How to calculate filter RF for different frequencies?

Hello!

I′m doing a project, and it needs to pass in some tests.
For example i will apply many frequencies to the product and it can′t oscilatte.
I having problems with 70MHZ - 130 MHZ ....
I think it comes by the cable.
How can i solve this problem?
Is there any software where i can calculate the filter?
sorry for my english

Try to build Butterworth filters because it is smoother than others (Chebychev and Elliptical).
In the website http://cnx.org/content/m10127/latest/ you can find some tips about this filter.
I don't remember very well the filter calculus, but is not difficult.

Good luck!

Thanks for the help
however i want a filter for High voltages...like 220vac

nobody?