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RC4 Knowledge Base

LumenDimM2micro External Antenna Connection

Two revisions of the LumenDimM2micro have been released.

R1.2 SEP2015 Is a green circuit board.  It is constructed to use the on-board chip antenna that is part of the LumenRadio TiMo RF module.  By default, the u.fl antenna connector is not active and attaching an antenna to that connector will NOT result in any performance improvement.  The chip antenna is the small white block at the corner of the TiMo.

R1.5 NOV2019 is a white circuit board.  It is constructed to use the TiMo RX u.fl antenna.  By default, the on-board chip antenna is not active.

The TiMo radio module is switched between the two antenna modes by jumpering pins 5 and 6 on the module.  The R1.2 green boards have these pins jumped on the board, below the module.  This makes it difficult to modify for use with an external antenna.  On special request, RC4 manufactured external-antenna versions of the 2micro by modifying the circuit board prior to assembly.

The R1.5 white boards leave these pins open on the board.  This makes it easy to add a jumper between pins 5 and 6 to select the chip antenna.  With either a modified R1.2 board, or any R1.5 board, a simple modification selected the antenna type that is active:

For external antenna via u.fl: NO jumper, no connection between pins 5 and 6.

For on-board chip antenna: a jumper should be added between pins 5 and 6.

Here is how the pin counting works:

This image shows both versions, with the jumper added.  The green one has been factory modified, it is not the stock version.  With the jumper added, these units use the on-board chip antenna, not the u.fl conector:

And here, we see these same units with the jumper removed.  Remember, the green unit here has been modified so that pins 5 and 6 are no longer connected on the circuit board below the TiMo RF module.  These units now both use the u.fl antenna.  They will not perform well without an antenna connected.  You must use an external antenna with these:

When using an external u.fl antenna, the metal connector should NOT touch the small capacitors positioned on both sides of the u.fl connector on the TiMo.  This is correct:

Below are examples of what to NOT DO.  These antenna cable positions are BAD because the metal connector is touching other components on the TiMo board.

Connector touching capacitor at left.  THIS IS BAD:

Connector touching capacitor at right.  THIS IS BAD:

It can’t be overstated! Don’t do this:

And again — ok, this is the last time! — don’t do this:

Thank you, and happy micro dimming!