Lesson 16. LORA. SignalMeter

  • The purpose of this lesson

    Hi! Today we will get acquainted with LORA modules not in words, but in deeds. Let's write a sketch for the receiver and transmitter using the M5 UI for Arduino IDE. We will conduct field tests with both the built-in antenna and the external homemade j-type antenna (Fig. 1).

    Figure 1

    This tutorial will teach you how to use M5 UI for Arduino IDE together with LORA wireless communication modules. Produce an external antenna J-type at a frequency of 433MHz. Perform field tests to measure the range of the wireless network.

    Short help

    List of components for the lesson

    • PC;
    • M5STACK (2 PCs . );
    • USB-C cable from standard set (2 PCs.);
    • Additional LORA modules (2 PCs.);
    • Plastic housing for antenna (2 PCs .);
    • Copper ground wire (16 mm2) 140 cm;
    • Hotmelt;
    • Soldering iron and solder;
    • Drill and drill bits;
    • Office knife;
    • Wire cutters . ;
    • Ruler;
    • Additional battery (2 PCs.).

    Let's start!

    Step 1 Add UI, so more beautiful and more convenient ;)

    Using the skills obtained in the previous lessons, we will create two graphical interfaces: one for the receiver, the second for the transmitter in the M5 UI Designer for Arduino IDE (Fig. 2).

    Figure 2

    On the transmitter: to start/stop the transmission, press the B button (on the device itself).

    On the receiver: no action is required from the user to get started.

    Step 2. Field test of built-in antenna

    Once we got acquainted with the LORA module (Fig. 3). The built-in antenna is a printed circuit Board with a printed track, the length of which corresponds to the wavelength.

    Figure 3

    The connection of the antenna to the LORA module does not inspire much confidence, as this antenna is designed primarily for laboratory testing; to use the greater potential of the module, it is necessary to connect an external antenna. Still, there is a built-in antenna, so do not let it out of sight - we will conduct field tests to measure the distance of the radius of action.

    In General, the transmission of packets is well carried out at a distance of only 20 meters from the transmitter (Fig. 3.1).

    Figure 3.1

    Figure 3.2 shows two pillars. On the near table is the transmitter. On the far post reception of the signal is almost impossible.

    Figure 3.2

    Step 3. J-type antenna manufacturer

    Take the copper ground wire and remove the insulation with a utility knife.

    Warning! Be very careful not to point the knife blade in your direction. If you are under the age of majority - ask adults to help you.

    Next, divide the wire into two equal parts using wire cutters (Fig. 4).

    Figure 4

    Now, strictly according to figure 4.1, make bends and marks where you want to connect the cable.

    Figure 4.1

    Take a drill, soldering iron, hot melt glue and fix the antenna and module on the body (Fig. 4.2).

    Figure 4.2

    Great! The antenna is ready for testing.

    Step 4. Field test of j-type self-made external antenna

    The first thing to do is to fix the transmitter on the same place on the same pole (Fig. 5).

    Please note: the antenna must be strictly perpendicular to the horizon to achieve maximum radio wave efficiency.

    Figure 5

    The second - let's go back to the second column, where the connection last time stopped (figure 5.1).

    Figure 5.1

    Wow! The link is now there, but do not forget that it is only about 20 m from the transmitter. Let's see where the antenna of the transmitter is directed, select the objects of the reference point (Fig. 5.2) and start removing.

    Figure 5.2. Objects of reference

    After arrival to the place of the first reference point (Fig. 5.3), which is located at a distance of ~200 m (Fig. 5.4).

    Figure 5.3. The first object of the landmark is the yellow tree

    Figure 5.4. Distance to the first landmark object

    The following data were received at the receiver (Fig. 5.5). Packets are received sequentially without delays or omissions. The signal RSSI -94 dB.

    Figure 5.5

    Since the first landmark has passed the test, we will continue to move to the second one (Fig. 5.6).

    Figure 5.6

    The second object of the reference point is located at a distance of ~700 m from the transmitter (Fig. 5.7).

    Figure 5.7

    On the screen of the receiver a packet arrives (Fig. 5.8), but provided that the antenna is perpendicular to the transmitter.

    Figure 5.8

    As the second reference point met our expectations. Let's try to get to the third landmark. Whoops! Failed, half way (~2.4 km) (Fig. 5.9) the signal disappeared completely (Fig. 5.10).

    Figure 5.9

    Figure 5.10

    Final step

    On this both experiment completed. Of course, a homemade external antenna J-type showed the best results compared to the built-in. The distance was increased approximately 50 times. This concludes the lesson. Make antennas, test them, achieve the best results!


  • Thank you for this awesome tutorial.

    I've got my copper wire on order, and am looking forward to putting it together. =D

    Thanks to some brilliant recent inventions, there's now antenna analysers for $50, called "NanoVNA". You can use them to perfectly tune the J Pole antenna, so as much of the transmit power as possible leaves the antenna.