# What Modulation Scheme does RFX400 can perform?

**URL:** <https://www.ruby-forum.com/t/what-modulation-scheme-does-rfx400-can-perform/201612>\
**Category:** GNU Radio\
**Created:** [January 11, 2011, 5:58pm UTC](https://www.ruby-forum.com/t/what-modulation-scheme-does-rfx400-can-perform/201612 "2011-01-11T17:58:45Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**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:** [January 11, 2011, 5:58pm UTC](https://www.ruby-forum.com/t/what-modulation-scheme-does-rfx400-can-perform/201612/1 "2011-01-11T17:58:45Z")

</div>

Same as Title, What Modulation Scheme does RFX400 can perfom?

If I draw a flow graph like below:  
[http://dl.dropbox.com/u/11382666/02\_RXTX/TX.grc.png](http://dl.dropbox.com/u/11382666/02_RXTX/TX.grc.png)

What Modulation Scheme is used by default?

Can I change it?

---

<div class="post-metadata">

**Author:** ![Songsong\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/49beb7/32.png) [@Songsong\_G](https://www.ruby-forum.com/u/Songsong_G)\
**Post date:** [January 11, 2011, 6:44pm UTC](https://www.ruby-forum.com/t/what-modulation-scheme-does-rfx400-can-perform/201612/2 "2011-01-11T18:44:01Z")

</div>

On Wed, 2011-01-12 at 01:57 +0900, Songsong G. wrote:

> Can I change it?  
> Songsong,

The modulation can be anything you want it to be. It’s a little  
confusing if you aren’t used to thinking about DSP and SDR. The USRP+RFX  
will happily output the raw samples you put into it, and it’s up to you  
to encode them with a reasonable modulation. The same works for receive.  
If you FM modulate your data, it will be FM modulated when it goes out  
on the air. If you AM modulate it, it will be AM modulated.

For another example, the process to AM demodulate a signal is just a  
complex-to-magnitude transform (i.e., y=|x|). So you can use  
gr.complex\_to\_mag as an AM demodulator. There are existing blocks to do  
FM demodulation as well. They can be found in gnuradio-companion under  
“Modulators”. Any other modulation scheme you can come up with can be  
used as well, if you can mathematically describe it and code it up.

Take a look at the examples in gnuradio/gnuradio-examples/python/usrp  
for an idea as to what I’m talking about. The AM and FM receivers are a  
good place to begin.

–n

---

<div class="post-metadata">

**Author:** ![Songsong\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/49beb7/32.png) [@Songsong\_G](https://www.ruby-forum.com/u/Songsong_G)\
**Post date:** [January 11, 2011, 6:58pm UTC](https://www.ruby-forum.com/t/what-modulation-scheme-does-rfx400-can-perform/201612/3 "2011-01-11T18:58:28Z")

</div>

On 01/11/2011 11:57 AM, Songsong G. wrote:

> Same as Title, What Modulation Scheme does RFX400 can perfom?

Any modulation scheme you can think of that can be represented  
efficiently as a series of  
mathematical operations producing a baseband waveform that is then  
up-converted by the  
RFX2400 to the final frequency.

In SDR, the hardware doesn’t “know” anything about modulation or  
demodulation, that’s up to the  
software. The only limitation of the hardware is the bandwidth of the  
resulting waveform.

The daughtercards typically anti-alias bandwidth limit the waveforms to  
about 25-30MHz or so, on  
the analog mixer inputs/outputs.

–  
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)**
>
> Temukan live draw hk tercepat melalui halaman hk pools yang resmi dan dapatkan result hk prize melalui live hk secara langsung di situs kami.

---

<div class="post-metadata">

**Author:** ![Songsong\_G](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/49beb7/32.png) [@Songsong\_G](https://www.ruby-forum.com/u/Songsong_G)\
**Post date:** [January 11, 2011, 8:09pm UTC](https://www.ruby-forum.com/t/what-modulation-scheme-does-rfx400-can-perform/201612/4 "2011-01-11T20:09:32Z")

</div>

Thank you for your anwer 🙂

Then, in short,

Does the flow graph I mentioned use carrier freq. 450 MHz or not?

From the file source, it is just a baseband signal

2011/1/12 Marcus D. Leech [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)