LaFonera Hardware Second-Antenna

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Stock la fonera PCB showing unused antenna connection.
Stock la fonera PCB showing unused antenna connection.

Adding a second antenna is not hard. Since I recently used these wiki pages to help me along the process up getting dd-wrt onto my fonera, I figured that I might as well make a contribution.

The process should be pretty self explainitory, though I'm sure others may have other things they can contribute to this for better performance. The first thing that I noticed upon opening my fonera was that where the antenna connected to the PCB there was a second free connection. The points on the board were labled Ant1 and Ant2 (interestingly enough, the one that is attached at factory is Ant2). So I knew right away I'd be connecting this up ASAP for better performance.


RP-SMA pigtail
RP-SMA pigtail

[edit] Buying parts

  • The DD-WRT shop sells RP-SMA pigtails here for €4.76.

[edit] Making room for the second antenna

The first thing that must be done is to make a hole to connect your second antenna connector to. You can do this with a drill, dremel, etc. Whatever works. Be sure to plan out exactly where it will go. I have chosen to use bigger omni directional antenna's than the stock 2db one. Because of the range of movement the antennas that I used will have, I had to make the hole for the second antenna slightly off centered. That allows me to leave the 2 antennas at 90degrees of one another without rubbing at the base.

Image of the hole that I dremeled.
Image of the hole that I dremeled.

[edit] Soldering

Time to warm up the soldering iron. This process is fairly simple, though you must be careful not to allow for any bridging. The wire casing for an antenna can be tricky. Within the outer casing is wiring for a ground. Below that is another plastic casing. Within that is the actual antenna cable.

This is a simple drawing showing the cabling layout. The black layers represent casing, grey for wire.


The area in red below is where you will actually be soldering.

Second antenna connection point is circled in red.
Second antenna connection point is circled in red.

The outer perimeter of this area contains 7.5 solder pads. Any of these can be used for the ground. In the center is where you solder the antenna wire.

Completed Soldering
Completed Soldering

[edit] Connecting Antenna

Probably the simplest of all steps, connect the RP-SMA connector to the unit. Simply push the connector through the hole you cut in step 1, and attach the washer and nut to secure it into place. For me, it was easiest to cross the connectors to the opposide side as they are on due to the length of the wire I used. This is definately not required.

Here is an internal picture with soldering completed and RP-SMA connector in place:

The completed soldering
The completed soldering

And an outside picture:

Dual RP-SMA connectors.
Dual RP-SMA connectors.

[edit] Attach the antennas

As mentioned above, I have chosen to go with a larger antenna with slightly more gain. Afterall, that is the main point in adding the second antenna right?

Simply screw your antenna in and position them how you see fit. Keep in mind the signal travels at a 90degree to the antenna.

[edit] Signal Strength Testing

I did a walk through of my house to several locations upstairs and down after adding the second antenna. I used the Windows tool 'Net Stumbler' to graph out the signal strengths with no antenna, one antenna, and both antennas. I also graphed with both the originally connected antenna and the second that I added.

If you test your signal strength and find that you have no difference between one and two antennas, it may signify a problem with your soldering.

I noted what were almost double SNR ratings. At the furthest point in my house from the La Fonera, and in the basement, SNR with one antenna was ~20dB. With the second antenna attached i got ~38dB.

[edit] testing the signal strength

this was made by wildblue!

I did some testing with two antennas and here are the results. I got about 7 dB more out of that little box, which results in a range expansion by factor 4.

  • 3 dB more Signal - 2 * power
  • 6 dB more Signal - 4 * power
  • 9 dB more Signal - 8 * power

I soldered the second antenna with a RG316 cable. It has better shielding-capacities than the original cable, so i got a little better results on second antenna (ANT 1 on the PCB). I also placed the second connector on the other side of the LaFonera, so the position for diversity is about 12cm apart for best results (we also don't know what we will do next with the GPIO-Connector near the original antenna)

These are the results of my comparison i did with netstumbler


[edit] Comparison of the different states you can select in dd-wrt

Diversity off

TX RX Zeit
1. primary primary 16:40 - 16:45
2. secondary secondary 16:45 - 16:50
3. diversity diversity 16:50 - 16:55
4. primary secondary 16:55 - 17:00
5. secondary primary 17:00 - 17:05

Diversity on

TX RX Time
6. primary primary 17:05 - 17:10
7. secondary secondary 17:10 - 17:15
8. diversity diversity 17:15 - 17:20
9. primary secondary 17:20 - 17:25
10. secondary primary 17:25 - 17:30

As You can see, the second ANT-connector gives more signal strenght, i think this is because of the better cable i used.

On the next few pictures i will give you an overview about my modification.

The outside view


The old Connector


The new Connector


The inside view of my LaFonera


I compared the cables of Ant1 and Ant2


The detailed view of the new connector


[edit] Configure DD-WRT

This step may be optional. Someone please confirm

Though I did have outstanding results without performing the following steps, the following should help even more. Within DD-WRT lies a setting for antennas. Enable "Antenna Diversity", which allows the La Fonera to use the two antennas in a proper fashion. Next choose whether or not you want one antenna to do transmitting and one receiving, of if you want them to both work equally. I currently use Diversity for Transmit and Diversity for Receive. For best results using antenna diversity, position your antennas 12.3cm apart (one 2.4GHz wavelength in air).

These settings are under Wireless settings in the web interface.

[edit] Final Product

Below is a side by side image of the original and the modified La Fonera.


--Psilocybe 02:38, 5 Mar 2007 (CET)