These are 5ghz and 2.4 ghz units with internal antennas. Two antennas are parallel third is perpendicular. They look like little folded dipoles but with one conductor.
Would that mean they are using two as a 2.4 ghz dipole and the third for 5ghz?
And do these little amplifiers allow RX to come back through the amp to the radio? I can't find any info on how these work. Such as does the router unit transmit and receive on at the same time a few MHz apart or does it pulse back and fourth? Would I need a transmit and receive antenna and use pin diodes network to quickly switch between the tx and rx antenna?
The technology is called MIMO (Multiple Input Multiple Output). Essentially the router transmits simultaneously over multiple antennas. The WiFi controller dynamically tunes the transmit power of each antenna, to minimize multipath distortion, interference and so on.
The internal antennas are “universal”, in that they’re tuned for the best range at both 2.4GHz *and* 5GHz.
I’d recommend you buy a standalone WiFi router (you can disable the router functions and use it as just an access point) that already has external antennas, instead of trying to retrofit your Fios router. Unless you really know what you’re doing, trying to bodge in external antennas is very likely to make the performance worse or break something.
If you’re in an area with a lot of 2.4Ghz networks, you’ll be better off buying a new access point with external antennas and setting it to 5GHz only. (You’d disable the WiFi functions of the FiOS router in that case.)
Alternatively, you could set the FiOS router to 5GHz only and then install several 5GHz repeaters around your house.
If you need a point to point link over a long distance, line of site, your best bet is, again, buy a new router with removable external antenna, install third party firmware (OpenWRT, etc.), disable the router functions (access point mode only), disable the MIMO functions (so it only uses a single antenna) and hook a 5GHz YAGI antenna up to it.
I’ve seen a $30 router running OpenWRT do close to a mile line of site, on 5GHz with no external amp (250mW TX power).
Several miles can be achieved with a 1W booster, but you start running into other issues and your speed will be limited.
(Actually, I’ve got a WiFi controlled quadcopter that can do about 1/2 mile via a special controller that’s essentially a WiFi router hooked to a directional antenna; others have gotten several miles with a power booster, under the right conditions, though it’s a one way trip due to battery power.)