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Author Topic: Mystery component on Yun board?  (Read 8871 times)
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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?

Cheers!

['DB]
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you guessed right. It is an antenna connector to extend the WiFi range.
The form factor of this antenna connector is called "U.FL"
« Last Edit: September 19, 2013, 05:55:34 pm by Federico Vanzati » Logged

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Thanks!  Very cool.

['DB]
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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.
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Does it mean that the only way to extend wifi is through USB port ?
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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?
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Those holes are for mounting a PoE module.
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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
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Here's an article on how these work:

http://www.murata.com/articles/ta0791.pdf

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. 

Digikey has these connectors: http://www.digikey.com/us/en/ph/Murata/SWF_Connector.html But the official male connector is not a latching type, like the U.FL types.  The one male plug available is http://www.digikey.com/product-search/en?site=us;lang=en;vendor=490;Keywords=MXHS83QE3000 but is ~US$50 and doesn't appear to have a holding "lip".

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.
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The reason external antenna is needed is:

  • On board chip antenna has average Gain  -0.5 dBi  
  • Yun's  transmit power is only 17 dBm.
  • Yun is siting at metal case.
  • The distance between Yun and WIFI router is far

Friis Transmission Formula with Propagation Law



  • R = Maximum range for communication link
  • N = Propagation Law (N=2 for line-of-sight, N=4 for urban environments)
  • PT= Transmit power
  • GT= Total antenna gain
  • λ = Wavelength
  • PR= Receiver sensitivity
  • FM= Fading margin

if in urban environments;-

  • Every 12 dBm receiver sensitivity gain will be double the distance.
  • Every 12 dBi antenna gain will be double the distance.
  • Every 12 dBm Transmitter power gain will be double the distance.


in line of sight environments;-

  • Every 6 dBm receiver sensitivity gain will be double the distance.
  • Every 6 dBi antenna gain will be double the distance
  • Every 6 dBm Transmitter power gain will be double the distance.

http://forum.arduino.cc/index.php?topic=175577.msg1304059#msg1304059








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An other reason is reduce interference.

The Omni type  antenna ( build in chip antenna)  has 360 degree field pattern

The pattern below is from a Yagi antenna : From this you can see the Yagi can block all other router signal outside from 60~120 degree.


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More Information about transmit power:

Maximum Transmit Output Power in the ISM bands.



http://wisp-router.com/page.php?11

The part 15 of the FCC rules.

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Did you ever find a solution for an antenna?
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Any high gain 2.4 Ghz antenna will work.

  • Pach Panel Antenna
  • Dish Antenna
  • Dipole Antenna
  • Yagi Antenna
  • Grid Parabolic Antenna






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Any high gain 2.4 Ghz antenna will work.

  • Pach Panel Antenna
  • Dish Antenna
  • Dipole Antenna
  • Yagi Antenna
  • Grid Parabolic Antenna


What about people saying that it woud for after a number of cycles? Would it be a feasible long term solution?

Thanks




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