U.FL Spark Core without an antenna can't configure [SOLVED]

I have two Spark Cores: one with a chip antenna, and one with a u.FL connector. The Core with chip antenna works fine, but I can’t get the other Core to configure.


Is a u.FL antenna absolutely required to communicate, or is the antenna needed just to get any decent range?

How picky is the choice of antenna? I salvaged a u.FL antenna from a broken laptop, connected it, and I still can’t configure the Core.

Is my Core defective?

Hi @timkay,

The u.fl core without an antenna would have an extremely limited / unreliable range. Here’s one antenna I like that’s fairly cheap: https://www.sparkfun.com/products/11320 . There was also a great community thread on this issue here: https://community.spark.io/t/recommendations-for-a-cheap-u-fl-antenna/840



I didn’t quite get an answer to my questions. (I had already read the forum posts that you recommended.)

You almost said that it should work without an antenna, but with very limited range. Is it true?

Also, I asked how picky it is about an antenna. I saw the post where they used a syringe-like thing, so I would guess it’s not too picky. If not, the u.FL antenna I salvaged from a laptop should work, but I still can’t configure it.

Given answers to those questions, we should be able to answer my third question: is my Spark Core defective? It doesn’t work with no antenna, and it doesn’t work with the salvaged antenna. Is my Spark Core defective?

(I also mentioned that I have a non-u.FL Core, and I have it working just fine, so it’s not something I am doing wrong.)


Hi @timkay,

Although some wifi configurations might allow some people to use a u.fl connector core without an antenna, it is expected that that setup generally won’t work and won’t be reliable. That’d be something like trying to use your iPhone buried in 10 feet of concrete and steel. :slight_smile: You might be able to do it if you had a wifi access point nearly touching your core (somewhere between a few inches or ~1 foot), but again, I don’t expect this will work.

We experimented with this as part of our manufacturing process, and we decided it would be better to instead attach a test antenna to every u.fl core during testing than trying to run them without an antenna.

As far as I know, the core is not very picky about an antenna, I’ve personally had a u.fl core working with a twist-tie. :smile:


I still don’t think I quite have my answer. From what you said, I am guessing that it should work, at least to some degree, without an antenna, or at least with the salvaged antenna. Since it does not work, we can conclude that my Core is bad.

Good timing. I just received a u.FL wifi antennal from Digi, and my Core still doesn’t work.

How do I get it replaced?

Hi @timkay ,

We’d be happy to get you a replacement if it’s not working. Could you try clearing wifi credentials + a factory reset (http://docs.spark.io/#/connect/troubleshooting-step-3-reboot-and-clear-memory + http://docs.spark.io/#/connect/appendix-factory-reset ) and configure over USB ( http://docs.spark.io/#/connect/connecting-your-core-connect-over-usb ) first? If that doesn’t work, follow up with me at hello@spark.io with your most current address and phone # and reference this thread. If you can also specify what the LED is doing that’d be handy too.

On a different note: The answer to your question of whether a uFL core will work without an antenna: No, not in a reliable way.



Just in general – If you have a u.fl core and you’re using it without an antenna, it will not work, and your core is probably not bad.

edit: My mistake I missed the part earlier about where you said you got a new antenna. They can be tricky to attach, can you describe what part isn’t working / or post a video?


Thank you!

Dave has very clearly answered my first question. If it doesn’t have any antenna, then it won’t work.

Joe answered my next two questions: if it doesn’t work even with an antenna, try a reboot-and-clear-memory. I am trying that now. It looks like I got past the wifi config issue. Now it is showing solid magenta. If it were flashing magenta, I’d know that it is updating the firmware. The instructions don’t say what solid magenta means. Finally I hit the reset button, and now it is flashing magenta. And now it is breathing cyan. Success!

Thanks for your help. I love this product!


1 Like

Heck to the yes @timkay ! Glad you are up and running!

Woot, same here, glad it’s running!

When the core does an over the air update, it flashes magenta for every packet of firmware going over the air. If it stops it can appear ‘solid magenta,’ (if a packet is dropped, etc) if it doesn’t recover from this after a few seconds, restarting the core is the way to go. Newer firmware does a better job of recovering from this, but the ‘fresh out of the factory’ version won’t have these improvements yet.


@anirudh, please refrain from posting the same/similar issue on the forum in 4 different threads.

This is the 2nd advice given to you for this week on forum behavior.

You can email hello@spark.io for assistance offline if the forum is unable to help rectify your issue.