Make an u.fl antenna within seconds using a cannula

Attached you’ll find a photo from a u.fl antenna I made during the Christmas holidays to get the core running while I was waiting for shipment of my ordered once.

I just took a green marked cannula, cutted the intravenous end, and reopened the cutted end it with another smooth press prependicular to the first cut. Matched perfected on the center pin of the coax connector and helped me getting started with the Spark Cores during the Christmas holidays.
EDIT: take a file or sandpaper, place it on the table and grind down the cannula between your fingers until it has a more round shape to not to damage the u.fl connector with too much press on it.

Connects to my router 15 ft. away thru a concrete ceiling.
This is of course a temporary solution, but available at your drugstore, or ask your country doctor for help :smile:
Keep it out of the reach of children!

But officer, I'm just using them as makeshift WiFi antenna, I swear!

Alternate Joke: @mf2105 Damn dawg, your Spark Core looks dope!


Ask your local (drug) dealer for more :slight_smile:

I love it! Lol…
Wrap some bailing wire around it and go all out hillbilly! Probably get better reception too!

This hack ranks right up there with the Pringles can antenna, IMO. Very nice.

Amazing. @mf2105 have you tested the range on that? I bet if you cut it the right length, you could get decent performance out of it… any RF experts around who could calculate the optimal length?

Awesome hack.
I smell a blog opportunity. :slight_smile:

Ok, well true, any conductor can act as an antenna. But I would caution running a u.fl core without an antenna or in this case a poorly matched antenna as the great majority of the RF power is not radiated which means the power is reflected back into the power amplifier. Without specific protection circuitry built in this has the potential to damage the PA.

@zach I do not any further testing on that, it works for the moment. But another idea: Maybe there’s a chance to deliver something like this (in the right length, isolated on the outside and tested for issues as @mattande mentioned) with the u.fl spark ?

@mf2105 we plan to stock external u.FL antennas in our store soon.
@mattande has raised a valid point. we should also make sure not to short the antenna with the GND contact while the Core is powered!

It appears that this antenna is made from a series of tubes.

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Be careful going out and buying IV needles at your local drug store, as it could get you in trouble with the police if you’re not a diabetic. (E.g., they do a traffic stop and see a box of needles sitting next to you.)

[Trust me, it’s not fun! The cops will tear your car apart and not even say “Sorry” afterwards.]

Antenna Length Calculation,

Frequency / 468

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Could you elaborate on that? Given that the the core is using 2.4GHz WiFi, what length (with units) do I need?

Maybe also take a look at this tutorial to make your own (more optimized) antenna.

Image of antenna

Also maybe this sparkfun product for an actual antenna if you were having trouble finding one (like I was).

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frequency (2.4Ghz) / 468 gives you a half wave dipole.

So, i’m going by memory here,

2400/468 = 5.12 inches.

that would give you a 1/2 wave antenna.

Just sharing here for laughs, but I couldn’t find a u.fl antenna at home this morning, and I remembered this thread so here is my twist-tie antenna. Can do OTA updates and it stays online very well, just don’t bump it!