What's special about this Pi 4 Model B?
Want to use an external antenna with the Raspberry Pi 4 Model B? These Raspberry Pi 4 boards are carefully hand-modified to add a U.FL connector and connect it up. This greatly expands the options for external antennas, and there is no additional dongle needed. 

For the greatest flexibility with your plans, these are available as the board only, with an included Molex antenna on the end of a 100mm flexible coaxial cable (Manufacturer part #206994-0100), or with a panel mount antenna with a +2dBi gain (Manufacturer part #SC0480). They are available with 2GB, 4GB, or 8GB of RAM.

Does the external antenna provide a better WiFi signal?
That depends on the choice of antenna. However, in my testing I've noticed an improvement over the built-in antenna when using even a mildly directional antenna, properly positioned. The largest reason to use an external antenna is if the Pi is being used in a project where the PCB antenna will be obscured (for example, inside a metal enclosure). In that case, using an antenna on the end of a short piece of coax can let you route the antenna onto the outside of the enclosure.

What quality assurance (QA) testing is performed?
Following the modification, every Pi is tested using a partially automated process to confirm that the new antenna connection is working properly. These are all logged by Pi serial number along with the test statistics to determine a PASS/FAIL state. A QA testing certificate is provided with every individual Pi following a successful PASS. There may be some cosmetic melting of the GPIO header plastic due to its close proximity with the modification area. However, this doesn't impact the functionality or performance of the device.

For general Raspberry Pi 4 Model B information, check out the official webpage: https://www.raspberrypi.org/products/raspberry-pi-4-model-b/

For information on the 100mm antenna (if you select an option that includes an antenna), check out the manufacturer's webpage: https://www.molex.com/molex/products/part-detail/antennas/2069940100 

For information on the panel mount antenna, check the product brief: https://datasheets.raspberrypi.org/cm4/cm4-antenna-kit-product-brief.pdf

FAQ/Troubleshooting:
Q: Does this impact bluetooth?
A:Yes, bluetooth and WiFi share the same antenna.

Q: Does this make the WiFi any faster?
A: It depends. With an antenna with higher gain (like the +2dBi whip antenna option), it might if the signal level was low enough that it impacts the speed substantially. But generally the impact on speed is only going to be marginal.

Q: My Pi keeps disconnecting from WiFi every 5 minutes, and doesn't reconnect!
A: There are a few things that can be causing this. The most common is you have power management turned on. Run iwconfig wlan0 and look at the output. If it says "Power Management: on" or "Power Mgmt: on" then to turn it off run sudo iwconfig wlan0 power off to turn it off. It can also be due to periodic interference from other devices, or due to a defective router.