Antenna design is a dark art, I like simple hacks like this.

> The two parts of the antenna are intentionally designed to create an omnidirectional radiation pattern without a pronounced directionality.

I worked on a project a while back to try to utilize this to detect the arrival direction of WiFi signals approximately based on received strength. Do this for enough base stations and you have a very crude positioning system.

It also immediately invalidates FCC modular component compliance, and may be illegal if operating on dual-use bands like 5G wifi.

Remember the rules limits use the ERP, and EEs may have added a crappy antenna on purpose to meet the legal limits.

https://en.wikipedia.org/wiki/Effective_radiated_power

There are also medical radiofrequency exposure guidelines, and they mitigate deep tissue burns or "G5 Mind control beams" concerns. lol =3

https://www.canada.ca/en/health-canada/services/health-risks...

Exactly… they would have added crappy antenna as they likely meet emission, spurious or harmonics requirements..

Engineer might be messing with other 2.4GHz devices by doing this

2.4GHz is already incredibly crowded and prone to interference (in urban environments). I remember once picking up emissions on a Bluetooth headset from a leaky microwave oven.

This seems very unlikely compared to the obvious answer that they added a crappy antenna to keep their BoM and assembly costs low.

The radios on these are weak and adding an Omni antenna is exceptionally unlikely to violate EIRP.

Could this design accidentally radiate something it's picking up from the board outside of 2.4ghz? Sure.

But practically it's quite unlikely to in this context.

That isn't how this works. There is no change in emission power, the antenna doesn't add power.

Well mostly true.

You can replace an inefficient (turns power into heat) antenna with a more efficient antenna which will then radiate more.

And some frequencies are regulated by effective radiated power, where they basically care about the strength of the signal in the strongest location, so a more directional antenna could push you over the limit.

You can just ignore the FCC.

They are completely toothless.

As an individual this is mostly true unless you're touching broadcasting proper. As a business this is absolutely not true and noncompliance is a ticking time bomb that will bankrupt you.

As someone in Southern California who uses HAM, this is both true and not true. There's an older gentleman who has already spent time in jail for sitting on frequencies without a license repeatedly. After he got out, he jumped right back on it. He's got tens of thousands if not more in unpaid fines, but as far as I'm aware they cant get blood from a stone.

Another anecdote, dozen or more years ago a friend had a fault cable modem that was spitting out radio traffic I assume on some important frequencies in a dense area. They got a knock on the door from an FCC team who were tracking the interference down.

HAM-is-not-ham

And your example must be one of those weirdos on 80m. What a pack of crazies.

The author is German and lists German contact information. They're a lot stricter in the EU about this.

I'm doing something similar, using the directionality of the antenna to turn an ESP32 into a high RPM gyroscope for use in a combat robot. Standard gyro chips top out well under 1000 RPM, and are much more expensive than an ESP32 board, plus the ESP can serve as the radio control link and brain of the bot at the same time.

cool idea. care to share more? my thought would be continuously measuring antenna impedance over time, and looking for a peak in this signal's spectrum near the rotation frequency. could also try with a photodiode (+ optional light source, or use ambient light) (this would be similar to an optical computer mouse), which i guess could be more directional, and thus give a stronger signal

Combat robots are more like RC cars than autonomous robots, the driver stays in control of the bot over a radio link. I use ESP-NOW, and get about 6000 packets per second from the transmitter to the ESP32 in the box, and each comes with radio link stats, signal strength and Channel State Information. Using autocorrelation on the signal strength gives you the rotation period, and using that you can establish a Phase Locked Loop to remove the drift of integrating rotation speed to get absolute rotation angle.

Silver-coated wire? I don't have that lying around.

Nothing special about it. https://amzn.eu/d/06dMTm5c

Handy to garrot werewolves too

Hell yeah!!

Paperclip has worked fine in my experience. I've got a bunch of these and the stock antenna really is just awful.

Paperclips can be very difficult to obtain sometimes :P (have you seen smiling friends?)

The antenna on these cheapo modules is bodged anyway. They don't get a good signal out and it's not just because of the size. I have other modules from waveshare that use the same antenna and they work way way better.

So yeah I also do this if I really need the WiFi or Bluetooth. Usually I don't though.

Edit: oh I see he goes into that later. Like the way they don't leave a copper free space around the antenna. Exactly. They are a bit compromised but they are so so cheap.