#291 External antennas and ESP32 Long-Range mode

everybody talks about Laura to bridge long distances today we will have a look into how we can extend the range of a normal ESP 32 you will also learn how to do that and stay legal and maybe we can even reduce the power consumption of the chip if we do not need the extended range and what we learn can also be used for your ordinary Wi-Fi network let's see youtubers here is the guy with a Swiss accent with a new episode and fresh ideas around sensors and microcontrollers remember if you subscribe you will always sit in the first row when I began this video I thought it will have a normal length after editing I saw that it had so many aspects that it became too long so I decided to cut it into two parts the second part will air next Sunday I'm sure you will find some useful stuff in both videos if you are interested in Wi-Fi in general and the ESP 32 in particular in the two videos we will understand the basics of antennas for wireless transmission introduce the new long-range mode for the ESP 32 invented by expressive see how we can attach external antennas to the ESP 32 modules this part applies also to esp8266 s find an easy way to compare Wi-Fi antennas compare the performance of some typical antennas commercially available and homemade reduce the TX power of the ESP 32 to stay illegal and check its effect on overall power consumption let's do a quick recap of wireless transmission we have a transmitter and an antenna on one side and an antenna and the receiver on the other side of the connection in the middle we have the space filled with air and much more if we follow the current discussions the transmitter produces power usually measured in DBM which is transferred through an antenna to space a standard antenna transmits 100% of this power to space it has a gain of 0 DB ie the I stands for isotropic and means that the antenna radiates evenly in all directions it is evident that most of the radiated power never reaches the receiving antenna this part has to be calculated as a loss for the receiver the longer the distance the more we lose to be precise 6 DB each time we double the distance let's also assume a zero TBI antenna at the receiving end then all received power is fed into the receiver which has a minimum sensitivity simply said if the input power is higher than its sensitivity the receiver gets the data otherwise it will not spit out anything simple we can now start to change this system and find out how these changes affect range if we increase the transmit power by 6 DB M we can bridge double the range if we add a thin 10 meter antenna cable we quickly lose 6 DB and are back where we were so use no cable or only a very short one between your ESP or router and the antenna a directional antenna obviously regains the lost power because it radiates mainly in the direction of the receiver and not in the useless areas looking from the receiver it produces a gain if our antenna has a gain of 6 DB I again we double the range the same applies to the receiving end if we use a directional antenna we gain range and an antenna cable destroys range and a receiver with a higher sensitivity increases range again just a small remark if you do not know where the counterpart is a directional antenna probably is not a good idea even if some suppliers promise there is no antenna with gain and without a restricted radiation pattern you might ask yourself why I used DP TBI and sometimes TPM DB can be seen as a number 4 power 0 DP is 110 DB is 10 and 20 DB is 100 minus 10 DB is 0.1 and minus 20 DP is 0.01 pay attention this is different if you work with voltages TBI as said before compares an antenna with an isotropic one if your antenna has 20 DB eye it radiates 100 times more power in the direction of the receiver than a isotropic antenna and DBM means power 0 DBM is 1 milli watt therefore 20 DBM is 100 milli watt and minus 20 DBM is 0 point 0 1 milli watt now we know enough about physics and we can go on to the other important topic the law all countries restrict power emissions into free space because it can't disturb receivers of a third party the regulations therefore are defined from the receivers angle they limit the power emitted in the direction of the receiver the relevant number is called erp effective radiated power or sometimes e IRP equivalent isotropic radiated power our ESP 30 tools are FCC approved and legally produce a maximum of 20 DBM output power and FCC accepts 2.4 gigahertz antennas with a maximum of 6 DB gain which is provided by the regular raat antennas on your routers simply set if we add a directional antenna with a higher gain on the transmitting site we have to reduce the power of our transmitter so antenna gain on the transmitting site does not affect the range if you decide to stay inside regulations but it potentially effects the power consumption of the ESP 32 if you followed closely you know by now where the high gain antenna can legally help yes on the receiving side unfortunately there is a huge problem if you use a regular Wi-Fi connection each ESP 32 transmits and receives in parallel so you have to reduce power on both sides now we are ready for expressives long-range mode in this patent they describe how they do it they use regular ESB 32 chips for the data transmission but reduce the data rate to less than one megabit this is a well-known trick used by all long range devices reduced data rate means more sensitivity for the receiver together with a data reduction bandwidth also could be reduced to improve sensitivity even more Laura & Seek Fox do that to an extreme we will let you see if this was done for the ESP 32 unfortunately your typical router does not understand these long range signals and will even not show it as an access point only ESP 30 tools see each other expressive promises a range of up to one kilometer for this mode of course we will test that with standard modules and the small PCB antennas but what if we want an external antenna for the additional gain or because the module sits in a metal case or is hidden somewhere then we have to buy a module with an antenna connector we get them in three versions with an antenna connector only with a PCB antenna and an antenna connector with an unpopulated PCB where we can try to solder a separately purchased UFL or IP x connector nothing for the in tarted I use this we're over module from expressive as a reference because it only has an antenna connector let's have a look at its rated output power in 802 11 B mode it outputs the legal maximum of 20 DBM because I do not precisely know how FCC certifies I choose the 11 B mode as a reference for my measurements now the setup I connect the ESP 32 port to my spectrum analyzer which is capable to display power patterns the cable from the ESP to the analyzer is shielded and does not emit power to space because I also want to see if the connection to a second DSP 32 works I need an antenna therefore I insert a directional coupler to measure the signal it transfers most of the power to the antenna and a little bit to the spectrum analyzer this signal is 10 DB less than the signal from the ESP 32 this signal is further attenuated a bit by cables and connectors and ends up at around minus 40 p.m. in the middle of the spectrum I take this as a reference by the way the signals of all four modes look very similar if we only compare the output power I do not see a bandwidth reduction for the long-range signal the reference is abort with only an antenna connector and no PCB or 3d antenna let's look now at ATT gomini it has a PCB antenna and a connector if we have a closer look at the diagram we see that the antenna pin of the ESP 32 is directly connected to the PCB antenna and also via a zero ohms resistor to the antenna connector let's check what this means I have three different ports two came without the zero ohms resistor only the PCB antenna was active without change your external antenna does not work the third came with the resistor mounted like that the PCB antenna and the connector are connected to the ESP 32 usually you have to terminate all transmission lines with 50 ohms otherwise you get a terrible SWR and lose power as soon as you connect an external antenna the two antennas are in parallel and you see this effect 10 DB loss on the external antenna compared with the reference remember 6 DB half's the range not good so I cut the connection to the PCB antenna on one board and got only 2 DB loss not bad for a small cut I also checked other ports with connectors like this tt go with an ePaper display also here both antennas are in parallel if you connect an external antenna at least we only have the expected 3 DB loss I also did not see a simple cut to get these 3 DB back the same way the TT co board with an LCD 4 DB loss and no easy solution please tell me if I missed something because I cannot measure the performance of the PCB or 3d antennas I cannot tell you the effect of an open connector but I assume it's not favorable this TT goal board uses the correct method a zero ohms resistor which can either be connected to the 3d antenna or the connector you have to change its direction if you want to use an external antenna I also found this concept on other boards but the resistors are tiny maybe you change them before your tenth coffee in the morning so you know now how you can check your new boards and if needed adapt it to your needs this quickly gets you quite some additional reach but if you want more the sequel will be for you we will build a helical and compare it with a commercial panel antenna and we will do some tests with our ESP 30 to long range mode and see if it is were while I hope this video was useful or at least interesting for you if true please consider supporting the channel to secure its future existence you find the links in the description thank you bye you

Channel: Andreas Spiess

Views: 205,564

Keywords: arduino, arduino project, beginners, diy, do-it-yourself, eevblog, electronics, esp32, esp32 datasheet, esp32 project, esp32 tutorial, esp32 weather station, esp8266, esp8266 datasheet, esp8266 project, greatscott, guide, hack, hobby, how to, iot, lorawan, nodemcu, project, simple, smart home, ttgo, wemos, wifi, antenna, esp32 external antenna, helix antenna, helical antenna, helical antenna wifi, internet of things, radio waves, do it yourself (hobby), do it yourself, long range wifi

Id: 2rujjTOPIRU

Length: 13min 57sec (837 seconds)

Published: Sun Oct 06 2019