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Using an external antenna for WiFi

Posted: Thu Feb 04, 2016 12:31 am
by wittend
I need to use an external directional antenna with my NanoPi2's. The availability of the ufl connector is one of the most useful features of this design for my needs. Do I need to remove the on-board antenna to use the the external antenna effectively?

I plan to house the entire project in a die-cast aluminum box. I anticipate housing another RF front end in the same box, though in a separate shielded enclosure of its own. It doesn't seem ideal to have an unneeded radiating antenna within the enclosure, but I'm unsure how difficult the SMT antenna would be to remove.

Re: Using an external antenna for WiFi

Posted: Thu Feb 04, 2016 8:33 am
by davef
I would remove the antenna. Hot-air gun from a SMT re-work station and some skill should enable you to remove it.

Had a look at the schematic and I would be asking if the chip antenna actually works to its capability with an open-circuit stub (the transmission line to the on-board connector) "hanging" off the main transmission line.

Likewise, when you remove the chip antenna you will be left with an open-circuit stub still "hanging-off" or in parallel with the main transmission line.

Determining the proper antenna environment requires a number of specialised bits of RF test gear.

I think the best you will do it to just remove it and accept the resulting performance.

Good luck,

Re: Using an external antenna for WiFi

Posted: Thu Feb 04, 2016 9:16 am
by davef
Thought it might be a good idea to have a closer look at the PCB! I think using two soldering irons with small tips would be a good approach. Or you could use some solder wick to suck the solder off each terminal. That might "break" the solder connection on one or both ends and the part should just fall off the PCB.

Further to my open-circuit stub issue ... the connector virtually sits on the main transmission line so its effect on the internal antenna might be relatively minor. However, when the chip antenna is removed there remains a significantly long bit of open-circuit transmission line "hanging-off" the RF connector.

Re: Using an external antenna for WiFi

Posted: Fri Feb 05, 2016 4:22 pm
by wittend

Thanks for your thoughts in this. My objective is to use a reasonably sized patch antenna to provide coverage for a group of sensors placed in a field by students. The default antennas used are fine for bench testing, but ill suited for many real applications. The ability to use an alternative is important to a lot of users.