Can someone explain why two ESP32 WROOM (U.FL) require antennae to talk to each using ESP-NOW?
U.FL w/o antenna can send to SPARKFUN THING PLUS ESP32 WROOM and the SPARKFUN THING PLUS ESP32 WROOM can send to the U.FL. But before two U.FLs will talk to each other, I had to add an external antenna to each. During all my testing, the two esp32s were about 2 feet from each other.
u.fl → wroom: success
u.fl ← wroom: success
u.fl → u.fl: failure
u.fl w/ant → u.fl/ant: success
I don’t think it was an incorrectly typed MAC address because the problem shows up even when the sender uses ff:ff:ff:ff:ff:ff as the broadcast address.
You have two radios and radios need antennas to work. Not using an antenna or directly connecting a radio to another radio with a cable will eventually damage both devices.
Thanks, YellowDog, but that wasn’t what I was looking for. When I don’t attach an external U.FL antenna onto my SparkFun Thing Plus - ESP32 WROOM (U.FL) WRL-17381, then it works perfectly as a sender or as a receiver when used with my SparkFun Thing Plus - ESP32 WROOM WRL-15663. I’m looking for an explanation of why my two SparkFun Thing Plus - ESP32 WROOM (U.FL) WRL-17381s require *external U.FL antennae to talk to each other when they didn’t need one to talk to the WRL-15663. BTW, I used PCB Antenna - U.FL (2.4GHz) WRL-18086.
All radios require antennas of some sort, in order to function at all. The better the antenna, the longer the range. Keep in mind that the antenna must be designed for the operating frequency and that the impedance should be closely matched to the RX/TX input/output impedances.
It is not clear from your posts which antennas are being used in the different scenarios. But it doesn’t really matter to us. Figure out what works best for you, and go with it.
There is no question that antennae are needed. The issue is I spent many days trying to figure out why the two SparkFun Thing Plus - ESP32 WROOM (U.FL) WRL-17381s with no external antennae weren’t speaking to each other, while The SparkFun Thing Plus - ESP32 WROOM (U.FL) WRL-17381 without an external antennae works perfectly well when talking to SparkFun Thing Plus - ESP32 WROOM WRL-15663.
WRL-17381 does not have an antenna; RF will leak out through the trace and the stub in the connector but that will be a very poor antenna (and may even damage the tranmitter). You may be getting enough signal out for the WRL-15663 (with a trace antenna) to work, but not enough for another WRL-17381 with no antenna to have a stable connection.