Conclusions
Due to time constraints I was not able to attach the second bellows and further investigate its potential as a bandpass filter. The data from a single bellows shows that it would be worth the time to investigate the directly-coupled bellows as a tunable bandpass filter. If a filter were to be built for experimental use a couple of problems would need addressed. In the current setup it is not easy to change the length of the filter because 10 nuts must be manipulated. The filter would be easier to use if the length could be changed by adjusting one or two nuts. In the current bellows setup it is hard to align all the components of the filter while keeping the bellows from bending. Misalignment breaks the degeneracy, adding bumps to the resonace. Finally the two bellows must be joined in a way that the bellows can be directly coupled while allowing the user to change the iris when moving to a new frequency range. If these problems can be overcome this setup has potential to e a very useful microwave filter.