[Discuss-gnuradio] FFT of one OFDM symbol

[Alice Lo Valvo]

Hi,
I'm working with the tx_ofdm.grc in the gr-digital example. I saw that I 
can choose a set of
subcarriers for each OFDM symbol. Is there a way (FFT plot, for example) 
to display these active subcarriers?
I tried, but FFT plot shows every active subcarriers for ALL OFDM 
symbols simultaneously and not one by one in sequence.
Thanks in advance,

Alice