AM Transmitter and Receiver 12262021 BBDNITM Lucknow Presented

AM Transmitter and Receiver 12/26/2021 BBDNITM, Lucknow Presented by: Ashutosh Rastogi Assistant Professor BBDNITM, Lucknow 1

AM TRANSMITTER Modulator OSCILLATOR 1000 KHZ CW or Mixer TRANSDUCER POWER AMPLIFIER 12/26/2021 BBDNITM, Lucknow 2

TRANSMITTER GROUP; GROUP OSCILLATOR 1000 KHZ CW TRANSMITTER – Generates a continuous wave (CW) carrier frequency with an additional signal intelligence impressed upon it, thus becoming an Amplitude Modulated (AM) signal. Once powered up the AM signal is put on the air as transmission RF waves via an antenna. Modulator 12/26/2021 BBDNITM, Lucknow 3

TRANSMITTER GROUP; MODULATOR Modulator OSCILLATOR 1000 KHZ CW or Mixer TRANSDUCER {Microphone} A. B. Input acquired from OSCILLATOR (1000 KHZ) A 2 nd signal from transducer is mixed with 1000 CW to produce and Amplitude Modulated (AM) signal or Carrier Transmission. PWR Amp 12/26/2021 BBDNITM, Lucknow 4

TRANSMITTER GROUP; A. B. POWER AMPLIFIER Power Amplifier Boosts the AM signal up and applies it to the Antenna. The AM – RF energy is transferred to the atmosphere in the form of Radio Frequency (RF) radiation. Modulator OSCILLATOR 1000 KHZ CW or Mixer TRANSDUCER POWER AMPLIFIER 12/26/2021 BBDNITM, Lucknow 5

Generalized Receivers Ø Two types of receivers: Receivers Tuned Radio Frequency (TRF) Receiver: Composed of RF amplifiers and detectors. No frequency conversion It is not often used. Difficult to design tunable RF stages. Difficult to obtain high gain RF amplifiers Superheterodyne Receiver: Downconvert RF signal to lower IF frequency Main amplifixcation takes place at IF 12/26/2021 BBDNITM, Lucknow 6

Tuned Radio Frequency (TRF) Receivers Ø Composed of RF amplifiers and detectors. Ø No frequency conversion. It is not often used. Ø Difficult to design tunable RF stages. Ø Difficult to obtain high gain RF amplifiers Active Tuning Circuit Detector Circuit Bandpass Filter Baseband Audio Amp Local Oscillator 12/26/2021 BBDNITM, Lucknow 7

Disadvantages of the TRF Receiver design § Bandwidth varied with tuning. § LC components varied with temperature and age. 12/26/2021 BBDNITM, Lucknow 8

Heterodyning All Incoming Frequencies 12/26/2021 Heterodyning (Upconversion/ Downconversion) Fixed Intermediate Frequency Subsequent Processing (common) BBDNITM, Lucknow 9

Superheterodyne Receivers Superheterodyne Receiver Diagram 12/26/2021 BBDNITM, Lucknow 10

Superheterodyne Receiver 12/26/2021 BBDNITM, Lucknow 11

Superheterodyne Receivers Ø The RF and IF frequency responses H 1(f) and H 2(f) are important in providing the required reception characteristics. 12/26/2021 BBDNITM, Lucknow 12

Superheterodyne Receivers RF Response f. IF IF Response 12/26/2021 BBDNITM, Lucknow 13

Superheterodyne Receivers 12/26/2021 BBDNITM, Lucknow 14

Superheterodyne Receiver Frequencies 12/26/2021 BBDNITM, Lucknow 15

Superheterodyne Receiver Frequencies 12/26/2021 BBDNITM, Lucknow 16

Frequency Conversion Process 12/26/2021 BBDNITM, Lucknow 17

Image Frequencies Image frequency is also received 12/26/2021 BBDNITM, Lucknow Image frequency not a problem. Eeng 360 18

AGC • • • AGC = Automatic Gain Control AGC samples the signal strength at the detector and then feeds back a control signal to adjust the gain of the earlier stages AGC keeps audio volume fairly constant if signals level vary RF Amp Mixer IF Amp AGC Circuit LO 12/26/2021 Detector BBDNITM, Lucknow 19

AM Radio Receiver 12/26/2021 BBDNITM, Lucknow 20

More on Super Heterodyne receiver 12/26/2021 BBDNITM, Lucknow 21

SUPERHETERODYNE RECEIVER GROUP; GROUP ANTENNA Antenna (aerial) RF RADIATION Is the device that intercepts the AM electromagnetic radiation waves. As the waves pass and are cut by the aerial, small amounts of current will be induced upon it. USPS 12/26/2021 BBDNITM, Lucknow Tuner 22

RECEIVER GROUP; GROUP TUNER A: Selects one signal from the many on the aerial by tuning a Parallel LC Tank circuit to resonate @ 1000 KHZ. B: The tuner is capable of tuning-in all the AM frequencies with in the AM spectrum of 540 KHZ – 1610 KHZ. ANTENNA C: The selected frequency of 1000 KHZ is applied to the converter or mixer. TUNER 1000 KHZ Tuner PC 38 12/26/2021 BBDNITM, Lucknow 23

RECEIVER GROUP; PC Antenna & Tuner PC 38 5 R 4 1 K Antenna R 1 Tuner T 1 C 1 A 47 2 K 3 Q 1 6 7 T 2 T 3 C 3 4 R 2 R 3 6. 2 K 22 K C 1 1 B 12/26/2021 O . 01 f Local Osc BBDNITM, Lucknow 24

RECEIVER GROUP; GROUP Local Oscillator [LO] TUNER 1000 KHZ CONVERTER or MIXER LOCAL OSCILLATOR 1455 KHZ 1. The LO Signal output is always the Tuner Frequency, Plus 455 KHz Regardless of what AM signal is tuned. 2. It is tuned simultaneously with the RF Tuner. 3. The output would be 1000 + 455 = 1455 KHZ CW. 4. The output of 1455 KHZ is sent to the Converter or Mixer. PC 38, LO 12/26/2021 BBDNITM, Lucknow 25

RECEIVER GROUP; GROUP Local Oscillator [LO] PC 38 5 R 4 1 K Antenna R 1 Tuner T 1 C 1 A 47 2 K 3 Q 1 T 2 T 3 C 3 R 2 R 3 6. 2 K 22 K C 1 1 B 12/26/2021 6 7 4 LO O . 01 f Converter / Mixer BBDNITM, Lucknow 26

RECEIVER GROUP; GROUP Converter / Mixer RF TUNER 1000 KHZ CONVERTER or MIXER LO 1455 KHZ F 1 RF 1000 KHZ F 2 LO 1455 KHZ F 2+f 1 SUM 2455 KHZ f 2 -f 1 DIFFERENCE The 1000 KHZ from the Tuner is heterodyned with a 2 nd signal from the Local Oscillator [1455 KHz] to produce 4 different output frequencies. 455 KHZ INTERMEDIATE FREQUENCY (IF) PC 38, Mixer 12/26/2021 BBDNITM, Lucknow 27

RECEIVER GROUP; Converter / Mixer PC 38 5 Antenna T 1 C 1 A R 4 1 K Converter R 1 Tuner 47 2 K 3 Q 1 T 2 R 3 6. 2 K 22 K C 1 1 B 12/26/2021 T 3 6 45 5 7 KH z C 3 4 LO O . 01 f IF Amp BBDNITM, Lucknow 28

RECEIVER GROUP; GROUP IF Amplifier CONVERTER or MIXER RF TUNER 1000 KHZ IF Amplifier 455 KHZ LO 1455 KHZ PC 39 PC 38 IF amplifier has the most receiver gain and is made up of 2 cascaded high gain amplifiers tuned to 455 KHZ. Sensitivity and bandwidth [T 4 & 5] are determined by this stage. The [IF] output is sent to the detector (demodulator). PC 39, IF Amps 12/26/2021 BBDNITM, Lucknow 29

RECEIVER GROUP; PC 39 IF Amplifiers 1 st IF Amp C 4 R 5 R 7 R 8 56 K 10 K 47 K R 11 2. 7 K 13 10 f 10 38 T 3 s car d Detector 2 nd IF Amp T 4 T 5 C 8 Test Operate 9 12 Q 2 11 C 6 10 f 14 R 6 C 7 R 9 C 9 8 12/26/2021 C 11. 05 f Q 3 BBDNITM, Lucknow R 10 C 10 D 1 R 13 100 K R 12 5 K O 17 15 Detector 30

RECEIVER GROUP; GROUP DETECTOR OR DEMODULATOR CONVERTER or MIXER RF TUNER 1000 KHZ IF amplifier 455 KHZ AM Detector LO 1455 KHZ PC 38 455 AM PC 39 Rectified Filtered Rectifies the modulated signal, then filters out the 455 KHz Leaving only the audio frequency or intelligence of 50 Hz – 20 KHz Which is sent to the AF amplifiers. 12/26/2021 BBDNITM, Lucknow PC 39 Detector 31

RECEIVER GROUP; PC 39 DETECTOR or DEMODULATOR 1 st IF Amp C 4 R 5 R 7 R 8 56 K 10 K 47 K R 11 2. 7 K 13 10 T 4 9 C 6 10 f Operate 8 12/26/2021 Filter 12 Q 2 C 11. 05 f Q 3 11 14 R 6 C 1 R 9 D 1 R 13 100 K 17 T 5 C 8 Test O Detector 10 f 38 car T 3 s d Detector 2 nd IF Amp C 9 R 1 0 BBDNITM, Lucknow C 1 0 R 12 5 K 15 AGC 32

RECEIVER GROUP; AVC or AGC CONVERTER or MIXER RF TUNER 1000 KHZ IF Amplifier 455 KHZ AM Detector LO 1455 KHZ AVC or AGC PC 38 PC 39 Automatic Volume Control or gain control is taken at the detector (demodulated and fed back to the first IF amplifier base. Required to overcome atmospheric and terrain conditions that adversely affect signal strength between the transmitter & receiver. PC 39, AGC 12/26/2021 BBDNITM, Lucknow 33

RECEIVER GROUP; PC 39 AVC or AGC 1 st IF Amp C 4 Detector 2 nd IF Amp R 5 R 7 R 8 56 K 10 K 47 K 10 PC T 3 s 38 AVC R 11 2. 7 K 13 10 f T 4 9 C 6 10 f Operate AVC 12/26/2021 12 Q 2 8 C 11. 05 f Q 3 11 14 R 6 C 1 R 9 D 1 R 13 100 K 17 T 5 C 8 Test O C 9 R 1 0 BBDNITM, Lucknow C 1 0 R 12 5 K 15 All Ckt PC 39 34

RECEIVER GROUP; PC 39 1 st & 2 nd IF Amp, Detector, AVC or AGC. 1 st IF Amp C 4 Detector R 5 R 7 R 8 56 K 10 K 47 K 10 T 4 9 Filter C 6 10 f Operate AVC 12/26/2021 12 Q 2 8 C 11. 05 f Q 3 11 14 R 6 C 1 R 9 D 1 R 13 100 K 17 T 5 C 8 Test O AVC R 11 2. 7 K 13 10 f 38 car T 3 s d Detector 2 nd IF Amp C 9 R 1 0 BBDNITM, Lucknow C 1 0 R 12 5 K 15 Audio Amps 35

RECEIVER GROUP; AUDIO AMPLIFIER CONVERTER or MIXER RF TUNER 1000 KHZ IF Amplifier 455 KHZ AM AUDIO Amplifiers Detector LO 1455 KHZ PC 38 PC 39 AUDIO AMPLIFIER 12/26/2021 AVC OR AGC PC 40 3 stages: Audio preamp Audio driver Audio push- pull BBDNITM, Lucknow PC 40 36

RECEIVER GROUP; PC 40 AUDIO AMPLIFIER Audio Pre Amp Audio Driver Audio Push Pull 28 29 R 23 T 6 R 17 R 15 24 25 22 19 18 E R 14 C 13 R 18 R 16 R 19 R 25 30 R 24 23 20 T 7 Q 5 27 C 14 12/26/2021 21 Q 4 C 12 Q 6 R 20 D 2 O R 21 BBDNITM, Lucknow 26 C 16 Q 7 C 15 31 37

Thanks 12/26/2021 BBDNITM, Lucknow 38