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Silly Antennas

Silly Antennas

Fun Trolling eBay for Sketchy Antennas

Here’s one for you … promising 18 dBi of 2.45 GHz gain, in a hand-held voodoo magic assembly. We bought it and 3D tested it. To exactly no one’s surprise, it doesn’t come close to that that kind of directivity. That kind of gain is sometimes available from Yagi arrays and is normally the domain of very large horns or reflector antennas. Anyways, peak gain was approximately +4.1 dBi (from the back of the antenna) and broadside gain was +1.9 dBi.

Past Contest – Eifagur 10 dBi Omni for Helium Mining, Week of April 11, 2022

The winner of this “Guess The Gain Contest” was Carlos Cabezas (@eb4fbz on Twitter) with his gain estimate of -3 dBi. The Eifagur’s actual sideways gain is -1.1 dBi … a far cry from the +10 dBi promised!

There is a lot of renewed interest in the old 902 to 928 MHz ISM band, this time for Helium network mining gateways. With this comes new antenna marketing, and sketchy claims. This Eifagur antenna on Amazon claims 10 dBi of omni-directional gain. It’s physically too small for this kind of directivity. You can see the full results here.

Past Contest – Copper Tape Horn Extension December 12, 2020

The winner of this silly antenna “Guess The Gain Contest” was Stuart McAndrew (@ssshocker on Twitter) with his gain estimate of 12.1 dBi.

Have you ever thought about just lengthening a horn antenna to make it more directive (increase gain)? It’s certainly possible – theory and practice show that a horn’s gain is proportional to it’s aperture size. 

Well we did just that! A simple “down and dirty” copper tape extension was applied to this K-band WR42 standard gain horn antenna. The aperture size was increased by 4 times over the 15 dBi original size, and the flair angles were simply extended. The unmodified horn’s peak gain was measured at +15.6 dBi. So can we expect a 6 dB gain increase (4 x power from 4x aperture increase)?

Nope! Electrically large antennas like this horn that is multiple wavelengths across, need precise geometries to form directive plane waves needed for high gain/directivity. The hand formed copper tape was simply too “wonky” to be effective. In fact, it decreased the gain and distorted the pattern. Peak gain fell to +13.1 dBi. The swept frequency 3D gain plot movie below illustrates some of the pattern distortions.   

Past Contest – Whisky Antenna August 21, 2020

The winner of this silly antenna “Guess The Gain Contest” was @OmgZilla1 on Twitter who guessed the Glenfiddich scotch bottle gain as +10.1 dBic (our actual measured gain is +9.8 dBic). Full test results can be downloaded HERE.

Past Contest – “Cantenna” 13 dBi eBay WiFi Antenna May 5, 2020

The winner of this silly antenna “Guess The Gain Contest” was Robert Watson (@robert_watson on Twitter) who guessed the Cantenna gain as 6.2 dBi (our actual measured gain is 5.8 dBi) at 2440 MHz (WiFi band center). Full test results can be downloaded HERE.

The Cantenna eBay link is HERE. Enjoy the pictures below including the eBay “datasheet” claims.

Past Contest – Baguette Helix Antenna, February 10, 2020

The winner of this silly antenna “Guess The Gain Contest” was Stuart McAndrew (@ssshocker on Twitter) who guessed the gain exactly at 8.6 dBic. The antenna is RHCP (with an axial ratio is 0.5 dB) and has peak gain at 1500 MHz. Full test results can be downloaded HERE.

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