# FSK modulation **URL:** \ **Category:** GNU Radio\ **Created:** [September 11, 2012, 12:23am UTC](https://www.ruby-forum.com/t/fsk-modulation/222792 "2012-09-11T00:23:12Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\ **Post date:** [September 11, 2012, 12:23am UTC](https://www.ruby-forum.com/t/fsk-modulation/222792/1 "2012-09-11T00:23:12Z")
Hello, I am quite new in GnuRadio Companion and I am just trying to transmit and receive a file through FSK modulation, but I am having some troubles. Attached is the block diagram that I am trying to implement. Do you know what is the problem here? I dont understand very well some block and how they work, such as the Chunks to symbols and Interpolating FIR FILTER. Can you give me a help? Thank you very much for your help. Best regards Joana ---
**Author:** ![Joana\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/b2d939/32.png) [@Joana\_G](https://www.ruby-forum.com/u/Joana_G)\ **Post date:** [September 13, 2012, 2:53am UTC](https://www.ruby-forum.com/t/fsk-modulation/222792/2 "2012-09-13T02:53:42Z")
On Mon, Sep 10, 2012 at 5:50 PM, Joana G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Thank you very much for your help. > > Best regards > Joana Joana, The chunks\_to\_symbols is a mapping block. It takes in a byte and converts that to the set of symbols defined by the block. Basically, the block takes in as its ‘Symbol Table’ argument a vector of complex numbers, call this sym\_table. The input stream to this block will be bytes, and those bytes are mapped to the complex symbols in sym\_table directly. So if the input value is 0, the output is sym\_table[0]; if the input is 3, the output is sym\_table[3]. That also means that your symbol table should be as large as the input value “chunks” are expected to be. The interpolating filter is a rate conversion filter. It interpolates a signal and then filters it to remove the images generated from the filtering. You definitely don’t want the taps of the filter to be all 1’s; that won’t filter out anything. You can use the ‘gr.firdes’ or ‘gr.optfir’ modules to build the filters for you. Remember that when building a filter for the interpolator, make sure you specify the sample rate as the sample rate /after/ the interpolation. Tom