TonyV225,
What's the difference between an A99, an Imax, and any other antenna? Electrical length, construction, input impedance matching, and ease of use. That's it. The rest is all 'opinion'.
Construction means how well it's put together, quality. Has nothing to do whether it's all metal, or has some plastic/fiberglass/whatever in how it's put together. (Fiberglass does not affect RF, RF sees right through it. It doesn't attract lightning. And all those other things you hear about it. I'm not very 'enthused' with it cuz it makes me itch.)
The determining factor for any antenna is it's radiation pattern, where the signal goes when it leaves the antenna. If that pattern is such that the signal goes where you want it to, that's good. If it doesn't, then that's not so good. Doesn't matter what antenna you're talking about, that holds true for all of them. An antenna's length determines the general shape of it's radiation pattern (size). What's around that antenna determines the radiation patterns shape, as in holes, spots where it doesn't go, distorts the 'classical' pattern to something else. That means that getting the @#$ thing away from stuff is good, to some ridiculous point. You can see further the higher you are, and an antenna is basically the same. Lot's of 'wiggle room' in that statement, but basically true.
And probably what makes the most difference in how well an antenna is 'liked' is how easy is it to set up, to adjust, and to just be able to lift the thing, you know? Both the A99 and Imax antennas are really about as 'easy' as it gets. Same for impedance matching. May not be 'perfect', but a lot easier to mess with than some others.
So much for that.
I've had an A99 up for a lot of years. It worked. Not 'perfect' in every case, but certainly 'good enough'. At times, an 80 meter looped worked just as well and sometimes better. But not most of the time. It isn't up any more. Not because I found a better one, but because fiberglass doesn't last very long around here, and since I hate messing with fiberglass, I didn't want to fix it. I tend to think that an Imax would be the same (fiberglass) and I don't want to mess with it either. (The loop is gone too. One too many ice storms, etc. I really hate that! Oh well.)
So. What did all that have to do with what you asked? The pertinent parts are there. You get to sort out the 'yeah, so what' parts!
- 'Doc
Crap! Gotta go to work. Later all ya'all.
("All ya'all" = plural. "Ya'all" = singular. End of redneck lesson.)