1. Shuswap Amateur Radio Club – Basic Qualification SESSION # 3 POWER SUPPLIES TRANSMITTERS RECEIVERS Instructors: Phil Baker & Rick Ryan-Lewis

2. Shuswap Amateur Radio Club – Basic Qualification POWER SUPPLIES TransformerRectifierFilter

3. Shuswap Amateur Radio Club – Basic Qualification Transformer Power In = Power Out Power Formula P = VI V = Volts I = Amps Output Voltage is directly proportional to turn ratio Output Current is inversely proportional to turn ratio POWER SUPPLIES

4. Shuswap Amateur Radio Club – Basic Qualification POWER SUPPLIES Alternating Current (AC)

5. Shuswap Amateur Radio Club – Basic Qualification Sine Wave POWER SUPPLIES

6. Shuswap Amateur Radio Club – Basic Qualification Half-Wave Rectifier – 1 diode POWER SUPPLIES

7. Shuswap Amateur Radio Club – Basic Qualification Full-Wave Rectifier – 2 diodes POWER SUPPLIES

8. Shuswap Amateur Radio Club – Basic Qualification Full-Wave Bridge Rectifier – 4 diodes POWER SUPPLIES

9. Shuswap Amateur Radio Club – Basic Qualification Filter Capacitor Ripple The magnitude of the ripple is inversely proportional to the capacitance of the filter Filter Capacitor is used to achieve a constant DC voltage with minimum ripple POWER SUPPLIES

10. Shuswap Amateur Radio Club – Basic Qualification Regulator ensures a constant output voltage for varying current loads and minor fluctuations of the input voltage Regulator POWER SUPPLIES

11. Shuswap Amateur Radio Club – Basic Qualification POWER SUPPLIES SAFETY Grounded Chassis Interlock Mechanisms Key Operated On/Off Bleeder Resistors As little as 1/10 of an Amp and 30 Volts can be fatal In case of an Emergency TURN OFF THE POWER FIRST !!

12. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Send information – message or baseband signal Must be converted to Radio Frequency (RF) signal RF Generator/Oscillator: Produces the carrier Modulator: Converts baseband signal to RF signal RF Power Amplifier: Increases RF signal power

13. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Continuous Wave (CW) On-off keying (O.O.K.) Morse Code is transmitted as an interrupted carrier Key click filter - choke in series with Key and a capacitor across the contacts suppresses RF clicks Power Supply

14. Shuswap Amateur Radio Club – Basic Qualification Modulation Combines Original information signal RF sine wave – Pure Carrier Types Amplitude Modulation (AM) Frequency Modulation (FM ) TRANSMITTERS BANDWITH If useful information is conveyed, then spectrum must be occupied

15. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Amplitude Modulation (AM) RF Generator carrier signal Baseband modulating signal RF Signal from Modulator

16. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Amplitude Modulation (AM) Envelop of carrier must not reach zero OVERMODULATION produces Splatter on adjacent frequencies AM signal bandwidth occupies twice the highest frequency sent to the modulator AM signal has 2 symmetrical sidebands Upper sideband - USB Lower sideband - LSB USB LSB

17. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Single Side Band (SSB) The carrier and one sideband are eliminated Requires less power and half the bandwidth Conventional AM Signal Carrier Removed (DSBSC) Unwanted Signal Removed By Balanced Modulator By Sideband Filter Fig. 1Fig. 2Fig. 3

18. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Single Side Band (SSB) Carrier f c suppressed

19. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Single Side Band (SSB) {} f c + f a f c - f a Filterf c + f a DSBSC Unwanted sideband removed

20. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Single Side Band (SSB) Balanced Modulator removes the carrier – (DSBSC) Variable Frequency Oscillator determines output frequency Mixer converts sideband signal to final output frequency Sideband Filter removes unwanted sideband 1 23 4

21. Shuswap Amateur Radio Club – Basic Qualification Baseband modulating signal RF Generator carrier signal Modulated Carrier Signal Frequency Modulation (FM) TRANSMITTERS

22. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Frequency Modulation (FM) Superior noise immunity Ease of tuning High audio quality The maximum limit of the instantaneous frequency in either direction is called the maximum deviation

23. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Frequency Modulation (FM) Frequency multiplier increases both frequency and deviation Over deviation causes out of channel emissions and signal distortion Normal deviation for two-way radio +/- 5 kHz

24. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Frequency Modulation (FM) No message signal – Output is an unmodulated carrier Normal bandwidth 10 – 20 kHz Not used below 29.5 MHz – exceeds bandwidth limits (6 kHz) Mic gain too high (talking too loud or too close) causes nearby frequency interference Reactance modulator connected to an RF Power Amp produces a phase modulation emission

25. Shuswap Amateur Radio Club – Basic Qualification TRANSMITTERS Power Amplifiers Class A Single sideband AM modulation Good linearity Class C FM modulation Non-linear High efficiency Approx ½ of the power supplied to the amplifier stage is released as heat

26. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Receiver Fundamentals Quality Parameters Frequency stability The ability of a receiver to stay tuned to an incoming signal for a long period. Sensitivity The ability to receive weak signals. Selectivity The ability to reject signals on adjacent frequencies. The narrower the band pass filter, the "higher" the selectivity.

27. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Receiver Fundamentals The Audio Stage Amplifies the signal from the detector and raises it to a level suitable for driving headphones or a speaker. A transformer is generally used to match speaker impedance The Automatic Gain Control (AGC) circuit in AM receivers, maintains constant audio output for varying RF signal strengths The Squelch circuit mutes audio output when there is no signal

28. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS “Block diagram" of a "superhetrodyne" receiver three amplifiers are shown, the RF amplifier, the IF amplifier, and the AF amplifier.

29. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS The Radio Frequency Amplifier Amplifies input signal to a usable level Ahead of Mixer to reduce noise. May contain a preselector Matches antenna’s impedance to that of the receiver

30. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS The Intermediate Frequency Amplifier Where most of the amplification in a receiver takes place There may be two or more stages of IF amplification

31. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS The Audio Frequency Amplifier The audio signal is amplified in the audio amplifier and passed on to a speaker or phones

32. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS The superhet receiver – Part 1 The RF amplifier and mixer/oscillator receive signals from the antenna and then convert them to the IF frequency. It is in the RF amplifier and mixer/oscillator sections of the receiver where the actual operator tuning takes place.

33. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Mixer/Oscillator The purpose of the mixer/oscillator is to translate the frequency of the incoming signal to the "intermediate frequency".

34. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Mixer In a mixer stage, the output contains the SUM and the DIFFERENCE of the input signal frequencies. RF Signal

35. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Band Pass Filter The filter block prior to the IF amplifier shapes the "passband" of the receiver.

36. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS The superhet receiver – Part 2 From IF amplifier onwards, it is a "fixed frequency receiver" pre-tuned and optimized for the reception of a signal on the IF frequency.

37. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Beat Frequency Oscillator (BFO) The BFO replaces the suppressed carrier signal

38. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Product Detector ( Demodulator) Converts the RF signal back to the original message signal

39. Shuswap Amateur Radio Club – Basic Qualification RF Signal 600kHz Mixer Oscillator 1,055 kHz f 2 + f 1 = 1,655 kHz f 2 – f 1 = 455 kHz Band Pass Filter 455 kHz IF Amplifier AM Radio receiver with an IF of 455 kHz Oscillator must produce a frequency 455 kHz below or above 600 kHz Another signal corresponding to 455 kHz plus the Oscillator frequency 1,055kHz (1510 kHz) will also be converted and demodulated - Image Frequency RECEIVERS f1f1 f2f2

40. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Typically has six stages A radio frequency (RF) amplifier Two conversion stages Two band pass filters A demodulator Double Superheterodyne Frequency is converted twice

41. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS Double Superheterodyne A high frequency IF is first chosen to bring a satisfactory image response A low-frequency IF to bring high selectivity and gain. Two IF stages reduces Image Frequency problems

42. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS The F M Receiver A receiver for FM signals follows the same general principles as a receiver for CW and SSB reception A "limiter" before the discriminator removes noise peaks and amplitude-changes before detection of the FM signal

43. Shuswap Amateur Radio Club – Basic Qualification RECEIVERS The F M Receiver Capture Effect: When more than one signal is present, only the loudest signal will be demodulated Frequency Discriminator recovers original message waveform from an FM signal

44. Shuswap Amateur Radio Club – Basic Qualification TRANSRECEIVERS Contains both Transmitter and Receiver When the unit goes into transmit mode, the receiver is muted and disconnected from the antenna, but not from the power source