Im looking into building an 11 meter ddrr antenna for my mobile. I curently have a 102 inch whip that works great for local transmissions. The ddrr loks like a simple and cheap build. However, I have had someone suggest a vacume veriable capacitor for tuning the antenna. Is this necessary? I work in the hvac industry and work with mf caps everyday. I am dumb about pf veriable caps. What pf value should i need. Is kv value related to voltage? More watts being pushed higher kv value needed?