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

[El El]

Hi, Marcus.
Thanks for the reply. I use antennas for the transmitter and receivers, I 
forgot to mention I use two N210 USRP platforms with WBX daughterboards. When 
the transmitter is off, there is no other signal in that frequency band. I 
believe I should try to make an advanced tuning in order to set an offset for 
the local oscillator, that might eliminate the spurious component. What other 
methods can I use in order to eliminate the spurious components? Is a band-pass 
filter at the receiver a good option?

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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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