Forum: GNU Radio Inverted spectrum

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Andrew Davis (Guest)
on 2013-07-14 02:54
(Received via mailing list)
Hello all,

When using pll_carriertracking_cc, the returned spectrum seems to be
inverted about 0MHz, when looking though the code line 113 of
looked odd:

> optr[i] = iptr[i] * gr_complex(t_real, -t_imag);

could someone explain why the the imaginary component of the NCO is

Thank you all,
Tom Rondeau (Guest)
on 2013-07-22 16:23
(Received via mailing list)
On Sat, Jul 13, 2013 at 8:54 PM, Andrew Davis <>
> Thank you all,
> Andrew


That block was written so that it would lock to a carrier at a tone
that is then used to downshift the signal. So you have a signal at fc;
the PLL would lock onto that and produce a tone at -fc. This is then
multiplied against the original signal to shift it down to baseband

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