# How it limesdr work TX below 30mhz on gnuradio, change code?

**URL:** <https://discourse.myriadrf.org/t/how-it-limesdr-work-tx-below-30mhz-on-gnuradio-change-code/2254>\
**Category:** LimeSDR\
**Created:** [18 January 2018 02:36 UTC](https://discourse.myriadrf.org/t/how-it-limesdr-work-tx-below-30mhz-on-gnuradio-change-code/2254 "2018-01-18T02:36:19Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![KAKAKs](https://avatars.discourse-cdn.com/v4/letter/k/b782af/32.png) [@KAKAKs](https://discourse.myriadrf.org/u/KAKAKs)\
**Post date:** [18 January 2018 02:36 UTC](https://discourse.myriadrf.org/t/how-it-limesdr-work-tx-below-30mhz-on-gnuradio-change-code/2254/1 "2018-01-18T02:36:19Z")

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I test some project control signal on 27mhz, but set frequency to below 30mhz result still 30mhz.  
How let it work change code and reprogram?  
I get similar code like “if (targetRfFreq \< 30e6) targetRfFreq = 30e6;”, i changed but not work.  
Whether some similar code on FPGA , driver or FX?  
Please help me !

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**Author:** ![andrewback](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@andrewback](https://discourse.myriadrf.org/u/andrewback)\
**Post date:** [18 January 2018 09:23 UTC](https://discourse.myriadrf.org/t/how-it-limesdr-work-tx-below-30mhz-on-gnuradio-change-code/2254/2 "2018-01-18T09:23:44Z")

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I think this is where you would need to engage the NCO. @IgnasJ should be able to advise.

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**Author:** ![KAKAKs](https://avatars.discourse-cdn.com/v4/letter/k/b782af/32.png) [@KAKAKs](https://discourse.myriadrf.org/u/KAKAKs)\
**Post date:** [18 January 2018 14:17 UTC](https://discourse.myriadrf.org/t/how-it-limesdr-work-tx-below-30mhz-on-gnuradio-change-code/2254/3 "2018-01-18T14:17:09Z")

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Ok how to set 😀

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**Author:** ![IgnasJ](https://avatars.discourse-cdn.com/v4/letter/i/278dde/32.png) [@IgnasJ](https://discourse.myriadrf.org/u/IgnasJ)\
**Post date:** [19 January 2018 07:31 UTC](https://discourse.myriadrf.org/t/how-it-limesdr-work-tx-below-30mhz-on-gnuradio-change-code/2254/4 "2018-01-19T07:31:54Z")

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GNU radio uses SaopySDR and as far as I know SoapySDR should be using NCO automatically when \<30MHz.