2.1km Mesh Potato Call

On 3 August Angelo (a local Electronic Engineer) and I made some phone calls over a 2.1km using V1.3 Mesh Potatoes. The V1.3 has an etched PCB antenna which is really just 17mm of PCB track. The antenna has a roughly omnidirectional pattern and the Mesh Potatoes transmit power is between 50 and 100mW (depending on the bit rate). The phone call voice quality was great.

See this Village Telco blog post for lots more information.

The photo below shows the MP01 V1.3 (bottom) with the two PCB antennas clearly visible. At the top of the photo are various prototype PCB and commercial antennas that we have tested. All of the antennas in the photo have a gain of about 2dB and are roughly omnidirectional.

Antennas checked during MP 1.3 testing

There are actually two antennas on the MP01 PCB. The left antenna is the tx/rx antenna, the right antenna is the diversity rx antenna. The Wifi driver chooses either the left or right antenna for reception based on signal strength. This helps when there is a lot of multipath, for example indoor use. When there is multipath interference, moving the antenna just a few cm can make the signals strength vary greatly. So if the signal is very low at one antenna it may be nice and strong at another antenna just a few cm away. That is why a lot of routers have two antennas. Even routers with just one visible external antenna may have a second, internal, antenna etched on the router PCB.

Links

Coincidentally a couple of friends sent me this link on PCB antenna design while I was working on PCB antennas this week.

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