is it true wifi extenders half the total isp speed when extending wirelessly (not using ethernet)? i was planning to buy extender as a cheap alternative to get wifi in dead zones. (So please dont recommend to buy more expensive router or extend a cable to the dead zone.Id rather not do any of these. Extender in wireless mode or no use ) I thought "High speed mode" solved this already. Some say (in other posts) that high speed mode or netgears fastlane tech solves this and extender halving speed was a thing in the past.  But then here in these community, many dozens of guys say "extender work in half duplex mode, you're only going to get half of your router speed always".   

If this is true

1. whats the use of high speed mode?

2. Why hasnt such an issue been solved these years? 

3. Working of High speed mode:> using 2.4ghz and 5 ghz at the same time between router > extender > client (dedicating one of the band between both).  So doesnt this solve the issue of speed getting halved? 

Who's wrong???