6 ms·

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 p

by bArray 2mo ago

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.

Joel_Mckay 2mo ago
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 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-safety/radiation/occupational-exposure-regulations/safety-code-6-radiofrequency-exposure-guidelines.html https://www.canada.ca/en/health-canada/services/health-risks...
- vkdelta 2mo ago
  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
  - tylerflick 2mo ago
    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.
  - dgacmu 2mo ago
    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.
  - sscaryterry 2mo ago
    That isn't how this works. There is no change in emission power, the antenna doesn't add power.
    - BenjiWiebe 2mo ago
      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.
- spacedoutman 2mo ago
  You can just ignore the FCC. They are completely toothless.
  - chemeril 2mo ago
    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.
  - deleted 2mo ago
    [deleted]
  - bikezen 2mo ago
    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.
    - ikidd 2mo ago
      HAM-is-not-ham And your example must be one of those weirdos on 80m. What a pack of crazies.
  - jubilanti 2mo ago
    The author is German and lists German contact information. They're a lot stricter in the EU about this.
TGower 2mo ago
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.
- flossEveryday 1mo ago
  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
  - TGower 1mo ago
    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.

by bArray 2mo ago

Joel_Mckay 2mo ago

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 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-safety/radiation/occupational-exposure-regulations/safety-code-6-radiofrequency-exposure-guidelines.html https://www.canada.ca/en/health-canada/services/health-risks...

vkdelta 2mo ago
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
- tylerflick 2mo ago
  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.
- dgacmu 2mo ago
  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.
- sscaryterry 2mo ago
  That isn't how this works. There is no change in emission power, the antenna doesn't add power.
  - BenjiWiebe 2mo ago
    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.
spacedoutman 2mo ago
You can just ignore the FCC. They are completely toothless.
- chemeril 2mo ago
  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.
- deleted 2mo ago
  [deleted]
- bikezen 2mo ago
  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.
  - ikidd 2mo ago
    HAM-is-not-ham And your example must be one of those weirdos on 80m. What a pack of crazies.
- jubilanti 2mo ago
  The author is German and lists German contact information. They're a lot stricter in the EU about this.

TGower 2mo ago

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.

flossEveryday 1mo ago
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
- TGower 1mo ago
  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.