What Use Is An F-call?

What use is an F-call? In our hobby we come across terms and names that we use and commonly understand, that is, we think we understand them. I mean, what's a velocity factor and what is a dielectric? Simple right? The velocity factor is something to do with coax and the dielectric is something to do with capacitors. Next. Hold on. Let's have a little closer look at this. The velocity factor is the wave propagation speed, or the velocity of propagation, relative to the speed of light. That is to say, it's a percentage of the speed of light. In a piece of RG58, the velocity factor is anywhere between 66% and 73% of the speed of light. You already know that the wavelength of a frequency is dependent on the medium it's traveling through, so when you calculate the wavelength of 21 MHz, you do some maths and out drops around about 15m. If you want to make a resonant antenna, it has to be some part multiple of that wave length, so a piece of wire 15m long will be a single wave length. Well, no. The velocity