Question: First order frequency response, no plot possible.

Hi guys,

I've had only a little experience with Maple, but I decided to use it for preliminary frequecy response calculations. The funny thing is, I have already the solution in some way, but I'm too stupid to get it working. I can't see the mistake, however, it should have something to do with the H_n(f) function and the other normalized functions.

NASA has published a nice paper which explains the calculations, however, they have used MathCAD. Anyway, I don't think this should be a problem. Here is the documentation: 

The error message is for example for the H_n(f) function:

Warning, expecting only range variable f in expression H__n(f) to be plotted but found name H__n


Please help me.

Maple file:

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