I was wondering. Can an antenna be too large for an ESP?
I was about to order an external antenna with sma connector + ufl to sma cable. But then I remembered I still have an old (ancient) 2.4GHz wifi router that is ready for the trash. It’s antenna is about 19cm long including the base/connector. The one I was about to order was probably half the length.
Could I reuse that for a esp32 and/or esp8266?
And just for my curiosity: What would happen if a 125m long antenna (1000x the wavelength) was to be connected to the ESP?
A 2.4ghz antenna from router will work. I use several. Make sure both are the same polarity. Wifi tends to use reverse polarity sma. 1/4 wave lenght tends to be most convenient. Multiplies of 1/4 wave length may work but not necessarily any better.
Antennas is a giant rabbit hole to go down.
I went down that rabbit hole some 8 years ago when playing with the RFM69 and RFM95 LoRa transmitter and trying to increase it’s range. It took me weeks to find my way out. And in the end, I still felt like I learned next to nothing. I came out more confused than when I fell into it… xD
Anyway. So in conclusion: Using the larger router antenna will not be worse, but probably also not (much) better than let’s say something like these:
€ 2,51 5%OFF | WiFi Antenna 2.4GHz/5.8GHz Dual Band 3dbi RPSMA/SMA Connector Rubber Aeria for Mini PCI Card Camera USB Adapter Network Router https://a.aliexpress.com/_EyHQvWv
P.S. Just to be sure: About the reverse polarity sma. That simply means the center pin is on the other end, right? Not that the center pin is ground and outer shell is signal?
I assume it must be the first, since in that latter case the connector would be unshielded.
Yes outer is ground and inner is signal on both. I think it was just to stop people using radio antenna on wifi. Just centre pin different as you say. Avoid those short rubber duck antennas though. Most wifi antenna are simple dipoles. You can’t believe the db gain in the advert either.
The reverse polarity SMA connector was developed to prevent people changing antennas and invalidating FCC certification. They are now extremely common, so it did not work.