Re: [Discuss-gnuradio] FFT for FM Tx and Rx

[Marcus Müller]

Hi El,

this is a bit hard to tell -- are you using a direct cable or antennas between TX and RX?
If you're using antennas, that might simply be something else transmitting there.

Also, if you transmit at 560 MHz, but only observe $\SI{562}{\mega\hertz}\pm\frac{\SI{0.2}{\mega\hertz}}{2}$, you can't see your transmit signal, so I can't compare the strength of that and what you see in your RX FFT plot.

Best regards,
Marcus

On 06/21/2015 03:47 PM, El El wrote:

Hi,

I implemented the FM transmitter and receiver from the tutorials (http://files.ettus.com/tutorials/labs/Lab_1-5.pdf), the carrier frequency is 560 MHz, audio rate = 48 kHz, and frequency deviation = 5 kHz. My question is why don't the FFT plots look similar? The FFT for the transmitter is centered on 562 MHz, but for the receiver, the highest amplitude component is centered on 561.97 MHz, also there is one more component on 562.09 MHz. Screenshots of the FFT plots are attached.

Thanks a lot,

El

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