Re: Encode and modulate a test message on GNU Radio 3.8

[Marcus Müller]

Hi Rodrigo,

please always have the mailing list in CC: (or directly reply to the mailing 
list), so
that the others see you didn't get lost :)

On 14.07.21 13:06, Rodrigo Ruiz wrote:
> I will try to explain myself a bit better. I want to send a file using the 
> LimeSDR, but
> first I need to use a NRZ codification or something similar and modulate it. 

"Or something similar": yes, you'll need to do something different. NRZ solves 
zero
problems, and doesn't yield a waveform that can sensibly transmitted and then 
later
received on its own. This is a bit like you saying "I want to design a car, 
with a sturdy
shaft where I affix the oxes that draw it":
you're mixing technology that only applies to wired communication with those 
for wireless
communication. Sure, your car can have oxes, but these oxes will not be drawing 
the car,
because then it would not be a car. Your car would probably be better without 
the oxes,
and something else instead.

> After this, I will configure the LimeSDR Tx block to transmit that file to a 
> certain
> frequency. 

Ah but an SDR doesn't transmit "files", it transmits discrete-time waveform 
samples. Your
GNU Radio flowgraph's job is to transform the data in the file into symbols, 
these into
waveforms, and *then* they can be transmitted.

> Then with another LimeSDR, the idea is to do the opposite process to get the
> original file.

Exactly, so the flow graph at the receiver needs to take the waveform it gets 
from the
limesdr (which has absolutely no idea of what kind of transmission you have), 
and analyze
it such that it sees the symbols that your transmitter put into a waveform, and 
gets the
data bits they corresponded to!

> I will keep studying and let you know about my progress.

Great!
Best regards,
Marcus