ESP-8266 and signal strength: select antenna type
Over the year since its inception, ESP-8266 has mutated from ascetic revision 01 into multi-legged monsters like ESP-201 or NodeMCU board, able to significantly move younger Arduins from the “measure temperature, blink LED” segment, giving a free WI-FI as a free bonus. Actually, in the quality of this very Wi-Fi in various revisions of the board, I propose to understand.
The idea of ​​this test appeared as a result of the designer’s mistake: the carefully thought-out, assembled and debugged pump station control unit, being installed at its place of work - in the bathroom, did not see the signal from the home router.
Advantageously, practicing juggling with low-literary turnovers of villages to google, which of the boards of the ESP-8266 family has a better signal, but, contrary to expectations, this information could not be found among tons of articles and forum rolls. Therefore, I decided to fill this gap: through the efforts of Uncle Liao, I got hold of four different revisions of the board with different types of antennas, which will participate in the signal level tests.
Let's first understand what types of antennas are put on boards with an 8266 chip. There are only three options:
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The test involved four boards:
ESP-01 is a printed antenna.
ESP-201 - printed, plus IPX-connector for the external.
ESP-07 is a ceramic, plus an IPX external connector.
ESP-12 - Printed
Additionally, a test of external antennas was carried out (the links below are given only for identifying antennas, and not as a recommendation of a store or marketplace):
- The wiring that comes with the ESP-201. The view does not bode well. I want to understand whether it will give at least some gain in comparison with the built-in antennas.
- Chinese antenna for $ 1. An ordinary antenna, most likely standing in most cheap routers.
- Antenna Banana Pi. Comes with computer, but also sold separately.
It is interesting whether it is worth using for its intended purpose or it is better to replace it immediately.
Upd: A little later, he conducted a rapid test with an antenna from the Asus rt-n13 router, the results were slightly worse than with antenna No. 2. The test is not reflected in the table. it was impossible to accurately reproduce the conditions.
The test was conducted on the street, in the countryside, other Wi-Fi networks in the detection radius was not. A smartphone with the WIFI Analyzer program was used to measure the signal level, so the results are relative.
This is what measurements (dBm) showed:
Findings:
The idea of ​​this test appeared as a result of the designer’s mistake: the carefully thought-out, assembled and debugged pump station control unit, being installed at its place of work - in the bathroom, did not see the signal from the home router.
Advantageously, practicing juggling with low-literary turnovers of villages to google, which of the boards of the ESP-8266 family has a better signal, but, contrary to expectations, this information could not be found among tons of articles and forum rolls. Therefore, I decided to fill this gap: through the efforts of Uncle Liao, I got hold of four different revisions of the board with different types of antennas, which will participate in the signal level tests.
Let's first understand what types of antennas are put on boards with an 8266 chip. There are only three options:
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- PCB (Printed Circuit Board) - antenna, “printed” on the board itself. Present in models ESP-01, ESP-12, ESP-13 (and its clone wroom 2), ESP-201, as well as on the NodeMCU board.
- Ceramic. In fact - the conductor baked inside the ceramic body. Due to the higher 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.
- Antenna is missing. At best, it is an IPX connector. If not, you have to go to the conclusions.
The test involved four boards:
ESP-01 is a printed antenna.
ESP-201 - printed, plus IPX-connector for the external.
ESP-07 is a ceramic, plus an IPX external connector.
ESP-12 - Printed
Nuance with ESP-201.
This board is generally a storehouse of "unconventional-oriented" engineering and design solutions. So the choice of the antenna is implemented very unusually: to switch between the built-in and external antennas, you only need to solder the SMD resistor, which acts as a jumper. The default is “on” the external antenna.
Another point that is worth paying attention to: on the ESP-201 of some series, the IPX-connector was soldered in reverse polarity - with a central contact on the ground. If the external antenna works really badly - it is worth checking.
Another point that is worth paying attention to: on the ESP-201 of some series, the IPX-connector was soldered in reverse polarity - with a central contact on the ground. If the external antenna works really badly - it is worth checking.
Additionally, a test of external antennas was carried out (the links below are given only for identifying antennas, and not as a recommendation of a store or marketplace):
- The wiring that comes with the ESP-201. The view does not bode well. I want to understand whether it will give at least some gain in comparison with the built-in antennas.
- Chinese antenna for $ 1. An ordinary antenna, most likely standing in most cheap routers.
- Antenna Banana Pi. Comes with computer, but also sold separately.
It is interesting whether it is worth using for its intended purpose or it is better to replace it immediately.
Upd: A little later, he conducted a rapid test with an antenna from the Asus rt-n13 router, the results were slightly worse than with antenna No. 2. The test is not reflected in the table. it was impossible to accurately reproduce the conditions.
The test was conducted on the street, in the countryside, other Wi-Fi networks in the detection radius was not. A smartphone with the WIFI Analyzer program was used to measure the signal level, so the results are relative.
This is what measurements (dBm) showed:
| Pay | 2m | 25m | 50m |
| Built-in 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 |
Findings:
- Mouse tail antennas in this case do not have significant advantages over 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 the printed ones tested.
- The printed antenna is quite suitable for use in 8266-based work devices, provided that it is normally matched to the board (my positive experience: ESP-01, ESP-12; negative - ESP-201), but slightly inferior to ceramic. Due to the specifics of PCB, I admit that in one series there may be cards that are significantly different in the sensitivity of the antenna. Also, this type of antenna is not recommended in conditions of high humidity (textolite is hygroscopic, characteristics of the antenna can float)
- ESP-201 with all types of antennas loses to the other boards, which, together with its other disadvantages, allows recommending it exclusively for experiments / prototyping.
Source: https://habr.com/ru/post/368863/
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