem, that the antenna switch extension is not working after a restart of the Kiwisdr server.
    You can click the buttons in the WebUI  but nothing happens at the frontend and backend!

    I always have to restart the complete Beagle to get it back working.

    Do you have the same issue?

  • Hi Dietmar,

    In the update tab, I have marked that Kiwi is rebooted after update. So far the antenna switch has been working after software updates. I think that the Kiwi should not restarted but rebooted when antenna switch extension is in use.


    Mauritz / SM2BYC

  • Hi Mauritz

    this option I missed - but in between Kari also fixed his code. Thanks for the hint.

  • edited September 2018
    I want to install this extension and use beagle-gpio. But some questions appear:
    1. What gpio port should I used ?
    P8 11 - GPIO 1_13
    P8 12 - GPIO 1_12
    P8 13 - GPIO 0_23
    P8 14 - GPIO 0_26
    P8 15 - GPIO 1_15
    P8 16 - GPIO 1_14
    P8 17 - GPIO 0_27
    P8 18 - GPIO 2_1
    P8 19 - GPIO 0_22
    P8 26 - GPIO 1_29

    2. Is there a place in a code where I could setting up this port ?

    This extension uses Beagle GPIO pins

    P8 pin 11 - GPIO_45 - Antenna 1
    P8 pin 12 - GPIO_44 - Antenna 2
    P8 pin 13 - GPIO_23 - Antenna 3
    P8 pin 14 - GPIO_26 - Antenna 4
    P8 pin 15 - GPIO_47 - Antenna 5
    P8 pin 16 - GPIO_46 - Antenna 6
    P8 pin 17 - GPIO_27 - Antenna 7
    P8 pin 18 - GPIO_65 - Antenna 8 (not available in webui yet)
    P8 pin 19 - GPIO_22 - Antenna 9 (not available in webui yet)
    P8 pin 26 - GPIO_61 - Antenna 10 (not available in webui yet)

    When you install the extension it will ask you which interface you wish to use.


    Martin - G8JNJ
  • Thank you!
    We have succesfully installed your extention and it works.

    In our case we have home made switch builded by following shem:

    With 3 relay we could switching between 4 antenas.
    If we want to use antena #4, we need to send hight level for GPIO0 and GPIO2. We could do this with antena mixing mode. But it's not clear for a user. It would be cool to have an ability to configure antenas name and gpio which should be use for the antenas to be enabled.

  • @ Kovalr

    Yes, some time ago I asked Kari if he could include the ability to map GPIO ports to specific antennas so that it would be easier to accommodate binary switching of banks of relays as you have done. Unfortunately he hasn't so far) been able to do this.

    You have two (or maybe more) options. You could modify Kiri's code to switch more than one GPIO pin at a time when an antenna is selected, or alternatively use some diodes to provide simple logic to 'steer' switching signals from each GPIO output to drive one or more relays at a time or as otherwise required.

    I use the second method, as I'm not really a software guy and diodes are cheap.


    Martin - G8JNJ
Sign In or Register to comment.