Electrically controllable inductors are known as saturable reactors. One quite interesting use is in the tuning of a synchrotron accelerating cavity. Here is a

Electrically controllable inductors are known as saturable reactors. One quite interesting use is in the tuning of a synchrotron accelerating cavity. Here is a paper on using varactors to tune a loop antenna: http://home.earthlink.net/~christrask/Varactor%20Tuned%20Loop%20Antenna.pdf http://home.earthlink.net/~christrask/Varactor%20Tuned%20Loo... He also has many other good papers on RF.