Components of BasicTX

GNU Radio
1

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)

Thank you

Mathias

2

On 12/21/2009 05:08 AM, Mathias C. wrote:

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