jerryandthecats :
I will buy a new wifi router (am open to suggestions) with appropriate antennas, my current modem/router is from centurylink with internal antennas.
The external antenna will be under a porch, so semi safe from weather.
The length of extension cable wud be 6-8'.
Thanks for your input.
6-8 feet isn't much, so you'd be fine signal-wise with LMR-240. (LMR series cables basically have their outer diameter in the name, so LMR-240 is 0.24 inches in diameter.) I'm getting ready to use LMR-600 to zone some sector antennas in the yard, but it's overkill unless you have hundreds of feet of cabling to run. eBay has a few merchants (Altelix and wifi expert among them) that would offer that much cable with the connectors you need. Usually, the router antenna port requires a cable with an RP-SMA male connector (no pin, but threads over the antenna port), but a lot of outdoor antennas connect to an N male connector. Impedance is 50 ohms. Also, some outdoor antennas would have 2 or more connectors for dual polarization or MIMO (higher throughput from multiple spatial streams on multiple antennas), so if it's dual polarized, you could get a T-shaped splitter plus jumper cables, or otherwise run 2 cables in that case.
For good all around routers, I came across this list online that's fairly recent.
Routers with 900+ mW output power, 3+ RP-SMA detachable antennas and spatial streams, 256+ MB of RAM, 128+ MB of flash storage, Gigabit Ethernet LAN ports, USB 3.0 expansion slots:
ASUS RT-AC1900
ASUS RT-AC1900P
ASUS RT-AC3100
ASUS RT-AC3200
ASUS RT-AC66U B1
ASUS RT-AC68U Extreme
ASUS RT-AC86U
ASUS RT-AC88U
D-Link DIR-880L rev A1
Linksys EA6900 v1.1
Netgear R6700v2
Netgear R6800
Netgear R6900v2
Netgear R7500v2
TP-LINK Archer C2600 & C3150