hi david, when you have no signal going into an adc, it will typically chatter between two values, around -1, 0 and +1, and you'll see a lot of RFI and interleave spurs, so the spectrum you sent around doesn't surprise me,
but if you put in a sine wave that is much larger than the ADC chatter, say Vpp ranging from -100 to +100 (out of -128 to +127 for an 8 bit ADC), then the power spectrum spurs should be very small compared to the sine wave power (about a factor of 10,000 in power (100 in voltage)). can you use the adcsnap shot to look at the samples coming from your adc, and see what the relative levels are of the sine wave to the noise? does the power spectrum agree with what you see in the snapshot? best wishes, dan On Tue, Jan 15, 2019 at 9:59 AM David Marsh <[email protected]> wrote: > Hi all, > > Sorry if this has already been explained/solved. > I programmed Tutorial 3 onto a SNAP board and noticed some unexpected > spikes in the spectrum. I have set up the hardware as explained in the > python script with a 10 MHz, 8dBm reference going into the SYNTH_OSC SMA > (3rd SMA from the left). > > The attached figure shows the spectrum with no input going into the SNAP > board. There are large spikes in the spectrum every 50 MHz with the largest > at 200 MHz. > > When I add a signal to the SNAP board, I can see it in the spectrometer at > the correct frequency > but the other spikes are still present. > > Do you know what is causing these spikes and how they can be removed? Any > help would be greatly appreciated. > > Thanks, > David > > -- > You received this message because you are subscribed to the Google Groups " > [email protected]" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > -- You received this message because you are subscribed to the Google Groups "[email protected]" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected].
