AFSK BELL 202 Modulator

This is a GNU Radio hierblock to create Bell 202 standard AFSK modulation. This block expecting input as a bitstream and outputs AFSK modulated real signal stream.

Tested on GNU Radio v3.7.11 - Ubuntu.

Index

1. Installation
2. AFSK Bell 202 Modulator in More Detail
3. Example
4. TODO

Installation

You have to have GNU Radio v3.7.10 (or newer) in your computer first.

$ cd
$ cd gr-HDLC-AFSK/hierblocks/afsk-bell202-modulator/
$ gnuradio-companion afsk_bell202_mod.grc

• Run the flowgraph (F6).
• Reload Blocks
• Finish. Now this hierblock will appear under HDLC AFSK category as AFSK Bell-202 Modulator block.

Detail

• This AFSK Modulator outputs 1700 Hz-centered AFSK signal with mark frequency is 1200 Hz and space frequency is 2200 Hz.

• Baudrate is fixed at 1200. Real baudrate implementation is through symbol repetition.

• The output of the modulator is pulse shaped using a root raised cosine filter. This filter ensures only bandwidth-limited modulation signal is produced.

The following is the AFSK Bell 202 Modulator’s bigger picture:

Example

File:

gr-HDLC-AFSK/hierblocks/afsk-bell202-modulator/afsk_bell202_mod-example.grc

TODO

// TODO