Accelerated Technician Class

1. Accelerated Technician Class Session #4

2. Data and RTTY • RTTY (radio teletype) was the forerunner of all modern digital mode transmission. • Today, amateurs use many kinds of intelligent on air networking modes. Collectively, the FCC refers to these intelligent modes as “Data.” • Both Data and RTTY require an interface between the Data or RTTY device and the transceiver.

3. Error correcting Store and forward networking Addressable Packet oriented Will interface with the internet Requires TNC to interface with radio No error correction Direct contact No addressing Continuous data stream No way!! Requires “modem” to interface with radio Data vs. RTTY

4. A Packet Network • With only a few watts, you can connect to an on-air network. Your data packets will be forwarded to hams all over the country. • Packet type protocols include: • Packet and APRS, • COVER, • PACTOR I, II & III (This is what TSA uses for HF Email) • G-TOR

5. A Packet Network

6. A Packet Network A digipeater is a packet-radio station capable of recognizing and selectively repeating packet frames. By the use of digipeaters, a packet can be reliably sent error free over great distances. All the stations on a packet network share the same frequency.

7. TNCs The “Terminal Node Controller” (TNC) interfaces your computer to your transceiver.

8. TNCs (like the old dial up modems we used to get on the Internet)

9. Test, SS and Pulse • Test emissions are simply unmodulated carrier. • SS (Spread Spectrum) are experimental frequency hopping modes. • Pulse emissions are used for telemetry.

10. What method of call sign identification is required for a station transmitting phone signals? A. Send the call sign followed by the indicator RPT B. Send the call sign using CW or phone emission C. Send the call sign followed by the indicator R D. Send the call sign using only phone emission

11. Which of the following would be connected between a transceiver and computer in a packet radio station? A. Transmatch B. Mixer C. Terminal node controller D. Antenna

12. What happens when the deviation of an FM transmitter is increased? A. Its signal occupies more bandwidth B. Its output power increases C. Its output power and bandwidth increases D. Asymmetric modulation occurs

13. Which type of modulation is most commonly used for VHF and UHF voice repeaters? A. AM B. SSB C. PSK D. FM

14. What can you do if you are told your FM handheld or mobile transceiver is over deviating? A. Talk louder into the microphone B. Let the transceiver cool off C. Change to a higher power level D. Talk farther away from the microphone

15. Antennas

16. Antennas and Feed lines • Most antenna systems are resonant - that is, they respond best at a certain frequency. • For best operation, the transmitter, feed line and antenna should all be matched to the same impedance. • The transmitting antenna induces a radio wave into the air. The radio wave travels to the receiving antenna, and induces a current in that antenna.

17. 468 f (MHz) Length of dipole in feet = The 1/2 Wave Dipole

18. The 1/2 Wave Dipole

19. The 1/4 Wave Vertical 234 f (MHz) Length of vertical in feet =

20. The 1/4 Wave Vertical A side view of the radiation pattern of a 1/4 wave vertical. From above the pattern is round like a doughnut. A perfect ground would be a car roof.

21. The Yagi (Type of Beam Antenna) • The yagi is the ham’s favorite directional antenna. • They usually consist of one driven element, and several “parasitic” (un-driven) elements. • Reflector (longer than driver) • Driven Element (1/2 wave dipole) • One or more Directors (shorter than the driven element)

22. The Yagi Driver The director acts like a lens The reflector acts like a mirror Boom Gain Director Reflector Feedline

23. The Yagi The yagi antenna focuses RF energy in one direction, giving the appearance of getting “free power.” This free power is called Antenna Gain.

24. The Yagi (Beam Antenna) A 3 element HF Yagi A VHF Yagi

25. Feed lines • Feed line connects your radio to the antenna. • Feed lines are either balanced (neither side grounded) like ladder-line or unbalanced (one side grounded) like coaxial cable. • Either type can be used in your station. • Coax is more popular and easier to work with.

26. Can be buried or run near metal objects. Less RFI since outer shield is usually grounded. Weatherproof Easy to handle and connect Very low signal loss Can tolerate high SWR Can tolerate high current Coax vs. Ladder Line

27. Coax All coaxial cable will feature a center conductor surrounded by a dielectric insulator and one or more layers of shielding and an insulating cover.

28. The Balun The balun converts from BALanced feed line to UNbalanced feed lines. Many antenna systems work better with a balun between the feed point and the coax

29. SWR • SWR (standing wave ratio) is a mathematical expression of the power going to an antenna and the power being reflected back. • The idea is to get as close to 1:1 as possible. • Most hams are happy with SWR of <1.5:1. • Most transmitters are happy with SWR of <2:1. • The best way to get a good SWR is to cut the antenna to resonance.

30. The Antenna Tuner “Antenna Tuners” do not really tune antennas. They provide an impedance match between the transmitter and antenna system.

31. What does an antenna tuner do? A. It matches the antenna system impedance to the transceiver's output impedance B. It helps a receiver automatically tune in weak stations C. It allows an antenna to be used on both transmit and receive D. It automatically selects the proper antenna for the frequency band being used

32. What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna? A. 6 B. 50 C. 112 D. 236

33. What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz? A. 112 B. 50 C. 19 D. 12

34. How would you change a dipole antenna to make it resonant on a higher frequency? A. Lengthen it B. Insert coils in series with radiating wires C. Shorten it D. Add capacity hats to the ends of the radiating wires

35. Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface? A. A ground wave antenna B. A horizontally polarized antenna C. A rhombic antenna D. A vertically polarized antenna

36. What type of antennas are the quad, Yagi, and dish? A. Non-resonant antennas B. Loop antennas C. Directional antennas D. Isotropic antennas

37. What is a disadvantage of the "rubber duck" • antenna supplied with most handheld radio • transceivers? • It does not transmit or receive as effectively • as a full-sized antenna • B. It transmits a circularly polarized signal • C. If the rubber end cap is lost it will unravel • very quickly • D. All of these choices are correct

38. What, in general terms, is standing wave ratio (SWR)? • A measure of how well a load is matched to a transmission line • The ratio of high to low impedance in a feedline • C. The transmitter efficiency ratio • D. An indication of the quality of your station’s ground connection

39. Intermission

40. RF Safety Can’t touch this.

41. 2 Types of Radiation • Ionizing • Gamma and X-ray • Can cause ionization of atomic structure • Not good for your DNA • Non-ionizing • Radio waves • Can cause heating of biological tissue • If sufficient energy is present, can cause burns

42. RF Heating • Radio waves can heat body tissue. • Works exactly like your microwave oven. • The area most likely to be injured is the eye as it lacks sufficient blood flow for cooling. • The eye can form cataracts from repeated exposure to high levels of RF energy. • NEVER touch an antenna or other RF source. You could be severely burned.

43. Controlled and Uncontrolled Environments • Controlled Environments • The amateur operators household and property • Persons here are aware of RF risks, and have control of the transmitting equipment. • Uncontrolled Environments • Your neighbors household and property • Persons here are generally not aware of RF risks and have NO control over the transmitter.

44. Exposure Averaging Times • Controlled Environments • The exposure averaging time is 6 Minutes • Uncontrolled Environments • The exposure averaging time is 30 Minutes

45. 3 Methods of RF Checking • Measure the RF fields • Requires costly equipment that you don’t have • Calculate the RF fields • Requires software that you may or may not have • Use the charts published by the FCC • The charts are free • Fairly simple to use

46. RF Safety for Dummies • Install your antenna away from people, especially your neighbors. The higher the better. • Make sure your antenna is not near or could fall on a power line. • Keep your hands and other body parts away from the antenna and feed lines.

47. Who is Exempt? Nobody -- The RF safety regulations apply to ALL amateur stations. However, the following stations are “categorically exempt” from having to do a routine station evaluation: • Mobile & hand-held radios using PTT control. • Any station that produces less than 50 watts PEP output.

48. What is the minimum safe distance from a power line to allow when installing an antenna? A. Half the width of your property B. The height of the power line above ground C. 1/2 wavelength at the operating frequency D. So that if the antenna falls unexpectedly, no part of it can come closer than 10 feet to the power wires

49. What is the maximum power level that an amateur radio station may use at VHF frequencies before an RF exposure evaluation is required? A. 1500 watts PEP transmitter output B. 1 watt forward power C. 50 watts PEP at the antenna D. 50 watts PEP reflected power

50. What could happen if a person accidentally touched your antenna while you were transmitting? A. Touching the antenna could cause television interference B. They might receive a painful RF burn C. They might develop radiation poisoning D. All of these choices are correct