# Two ESP32 WROOM (U.FL) wrl-17381 require antennae to talk over ESP-NOW. **URL:** \ **Category:** ESP32\ **Created:** [April 9, 2022, 9:30pm UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744 "2022-04-09T21:30:29Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![heedthespark](https://avatars.discourse-cdn.com/v4/letter/h/958977/32.png) [@heedthespark](https://community.sparkfun.com/u/heedthespark)\ **Post date:** [April 9, 2022, 9:30pm UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744/1 "2022-04-09T21:30:29Z")
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. ---
**Author:** ![YellowDog](https://yyz1.discourse-cdn.com/sparkfun/user_avatar/community.sparkfun.com/yellowdog/32/1782_2.png) [@YellowDog](https://community.sparkfun.com/u/YellowDog)\ **Post date:** [April 10, 2022, 6:39am UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744/2 "2022-04-10T06:39:15Z")
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**. ---
**Author:** ![heedthespark](https://avatars.discourse-cdn.com/v4/letter/h/958977/32.png) [@heedthespark](https://community.sparkfun.com/u/heedthespark)\ **Post date:** [April 10, 2022, 10:15am UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744/3 "2022-04-10T10:15:44Z")
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. ---
**Author:** ![jremington](https://yyz1.discourse-cdn.com/sparkfun/user_avatar/community.sparkfun.com/jremington/32/6595_2.png) [@jremington](https://community.sparkfun.com/u/jremington)\ **Post date:** [April 10, 2022, 2:58pm UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744/4 "2022-04-10T14:58:30Z")
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. ---
**Author:** ![heedthespark](https://avatars.discourse-cdn.com/v4/letter/h/958977/32.png) [@heedthespark](https://community.sparkfun.com/u/heedthespark)\ **Post date:** [April 10, 2022, 3:11pm UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744/5 "2022-04-10T15:11:29Z")
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. ---
**Author:** ![heedthespark](https://avatars.discourse-cdn.com/v4/letter/h/958977/32.png) [@heedthespark](https://community.sparkfun.com/u/heedthespark)\ **Post date:** [April 10, 2022, 3:20pm UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744/6 "2022-04-10T15:20:36Z")
> jremington: > It is not clear from your posts which antennas are being used in the different scenarios My previous post indicated that I used the “PCB Antenna - U.FL (2.4GHz) WRL-18086” _external_ antennae. ---
**Author:** ![n1ist](https://avatars.discourse-cdn.com/v4/letter/n/5daacb/32.png) [@n1ist](https://community.sparkfun.com/u/n1ist)\ **Post date:** [April 10, 2022, 11:40pm UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744/7 "2022-04-10T23:40:28Z")
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. ---
**Author:** ![heedthespark](https://avatars.discourse-cdn.com/v4/letter/h/958977/32.png) [@heedthespark](https://community.sparkfun.com/u/heedthespark)\ **Post date:** [April 11, 2022, 12:17am UTC](https://community.sparkfun.com/t/two-esp32-wroom-u-fl-wrl-17381-require-antennae-to-talk-over-esp-now/43744/8 "2022-04-11T00:17:07Z")
Ah! A leak. That does sound possible. Thank you.