My Canadian Amateur Radio Basic Qualification Study Guide tells me that my antenna length is specific to the wavelength I wish to broadcast on and gives a formula that equates to antenna length = half the desired wavelength. In a number of places it also suggests that the length of the antenna must support a standing wave of the radiated frequency exactly in its length.
Given the propagation effects of the atmosphere, I'm guessing that I am going to need to chop and change between bands in order to talk to people locally and around the world depending on the time of day, phase of the moon and whether it's raining in Helsinki while my Uncle Bob is having his coffee in Copenhagen. Will I need different length antennas to be able to do this?
I have a handheld Yaesu VX-7R radio which appears to do okay on multiple bands, but I clearly don't change the antenna to flick between them. My bedside clock radio also doesn't require a different length antenna for each frequency... so all of my practical experience of radio (which admittedly is virtually nil) tells me that I'm not understanding what the book is telling me. Can I broadcast to higher frequencies using an antenna designed for the 160m band?
Can someone clarify what my book means when it says "exactly in its length"?