Limit WiFi range

Installing and Using OpenWrt
1

Hi forum
I want to install an dumb wireless AP with a very limited range.
I tried setting the maximum transmit power to 1 dB (1 mW), although weaker, the signal still reaches though several walls. I am using the Zyxel WSM20.
My question is, is there another way how I could limit wifi rage?

2

Flat antennas. 5g

or

Buying the worst rated antennas on aliexpress..

Flat is positional.
You can lay one on the floor of a basement and it will only scatter 45 degrees from the first/ground floor up.

^
Looks like that, but upside down.

2.4 goes through everything. 5 won't..

3

That's a good idea. Won't work with my WSM20 tho.

4

which idea?

5

To exchange the antennas. The WSM20 has no outside/exchangable antennas. But I could try laying the device on the side.

6

Try 5G.
5910

7

I should have given more context.
I need to give WiFi access in my flat to a few devices (they are all very close to each other) which only work with WPA2, but I would prefer to use WPA3 for my network.
So my idea was to add an AP with a very limited range just for these devices to reduce exposure of the not so secure WPA2 WiFi.

8

So, we can go back to my first reply?
Seems you are going to buy something...

9

I guess so :sweat_smile:
I just read that aluminium foil can reduce the signal, but it kindof feels a bit esotheric :flying_saucer: Might give this a try before I buy something.

10

Without getting technical enough for some fool to argue with me:
the 'reflection' back into the radio, could fry it.

11

Thanks for the hint :+1:, I will monitor the temperature.

12

For the records, aluminum foil does indeed cause increased heat in the WiFi chipset.
After 100 seconds of iperf3 the temperature got from 64°C to 84°C, whereas when measured without aluminum, the temperature does not really increase (measured with collectd-mod-sensors).

13

I took physics at the J.B. School of Engineering.

I had to pass their weed out class; 198 and 199.

I appreciate the field test.

14

Weird that it would get hot with only 0dBm (1mW) of power out, even if there was total reflection.

Maybe some kind of lossy material would work better than a reflective one? Not sure what lossy materials are available without spending money on RF absorber, though.

This is a total spitball here, but what about completely coating a sheet of paper in pencil graphite, taping another sheet on top of it so that it doesn't make a mess when touched, and then folding it around the antennas (or just the whole router if internal antennas)? No idea if that would cause an appreciable amount of attenuation, though.

Edit, another idea would be steel wool. Ferromagnetic materials like iron would be way more lossy at GHz frequencies than aluminum.

15

Is there another technical aspect we should be aware of. For example, perhaps another AP with the same SSID nearby, or you don't want your neighbors to see the AP.

I have a feeling you created 2 APs with identical SSIDs, one WPA2, and another WPA3?

If so, is there a reason the devices that only support WPA2 must have an identical SSID?

Or is it just you do not desire the WPA2 SSID to have as large of range?

16

I will only run MQTT traffic over this AP, so I guess this will not cause a problem.
So aluminum should already work :crossed_fingers:

17

I do not want (ideally) anybody to "see" the AP to reduce WPA2 exposure. I figured that one good way is to reduce the signal strength. Not a perfect solution but I guess that way only two close neighbors will be within signal range, whereas now you can even catch the signal outside the house.

No, the WPA2 devices will get their own SSID.

Yes, I am trying to minimize it as much as possible.

18

Silly ideas:

  1. run conducted paths (aka coaxial cable) between the devices
  2. place all of the into the same Faraday cage
  3. check whether the radio actually honors your power settings in the first place
19

Other silly ideas:

  • make the SSID and key a long, maximum, random lengths
  • copy them via LuCI or current SSID connection
  • make this SSID
  • Hide it/connect devices

Some devices may not like to connect to the same now hidden SSID, some will, so the order of the last step depends on your success. It's also possible some devices won't accept the length, etc. - totally understandable as well.

If you want to reduce the signal still, I like the silly ideas moeller0 mentioned.

Cool.

I assume this is a layman's term meaning your neighbors shouldn't see it listed on air in their WiFi scans. :wink:

Or something different?

20

Nice ideas! Difficult to realize in my living room setting tho :sweat_smile: I will go with the aluminum foil for now and observe.

Not sure now to check this in detail. I used iperf3 on my phone (iperf3 server is not on the router) and walked away from the router. The signal was definitively weaker when I set the power to 1 dBm compared to 20 dBm, but it was still quite strong. Not sure to what extend the radio honored my setting, but it did at least to some extend.

Also nice ideas :star_struck: I will hide hide the SSID for extra security.
Regarding the other ideas, this would require me to reflash one of my devices (ESP8266) which is not easily possible. So I keep them in mind in when I would need to work on my device at some point in time.

Yep :laughing: