Basic radioteletype transmit and receive functions
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: (a) RTTY transmitter, (b) RTTY receiver, and (c) gr-webserver terminal. They all can be on the same computer or on two or more separate computers by adjusting the ZMQ socket addresses. See ZMQ PUB Sink for an explanation of Addresses.
Updates have been made for the filters in the flowgraphs. They have been tested on GNU Radio versions 3.8.4.0, 3.9, and 3.10.0.0. See Porting Existing Flowgraphs to a Newer Version for differences in versions.
An Eye Sink display has been added to the RTTY receiver to aid in tuning. When correctly tuned, the eye pattern will cross at the zero axis.
See What is GNU Radio? and Installing GNU Radio for background information.
Note: These instructions are written for a Linux OS. Similar commands work for Mac and Windows.
- Open a terminal window.
- Change to the home directory.
cd ~/
- If you don't have 'git', enter
sudo apt install git
- Clone the repository:
git clone https://github.com/duggabe/gr-RTTY-basics.git
Go to gr-webserver and follow the instructions to install and start it using a separate terminal screen. Note: Version v1.0.16.0 is needed to work with this program.
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.
- Open a terminal window.
- Go to the gr-RTTY-basics/RTTY_xmt folder.
cd ~/gr-RTTY-basics/RTTY_xmt
- Execute Gnu Radio Companion.
gnuradio-companion
- Open RTTY_vco.grc from the file menu.
- Click 'Run' and 'Execute' or press F6.
- A new window titled "RTTY_vco" will open showing a scope trace with the transmitted signal.
- To Terminate the program, click the 'x' in the corner of the title line.
- Open a terminal window.
- Go to the gr-RTTY-basics/RTTY_rcv folder.
cd ~/gr-RTTY-basics/RTTY_rcv
- Execute Gnu Radio Companion.
gnuradio-companion
- Open RTTY_receive.grc from the file menu.
- Click 'Run' and 'Execute' or press F6.
- 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.
There are two tests which can be done: Loop-back and online RTTY news.
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.
If you connect the audio output of the computer to the audio input of the receiver using a patch cable, you can go to http://internet-tty.net:8000/ITTY and start the input. You must select the 'Reverse' tones. A RTTY news feed will be displayed.