# USRP2/Gnuradio - satellite application **URL:** \ **Category:** GNU Radio\ **Created:** [June 1, 2015, 6:17am UTC](https://www.ruby-forum.com/t/usrp2-gnuradio-satellite-application/242155 "2015-06-01T06:17:36Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\ **Post date:** [June 1, 2015, 6:17am UTC](https://www.ruby-forum.com/t/usrp2-gnuradio-satellite-application/242155/1 "2015-06-01T06:17:36Z")
Good evening, I will appreciate your help and guidance. since 3 weeks I’m trying to implement an application to derive the sky noise and attenuation from a beacon satellite signal. Using gnuardio and USRP2 (Ettus N210) I’m able to receive the and see the beacon signal at a defined frequency (FFT plot). What I need is write an application in python or C++ that allow to me to retrieve and plot the skynoise and attenuation values. The problem I have is when using the blocks in gnuradio how to retrieve the signal power so then I can use a math formulas to derive both attenuation and skynoise and then plot them again in new graph to show them? I would appreciate any help from your side. Thank you and best regards _Abdeslam B._ ---
**Author:** ![Abdeslam\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/97f17d/32.png) [@Abdeslam\_B](https://www.ruby-forum.com/u/Abdeslam_B)\ **Post date:** [June 1, 2015, 8:27am UTC](https://www.ruby-forum.com/t/usrp2-gnuradio-satellite-application/242155/2 "2015-06-01T08:27:52Z")
Hi Abdeslam, I assume you already have definite formulas that define the estimator for these two numbers. Unless you can directly “click together” that estimator in GRC, you will most likely have to implement it. In many cases, doing this in Python is rather easy (especially if you come from a python or matlab background), so I’d recommend reading at least the first 3 chapters of [https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided\_Tutorials](https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorials) Best regards, Marcus ---
**Author:** ![Abdeslam\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/97f17d/32.png) [@Abdeslam\_B](https://www.ruby-forum.com/u/Abdeslam_B)\ **Post date:** [June 1, 2015, 8:30am UTC](https://www.ruby-forum.com/t/usrp2-gnuradio-satellite-application/242155/3 "2015-06-01T08:30:47Z")
Hi, > The problem I have is when using the blocks in gnuradio how to retrieve the > signal power You mean you want the signal power as a dBm value ? Just won’t happen … Too many things in the chain, you’d have to calibrate it for a specific freq / board / gain / temp / phase of the moon / … Cheers, Sylvain ---
**Author:** ![Abdeslam\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/97f17d/32.png) [@Abdeslam\_B](https://www.ruby-forum.com/u/Abdeslam_B)\ **Post date:** [June 1, 2015, 10:28pm UTC](https://www.ruby-forum.com/t/usrp2-gnuradio-satellite-application/242155/4 "2015-06-01T22:28:33Z")
Hi, @Marcus : Yes I have already the formulas ad now trying to implement in C++. The problem I have is I need the output from the “USRP source” as number for instaance and then apply formuas and again show it in time axis. I will go back again to the s first chapter maybe I miss something. @Sylvain : Yes that’s true from the “USRP source” I need the value as a dBm or dB. The calibration part will do it after getting the value from the source then I will derive the attenuation from noise within formuals. I already did the link budget need just now to values from the source. Thank you and best regards Abdeslam _Abdeslam B._ ---
**Author:** ![Abdeslam\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/97f17d/32.png) [@Abdeslam\_B](https://www.ruby-forum.com/u/Abdeslam_B)\ **Post date:** [June 2, 2015, 11:23am UTC](https://www.ruby-forum.com/t/usrp2-gnuradio-satellite-application/242155/5 "2015-06-02T11:23:48Z")
Dear Abs, you’ve asked this question on discuss-gnuradio and already got two answers. In case you’ve missed those, and to avoid that people tell you what you already know: Sylvain wrote that, due to a large number of factors contributing to what you see as digital amplitude, you will need to calibrate yourself, using exactly the system you want to use to measure power: > You mean you want the signal power as a dBm value ? > > Just won’t happen … Too many things in the chain, you’d have to > calibrate it for a specific freq / board / gain / temp / phase of the > moon / … And I explained that if you have a mathematical representation of how your estimator works, you might be able to write a custom estimator block for both of your values of interest: > I assume you already have definite formulas that define the estimator > for these two numbers. > Unless you can directly “click together” that estimator in GRC, you > will most likely have to implement it. > In many cases, doing this in Python is rather easy (especially if you > come from a python or matlab background), > so I’d recommend reading at least the first 3 chapters of > [https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided\_Tutorials](https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorials) If these answers didn’t help you out, I think it would be wise to explain what these answers are lacking, instead of just re-posting the same question. Best regards, Marcus ---
**Author:** ![Abdeslam\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/97f17d/32.png) [@Abdeslam\_B](https://www.ruby-forum.com/u/Abdeslam_B)\ **Post date:** [June 2, 2015, 3:40pm UTC](https://www.ruby-forum.com/t/usrp2-gnuradio-satellite-application/242155/6 "2015-06-02T15:40:16Z")
Dear Marcus, I thought too differents forums I posted the same question at the same time. OK let’s continue here this is my reply : _Hi,_ _@Marcus : Yes I have already the formulas ad now trying to implement in C++. The problem I have is I need the output from the “USRP source” as number for instaance and then apply formuas and again show it in time axis. I will go back again to the s first chapter maybe I miss something._ _@Sylvain : Yes that’s true from the “USRP source” I need the value as a dBm or dB. The calibration part will do it after getting the value from the source then I will derive the attenuation from noise within formuals. I already did the link budget need just now to values from the source._ _Thank you and best regardsAbdeslam_ _Abdeslam B._ ---
**Author:** ![Abdeslam\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/97f17d/32.png) [@Abdeslam\_B](https://www.ruby-forum.com/u/Abdeslam_B)\ **Post date:** [June 2, 2015, 8:00pm UTC](https://www.ruby-forum.com/t/usrp2-gnuradio-satellite-application/242155/7 "2015-06-02T20:00:55Z")
Hello, I need to communicate with the USRP and receive data like these : 2015-06-02 02:32:29.246055 center\_freq 1000775000.0 freq 1000718750.0 power\_db 5.59449106566 noise\_floor\_db -121.702764103 2015-06-02 02:32:29.246138 center\_freq 1000775000.0 freq 1000725000.0 power\_db 5.80020853614 noise\_floor\_db -121.702764103 2015-06-02 02:32:29.246236 center\_freq 1000775000.0 freq 1000731250.0 power\_db 6.41043187666 noise\_floor\_db -121.702764103 2015-06-02 02:32:29.246343 center\_freq 1000775000.0 freq 1000737500.0 power\_db 5.72799835886 noise\_floor\_db -121.702764103 2015-06-02 02:32:29.246443 center\_freq 1000775000.0 freq 1000743750.0 power\_db 8.61943426588 noise\_floor\_db Regards Abdeslam _Abdeslam B._ On 1 June 2015 at 22:36, Abdeslam B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)