# Limesdr gnuradio and fm

**URL:** <https://discourse.myriadrf.org/t/limesdr-gnuradio-and-fm/1081>\
**Category:** Uncategorized\
**Created:** [6 April 2017 12:58 UTC](https://discourse.myriadrf.org/t/limesdr-gnuradio-and-fm/1081 "2017-04-06T12:58:15Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Mitchell](https://avatars.discourse-cdn.com/v4/letter/m/e19adc/32.png) [@Mitchell](https://discourse.myriadrf.org/u/Mitchell)\
**Post date:** [6 April 2017 12:58 UTC](https://discourse.myriadrf.org/t/limesdr-gnuradio-and-fm/1081/1 "2017-04-06T12:58:15Z")

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FM reciever in gnuradio with limesdr? Anyone has a example?

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**Author:** ![TegwynTwmfatt](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/tegwyntwmfatt/32/193_2.png) [@TegwynTwmfatt](https://discourse.myriadrf.org/u/TegwynTwmfatt)\
**Post date:** [6 April 2017 14:38 UTC](https://discourse.myriadrf.org/t/limesdr-gnuradio-and-fm/1081/2 "2017-04-06T14:38:47Z")

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Check out the downloadable files on my Hackaday page:

[https://hackaday.io/project/20500/files](https://hackaday.io/project/20500/files)

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**Author:** ![bardia1990](https://avatars.discourse-cdn.com/v4/letter/b/91b2a8/32.png) [@bardia1990](https://discourse.myriadrf.org/u/bardia1990)\
**Post date:** [8 April 2017 06:07 UTC](https://discourse.myriadrf.org/t/limesdr-gnuradio-and-fm/1081/3 "2017-04-08T06:07:44Z")

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hi. how to set osmocom source device argument (driver=lime,soapy=0) in gnuradio to use two receive channel independently(by USB interface) ? or how to set this argument to use two LimeSDR to use four receive channel independently?  
Thanks lot

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**Author:** ![TegwynTwmfatt](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/tegwyntwmfatt/32/193_2.png) [@TegwynTwmfatt](https://discourse.myriadrf.org/u/TegwynTwmfatt)\
**Post date:** [8 April 2017 08:57 UTC](https://discourse.myriadrf.org/t/limesdr-gnuradio-and-fm/1081/4 "2017-04-08T08:57:28Z")

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Yes - I’ve asked the same question @bardia1990 . It appears that the person that can help us - @joshblum - may well have been abducted by aliens 😞 .Maybe @andrewback can shed some light on his whereabouts?

From what I understand, which is not very much, the Soapy drivers need to be updated with the ability to turn MIMO on/off ?

Neither Pothos nor GNU radio seem to be able to perform duplex operation, which is a massive PITA for getting my current project finished.

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**Author:** ![joshblum](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/joshblum/32/18_2.png) [@joshblum](https://discourse.myriadrf.org/u/joshblum)\
**Post date:** [8 April 2017 20:42 UTC](https://discourse.myriadrf.org/t/limesdr-gnuradio-and-fm/1081/5 "2017-04-08T20:42:54Z")

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> [@bardia1990](#):
>
> hi. how to set osmocom source device argument (driver=lime,soapy=0) in gnuradio to use two receive channel independently(by USB interface) ? or how to set this argument to use two LimeSDR to use four receive channel independently?  
> Thanks lot

The gr-osmosdr source can be configured for two channels, which should give you two streams. You cant actually have two separate gr-osmosdr sources for one single LimeSDR because the channel 0 and channel 1 streams are physically aligned as they flow from the lms7 to the fpga to the usb…

Multiple gr-osmosdr sources can be used for multiple LimeSDRs. Use the serial from the `LimeUtil --find` or `SoapySDRUtil --find` to specify a particular device. `driver=lime,soapy=0,serial=1234`

So four receive channels for two LimeSDR devices would involve two gr-osmosdr sources, each configured for two channels, and different serial numbers.

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**Author:** ![Ismas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ismas/32/718_2.png) [@Ismas](https://discourse.myriadrf.org/u/Ismas)\
**Post date:** [10 April 2017 07:55 UTC](https://discourse.myriadrf.org/t/limesdr-gnuradio-and-fm/1081/6 "2017-04-10T07:55:27Z")

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The two receiver channels share CLK, so you can’t separate much, but you can sintonize any number of channels (while computer resources last) within the sampled spectrum, as can be seen in SDR Console for example.

For beginners (as me) just a little SDR theory. To see an example, see this diagram (sorry for linking to myself)  
[http://doublepanic.com/wp-content/uploads/2017/04/LimeSDR\_receiver\_diagram.png](http://doublepanic.com/wp-content/uploads/2017/04/LimeSDR_receiver_diagram.png)  
As you can see, sampled spectrum is multiplyed with a co/senoid signal source, a BFO. This is math equivalent to frecuency mixing as in heterodyne. The result is the spectrum shifted towards zero the amount of frecuency of BFO. More especifically, you get f1+f2, f1-f2, and f2-f1. If you low-filter the f1+f2 freq (as seen in next block, low past filter) then you get the f1-f2 and have sintonized a part of the total spectrum. Positive and negative BFO gets you to one side or other of the central frequency in this I/Q sample. Filter bandwith is the decoded signal bandwidth. Then you can demodulate and sound.  
You can repeat the BFO-Multiply-Filter block with different BFO frequencies within sampled spectrum bandwith as you want. You can see an example down my page, where 3 signals can be decoded (no more linking 🙂)