I have setup a repeater with B1300 but I still see WhatsApp call drops if I move away from B1300 and close to Tplink repeater. Repeater is set to extend 2.4Ghz (not guest WiFi) as well 5Ghz guest wifi singals.
Past being unlawful in most jurisdictions as it violates the certification of the device, changing antennas is one of those “If you have to ask, the answer is no” things. Without well over US$10,000 of test equipment, even if you were licensed to do so, you’re most likely to make things worse. Once over a few hundred MHz, wires aren’t “just wires” anymore like they are if you’re hooking up a motor or an LED on a breadboard.
Edit: If u.FL connectors on the board, and not Murata(-style) test points, the RF task is much easier.
In many countries now routers have to pass from local telecom regulatory authorities, using VPN isn’t allowed, using a high power WiFi amplifier is not legal, facebook and other social media channels have restrictions.
Now that the legalities are out of the way, the B1300 has u.FL connectors on the board. Just get a u.FL to SMA pigtail from Amazon and buy some Wifi Antennas. You will need one for 2.4ghz and one for 5ghz for some basic testing.
Once you have a setup you like, you can get 2 more antennas to get longer range Mimo working too.
FWIW - I am licensed, and have the test equipment… but here’s a better answer.
Don’t do the antenna mod - the internal antennas are just fine, and they’re matched and calibrated at the factory for best performance. So unless one has the skills, test equipment, and SW tools to calibrate the radio (which most folks don’t have, and there, yes, can be found on the grey web) - better to just leave well enough alone.
And with the IPQ40xx chips, they’re a fair amount more complex than the older WiFi SoC’s at this level.