# How can Receiver separate between two different frequency's input

**URL:** <https://www.ruby-forum.com/t/how-can-receiver-separate-between-two-different-frequencys-input/213406>\
**Category:** GNU Radio\
**Created:** [November 1, 2011, 8:31am UTC](https://www.ruby-forum.com/t/how-can-receiver-separate-between-two-different-frequencys-input/213406 "2011-11-01T08:31:40Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\
**Post date:** [November 1, 2011, 8:31am UTC](https://www.ruby-forum.com/t/how-can-receiver-separate-between-two-different-frequencys-input/213406/1 "2011-11-01T08:31:40Z")

</div>

I am working on an application where i receive input at audio\_sink and  
check for tone or data.  
Data is FSK modulated at 1k and 3k whereas Tone is of 2k (i.e Tone lies  
in  
the middle).

I have written a flow graph which consists of two heirarichal flow  
graphs  
(tone\_rx and data\_rx).  
Input is received at audio\_sink and then forwarded to both sub-graphs.

My code works fine when tone is received but there is a problem when  
Data  
is received.  
Because Data consists of FSK code and it has 2k components in it which  
also  
triggers Tone graph.

So i want to ask is there any GnuRadio Block by using which i can avoid  
triggering of tone while receiving Data  
as i need to eliminate 2k component for Data but retain it when input it  
is  
Tone. OR  
is there any such method by which we identify at the start whether it is  
data or tone.  
i am using laptop sound card (not usrp).

```
                 ____________________
                                      -------> | Tone Rx Flow Graph

```

|  
\_\_\_\_\_\_\_\_\_\_ | |\_\_\_\_\_\_\_\_\_\_\_\_\_\_**|  
| audio\_sink |**|  
|\_\_\_\_\_\_\_\_\_\_| |  
|

* * *

```
                                      ------- > | Data Rx Flow 

```

Graph  
|  
|\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_|

–  
\*  
Best Regards

Niaz A.\*  
Lab Engineer  
NUCES-FAST, Islamabad Campus  
EXT-271

Engineers motto: cheap, good, fast: choose any two

---

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**Author:** ![arif](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/74df32/32.png) [@arif](https://www.ruby-forum.com/u/arif)\
**Post date:** [November 1, 2011, 10:25pm UTC](https://www.ruby-forum.com/t/how-can-receiver-separate-between-two-different-frequencys-input/213406/2 "2011-11-01T22:25:54Z")

</div>

> My code works fine when tone is received but there is a problem when  
> i am using laptop sound card (not usrp).

Simple first approximation. Use the short-term-average power calculated  
over the data channels (1KHz and 3KHz), to drive a squelch  
function on the 2KHz channel. I’ll leave the details up to you, but  
I’d basically have some logic that said “if energy at 1KHz and energy at  
3KHz,  
squelch the 2KHz tone channel.”

–  
Marcus L.  
Principal Investigator  
Shirleys Bay Radio Astronomy Consortium

> **[Live Draw HK Tercepat | Result HK | HK Pools | Live HK | HK Prize Hari Ini](https://www.sbrac.org/)**
>
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---

<div class="post-metadata">

**Author:** ![arif](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/74df32/32.png) [@arif](https://www.ruby-forum.com/u/arif)\
**Post date:** [November 4, 2011, 5:59am UTC](https://www.ruby-forum.com/t/how-can-receiver-separate-between-two-different-frequencys-input/213406/3 "2011-11-04T05:59:12Z")

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Thanks Marcus,  
I appreciate your approach and i guess i will need goertzel transform  
over  
these frequencies.

On Wed, Nov 2, 2011 at 2:25 AM, Marcus D. Leech [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> > My code works fine when tone is received but there is a problem when Data  
> > i am using laptop sound card (not usrp).  
> > –

[https://lists.gnu.org/mailman/\*\*listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/**listinfo/discuss-gnuradio)[https://lists.gnu.org/mailman/listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)

> 

–  
_Niaz A._

We are always more anxious to be distinguished for a talent which we do  
not possess, than to be praised for the fifteen which we do possess\*  
: Mark  
Twain [http://thinkexist.com/quotes/mark\_twain/](http://thinkexist.com/quotes/mark_twain/)\*

- [http://thinkexist.com/quotes/mark\_twain/](http://thinkexist.com/quotes/mark_twain/)\*