Add external antenna to chip-antenna core?

I’ve found that I get poor reception at one end of my apartment with my chip-antenna core. Is it possible to add an external antenna to this model? I can see two small solder pads where the u.FL connector would normally go. Can I buy one of these: https://www.sparkfun.com/products/11320 or similar, snip the wire and connect to the two pads? Sounds a bit too easy, I’m probably missing something…

edit: on second thought’s, I have an old airport express lying around I could use to extend my network, might be the easiest option. Would still be interested in the answer to this though.

As long as you are buying an antenna… buy a uFL connector as well :slight_smile: https://www.sparkfun.com/products/9144

I pretty sure you would want to remove L1 as well, so the two signals are not fighting each other.

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Yep if you buy one of these, desolder L1, and solder on the u.FL connector, you’ll be good to go :slight_smile:

If you were to go the other way (converting u.FL to chip antenna) the inductor and capacitor on the chip antenna circuit need to be RF components, specified for frequencies beyond 2.4Ghz.

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What’s “L1”? Is it the chip antenna?

L1 is the little itty bitty inductor that shares a pad with the u.FL connector

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Cool! That looks like an operation within range of my abilities! Good to know. Cheers

if I remove the L1 inductor, does that disable the chip antenna? I’d like to be able to use either the uFL or chip antenna

You can’t use both, sorry. The antenna matching circuit only supports one or the other.

I’m not a RF designer but would a redesign of the antenna circuit using a solder bridge “selector” be possible?

Ie, you have three tiny SMD pads. The center one goes to the CC300. The left one goes to the UF socket. The right goes to the chip antenna. By changing which pads are bridged to the center one you could “select” which antenna you want to use.

We do that with the inductor right now, at assembly time.

That is how we designed it.

Ah ok. To go further would be be possible, in perhaps a newer revision to expose such a “solder switch” to the user so that no soldering of components would be required to switch between antennas? I imagine the cost of the board would go up but there would functionally be almost no difference between a uF core and an antenna core after such a change.

That is an additional product requirement.
The follow-on product may try to accommodate this requirement (albeit a better way that doesn’t involve soldering) - however, the production design is not finalized yet - stay tuned.

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Oh no, I understand that it wold be a additional product requirement. I was merely asking, from someone who does not do RF design, if it would be possible.

If such a enhancement made it to the Photon that would be icing on the cake.

Dear all,
I would like to convert my Core as well… so let me please recap to see if I understood correctly.

L1 inductor, must be necessarly removed in order to work.
Looking from the bottom of the u.FL connector, A, B, C, pins should be soldered as follows:

Is this correct?

Any advice for such small and tiny soldering?
Thank you,
dk

@d82k Use a soldering iron that lets you control the power (something like a WES51), I recommend an .8mm tip for the iron, some solder removal wick (its a wire mesh with flux) and solder flux. Be careful with the heat of the iron, you only want to use enough heat to melt the solder - too much heat can damage the pad on the board. You will also want a tool to remove the inductor - I find an x-acto knife works well.

First you need to remove the inductor - Lay some flux on the part, lay the removal wire, near the pad and heat. Wait for the solder will flow into the wire. Do this on both sides. Then remove the wick and heat one of the pads with the iron, try and pry the inductor up a bit on the heated side and then heat the other side to complete the removal. (this is tricky as too much force may pull the pad away from the board. The correct tool is a soldering iron with two tips that can heat both sides of the inductor at the same time.

Once the inductor is removed clean the pads using the solder wick again and apply flux, place the new part, add some solder and there you go!

It takes a steady hand and patience

If you don’t have these tools it would be much less expensive to just purchase a core with the u.fl connector already on it :smile:

I made the mistake a few people have made and ordered Core with a u.FL connector instead of the chip antenna. I ordered some external antennas but I think they must be coming from Mars and not China they’ve taken so long.

Your post inspired me to simply solder a piece of wire to the pad on the right of the 3n3H inductor indicated as B on the image and use this as the antenna. So I did just that with a 12.5cm piece (figuring this is the wavelength of a 2.4GHz signal) and it works fine. In fact it’s rather more stable than my other Core which has a chip antenna when used in the poorest signal areas of my apartment - but that might be because that one is older with older software.

It’s not especially attractive, but it works. Here are some images. The tricky thing, which you cannot really see from the pictures, is to solder the wire so that it’s on the solder pad and doesn’t touch the shielding part of the connector: it’s pretty tight and with my eyesight and shaking hands…

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Thank you for your reply.
I was able to remove the inductor, but not really to solder the connector :frowning: actually it was but not enough…
One more question, are A and C points connected together on the board?
Thank you,
dk

Yes, A & C are connected on the PCB. You will need both for mechanical stability and for good RF performance.

Thank you, since I was not able to solder the connector I directly soldered the coaxial cable with the sma connector cutting away the u.FL one.
I still have to investigate RF performances…

If you’re just soldering micro-coax to the pads, you only need to use one of A or C.