# Convolutional Code output does not match polynomial **URL:** \ **Category:** GNU Radio\ **Created:** [September 1, 2015, 11:56am UTC](https://www.ruby-forum.com/t/convolutional-code-output-does-not-match-polynomial/243201 "2015-09-01T11:56:29Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Sadaf\_N](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@Sadaf\_N](https://www.ruby-forum.com/u/Sadaf_N)\ **Post date:** [September 1, 2015, 11:56am UTC](https://www.ruby-forum.com/t/convolutional-code-output-does-not-match-polynomial/243201/1 "2015-09-01T11:56:29Z")
I am trying channel coding in gnuradio. I am using convolutional encoder with K=7 and R=1/2 with polynomials [109, 79] (default). However I am not getting the expected result. I input a known bit sequence, single frame using head block, and observe the output of the encoder using file sink. The output I think is not correct according to the given polynomials. Input bit stream is > **[00 00 00 00 00 00 00 00 01 00 00 00 01 00 01 01 00 00 01 01 01 01 01 00 01 00...](https://pastebin.com/thsYtLFG)** > > Pastebin.com is the number one paste tool since 2002. Pastebin is a website where you can store text online for a set period of time. I am getting this output > **[00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 01 00 01 01 01 01 01 01 01...](https://pastebin.com/P42QNjiE)** > > Pastebin.com is the number one paste tool since 2002. Pastebin is a website where you can store text online for a set period of time. However, I am expecting (in hex) 00 00 E3 32 63 D7 4B FA D3 … I have attached the flowgraph I am using for this purpose. I did a dry run by drawing a diagram of the encoder and inputing initial two bytes. Diagram of the encoder is also attached. I also used MATLAB script to test and found that my dry run output matches with MATLAB but not with Gnuradio output. I also played with the endianness but could not get the desired result. Maybe I am doing something wrong in configuring the encoder? Also another thing I noticed is that in QA codes of gr-fec I found import fec\_swig as fec import blocks\_swig as blocks I think this should be from gnuradio import fec, blocks Am I right? I am using gnuradio 3.7.8. ---
**Author:** ![bob\_wole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/b4bc9f/32.png) [@bob\_wole](https://www.ruby-forum.com/u/bob_wole)\ **Post date:** [September 8, 2015, 8:14am UTC](https://www.ruby-forum.com/t/convolutional-code-output-does-not-match-polynomial/243201/2 "2015-09-08T08:14:55Z")
On Tue, Sep 1, 2015 at 2:55 PM, bob wole [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > and found that my dry run output matches with MATLAB but not with Gnuradio > > from gnuradio import fec, blocks > > Am I right? I am using gnuradio 3.7.8. > > – > Bob I am still waiting to get a reply on this. Anyone else verified the output of the convolutional encoder?