[Discuss-gnuradio] How to hold a values from file source

[songsong gee]

Currently I am trying to make an ASK (Amplitude Shift Keying)

I use GNURadio Companion,

The program gets the input from file source and multiplies it with signal source.

And I monitors via Scope and FFT plots

You can see a diagram ASK.grc (image)

And the result is somewhat weird. Plots (image)

It seems sinusoidal, but the shape looks like sawtooth!

I thought that the program couldn't hold values from file source

So, I am wandering whether there is a method for holding a value