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XueHai8
Posts: 82
Joined: Mon Jul 24, 2017 12:19 pm

How to improve Wifi signal?

Sun Mar 07, 2021 5:17 am

Looking for creative solutions.

I have a Raspberry Pi 3A+ installed inside a 3D Printer running OctoPrint.

And because it's inside a metal chamber of the printer, the wifi signal is not that great - even at only a few meters from the router.

I've been looking at hacks to attach a wifi antenna to it, much like the one available for the CM4, so I can mount it to the outside of the case. But I've seen mention that this can get you in trouble with the FCC (if they ever found out), will void the warranty, and probably damage the Pi if I screw it up (likely).

I could switch to a 3B+ and use a USB antenna with an extension, but seems kind of a waste since it already has Wifi.

Perhaps a 2B with a wifi antenna, but I'd rather have the faster 3B as I do a lot of timelapses - maybe that doesn't make an difference?

So I'm look for creative solutions to this problem.

Any ideas I may be overlooking?

Thanks!

Heater
Posts: 18257
Joined: Tue Jul 17, 2012 3:02 pm

Re: How to improve Wifi signal?

Sun Mar 07, 2021 5:46 am

Mount the Pi on the outside of the metal box.
Put a plastic cover over it.

Thinking outside the box as they say.
:)
Memory in C++ is a leaky abstraction .

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Milliways
Posts: 702
Joined: Fri Apr 25, 2014 12:18 am
Location: Sydney, Australia

Re: How to improve Wifi signal?

Sun Mar 07, 2021 6:18 am

The wavelength @2.4GHz is ~125mm. A cutout of this size should permit propagation, but this is larger than the Pi3A+.
In fact mounting the antenna closer that this to any cutout should help.

You can see the faint outline of the antenna as a faint trapezoid shape near the SD Card slot, so mounting the Pi3A+ with this near the cutout should help. NOTE that this is quite small.

My Pi4 in a metal heatsink case (which has similar antenna) has no propagation issues.
Last edited by Milliways on Sun Mar 07, 2021 6:38 am, edited 1 time in total.

cleverca22
Posts: 3792
Joined: Sat Aug 18, 2012 2:33 pm

Re: How to improve Wifi signal?

Sun Mar 07, 2021 6:34 am

Milliways wrote:
Sun Mar 07, 2021 6:18 am
The wavelength @2.4GHz is ~80mm. A cutout of this size (or larger) should permit propagation.
several of my previous laptops, had such a cut-out in the metal body, with a plastic insert filling the hole

some models just tried to hide it with the same color, others used the plastic as part of the design and style

Heater
Posts: 18257
Joined: Tue Jul 17, 2012 3:02 pm

Re: How to improve Wifi signal?

Sun Mar 07, 2021 7:53 am

Milliways wrote:
Sun Mar 07, 2021 6:18 am
The wavelength @2.4GHz is ~125mm. A cutout of this size should permit propagation, but this is larger than the Pi3A+.
In fact mounting the antenna closer that this to any cutout should help.
Indeed. Now here is a trick...

The cutout need not be a huge round or square hole the diameter/width of a wave length. It can be just a long thin slot cut in the wall of the box. Often only a half a wavelength long slot will do.

How so? We are talking about electro-magnet waves here. That is to say there is an electric field and a magnetic field at right angles to each other. Both at right angles to the direction of travel. If we can get the electric field through the metal wall it will propagate out the other side. A Long thin slot will do that. Think of it like trying to push a ling stick sideways through a slot, line it up right and it falls through, turn 90 degrees and it won't.

This all sounds a bit magical but I was surprised by an experiment I did a few years ago. On a lark I put my mobile phone in an aluminium box and screwed down the lid with 6 screws. I was amazed to find that when I called the phone in rang! Turns out the very thin gap between lid and body was enough to let some signal in. Thin enough you could not slide a sheet of paper between. I had to wedge some rolled up steps of tin foil at regular intervals along that gap, which eventually kills the signal when they were close enough.
Memory in C++ is a leaky abstraction .

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Milliways
Posts: 702
Joined: Fri Apr 25, 2014 12:18 am
Location: Sydney, Australia

Re: How to improve Wifi signal?

Sun Mar 07, 2021 11:21 am

Heater wrote:
Sun Mar 07, 2021 7:53 am
Milliways wrote:
Sun Mar 07, 2021 6:18 am
The wavelength @2.4GHz is ~125mm. A cutout of this size should permit propagation, but this is larger than the Pi3A+.
In fact mounting the antenna closer that this to any cutout should help.
Indeed. Now here is a trick...

The cutout need not be a huge round or square hole the diameter/width of a wave length. It can be just a long thin slot cut in the wall of the box. Often only a half a wavelength long slot will do.

How so? We are talking about electro-magnet waves here. That is to say there is an electric field and a magnetic field at right angles to each other. Both at right angles to the direction of travel. If we can get the electric field through the metal wall it will propagate out the other side. A Long thin slot will do that. Think of it like trying to push a ling stick sideways through a slot, line it up right and it falls through, turn 90 degrees and it won't.

This all sounds a bit magical but I was surprised by an experiment I did a few years ago. On a lark I put my mobile phone in an aluminium box and screwed down the lid with 6 screws. I was amazed to find that when I called the phone in rang! Turns out the very thin gap between lid and body was enough to let some signal in. Thin enough you could not slide a sheet of paper between. I had to wedge some rolled up steps of tin foil at regular intervals along that gap, which eventually kills the signal when they were close enough.
When I completed my undergraduate degree (more than 50 years ago) I could solve waveguide calculations, even work out how a yagi worked.

Later, when working as a GSM planner, phones had external (usually < 1/4λ) antenna until Nokia introduced a phone with a "ceramic" antenna enclosed in the case. These obviously worked, because they are now ubiquitous, and while I appreciate the dialectic and magnetic properties of the materials make this possible (e.g. the tiny ceramic device on the Pi3) I never really understood this.

My experience as an engineer has shown that the theory about Faraday cages is OK but signals you don't want slip out of the tiniest slots (indeed these work better than cutouts) unless you use measures like the 1/4λ stubs in microwave ovens.

Heater
Posts: 18257
Joined: Tue Jul 17, 2012 3:02 pm

Re: How to improve Wifi signal?

Sun Mar 07, 2021 1:14 pm

Oh boy, I too spent a lot of time with Maxwell, wave guides and such as part my Physics degree back in nineteen seventy.. mumble, mumble... Hardly remember any of it. I do recall doing some neat experiments with microwave horns, aluminium grids as polarisers, aluminium rings as Fresnel lenses and such. Wonderful times. Even worked at the Marconi Radar Company on a phased array radar project for some years but by then I was on the software end things.

Now, where are those 1/4λ stubs in microwave ovens hiding? Not immediately obvious when I look at mine.
Memory in C++ is a leaky abstraction .

SaraJennifer
Posts: 1
Joined: Wed Mar 03, 2021 1:11 pm

Re: How to improve Wifi signal?

Sun Mar 07, 2021 3:07 pm

Expressions of remorse if this isn't the correct sub for this inquiry. I have Optimum with the standard modem and WiFi switch on the first floor of my home. The wifi sign and speed needs enhancement for the second floor since I have my work PC arrangement which involves meeting video calls.

What is the least demanding approach to improve Wifi signal unwavering quality and speed on the second floor of my home?

I've taken a gander at buying switch reception apparatuses that are "high acquires 9dBI" which have all the earmarks of being a modest simple alternative anyway I don't perceive how that can associate with my present switch - see connected photographs

Would a cross section extender/supporter be a simple arrangement for my subsequent floor? Does anybody have suggested items that you can send me the connections for procurement? An ideal supporter would have an ethernet port for my PC and furthermore help the Wifi signal for my iPhone.

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