Swapping spectrum on the FCD

Hi,
I’m using a FunCube Dongle to FFT monitor the 69MHz if of my Yaesu FT950
ham transceiver.
Unfortunately spectrum is shown inverted, with signals 10kHz above my
center frequency shown instead 10kHz below.

This isn’t something new and I’ve seen I/Q swapping options in other
instances.
Is there any fairly simple way to do it in GnuRadio when using FCD as a
source?

Thank you
Stefano IZ0MJE

On Sat, Dec 15, 2012 at 11:55 AM, Stefano S. [email protected]
wrote:

Hi,
I’m using a FunCube Dongle to FFT monitor the 69MHz if of my Yaesu FT950 ham
transceiver.
Unfortunately spectrum is shown inverted, with signals 10kHz above my center
frequency shown instead 10kHz below.

This isn’t something new and I’ve seen I/Q swapping options in other
instances.
Is there any fairly simple way to do it in GnuRadio when using FCD as a
source?

The I/Q order in the FCD source should be correct unless there is some
other swapping happening in the audio setup of your OS.
Are you sure it’s not some frequency error you are experiencing? Do
the signals move in the wrong direction when you change the frequency?

To answer your question, yes, it is very simple to swap I/Q: you take
a complex-to-float and float-to-complex blocks and cross wire, i.e.
real->imag and imag->real them.

Alex

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