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[Discuss-gnuradio] Fwd: Carrier Phase Measurement

From: Raydel Abreu (CM2ESP)
Subject: [Discuss-gnuradio] Fwd: Carrier Phase Measurement
Date: Tue, 22 Oct 2013 16:50:10 +0000

One more thing....

The Quadrature Demodulator produces a stream of floats. I used as previously recommended Keep One in N for sample only 5 times by second. However, which method can I use to save the Float Stream into a plain text file. The File Sink Block outputs a binary file?

Best wishes,


---------- Forwarded message ----------
From: Raydel Abreu (CM2ESP) <address@hidden>
Date: 2013/10/22
Subject: Re: [Discuss-gnuradio] Carrier Phase Measurement
To: Marcus Müller <address@hidden>
Cc: address@hidden

Hi Marcus,

Thanks for the tip. In a previous e-mail Marcus D. Leech recommend me to use the Quadrature Demodulator Block as something not perfect, but usable to check for phase changes.

It works for me, as long as there is a pure carrier without phase changes, and without care the amplitude, the Quadrature Demod outputs a float number, quite constant, if there is a phase change, the resulting float number changes.

Now, help me with a doubt regarding PLL. Let's assume the carrier is steady (zero drift), if there is a phase change (not changing in freq) when passed through the PLL, the phase changes are not conserved???

The idea of my small project is to correct any possible frequency drift due to poor receiver stability while conserving the incomming phase changes which is in part produced by the ionosphere.

So, how can I correct the drift while keeping the incoming changes of phase?

Kind Regards,


2013/10/22 Marcus Müller <address@hidden>
Hi Raydel,
try Keep N in M (keep 1 in N) for the "sampling".
However, if you correctly employ a PLL, your phase will be static; if it's not, than the PLL is not doing it's job well.


On 10/22/2013 05:21 PM, Raydel Abreu (CM2ESP) wrote:
Hello all,

I am new to GNU Radio and I am still learning the basic. I have a quick question. What blocks and which way can I use in order to "sample" and know the phase of a tuned carrier at regular intervals.

General idea: Let's suppose there is a carrier, after applying proper tuning (Freq Xlating FIR Filter, etc), I apply a PLL module (not sure which: PLL Carrier Tracking or PLL Ref Out) in order to remove possible drift from the receiver and output a steady carrier. How can I sample at regular interval that corrected carrier phase. Assuming that intervals are really equals I guess every time I should obtain the same phase value.

I will really appreciate any help in this matter, perhaps someone could point me in the right direction.

My purpose is to observe ionospheric phase scintillation from a geostationary satellite beacon, which outputs a steady carrier. Frequency drifting should be related to RTL-SDR dongle and part of phase changes related to ionospheric irregularities.

I attempted something similar with SpectrumLab and an analogue receiver but due to receiver drifting and sound card poor sampling stability the phase result was a phase rotation of several degrees by measured interval. Perhaps GNU Radio and the PLL functions it has could help to overcome the frequency drift in the measured carrier.

Thanks in advance,


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