Coketenna - easy, cheap, effective homemade ADS-B antenna

Good receive performance combined with easy construction, costs less than $1.
Inspiration and starting point was the "cantenna" concept developed and popularised by ADS-B antenna guru abcd567, with the following alterations:
- no connectors, soldering, or power tools = only a knife needed,
- standard soft drinks / beer / beverage cans instead of metal tins, can diameter is perfect and more or less the same all around the world, plus an empty soda can costs nothing,
- can be used with any coax cable including supplied in bundles,
- easy weatherproofing.



I named the result "Coketenna", primarily to prevent ambiguity, as "cantenna" can refer to waveguides for WiFi signals made from a Pringles can, secondarily because in an ADS-B context, "cantenna" also refers to solutions made from different diameter food tin cans. Underlying concept and method of operation is essentially the same, only difference is ease of construction with the Coketenna.
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Proof


Itsy-bitsy nuances in February's testing notes, FA antenna and Coketennas side-by-side:



Comparative performance figures ranged from 80% to 105% using the same back-end setup with 15% margin of error, but don't take my word for it:
Independent tester running an amplified and filtered indoor setup (Pro Stick+FA filter) swapped a FlightAware antenna to a Coketenna, and shared the following:

"last 7 days are for your cantenna. CPU utilisation is interesting as well: seems it needs to work harder to decode signals from cantenna compared to FA antenna"


(arrows indicating when Coketenna was swapped).
Back to my location, on identical back end computing: a semi-pro setup consisting of an rtl-sdr.com v.3, Uputronics 1090 Mhz filtered preamp and FlightAware antenna versus Pro Stick Plus with Coketenna:


More data in the ADS-B long term testing post.
Every location and setup is different, so you won't get the same performance, point is: build one in ten minutes, see for yourself, then get in touch with your results.

In short


- Diameter and height of can is around 69 mm,
- coax center conductor is pushed through hole cut in bottom,
- braid piles up and touches can,
- top element is 69 mm long.
That's it, simple as jacket potatoes.

Construction


One measurement, 68.80mm or thereabouts, common RTL-SDR objects as template:



It's not the end of the world if dimensions are off by a few mm, but strive for accuracy.
Stand can on bottom, mark can, cut off top. Knife, scissors, laser beam, choose your weapon.



Stand can, punch the middle of the bottom with a knife from inside to outside.



Do this on a chopping board or other sacrificial surface, not on the kitchen counter, divorce lawyers are expensive.
Strip off outer insulation from coax for about a handspan, 8 inches / 20 cm is more than enough. Coax is not bleeding, your palm cut on the edge of the can does, so 8 inches / 20 centimeter length is necessary, no pain. Try not to cut into coax, I do a circle around the bottom, then cut gently lengthwise, only cut hard at the top - easier to peel off plastic.
Push coax center (white squashy bit) through bottom of can. Small metal edges will keep coax in place, braid will pile up below.



Cut coax sticking out to 69 mm, weatherproof with hot glue or chewing gum. Alternatively, cut off bottom of a plastic bottle and place on top - easier and better, water will not pool in hollow of can.



Give it a go


The Coketenna is just a simplified construction method cantenna, and cantennas work - once more, credit for the original idea to abcd567, his work in the field is unparalleled.
Is it as good as a FlightAware antenna? Definitely not, that's the golden standard of the ADS-B world: it's not a coincidence that two independent testers contributing to this site use a FlightAware antenna as reference.
However, $45 is a lot in dark parts of the world, exactly where we need more feeders, not +10% higher totals or plus 10 mile range:


If want to build your first dedicated ADS-B antenna with minimum hassle, without power tools, in ten minutes, a Coketenna is a good choice. I haven't came across an easier, simpler, or cheaper antenna with comparable performance, but if you did, please get in touch, and share your wisdom.

4 comments:

  1. How does it stack up against, say, a stock magmount, and a magmount trimmed to 1/4 wave? I'm running the later, in a reasonable location, but actually felt there was a drop in reports after trimming from stock...

    ReplyDelete
    Replies
    1. Try placing magmount on a metal can, diameter and height should be around 69mm, small vegetable tins in Europe are perfect. Or any metal can, see February testing notes for ideas and images. Good luck!!!

      Delete
  2. I am definitely making one. Too much fun to miss out on.

    ReplyDelete