# Limesdr USB How to output hf 1~35MHz

**URL:** <https://discourse.myriadrf.org/t/limesdr-usb-how-to-output-hf-1-35mhz/3981>\
**Category:** General Discussion\
**Created:** [11 January 2019 13:57 UTC](https://discourse.myriadrf.org/t/limesdr-usb-how-to-output-hf-1-35mhz/3981 "2019-01-11T13:57:45Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![hmbbc](https://avatars.discourse-cdn.com/v4/letter/h/ea5d25/32.png) [@hmbbc](https://discourse.myriadrf.org/u/hmbbc)\
**Post date:** [11 January 2019 13:57 UTC](https://discourse.myriadrf.org/t/limesdr-usb-how-to-output-hf-1-35mhz/3981/1 "2019-01-11T13:57:45Z")

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Hello！  
I am debugging with GnuRadio,  
When setting the RF frequency to 35MHz,  
The frequency meter shows a frequency of 40.23245MHz.  
The same is true for the 20MHz frequency.  
How to use limesdr usb to output HF?  
Such as: TX1 1MHz ~ 35MHz

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**Author:** ![siddiki](https://avatars.discourse-cdn.com/v4/letter/s/f6c823/32.png) [@siddiki](https://discourse.myriadrf.org/u/siddiki)\
**Post date:** [10 September 2019 14:14 UTC](https://discourse.myriadrf.org/t/limesdr-usb-how-to-output-hf-1-35mhz/3981/2 "2019-09-10T14:14:08Z")

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I have the same question, I am unable to generate frequencies below 30 MHz. Dont know what to do.

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**Author:** ![yt7pwr](https://avatars.discourse-cdn.com/v4/letter/y/ecd19e/32.png) [@yt7pwr](https://discourse.myriadrf.org/u/yt7pwr)\
**Post date:** [10 September 2019 15:34 UTC](https://discourse.myriadrf.org/t/limesdr-usb-how-to-output-hf-1-35mhz/3981/3 "2019-09-10T15:34:04Z")

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For HF below 30MHz use NCO, downconverter for transmit and upconverter for receive. Also, dont forget to set LPF high enough.