I have tried today to design high pass filter using http://www-users.cs.york.ac.uk/~fisher/lcfilter/ and here is what I've got so far.On the first picture is a result of modelling, on the second - measured frequency response of this filter and on the third picture - input to amplifier+filter and its output.It looks like cut-off frequency has to be increased by 1-2 MHz...

 

Hello,

What is your frequency of interest?
What are unwanted frequencies that are giving you trouble?

Greetings,
Bertus