Thanks! Just received my Yun from Adafruit and had great fun setting up the WiFi and loading my first sketches. What a great way to make Arduino control and programming available over the Web and through a WiFi hotspot!
I asked about the following over at Adafruit Forum--they said they didn't know and the question might be asked here:
Say, what's that 'mystery component' on the front of the board, at the upper right corner of the MIPS shield? Looks kind of like a micro switch with the button missing--shown on the Arduino layouts and images on your (Adafruit) site and Arduino.cc, but not openly identified. Could it be something like an external antenna connector for the WiFi, or is that just wishful speculation?
Be careful. It looks like U.FL but it’s NOT! Actually it’s SWF connector. Unfortunately purpose of this connector is mainly during product testing, so counterpart is far less available than U.FL connector.
An other mysterious formation is the four slight diagonal THT holes for header pins on the Wifi side and the six on the Ethernet plug. No labeling, any idea?
I've just received an answer from the hardware guy: the connector is a MM8430-2610 (see this). You can plug in a MXGS83RK3000/MM126036: once plugged in, the switch connector will turn the internal antenna off and use the probe as an external antenna
These are for test...Not intended to be used as a permanent connector for range extension. You may get lucky. It is rated at 100 cycles max. (Remember they probably used a number of these cycles during manufacturing.)
Summary. It is a Microwave Switch Connector. No observable "lip" on connector to hold a connection permanently. It is a N/C connector and passes the signal through to the on-board antenna. When interrupted by the male pin, inserted during test, it re-routes the signal to the contacting pin, disconnecting the on-board antenna.
They are completely incompatible with the U.FL type.... No amount of forcing, twisting or whining is going to get these to mate.
It COULD BE that someone clever could replace that SMT connector with a pinout-compatible U.FL type, (voiding any warranty, and possibly messing things up,) but some hacker might get lucky and post the results here. We are probably all anxious to be able to find a way to have the Yún in a metal enclosure and yet still have WiFi connectivity.