# LIMESDR - How to change the bandwidth of the signal (Sweep)?

**URL:** <https://discourse.myriadrf.org/t/limesdr-how-to-change-the-bandwidth-of-the-signal-sweep/6749>\
**Category:** LimeSDR\
**Created:** [3 December 2020 17:35 UTC](https://discourse.myriadrf.org/t/limesdr-how-to-change-the-bandwidth-of-the-signal-sweep/6749 "2020-12-03T17:35:42Z")\
**Posts on this page:** 4\
**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:** [3 December 2020 17:35 UTC](https://discourse.myriadrf.org/t/limesdr-how-to-change-the-bandwidth-of-the-signal-sweep/6749/1 "2020-12-03T17:35:42Z")

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Hello,

I’ve been trying to change the bandwidth of the signal I am Transmitting but it seems that it doesn’t exceeds the 200 KHz margin (spectrum analyzer). I have literally tried every configuration, that my knowledge is capable of. The following config is the one I have managed to have some kind of variation by changing the amplitude of the source signal. Knowing that the LimeSDR is capable of achieving 60 MHz bandwidth.

I would really appreciate any tips to increase the bandwidth and the basis of it. Actually, the results I get on Gnuradio’s Frequency Sink doesn’t match with the ones I get on the spectrum analyzer, in terms of frequency magnitudes.

Below I post one of my recent config.

Thank you.

 ![Screenshot from 2020-12-03 17-25-32](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/a/aa87d54e91b42ebfb38306feee5d92d0c0198367.png)

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**Author:** ![cmrincon](https://avatars.discourse-cdn.com/v4/letter/c/2bfe46/32.png) [@cmrincon](https://discourse.myriadrf.org/u/cmrincon)\
**Post date:** [4 December 2020 07:56 UTC](https://discourse.myriadrf.org/t/limesdr-how-to-change-the-bandwidth-of-the-signal-sweep/6749/2 "2020-12-04T07:56:12Z")

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Your signal is not 200 KHz wide, whatever gnuradio says you are not getting correct values for bandwitdh unless you adjust bandwidth QT GUI Sink block parameter correctly ( sample rate of your signal, 4M above, 20.1689M / 5 below)

I suggest you the [gnuradio tutorials](https://wiki.gnuradio.org/index.php/Tutorials) as i can see many other basic things wrong in your flowgraph.

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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:** [4 December 2020 10:47 UTC](https://discourse.myriadrf.org/t/limesdr-how-to-change-the-bandwidth-of-the-signal-sweep/6749/3 "2020-12-04T10:47:07Z")

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The signal is not 200 KHz wide but the bandwidth of my sawtooth sweep is. And I need it to be wider.  
The sample rate is wrong, yes. When I took this print I was making some tests, but notice that either way I resample it to be in the same rate as Tx.

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**Author:** ![cmrincon](https://avatars.discourse-cdn.com/v4/letter/c/2bfe46/32.png) [@cmrincon](https://discourse.myriadrf.org/u/cmrincon)\
**Post date:** [4 December 2020 12:09 UTC](https://discourse.myriadrf.org/t/limesdr-how-to-change-the-bandwidth-of-the-signal-sweep/6749/4 "2020-12-04T12:09:40Z")

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Do you mean the pulse width you see in the spectrum analizer? In theory it should have 0 width and should be slowly bouncing around 2GHz, of course you can apply some easy tricks:

Reduce FFT size to 64 or 32 and use blackman-harris window.

Another option would be reduce the spectral purity of the vco ouput by multiplying the output by a real cosine signal of frequency 50 KHz ( play with this value) and maintain amplitude to 1 and offset to 0 too.

I don’t know why you want this, but this is not practical.