Re: [Discuss-gnuradio] USRP - GNURADIO AGC

[Marcus Müller]

Hi Simone,

On 25.07.2014 15:55, Simone Ciccia S210664 wrote:
> Hi Marcus,
> thank you for your answer...
>
> Ok, suppose that we are in reception,
> I said before the PGA thinking that at this stage the signal is already in
> baseband ( MIXER -> FILTER -> PGA -> ADC ), so in this way I will have
> compared signal level before PGA with the full scale of ADC.
Actually, compare the schematics I linked to: the variable attenuation
comes before the mixer, so
Antenna->LNA->PGA->mixing->ADC is the order.
> But your are right, comparing energy is more simple!
> Just another question...
> Using the USRP as receiver, we set the gain as "variable" in UHD source
> block "options".
> Now, the changes of this variable take effect on the USRP during runtime???
> or just set the initial value and we need to use set_gain() ???
I suppose we're talking about GRC flow graphs now :)
Yes, there is a callback that will automatically set the gain when you
change the variable at runtime.
You *can* use set_gain() directly, too.


Greetings,
Marcus