Problem with retrieving a correct impulse response of a system

In system, we know the input signal X(t) convolution H(t) equals Y(t).
Mathmatic notation is X(t)*H(t)=Y(t).
In my lab, I do an interesting experience.
I input a unit step signal, ch1 into a system(a band pass filter), and measuring its output signal, ch2.
Then, I use deconvolution formula to retrieve system's Impulse response.
In matlab, it is presented as [q,r]=deconv(y,x).
Then, FFT(q), and got the frequency response.
Am I right?
But, unfortunately, the result is wrong.
Why???
Please refer to as following matlab code.
ch1--> **broken link removed**
ch2--> **broken link removed**
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load ch1.txt;
plot(ch1);
hold on;
load ch2.txt
plot(ch2,'r');
hold on;
[q,r]=deconv(ch2,ch1);
plot(q,'g');

q_fft=abs(fft(q(1:250))).^2;

figure;
plot(q_fft);
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P.S. scope sampling frequency is 1GHZ.

Re: Impulse Response?

why u use step input? i am not sure but i think fft command is not suitable in ur case.i will try ur problem and later i will u detailed answer.

Re: Impulse Response?

sorry, it should be revised to....
=================

q_fft=abs(fft(q)).^2;

figure;
plot(q_fft(1:250));