Add link in README to instructions on how to get a new Horus 4FSK payload ID

README.md

@@ -61,6 +61,7 @@ The main features the RS41ng firmware are:
     * Option to transmit APRS weather reports using readings from an external BMP280/BME280 sensor
   * [Horus 4FSK v1 and v2 modes](https://github.com/projecthorus/horusdemodlib/wiki) that has improved performance compared to APRS or RTTY
     * There is an option to use continuous transmit mode (for either V1 or V2 mode), which helps with receiver frequency synchronization and improves reception.
+    * In order to use Horus 4FSK mode on a flight, you will need to request a new Horus 4FSK payload ID in GitHub according to the instructions at: https://github.com/projecthorus/horusdemodlib/wiki#how-do-i-transmit-it
   * Morse code (CW)
   * JT65/JT9/JT4/FT8/WSPR/FSQ digital modes on HF/VHF amateur radio bands using an external Si5351 clock generator connected to the external I²C bus
   * "Pip" mode, which transmits a short beep generated using CW to indicate presence of the transmitter
@@ -100,6 +101,7 @@ On an external Si5351 clock generator connected to the external I²C bus of the
 * The Horus 4FSK v1 and v2 modes have significantly [improved performance compared to APRS or RTTY](https://github.com/projecthorus/horusdemodlib/wiki).
 * Use [horus-gui](https://github.com/projecthorus/horus-gui) software to receive the 4FSK mode and to submit packets to [Habhub](http://habhub.org/) high-altitude balloon tracking platform.
 * See [horus-gui installation and usage instructions](https://github.com/projecthorus/horusdemodlib/wiki/1.1-Horus-GUI-Reception-Guide-(Windows-Linux-OSX)) and [horusdemodlib](https://github.com/projecthorus/horusdemodlib) library that is responsible for demodulating the signal.
+* In order to use Horus 4FSK mode on a flight, you will need to request a new Horus 4FSK payload ID in GitHub according to the instructions at: https://github.com/projecthorus/horusdemodlib/wiki#how-do-i-transmit-it
 
 ### External sensors