Re: This flow graph is radiating negative Tx power

I've suggested this to you before. 

Start with a pure some way at your target frequency—what does your spectrum analyzer say about power. Now

Modulate it to produce a bandwidth of 1khz—what does your spectrum analyzer say about the power in each bin? Now what about with 10khz of modulation bandwidth, what of 100khz?

Sent from my iPhone

On Mar 16, 2021, at 1:52 PM, AKINYELE ITAMAKINDE <aitamakinde@abuad.edu.ng> wrote:



connected the antenna to the good channel Rx/TxThanks, I have been checking out your suggestions.

What i meant by "negative Tx power" is that the Tx power is giving negative value (-30dbm)

1. I have upgraded to GNURadio >=3.8 but it is giving this warning message after trying to import QT GUI sink

Block paths:
/home/elect/gnuradio/share/gnuradio/grc/blocks
Warning: restarting the docstring loader (crashed while loading 'qtgui_bercurve_sink')
Warning: restarting the docstring loader (crashed while loading 'qtgui_const_sink_x')
Warning: restarting the docstring loader (crashed while loading 'qtgui_edit_box_msg')
Warning: restarting the docstring loader (crashed while loading 'qtgui_freq_sink_x')
Warning: restarting the docstring loader (crashed while loading 'qtgui_histogram_sink_x')
Warning: docstring loader crashed too often

Pls, can you help to solve this problem?

2. For QT GUI Sink bandwidth, I will do that when the above problem is solved.

3.  Yes I measured the signal power using a spectrum analyzer.

4.  Did you check your signal amplitude at USRP bloc input? i don't know how to do this but check it when i solve the problem

5. yes, i connected the antenna to the good channel Rx/Tx.

On Fri, Mar 12, 2021 at 3:30 PM Christophe Seguinot <christophe.seguinot@orange.fr> wrote:

Hi

- What does "negative Tx power" means ?

A few suggestions:

• move to GNURadio >=3.8 (most of us uses GR 3.8 or 3.9 so it's difficult to help for outdated GR 3.7)
  
• QT GUI Sink : Bandwith should be equal to sample rate of the block incoming signal, i.e. samp_rate at the RRC Filter output (the FFT Sink does not work as a real spectrum analyzer)
  
• Did you measure the signal power using a spectrum analyzer ? When do so, the receiving antennna being close to the emitter antenna, you should get the -20 to -30 dB as compared to the emitted power (frequency close to 1GHz and 6dBi antennas (Indoor panel), this is depending on frequency and antenna gain). If your emitted power is +20 dBm, you should measure something in the range 0 dBm to -20 dBm. If not, there is something wrong in the transmission chain.
  
• Did you check your signal amplitude at USRP bloc input (The maximum value should be 1 Volt to get maximum RF  power which also depend on USRP settings
• Did you connected the antenna to the good channel Rx/Tx ?

Sincerely, Christophe

On 12/03/2021 15:08, AKINYELE ITAMAKINDE wrote:

Good day to  all community members.

Please, I need you to help correct this flow graph configuration. The Tx power radiating is too minimal. I have adjusted and also added some other blocks to boost the signal but all to no avail. The flow graph is been used for propagation channel measurement. I will like someone to take me through or send video and other link on how to solve this problem. The flow graph is attached.

 Thank you.

Akinyele.