The electrical characteristics of an antenna depend on it's physical characteristics, and neither of those has much, if anything, to do with it's appearance, OR, convenience.
An antenna's electrical characteristics include resonance and impedance, the pattern of it's radiation, and efficiency.
Resonance means there are no unwanted reactances. Why? Cuz reactances don't contribute to anything being radiated unless they are neutralized. Reactances comes in two kinds, a (+) inductive and a (-) capacitive. If you've got too much of the inductive (+) kind then add some capacitive (-) kind and they equal '0', which means they are effectively gone. (Gotta be the right sizes though.)
Impedance matching is a fairly well known thingy. It can get complicated real quick cuz impedance is made up of two thingys, resistance and reactance. If the antenna is resonant, then there's no reactances present and then you only have to worry about resistance. The 'ideal' resistance would be 50 ohms because that's what the feed line impedance is (probably) and that's what the radio's output impedance is (hopefully). Unfortunately there are no 'naturally' occurring antenna input impedances that are 50 ohms. So, things get even more complicated because you have to do some "magical" juggling with reactances to make the antenna 50 ohms resistive.
[You said get rid of reactances, not add some! Right, but it makes a big difference -where- and -how- that reactance is added. (There's nothing "magical" about this stuff, it's just complicated, which means it might as well be "magic", right?)]
Physical characteristics and efficiency and 'convenience'.
There are things like size of an antenna that can make them very inefficient to make mobile. A 1/4 wave antenna is roughly something like 9 feet long. That means it's going to be 'large' if placed on a vehicle of any kind, which means it's going to hit/drag on things cuz there aren't many places where you will have at least 12 - 15 feet of clearance. Okay, so shorten the thing by 'loading' it. 'Loading means adding some 'small' inductance to make the thing seem like it's 9 feet tall. That does work! But it changes some of the other characteristics of the antenna such as efficiency, and it's radiation pattern (where it can put the signal). A very rough estimate of that 'shortening' ability/usefulness is maybe half the height, or around 4.5 feet. After that, it get's very inefficient. the radio may be 'happy' with it, but the signal just doesn't get anywhere, you know? But it's sure a lot more convenient. Just depends on how 'convenient' you can put up with. Which says absolutely nothing about what the @#$ thing ~looks~ like!
Antennas tend to like being above metal or stuff. Ain't happy with being beside metal or stuff. And don't like being under metal or stuff. That's a fairly good thing to remember! 'Playing' around with the antenna's happiness is certainly possible, and is done very often. Sometimes that's the only way you can make them convenient enough to even have at all! It ain't happy, but you are, so it sort of balances out... kind of.
Propagation.
Antennas 'propagate', produce signals that scatter around in a particular way. But propagation usually refers to how that 'scattering around' occurs, and we have no control over that at all. That belongs to 'Momma Nature' and 'she' don't let nobody mess with it but 'her'. Don't get too big for your britches and think you have any way of controlling propagation, or 'Momma Nature' will tan those britches! You can certainly take advantage of what 'Momma' provides (just like with your own mother?), but that's about it, you know?
Just somethings to think about...
- 'Doc