Re: [Discuss-gnuradio] Components of BasicTX

[Matt Ettus]

On 12/21/2009 05:08 AM, Mathias Coinchon wrote:
> Hi,
>
> I am using BasicTX daughterboard to generate a VHF signal around 228MHz.
> For this a complex signal is generated at -28MHz  leading normally to harmonic 
> components at
> 128MHz-28=100MHz
> 256-28MHz=228MHz (wanted signal)
> 384-28MHz=356MHz
>
> However looking at the spectrum (see attached), I still see powerful components 
> at
> 128+28=156MHz
> 256+28=284MHz
>
> Is it normal or is is a missconfiguration from my side or an I/Q gain inbalance 
> ?
> Is there a way to avoid these 156 and 284MHz components ? (they are hard to 
> filter compared to other one actually)


You are looking only at one of the outputs from the BasicTX, so it is a 
real signal, not complex.  Thus you will see the +28 MHz components as 
well.  If you were to use both outputs and put them into a quadrature 
mixer you would see that the other components cancel.

Matt