How to increase the transmission range by increasing the height of the Tx antenna?
Bottom:
There are two methods to increase the transmission range of the 434 MHz RF Tx module.
1. Increase applied input power – transmitted power
2. Connect an antenna to the Tx module
In the previous article, I explained the first method. See the previous article in this series. In this session we will look at another method. This means we will attach an antenna to the Tx and Rx module. The antenna is a special type of transducer, which can convert alternating current into radio frequency fields and vice versa. The transmitting antenna generates RF fields and the receiving antenna converts RF fields into alternating current.
In this project I will attach antenna to the transmitter and receiver and try to increase the range.
In this project, we will keep other factors constant such as the applied input power and connect a suitable length of antenna and achieve a long range.
Description:
In this project the antenna plays a vital role. Any simple conductor can act as an antenna. But when we have to connect an antenna, we have to do some calculations based on the theory of radio technology. Any length of conductor can act as an antenna, but due to various factors we have to calculate the size of the antenna, as well as the gain of the antenna, etc.
Antenna calculations are mainly for the height of an antenna. To calculate antenna height, wavelength, speed and frequency are the main factors.
Based on the frequency and wavelength, the size of the antenna varies. The basic calculations for the 434 MHz antenna are as follows.
Antenna size calculations:
The RF carrier frequency is = 434 Mhz.
Frequency = cycles/s
= 434 M/s
Time period = 1/ frequency
= 1/434×106
= 2.3 nsec
Speed of light (c) = 3×10 m/s
Then,
Wavelength = speed/frequency.
= speed × period of time
= 2.3 nsec × 3×108 m/sec
= 0.69m
According to antenna theory, the size of the antenna should be half or quarter of the wavelength.
Then
Quarter wavelength = 0.69 m/4
= 17.25 cm.
Required components and other equipment:
Mr. No. Required Qut component name
1 RF Tx module (434 MHz) 1
2 RF Rx Module (434 MHz) 1
3HT12E1
4HT12D1
5 LED 5
6 Resistor – 1KΩ (a quarter of a watt) 8
7 Resistor – 1MΩ (a quarter of a watt) 1
8 Resistor – 50KΩ (a quarter of a watt) 1
9 Button 4
11 Battery – 9V 2
15 Breadboard 2
18 connecting wires —
Circuit Diagram:
Description:
Procedure:
Transmitter Section:
Step 1: connect the four buttons to the data input pins (10, 11, 12, 13) of the HT12E, with 1 K pull down resistors.
Step 2: connect the 1MΩ resistor between 15 and 16 pins of the HT12E.
Step 3: Connect 17 pins to 2nd pin of RF transmitter and 14 pins connect to ground.
Step 4: 1-8 pins of HT12E are address pins, connect them all to ground. And connect pin 18 to Vcc and pin 9 to ground.
Step 5: Connect RF Tx module pin 1 to ground, pin 3 to Vcc and pin 4 to antenna.
Step 6: Calculate antenna size using antenna theory and connect to 4th pin of Tx module
Receiver Section:
Step 1: connect four LEDs to the output pins (10, 11, 12, 13) of the HT12D, with pull down resistors.
Step 2: connect the 50KΩ resistor between 15 and 16 pins of the HT12D.
Step 3: Connect pin 14 of the HT12D to the second pin of the RF transmitter. Connect pin 17 to LED indicator (it will light up when signal is received)
Step 4: Pins 1-8 of HT12D are address pins, connect them all to ground. Connect pin 18 to Vcc and pin 9 to ground.
Step 5: Connect RF Rx module pins 1, 6, 7 to ground, pins 4 and 5 to Vcc, and pin 8 to antenna.
Step 6: calculate the antenna size using antenna theory and connect to the 8th pin of the Rx module
Now let's take a look at the operation of the circuit
Working:
1. When any key is pressed on the encoder input pin, the encoder generates a data sequence on the 14th pin which is fed to the 2nd pin of the Tx module. The Tx module transmits signal as ASK modulated signal with data in amplitude variations. On the receiver side, the received signal is sent to pin 14 of the decoder chip from pin 2 of the Rx module. As an output, the respective LED will light up on the decoder output pins
2. Record distance readings as transmitted line-of-sight and non-line-of-sight range with 9V battery without connecting antenna to either side
3. Now connect the antenna (size should be as per calculations) and test wireless communication of site line and site wireless line between Tx and Rx. Write down the distance readings and compare the current readings with previous readings.
Without antenna With antenna
Range -> 70m 156m
photo res:
Precautions:
1. The address lines must be the same on both the transmitter and receiver sides.
2. On the transmitter, the 14th pin of the HT12E must be connected to ground or connect a switch between ground and the 14th pin to reset the encoder.
3. On the transmitter side, the resistor between 15 and 16 pins of the HT12E must be between 750MΩ to 1MΩ and on the receiver side, the resistor between 15 and 16 pins of the HT12D must be between 30KΩ to 50KΩ.
4. If you want to use any other battery, check the HT12E/HT12D data sheets first.
Project source code
Project source code
Circuit diagrams
| RF-Basic-1 |
 |
