We have already managed to make the first prototype of a helical antenna around a steel core. 

After testing this first prototype and seeing the results obtained, we have realized that we must use a non-magnetic core. 

First, we did tests on a solid polyurethane core. It is a material that is not very rigid and it is quite elastic, which makes the winding process way more difficult. It is also a material that does not adequately resist the temperatures required for the cable's self-bonding treatment, which helps us a lot in this laborious manufacturing process. 

We are looking for a material that is better suited to this task and that has the appropriate dielectric properties.

 After our failed firsts approaches we were in search of a new material that is rigid enough to be wound, that is non-magnetic and withstands temperatures of at least 160°C. 

We have found that most of the materials within our reach were not very rigid but they did meet the rest of the necessary conditions. So our team is studying a way to work with theese kind of materials.