# Multiply block problem in GRC 3.6.5.1 **URL:** \ **Category:** GNU Radio\ **Created:** [March 27, 2014, 11:32pm UTC](https://www.ruby-forum.com/t/multiply-block-problem-in-grc-3-6-5-1/240107 "2014-03-27T23:32:15Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [March 27, 2014, 11:32pm UTC](https://www.ruby-forum.com/t/multiply-block-problem-in-grc-3-6-5-1/240107/1 "2014-03-27T23:32:15Z")
Hello GRC community, I’m initiating with grc, trying to make a simple BASK. I searched a lot in the mailing list and in the tracker (I don’t know if it’s called that way) but I was unable to find anything about. It’s a simple problem (maybe due my GRC version) that does not ruin my projects at all.When I use the multiply block, inputing a cossine(12kHz) and a rectangular(1kHz) wave from the signal generator block, I don’t get the nice BASK that we should (Viewed from a wx osciloscope). Instead, the cossine change the amplitude in the middle 3 cycles and last longer 3 other cycles than it should. The fact is that it just happen when I use complex outputs and inputs. Both the I and Q wave have the same style. When I use real inputs, or if I separete the real and imag part, multiply they separately and then put together in a complex signal, it works like it should be. Maybe it can be an old and corrected bug Sorry for my bad english. Best regards Att.: Winderson Luiz Franzoi Speranzini ---
**Author:** ![Winderson\_Luiz\_Fran](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7cd45c/32.png) [@Winderson\_Luiz\_Fran](https://www.ruby-forum.com/u/Winderson_Luiz_Fran)\ **Post date:** [March 28, 2014, 12:18am UTC](https://www.ruby-forum.com/t/multiply-block-problem-in-grc-3-6-5-1/240107/2 "2014-03-28T00:18:59Z")
On Mar 27, 2014, at 15:10, Winderson Luiz Franzoi Speranzini [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Hello GRC community, > I’m initiating with grc, trying to make a simple BASK. I searched a lot in the > mailing list and in the tracker (I don’t know if it’s called that way) but I was > unable to find anything about. It’s a simple problem (maybe due my GRC version) > that does not ruin my projects at all. > When I use the multiply block, inputing a cossine(12kHz) and a rectangular(1kHz) > wave from the signal generator block, I don’t get the nice BASK that we should > (Viewed from a wx osciloscope). Instead, the cossine change the amplitude in the > middle 3 cycles and last longer 3 other cycles than it should. I wasn’t sure myself what a complex square wave actually ought to be, so I took a look at the source code and found this statement: /\* Implements a real square wave high from -PI to 0. - The imaginary square wave leads by 90 deg. \*/ This would explain your observation, I think: the complex square wave provided by GR is zero only 1/4 of the time. It probably isn’t what you want. > The fact is that it just happen when I use complex outputs and inputs. Both the > I and Q wave have the same style. When I use real inputs, or if I separete the > real and imag part, multiply they separately and then put together in a complex > signal, it works like it should be. Maybe it can be an old and corrected bug GR’s multiply\_cc block follows the rules of complex arithmetic as it should. Complex multiplication is not component-wise multiplication. To get the result I think you had in mind, then you should multiply the complex sinusoid by a _real_ square wave. That is, set your square wave signal generator to have a float output, convert the output to complex (leaving the imaginary input unconnected, implicitly zero), then multiply it with the sine. – Kevin R. [http://switchb.org/kpreid/](http://switchb.org/kpreid/) ---
**Author:** ![Winderson\_Luiz\_Fran](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7cd45c/32.png) [@Winderson\_Luiz\_Fran](https://www.ruby-forum.com/u/Winderson_Luiz_Fran)\ **Post date:** [March 28, 2014, 1:00am UTC](https://www.ruby-forum.com/t/multiply-block-problem-in-grc-3-6-5-1/240107/3 "2014-03-28T01:00:27Z")
Oh, thank you friend for this quick reply. I will do what you said By the way, where can I find the blocks source codes? Thank you again! Att.: Winderson Luiz Franzoi Speranzini