crisbour / gr-rtty-basics

Basic radioteletype transmit and receive functions

gr-RTTY-basics

Basic radioteletype transmit and receive functions

Overview

This package contains GNU Radio flowgraphs for a RTTY transmitter and a RTTY receiver. They work in conjunction with gr-webserver which provides a user screen with keyboard input and display output. Whatever is typed on the keyboard is sent by the RTTY transmitter. Whatever is received by the RTTY receiver is displayed on the screen in a scrolling area showing the last 20 lines.

The package uses three separate processes. They can all be on the same computer or on two or three separate computers as the user sees fit. It has been tested on GNU Radio versions 3.8.1.0 and 3.9 pre-release.

Installation

See What is GNU Radio? and Installing GNU Radio for background information.

gr-RTTY-basics

Note: These instructions are written for a Linux OS. Similar commands work for Mac and Windows.

1. Open a terminal window.
2. Change to the home directory.

cd ~/  

3. If you don't have 'git', enter

sudo apt install git  

4. Clone the repository:

git clone https://github.com/duggabe/gr-RTTY-basics.git

gr-webserver

Go to gr-webserver and follow the instructions to install and start it using a separate terminal screen.

Operation

RTTY transmitter

There are three programs to transmit RTTY:

• one for audio output - RTTY_vco
• one for direct USRP output - RTTY_xmt
• one for sending continuous LTRS characters for tuning - RTTY_test_ltrs.

The instructions below are for RTTY_vco, the audio output version, but they all operate in the same manner.

1. Open a terminal window.
2. Go to the gr-RTTY-basics/RTTY_xmt folder.

cd ~/gr-RTTY-basics/RTTY_xmt

3. Execute Gnu Radio Companion.

gnuradio-companion

4. Open RTTY_vco.grc from the file menu.
5. Click 'Run' and 'Execute' or press F6.
6. A new window titled "RTTY_vco" will open showing a scope trace with the transmitted signal.
7. To Terminate the program, click the 'x' in the corner of the title line.

RTTY receiver

1. Open a terminal window.
2. Go to the gr-RTTY-basics/RTTY_rcv folder.

cd ~/gr-RTTY-basics/RTTY_rcv

3. Execute Gnu Radio Companion.

gnuradio-companion

4. Open RTTY_receive.grc from the file menu.
5. Click 'Run' and 'Execute' or press F6.
6. A new window titled "RTTY_receive" will open showing a chooser block with 'Normal' and 'Reverse'. If the received signal has reversed Mark and Space tones, click the 'Reverse' button. A scope trace shows the received signal.

Loop-back test

Using RTTY_vco, if you connect the audio output of the transmitter to the audio input of the receiver using a patch cable, you can perform a loop-back test. Whatever you type in the gr-webserver screen will be displayed as received, preceeded by a less-than sign, in all capital letters. There will be a delay in the response.