User Manual for Skylark v4.4 with RTL-SDR or SDRx

NOTE: Outernet and Skylark are both in beta

How Outernet Works

Outernet provides a unique service, broadcasting digital media content at no charge. We send files over geostationary satellites that transmit in the L-band frequency range. The receiver converts these analog waves into data files. The receiver creates a local WiFi hotspot, and users access content over WiFi and view that content through any web browser.



3 versions of the receiver kit exist; they have identical capabilities for receiving the Outernet broadcast.

There are 5 components required to build and operate an L-band receiver with an RTL-SDR component:

There are 4 components required to build and operate an L-band receiver with an Outernet-branded SDRx component:

For hobbyists, the L-band hardware can also be used for Inmarsat reception, including SafetyNET, EGC, and AERO.


Hardware Specifications

L-Band Air Gap Patch Antenna:


SDRx - Software Defined Radio:


Software Defined Radio Dongle


Power: The receiver requires 5V/1.5A power source. A 1A power supply may work, but we do not recommend it.

How The Components Work Together

Antenna                                         The antenna receives satellite signals in a particular bandwidth.

SDRx                                                This software defined radio is designed for L-band reception. It tunes into a particular frequency within the bandwidth and passes the signal to the computer running the demodulation software.

Computer                                      The computer demodulates and decodes the signal and manages and stores the received files.

Power                                             An external battery or other USB power source powers the receiver.          

Getting Started

DIY Receiver Assembly

1. Remove the components from packaging. Leaving the components inside of packaging may lead to overheating and long-term damage to the components.

2. Connect the male connector of the Antenna to the female connector on SDRx.

3. Connect SDR unit to CHIP:

3a. Insert the SDRx full-size male USB-A plug into the USB port of CHIP or

3b. Insert the RTL-SDR full-size male USB-A plug into the USB port of CHIP or

3c. insert male micro-USB-B plug of cable into the micro-USB port on the SDRx and insert the full-size male USB-A plug into the USB port of CHIP

4a. For RTL-SDR units, connect the LNA to the RTL-SDR by screwing the male connector of LNA onto the female connector of the RTL-SDR.

4. Connect power to the CHIP through the micro-USB-B port on the CHIP. You cannot power the receiver through the micro-USB port on the SDRx. Most standard phone chargers or USB power packs will provide sufficient power for the receiver. We recommend any 1.5 -amp power source. 1-amp sources may also work, but we do not recommend using a lower-amp source.

If the CHIP does not light up, press the CHIP power button, a very small circular button located on the side opposite of the USB connectors.

Handle the CHIP with care! The CPU and other sensitive components are exposed. Always be sure to place the CHIP with black plastic headers down when resting it on a surface. Do not allow the CPU (marked as R8) to touch any surface.


 Setting Up the Receiver

After assembly, use a WiFi enabled device to complete the receiver set-up:

1.   Open the list of WiFi networks on a WiFi-enabled device and connect to the wireless access point named “Outernet.

2.   Open any browser and type or in the address bar.

3.   Log into Skylark using the the administrator credentials: username “outernet” and password “outernet” (both without quotation marks).


Outernet Software: Skylark

View the code on GitHub:

How Skylark Works

Outernet encodes and modulates data files and sends them to several Inmarsat satellites. These satellites transmit the radio waves in the L-band frequency range. The waves are received by the SDR radio component of the receiver and then demodulated by the CHIP component of the receiver. Demodulation turns the analog signal into bits and then passes them onto the decoder, which extracts the file information from the data and reconstructs the files on the receiver’s on-board storage. You can then access the stored files through Skylark.


Initial use instructions:

  1. Once you have assembled the receiver, connect it to a power source through the micro-USB port on the CHIP. You cannot power the receiver through the micro-USB port on the SDRx.
  2. When the CHIP has finished booting (about 60 seconds), one of its lights will blink.
  3. A Wifi network called “Outernet” will become available for you to connect to. Connect to this network and go to or in a browser. You will see a login window:


 Satellite Reception Guide

To receive files, two things are required:

  1. A lock on the satellite signal. A lock is required to receive data packets.
  2. Reception of data packets. A weak signal or high error rate can prevent packet reception. In Skylark, check the Tuner app.

Tuner App

Once logged into Skylark, click the icon in the upper-left corner for Applications. Then click on the icon for Tuner. There are three tabs: Satellite, Custom, and Status.  Click on Satellite to find information about the satellite:




To change the satellite, choose from the dropdown and click “Apply.” For more information, see Appendix.


Click on the Status tab and you will find a list of changing values. You may need to make adjustments to the antenna positioning if these values are not acceptable. See the next section, POINT THE ANTENNA, for information on adjusting the antenna.

You will want to pay attention to:


The other values described include:


Point The Antenna

To achieve a signal lock and an acceptable SNR, the antenna needs to have a clear view of the satellite:

  1. Determine which satellite you will be getting service from and which direction it is relative to the device’s current location (see Appendix).
  2. Find a location for the receiver with a clear view of the sky.
  3. Point and angle the antenna in the direction of the satellite.
  4. Roughly speaking, an antenna’s angle relative to the ground corresponds to its latitude. At the equator (0°), the antenna would be flat on the ground. At 30°N, the angle of the antenna facing south would be 30° relative to the ground.  At 65°N, the angle of the antenna facing south would be 65°.
  5. Move any objects in the periphery of the antenna that may create interference.
  6. Connect to the device via WiFi, and check the Tuner app.
  7. If you do not have a signal lock, adjust the direction and angle of the antenna.
  8. Use the Tuner app to help make the proper adjustments.

If you have achieved signal lock and the device is receiving data, you should be able to see files in Skylark.  If the device has signal lock but is not receiving packets, you will need to readjust the antenna.


The DIY Kit utilizes the NAND flash on Alpha CHIP, and 3GB is available for received content. Adding external storage via USB allows for content that is received to be backed up against the larger external drive. Content is backed up every hour. The data on the external drive is available through the home/external directory in the File Manager app.  External storage can also be used to add content to the receiver. Only one external storage device can be used at a time.

External storage may be formatted using one of the following file system formats: NTFS, FAT32, and Ext2, Ext3, and Ext4 (on Linux). Once the external drive is added, Skylark will re-index any content already saved on internal storage. This process may take up to several minutes.


Skylark Guide

Skylark is the content management software of the receiver. Outernet continuously sends content over its data broadcast. Once received, that content is displayed in Skylark.



The Outernet Logo in the upper left will launch Applications, displaying your options for interacting with the software.



Skylark’s File Manager organizes content in a file structure format, the way a computer organizes files.  Click through the folders to find content. To delete a file or folder, right-click its name and select Delete. You may interact with files while connected to the receiver, or, for off-line access, right-click on the file and select “Download to computer” to download onto your device for later use.



The network application provides information and settings for the built-in WiFi. We do not recommend that you modify the preconfigured network settings unless you are confident in what you are doing. If you choose to modify Skylark’s network settings, you can do so in the following ways:


The weather application delivers live interactive weather information (using NOAA data). Data you can access includes but is not limited to wind vectors, temperatures, relative humidity, total precipitable water, total cloud water, mean sea level pressure and ocean currents.  


In What’s New, you can see the files your receiver has most recently downloaded. You can choose to view files received in the last 3 days or the 100 most recent downloads.


If you have no signal lock:

If applications are not receiving data:

Appendix: Choosing A Satellite

Outernet broadcasts over three Inmarsat satellites offering coverage on every continent and on open waters. All satellites use L-Band and have a bitrate of 2kbps, or roughly 20MB of content per day.



I-4 F3 Americas at 98°W covers North, South, Central America, Pacific and Atlantic Oceans.

Outernet Frequency: 1539.8725 MHz


Alphasat at 25°E covers Europe, Africa, Middle East, East Asia, Atlantic and Indian Oceans.

Outernet Frequency: 1545.94 MHz


I-4 F1 APAC (Asia-Pacific) at 144.0°E covers Asia, Australia, Pacific and Indian Oceans.

Outernet Frequency: 1545.9525 MHz