What Use Is An F-call?

What use is an F-call? I love it when I get feedback about things I talk about. It helps me understand when I know what's going on and when I'm being a doofus. Recently I was talking about building an antenna in preparation for a contest. It was intended for 80m, but turned out to be perfectly resonant on 160m. Not what I had intended. And to add insult to injury, I broke one of the segments of my squid-pole. In the telling of my tale of woe, I received an interesting comment from a fellow amateur who has been around the block a few times. He pointed out that we work with harmonics all the time, 160m, 80m, 40m, 20m, 10m and so on. Wavelength halves, antenna size halves. Proportionally all of it is related. There is no need for me to build an 80m antenna with 80 meters of wire hanging off a 12m squid-pole to test my design, I can make a 2m version with 2m of wire and a 30cm centre pole. Something I could conceivably hold in my hand, rather than fill-up a back-yard, spend ages stringing up, attempting to tr