Re: [Discuss-gnuradio] User Generated Signals

[Jonathan Shan]

On Sat, 7 Apr 2007, Jonathan Shan wrote:

> I am trying to transmit and receive a signal that the user defines. I am 
> following the directions written by Eric Blossom on independently generating 
> signals and then transmitting them.
> "
>  u = usrp.sink_c(...)
>
>  i = <generate I somehow>
>  q = <generate Q somehow>
>  f2c = gr.float_to_complex()
>  fg.connect(i, (f2c, 0))
>  fg.connect(q, (f2c, 1))
>  fg.connect(f2c, u)
> "
>
> i = [1000, .... , 923]   // 16 values in this array, one period of cosine
> q = [0, .....,  -383]   // calculated using hilbert transform, 16 values
>
> When I connect f2c to gr.filesink, I see a cosine wave. However, the received 
> signal looks like noise centered around 51.

I tried changing the number of samples in i, q to larger values. Same 
result. I also tried setting the transmit gain to max.

I think the problem is modulation / de-modulation. But what is 
usrp.tune(carrier_freq) for? I can transmit and receive correctly 
gr.sig_source_c just using usrp.tune on both ends.

Jonathan Shan