in GRC for this source block ?

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1 Answer 1


The "Frequency" is the center frequency of the signal the block produces.

The "Freq. Corr." is a value in "parts per million" that the frequency is multiplied by, to correct for tuning inaccuracy separately from specifying the intended frequency. That is, the frequency sent to the hardware is

$$\text{Frequency} \times \left(1 + \frac{\text{FreqCorr}}{1000000}\right)$$

The best way to adjust this correction is to use a program like Gqrx which lets you set it and see the effects — find a continuous transmission of stable known frequency (such as NOAA weather radio in the US) and adjust the correction value until the displayed peak lines up with the number.

  • $\begingroup$ and that 63 ppm frequency correction - does it affect it in any way ? $\endgroup$
    – kellogs
    Nov 23, 2019 at 20:06
  • $\begingroup$ @kellogs I've updated my answer to cover that. $\endgroup$
    – Kevin Reid AG6YO
    Nov 23, 2019 at 21:42

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