Hi using the router TL-MR6400 and version 4

Live right out in the stick fibreoptics is a nightmare so using wifi instead.
Difficult to get signal so got two outdoor antennas which are the "omni seritaa arials" for £20 each, seemed maybe to good to be true.
Have worked wonders to a degree, as went from having 1 bar to no bars now to 3 bars.
But the signal fluctuates constantly from 3,2,1 bar and zero and cutting out so i have to restart it every few hours.
Now would this inconsistant signal be down to having 2 ariels seperated quite far apart or is this simply down to them not picking up the internet well enough?

And most importantly what outdoor arial would anybody recommend to help catch the signal better?? dont mind the price but cheaper the better i guess. just want a half decent one that works well and with a better consistancy..
Rather then me buying loads of differant ones and trying them out hope some of you may have some tips and advice to save me time and money

Thanks :)