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1. 12:30 AM - Re: interesting antenna discovery (Bob Verwey)
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| Subject: | Re: interesting antenna discovery |
Geez Bob...the stuff I have learned on this forum!
On Thu, 27 Oct 2022, 23:09 Robert L. Nuckolls, III, <
nuckolls.bob@aeroelectric.com> wrote:
> Found a broken WiFi antenna in a box of 'stuff'
> a few days ago. Peeled of the outer jacket and
> found this inside.
>
> It's a classic 'coaxial' dipole . . . 1/4 wave
> radiator and 1/4 wave coaxial sleeve.
>
> The dimensions were a puzzling at first, they
> are too short for free space resonance in the
> 2450 MHz WiFi band.
>
> Then I recalled installing j-pole antennas
> fabricated from 450 Ohm 'ladder-line' for a
> customer some years ago. I erected radomes
> fabricated from PVC pipe and found that when
> the antenna was a tight fit in the pipe, proximity
> of the dielectric depressed the resonant frequency
> of the antenna. The use of 3" PVC and with
> cardboard spacers to center the antennas brought
> them back to design resonance.
>
> I suspect that's what happens here. The antenna
> is physically modified to accommodate proximity
> effects of the jacket.
>
> Kinda cool . . .
>
> Bob . . .
>
> Un impeachable logic: George Carlin asked, "If black boxes
> survive crashes, why don't they make the whole airplane
> out of that stuff?"
>
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