Hello! I am interested in building a dual band 17m and 12m yagi. I am thinking of a reflector and driven element on 17m and would like to try and put a driven element and director in front for 12m. I want to use one feed to the 17m driven element and use open sleeve coupling to excite the 12m driven element. I would be using full size, lightweight telescopic aluminium elements and would like to know the following....
1. How to calculate the close spacing between the driven elements? Is it trial and error?
2. Would the 12m driven element have to be in 2 parts and isolated from the boom?
3. What the charcteristic feed imedance would be for the 17m driven element?
4. Could I use one hairpin (beta type match) for both bands?
Any help and suggestions regarding building this type of antenna would be appreciated. I have never used this type of coupling system before but am interested in trying to build it.
Thanks in advance! Cheers Jess