# FSK receiver **URL:** \ **Category:** GNU Radio\ **Created:** [August 28, 2015, 11:21pm UTC](https://www.ruby-forum.com/t/fsk-receiver/243177 "2015-08-28T23:21:12Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\ **Post date:** [August 28, 2015, 11:21pm UTC](https://www.ruby-forum.com/t/fsk-receiver/243177/1 "2015-08-28T23:21:12Z")
Dear all, I have just built a FSK receiver aim to receive Cubesat data with FSK modulation with 9600 baud rate, below is my flow graph. I have just tested it with usb dongle RTL-SDR, however when I’m using audio sink, I received OOOOO (overrun I think) continuously . Does it have anything wrong with my set up ? samplerate 2M cut off freq 9600 transition 4800 I really appriciate for any comment on my FSK receiver flowgraph, I am a newbie 🙂 Thank you and best regard, Hoang ---
**Author:** ![trbhoang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/48db29/32.png) [@trbhoang](https://www.ruby-forum.com/u/trbhoang)\ **Post date:** [August 29, 2015, 1:05am UTC](https://www.ruby-forum.com/t/fsk-receiver/243177/2 "2015-08-29T01:05:12Z")
Hi Hoang, Yes it’s a problem with your design. You have 2 Msps feeding into an audio sink that probably goes up to 48 ksps. You need to change your sample rate from 2 Msps to a rate your sound card supports. I would target one of the default rates you can select from the audio sink. You can use polyphase arbitrary resampler block with the proper resampling ratio 2M/48k entered leaving the taps blank and the other parameters to default. Hope that helps, Rich On Fri, Aug 28, 2015 at 2:19 PM, Hoang Nguyen T. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![trbhoang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/48db29/32.png) [@trbhoang](https://www.ruby-forum.com/u/trbhoang)\ **Post date:** [September 1, 2015, 1:33am UTC](https://www.ruby-forum.com/t/fsk-receiver/243177/3 "2015-09-01T01:33:09Z")
Thank you Rich, I have added Rational Resample with the formular : Fs\_out = Fs\_in x Interpolation / Decimation Then the grc run without error. On Fri, Aug 28, 2015 at 7:03 PM, Richard B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![trbhoang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/48db29/32.png) [@trbhoang](https://www.ruby-forum.com/u/trbhoang)\ **Post date:** [September 3, 2015, 7:04am UTC](https://www.ruby-forum.com/t/fsk-receiver/243177/4 "2015-09-03T07:04:38Z")
Hi Rich, I am continue with the transmitting part ? However, I cannot fine the FSK modulate block or Quadrature mod in GNU radio companion. Is there another block that use for FSK modulation in GNU radio ? I found DPSK mod, GFSK mod, GMSK mod … however not FSK. Do you have any example for transmitting flow graph in GNU radio with USRP ? If yes, could you please give any hint ? Thank you and best regard Hoang On Mon, Aug 31, 2015 at 7:31 PM, Hoang Nguyen T. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![trbhoang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/48db29/32.png) [@trbhoang](https://www.ruby-forum.com/u/trbhoang)\ **Post date:** [September 5, 2015, 3:13pm UTC](https://www.ruby-forum.com/t/fsk-receiver/243177/5 "2015-09-05T15:13:11Z")
Thank you Marcus. On Thu, Sep 3, 2015 at 4:05 AM, Marcus Müller [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![trbhoang](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/48db29/32.png) [@trbhoang](https://www.ruby-forum.com/u/trbhoang)\ **Post date:** [September 3, 2015, 10:06am UTC](https://www.ruby-forum.com/t/fsk-receiver/243177/6 "2015-09-03T10:06:20Z")
Hoang, there’s the frequency modulator block. I think this is what you’re looking for. Best regards, Marcus