November 3, 2015 at 12:05ESP-8266 and signal strength: antenna type selection
Over the past year, ESP-8266 has mutated from ascetic revision 01 to multi-legged monsters like the ESP-201 or NodeMCU board, which can significantly move the younger Arduins from the “measure the temperature, blink the LED” segment, giving out a full-fledged WI-FI as a free bonus. Actually, I propose to figure out the quality of this Wi-Fi in different revisions of the board.
The idea of this test appeared as a result of a designer’s mistake: a carefully thought-out, assembled and debugged control unit for the pump station, being installed in its place of work - in the bathroom, did not corny see the signal of the home router.
Having plenty of practice in juggling with low-literary turns, I sat down to google which of the ESP-8266 family boards had a better signal, but, contrary to expectations, I could not find this information among tons of articles and forum rolls. Therefore, he decided to fill this gap: through the efforts of Uncle Liao, he got hold of four different revisions of the board with different types of antennas, which will participate in signal strength tests.
First, let's figure out what types of antennas are put on boards with a chip 8266. There are only three options:
Four boards participated in the test:
ESP-01 - printed antenna.
ESP-201 - printed, plus an IPX connector for external.
ESP-07 - ceramic, plus an IPX connector for external.
ESP-12 - Printed
In addition, a test of external antennas was carried out (the links below I give only for identification of antennas, and not as a recommendation of a store or trading platform):
- Postings that come with the ESP-201. The view does not bode well. I want to understand if it will give at least some gain in comparison with the built-in antennas.
- Chinese antenna for $ 1. The usual antenna, most likely standing in most cheap routers.
- Antenna Banana Pi. It was bundled with a computer, but also sold separately.
I wonder if it should be used for its intended purpose or is it better to immediately replace it.
Upd: A little later I conducted an express test with an antenna from the Asus rt-n13 router, the results came out a little worse than with antenna No. 2. In the table, the test is not reflected, because it was impossible to accurately reproduce the conditions.
The test was conducted on the street, in the countryside, there were no other Wi-Fi networks in the detection radius. To measure the signal level, a smartphone with the WIFI Analyzer program was used, so the results are relative.
Here is what the measurements (dBm) showed:
Conclusions:
The idea of this test appeared as a result of a designer’s mistake: a carefully thought-out, assembled and debugged control unit for the pump station, being installed in its place of work - in the bathroom, did not corny see the signal of the home router.
Having plenty of practice in juggling with low-literary turns, I sat down to google which of the ESP-8266 family boards had a better signal, but, contrary to expectations, I could not find this information among tons of articles and forum rolls. Therefore, he decided to fill this gap: through the efforts of Uncle Liao, he got hold of four different revisions of the board with different types of antennas, which will participate in signal strength tests.
First, let's figure out what types of antennas are put on boards with a chip 8266. There are only three options:
- PCB (Printed Circuit Board) - an antenna “printed” on the board itself. Present in the models ESP-01, ESP-12, ESP-13 (and its clone wroom 2), ESP-201, as well as on the NodeMCU board.
- Ceramic. In fact - a conductor baked inside a ceramic case. Due to the greater dielectric constant of ceramics, it is possible to make such antennas more compact. Such antennas are present on the ESP-03, ESP-07, and ESP-11 boards.
- There is no antenna. At best, there is an IPX connector. If not, you have to solder to the conclusions.
Four boards participated in the test:
ESP-01 - printed antenna.
ESP-201 - printed, plus an IPX connector for external.
ESP-07 - ceramic, plus an IPX connector for external.
ESP-12 - Printed
Nuance with the ESP-201.
This board is generally a storehouse of “non-traditionally oriented” engineering and design solutions. So the choice of antenna is implemented very unusual: to switch between the built-in and external antennas, you just need to re-solder the SMD resistor, which acts as a jumper. By default, the external antenna is “turned on”.
Another point worth paying attention to: on the ESP-201 of some series, the IPX connector was soldered in reverse polarity - a central contact to the ground. If the external antenna works very badly, it’s worth checking.
Another point worth paying attention to: on the ESP-201 of some series, the IPX connector was soldered in reverse polarity - a central contact to the ground. If the external antenna works very badly, it’s worth checking.
In addition, a test of external antennas was carried out (the links below I give only for identification of antennas, and not as a recommendation of a store or trading platform):
- Postings that come with the ESP-201. The view does not bode well. I want to understand if it will give at least some gain in comparison with the built-in antennas.
- Chinese antenna for $ 1. The usual antenna, most likely standing in most cheap routers.
- Antenna Banana Pi. It was bundled with a computer, but also sold separately.
I wonder if it should be used for its intended purpose or is it better to immediately replace it.
Upd: A little later I conducted an express test with an antenna from the Asus rt-n13 router, the results came out a little worse than with antenna No. 2. In the table, the test is not reflected, because it was impossible to accurately reproduce the conditions.
The test was conducted on the street, in the countryside, there were no other Wi-Fi networks in the detection radius. To measure the signal level, a smartphone with the WIFI Analyzer program was used, so the results are relative.
Here is what the measurements (dBm) showed:
| Pay | 2m | 25m | 50m |
| Integrated antennas | |||
| ESP-01 (printed) | -51 | -67 | -84 |
| ESP-07 (ceramic) | -55 | -75 | -82 |
| ESP-12 (printed) | -63 | -84 | -85 |
| ESP-201 (printed) | -66 | -93 | - |
| External antennas | |||
| ESP-07 (Antenna No. 1) | -62 | -74 | -81 |
| ESP-07 (Antenna No. 2) | -52 | -66 | -74 |
| ESP-07 (Antenna No. 3) | -49 | -58 | -67 |
| ESP-201 (Antenna No. 1) | -69 | -76 | -88 |
| ESP-201 (Antenna No. 2) | -59 | -71 | -88 |
| ESP-201 (Antenna No. 3) | -44 | -67 | -80 |
Conclusions:
- Antennas of the “mouse tail” type in this case do not have significant advantages over the built-in ones. The only thing when their use is justified is the shielding case of the device and the requirements for minimizing weight / size.
- Ceramic antenna with its compactness has slightly better characteristics than tested printed ones.
- The printed antenna is quite suitable for use in working devices based on 8266, provided that it is normally matched with the board (my positive experience: ESP-01, ESP-12; negative - ESP-201), but slightly inferior to ceramic. Due to the specifics of the PCB, I admit that in one series there may be boards that differ significantly in antenna sensitivity. Also, this type of antenna is not recommended in conditions of high humidity (the textolite is hygroscopic, antenna characteristics may float)
- ESP-201 with all kinds of antennas loses to the rest of the boards, which, coupled with its other shortcomings, allows us to recommend it exclusively for experiments / prototyping.
