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Chapter 5

Chapter 5. Amateur Radio Equipment. Chapter 5 Amateur Radio Equipment. Today’s agenda Basic operation of transmitters and receivers Special features of handheld transceivers Power supplies and batteries Digital mode basics and setup RF interference – symptoms and cures

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Chapter 5

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  1. Chapter 5 Amateur Radio Equipment

  2. Chapter 5 Amateur Radio Equipment • Today’s agenda • Basic operation of transmitters and receivers • Special features of handheld transceivers • Power supplies and batteries • Digital mode basics and setup • RF interference – symptoms and cures • RF grounding Technician - 1 Jul 10 - 30 Jun 14

  3. Chapter 5 Transmitters & Receivers • During this review we’ll try to get you familiar with some of the common radio controls and their functions. • Your radio will probably be different but the concepts are common if not exactly the same. Two recommendations: • 1. Review your users manual when you purchase any equipment. Become familiar with the buttons, knobs and switches, etc. • 2. Ask if any local hams have the same equipment and seek their knowledge and guidance. Technician - 1 Jul 10 - 30 Jun 14

  4. Chapter 5 Transmitters & Receivers Most likely you’ll buy a transceiver which, of course, combines the transmitter and receiver in one box. It doesn’t matter what you get because the controls and functions for a separate receiver and a separate transmitter are virtually the same in a transceiver and are applied in the same manner. One of the unique things about amateur radio is that hams are not required to used “channels” assigned by the FCC except in the 60m band. While repeaters do operate on fixed channels, hams developed that system on their own. Technician - 1 Jul 10 - 30 Jun 14

  5. Chapter 5 Transmitters & Receivers • When there are a few steps to take before you start actually transmitting: • 1. Select a frequency band • Select a frequency • A. Enter the frequency using the tuning knob (That’s the big knob on the front of the radio faceplate. This knob controls the Variable Frequency Oscillator (VFO) which controls a microprocessor that sets the frequency). Technician - 1 Jul 10 - 30 Jun 14

  6. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  7. Chapter 5 Transmitters & Receivers • Select a frequency (Cont’d) • B. Enter the frequency using the keypad on the radio or microphone • Select a frequency from a memory channel (Most radios allow you to store dozens of frequency and mode combinations so you can quickly tune to your favorite freq or activity such as a net.) • 3. Select a signal mode (AM or SSB; FM; CW; Data) Technician - 1 Jul 10 - 30 Jun 14

  8. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  9. Chapter 5 Transmitters & Receivers In radios that use AM/SSB and CW, the transmitter output is controlled by the RF power control and can also be controlled by the “microphone gain” control. Most radio have a “speech compressor” or “Speech Processor” control. These circuits increase the average power of the transmitted signal by applying more amplification to the weak parts of the speech signal. A note of caution - Too much compression or processing can cause severe distortion and can cause interference on nearby frequencies. Technician - 1 Jul 10 - 30 Jun 14

  10. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  11. Chapter 5 Transmitters & Receivers Peak envelope power (PEP) is the measure of an AM or SSB signal’s power. PEP is the transmitter output power when speech into the microphone is the loudest. CW and FM transmissions have a constant power output so PEP is equal to that constant level. To avoid interfering with other station while you’re adjusting your transmitter or measuring its output power, you should use a “dummy load” which is a heavy-duty resistor that can absorb and dissipate the output power from a transmitter. Technician - 1 Jul 10 - 30 Jun 14

  12. Chapter 5 Transmitters & Receivers Dummy loads Technician - 1 Jul 10 - 30 Jun 14

  13. Chapter 5 Transmitters & Receivers Compare this radio and its “faceplate features” with the examples that follow. 80m – 10m Technician - 1 Jul 10 - 30 Jun 14

  14. Chapter 5 Transmitters & Receivers Similar to the previous radio but different. 80m – 70cm Technician - 1 Jul 10 - 30 Jun 14

  15. Chapter 5 Transmitters & Receivers 160 - 6m Technician - 1 Jul 10 - 30 Jun 14

  16. Chapter 5 Transmitters & Receivers 160m – 6m w/ available 2m add-on Technician - 1 Jul 10 - 30 Jun 14

  17. Chapter 5 Transmitters & Receivers 160m – 10m Technician - 1 Jul 10 - 30 Jun 14

  18. Chapter 5 Transmitters & Receivers If you looked closely, you saw that each of these radios had most of the same buttons, knobs and switches. The primary differences being location and size. In some instances the same functions were accessible via a menu. The radio below is a little more simple. In theory. Like the bigger radios, it has a tuning knob albeit smaller and has functions accessible via a menu. Technician - 1 Jul 10 - 30 Jun 14

  19. Chapter 5 Transmitters & Receivers 2m FM Mobile transceiver VOL SQL Tuning Technician - 1 Jul 10 - 30 Jun 14

  20. Chapter 5 Power Supplies & Batteries Excessive modulation of all types of speech results in distortion of the transmitted speech and unwanted or “spurious” transmitter outputs on adjacent frequencies which result in interference. An overmodulated FM signal has excessive deviation as a result of speaking too loudly into the microphone or the transmitter is misadjusted internally. To reduce overdeviation, simply speak more softly or move the microphone farther from your mouth. You’re splattering 10 kHz away! Technician - 1 Jul 10 - 30 Jun 14

  21. Chapter 5 Transmitters & Receivers Overmodulation of an AM or SSB signal is caused by speaking too loud or by setting the microphone gain or speech compression too high. The result is a transmitted signal that is distorted. Speak more softly or reduce the microphone gain or speech compression to eliminate overmodulation. The “automatic level control” (ALC) automatically reduces output power as the transmitter’s limit is reached. The ALC is not foolproof but it will help keep your signal clean. Technician - 1 Jul 10 - 30 Jun 14

  22. Chapter 5 Transmitters & Receivers Always check your owner’s/user’s manual for the correct procedures. A signal that sounds overmodulated could be a victim of “RF feedback”. Signals from you own transmitter could be picked up by the microphone input circuit and distort the speech signal. “CW clicks” can occur during CW transmissions and cause interference near the offending signal. Technician - 1 Jul 10 - 30 Jun 14

  23. Chapter 5 Transmitters & Receivers The choice of a microphone or a key is always a personal choice. A hand-held microphone is provide with your radio and for many hams that just what they want. As you evolve, your microphone preferences may change. You may decide you want a “desk mike” instead of the hand-held mike. Technician - 1 Jul 10 - 30 Jun 14

  24. Chapter 5 Transmitters & Receivers One of the advantages of most desk mikes is that they feature automatic “voice operated transmissions” or “VOX” so the operator can talk “hands free”. Many hams prefer to use headsets with a built-in boom mike. Headsets with a built-in boom mike are very popular with those hams who enjoy contesting. Technician - 1 Jul 10 - 30 Jun 14

  25. Chapter 5 Transmitters & Receivers The boom microphone can be operated by a handheld switch, a foot switch or by VOX. Technician - 1 Jul 10 - 30 Jun 14

  26. Chapter 5 Transmitters & Receivers When buying a microphone of any kind you want to make sure it’s compatible with your transmitter/transceiver. Each brand of radio has it’s own wiring connection design so you if choose a different brand of microphone that your transmitter, you’ll have to buy an adaptor of some kind. The microphone connector of a transceiver is likely to include push-to-talk connections and also supply voltage for powering electret-style headsets. Technician - 1 Jul 10 - 30 Jun 14

  27. Chapter 5 Transmitters & Receivers Morse code keys are similar to headsets in that you’ll evolve. You might start with a straight key and then progress to “paddles”. Technician - 1 Jul 10 - 30 Jun 14

  28. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  29. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  30. Chapter 5 Transmitters & Receivers A keyer is a device that connects to your CW paddles and your radio and allows you to send code much faster than with a straight key. Nearly all transceivers today have a built-in keyer although many hams prefer an external keyer. There is also software available that will allow you to send CW using a keying interface connected to the key input of the radio. All you have to do is type the characters using the keyboard and suddenly you’re sending Morse code although CW purists will say that you’re not. Technician - 1 Jul 10 - 30 Jun 14

  31. Chapter 5 Transmitters & Receivers The buttons on top serve as function keys and can also be used to store short prerecorded information to be transmitted: Call-up, your ID, the exchange info, one-up serial numbers, etc. Technician - 1 Jul 10 - 30 Jun 14

  32. Chapter 5 Transmitters & Receivers At the start of this review we discussed various transmitter functions and now we’re going to discuss receiver functions. The most familiar receiver control on the radio is the “AF gain” or “volume” control. On an HF rig the “RF gain” control will be nearby – usually it’s collocated with the AF gain control. The RF gain adjusts the sensitivity of the receiver to incoming signals. “Attenuators” are used to reduce the strength of signals at the receiver input. Technician - 1 Jul 10 - 30 Jun 14

  33. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  34. Chapter 5 Transmitters & Receivers • The “automatic gain control” (AGC) circuitry constantly adjusts the receivers sensitivity to keep the output volume relatively constant for both weak and strong signals. The AGC is adjustable. • A fast AGC response is used for CW and Data • Slow AGC response is used for AM and SSB • FM receivers do not use AGC Technician - 1 Jul 10 - 30 Jun 14

  35. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  36. Chapter 5 Transmitters & Receivers The “squelch circuit” was invented so that you don’t have to listen to constant noise when no signals are present. Sometimes called the “carrier squelch”, the squelch circuit mutes the receiver’s audio output when signals are not present. The squelch threshold, controlled by the squelch control, is the signal level where muting is turned off and the signal becomes audible. If the receiver’s output is not muted the squelch is “open”. Technician - 1 Jul 10 - 30 Jun 14

  37. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  38. Chapter 5 Transmitters & Receivers Receivers reject unwanted signals by using “band-pass filters” which are installed at the receiver input and pass only signals from the selected band. Further into the receiver the signal passes through “intermediate frequency” or “IF” which are narrow enough to reject signals on the same band as the desired signal. IF filters are specified by their bandwidth in Hz or kHz. Technician - 1 Jul 10 - 30 Jun 14

  39. Chapter 5 Transmitters & Receivers Wide filters (around 2.4 kHz) are used for SSB reception on phone. Narrow filters (around 500 Hz) are used for Morse code and data. Having multiple filters allows you to reduce noise or interference by selecting a filter with just enough bandwidth to pass the desired signal. Technician - 1 Jul 10 - 30 Jun 14

  40. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  41. Chapter 5 Transmitters & Receivers A “notch filter” removes a very narrow range of frequencies from a receiver’s audio output. Most receivers feature “noise reduction” which removes audio noise by using digital signal processing. Another useful tool is the “receiver incremental tuning” or “RIT” control. This fine tuning control is used for SSB and CW operation. Technician - 1 Jul 10 - 30 Jun 14

  42. Chapter 5 Transmitters & Receivers The RIT control allows the operator to adjust the receiver frequency without changing the transmitter frequency. For example, using the RIT control allows you to tune in a station that is slightly off frequency or to adjust the pitch of an operator’s voice that seems too high or too low. On some radios the RIT is called a “clarifier” (CLAR). A “noise blanker” is used to mute sharp pulses from arcing power lines, motors, or vehicle ignition systems. Technician - 1 Jul 10 - 30 Jun 14

  43. Chapter 5 Transmitters & Receivers Technician - 1 Jul 10 - 30 Jun 14

  44. Chapter 5 Transmitters & Receivers Handheld transceivers or handhelds or HTs are very popular and offer many features. HTs can be carried by the operator and used while in motion. They’re particularly useful for emergency communications. Dual band models usually cover 2m and 70cm. Multiband models add 6m or 1.25m or even 23cm. Technician - 1 Jul 10 - 30 Jun 14

  45. Chapter 5 Transmitters & Receivers • Like the “big rigs”, there are a variety of accessories available for HTs to include: • Speaker mikes • Headsets with or without a microphone • Headsets with microphones that offer PTT and VOX • If your HT is having difficulty accessing distant repeaters or making simplex contacts, an RF amplifier can be used to increase the output power by a factor of five or more. • Be sure to use an external antenna rated for the higher power. Technician - 1 Jul 10 - 30 Jun 14

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