I have a few things to say.
First off, most of the guys involved with this group don't come to this board anymore.
2nd, Many of them no longer volunteer information. It's like they don't care anymore or ever did.
The smaller you make the antenna the less gain it will have. yes you could make it smaller for that usage or keep it full size depending how you mount it.
A beam built for the freq you want will be better but if you want broad band then you will need to do some testing and think about what band and range you want it for. As for a multiband beam, don't even think about it. You could only make a couple bands work together and not very good. It will get you into an area maybe.
I hope that helps.
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