# LimeSDR FM transceiver GnuRadio

**URL:** <https://discourse.myriadrf.org/t/limesdr-fm-transceiver-gnuradio/6631>\
**Category:** LimeSDR\
**Created:** [20 October 2020 11:11 UTC](https://discourse.myriadrf.org/t/limesdr-fm-transceiver-gnuradio/6631 "2020-10-20T11:11:17Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![andremartins4](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@andremartins4](https://discourse.myriadrf.org/u/andremartins4)\
**Post date:** [20 October 2020 11:11 UTC](https://discourse.myriadrf.org/t/limesdr-fm-transceiver-gnuradio/6631/1 "2020-10-20T11:11:17Z")

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Hello everyone,

I am afraid this is a dumb question but, I am trying to transmit a sound file using GnuRadio and all i can ear (on Rx side of the same limeSDR) is noise. This is my Gnuradio file:

 ![Screenshot from 2020-10-20 12-07-56](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/8/84b4cba064b21fd2e01cf9138ebb31a33840ce0c.png)

Can someone spot anything wrong with my configurations?

Btw, i have two antennas connected to RX1\_H and TX2\_1

Thank you in advance.

André Martins.

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**Author:** ![RightHalfPlane](https://avatars.discourse-cdn.com/v4/letter/r/46a35a/32.png) [@RightHalfPlane](https://discourse.myriadrf.org/u/RightHalfPlane)\
**Post date:** [20 October 2020 15:17 UTC](https://discourse.myriadrf.org/t/limesdr-fm-transceiver-gnuradio/6631/2 "2020-10-20T15:17:46Z")

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On the transmit side - the decimation should be 48k

On the receive side - If you want to tune the frequency received, use the “Frequency Xlating FIR Filter”.

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**Author:** ![andremartins4](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@andremartins4](https://discourse.myriadrf.org/u/andremartins4)\
**Post date:** [21 October 2020 10:31 UTC](https://discourse.myriadrf.org/t/limesdr-fm-transceiver-gnuradio/6631/3 "2020-10-21T10:31:30Z")

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Thank you for your answer but still doesn’t work, can’t listen anything but noise.

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**Author:** ![RightHalfPlane](https://avatars.discourse-cdn.com/v4/letter/r/46a35a/32.png) [@RightHalfPlane](https://discourse.myriadrf.org/u/RightHalfPlane)\
**Post date:** [21 October 2020 15:01 UTC](https://discourse.myriadrf.org/t/limesdr-fm-transceiver-gnuradio/6631/4 "2020-10-21T15:01:03Z")

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Here is a narrow band fm receiver for 2 meters from the gnu website -

[https://wiki.gnuradio.org/index.php/NBFM\_Receive](https://wiki.gnuradio.org/index.php/NBFM_Receive)

perhaps you could use that as a starting point.

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**Author:** ![phoenix](https://avatars.discourse-cdn.com/v4/letter/p/0ea827/32.png) [@phoenix](https://discourse.myriadrf.org/u/phoenix)\
**Post date:** [29 October 2020 00:48 UTC](https://discourse.myriadrf.org/t/limesdr-fm-transceiver-gnuradio/6631/5 "2020-10-29T00:48:32Z")

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Hi @andremartins4,

For LimeSDR source block, I found calibration bandwidth to set 0 significantly improves the sound quality.

This is my fm-receiver block in gnuradio 3.8:

 ![image](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/0/03c4b9394f3503a8bda4c1e37f03ee14535f3820.png)

here is the properties for limesdr source block that works for me for both commercial FM channels and my own fm transmission test

 ![image](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/8/8fdc681ced8ec1534ad95db36b9fecf9cc552db8.png)

another important thing to note is the sample rate, which I decreased from 2MHz (on limesource) to 48KHz (audio sink) gradually in each block operation.

Hope this help…

cheers!!!

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**Author:** ![andremartins4](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@andremartins4](https://discourse.myriadrf.org/u/andremartins4)\
**Post date:** [31 October 2020 10:06 UTC](https://discourse.myriadrf.org/t/limesdr-fm-transceiver-gnuradio/6631/6 "2020-10-31T10:06:09Z")

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Hello @phoenix awesome tip, in the mean time I’ve managed to put it to work properly aswell, had the antenna on tx2\_1 and it wasn’t transmitting anything. Thank you!