Category Archives: radio

Working LilacSat-1

Working LilacSat-1 (LO-90)

Overview

The following instructions detail the steps for working the amateur radio repeater on the LilacSat-1 (LO-90) satellite using a FUNcube Dongle Pro+ Software Defined Radio (SDR).

Computer Setup

  1. Read the LilacSat-1 Overview first: LilacSat-1 Radio Info
  2. Download the LiveCD, burn, and boot. For instructions on this, go here: Chertsey Radio Club LilacSat-1 Tutorial
  3. Additional Requirements: The computer will need an SDR and an internet connection to receive LilacSat-1.

Note: for the purposes of the instructions that follow on this page, I am using a FUNcube Dongle Pro Plus as the SDR. For other SDRs like RTL-SDR, use the equivalent GNU Radio Companion files.


Testing Audio Decode

  1. Learn about the downlink audio codec, and then test the audio decode by following these instructions by Daniel Estévez (EA4GPZ): LilacSat-1 Codec 2 downlink/
  2. You can download the LilacSat-1 Downlink IQ Record file for testing from this page: https://github.com/bg2bhc/gr-lilacsat/blob/master/README.md
  3. To perform the test, you will use the demod_lilacsat-1.grc and replay_lilacsat1_rx.grc flows, located in the LilacSat-1 folder on the desktop.
  4. When the test is successful, it should sound like the audio clip included on Daniel Estévez’s page linked above.

Tweaking GNU Radio Companion Flows

Note: credit for the following modifications goes to Scott Chapman, K4KDR.

  1. Open the frontend_lilacsat1_rx_fcdpp.grc flow, and modify properties on the QT GUI Entry block to change the IF Gain value to 15, as shown in the screenshot below.
  2. Open the demod_lilacsat-1.grc flow, and modify the following properties, as shown in the screenshot below:
    • On the Plan13 CC block, change the value of Verbose to “Off”.
    • On the Low Pass Filter block, change the value of Cutoff Freq to “20e3”.
    • On the Low Pass Filter block, change the value of Transition Width to “1e3”.

LilacSat1 FUNcube Dongle Pro+ Flow
Figure 1: frontend_lilacsat1_rx_fcdpp.grc

LilacSat1 Demod Audio Flow
Figure 2: demod_lilacsat-1.grc

Download a comprehensive flow that supports image download and decoding: demod_lilacsat-1-k4kdr.grc (Note: Requires gr-satellites not included on the LiveCD.)

SDR Receiver, Transmitter, and Antenna Setup

When working LilacSat-1, I use an Arrow satellite antenna for both the uplink and downlink. I protect my SDR from interference/damage by using the Arrow 10w duplexer. Here’s a block diagram of my setup:

UHF Driven Element → duplexer → SDR
VHF Driven Element → HT

You can read more of Patrick’s (WD9EWK) comments on a similar setup in this forum discussion: https://forums.qrz.com/index.php?threads/sdrplay-as-satellite-downlink-receiver.490793/

Working the Sat

Note: you can essentially follow the instructions in the tutorials here. I have listed some key steps below.

  1. Make sure you have an active internet connection.
  2. Make sure your SDR is plugged-in.
  3. Make sure your computer audio volume is turned up.
  4. Setup the LilacSat-1 Proxy by double-clicking the “01-Setup LilacSat-1 proxy” script, located in the LilacSat-1 folder. The password is “lilac”.
  5. Run the LilacSat-1 Downlink Proxy by double-clicking the “02-LilacSat-1 proxy” script.
    • Enter your callsign (nick name) and location information (latitude, longitude, and altitude).
    • Click the “Save Settings” button.
    • Click the “Update Orbit” button and wait for the “Orbit Data Successfully Updated” message in the message console.
    • Click the “Start Proxy” button, which should change its label to “Stop Proxy” when running.
  6. Run the frontend_lilacsat1_rx_fcdpp.grc flow, clicking the green triangle “Play” button. This requires the Proxy to be running, as the proxy feeds Doppler correction data to this flow.
  7. You should see the SDR waterfall now.
  8. Run the demod_lilacsat-1.grc flow, clicking the green triangle “Play” button.
  9. You should see the Demod Signal view now, just like you saw when testing the recording above.
  10. At this point, you can work LilacSat-1 like you would any other Amateur Radio Satellite, transmitting with your transmitter (HT) and receiving with your SDR and computer.

LilacSat-1 Proxy
Figure 3: LilacSat-1 Proxy

Good luck!

Screen and Audio Recording

Note: If you want to record the screen and audio of your session, follow these instructions:

  1. Install GTK-recordmydesktop and PulseAudio Volume Control by running the following command from a terminal. The root password is “lilac”.
    sudo apt-get install gtk-recordmydesktop pavucontrol
  2. Open the Pulse Audio Volume Control dialog: Applications > Sound & Video > PulseAudio Volume Control
  3. Open gtk-recordmydesktop.
  4. In gtk-recordmydesktop advanced preferences, “Sound” tab, set “Device” to pulse
  5. In gtk-recordmydesktop start a recording.
  6. In Volume Control go to the Recording tab and change the recordmydesktop entry to “Monitor of Built-in Analog Audio Stereo”.
  7. IMPORTANT: In Volume Control go to the Configuration tab and change the FUNcube Dongle profile to “Off”.

GTK-recordmydesktop

PulseAudio Volume Control Settings 1

PulseAudio Volume Control Settings 2