SUBELEMENT T9 – Radio waves, propagation, and antennas - 3 exam questions – 3 groups
T9A Antenna types – vertical, horizontal, concept of gain, common portable and mobile antennas, losses with short antennas, relationships between antenna length and frequency, dummy loads.
What is a beam antenna?
What is an antenna that consists of a single element mounted perpendicular to the Earth's surface?
What type of antenna is a simple dipole mounted so the elements are parallel to the Earth's surface?
What is a disadvantage of the "rubber duck" antenna supplied with most hand held radio transceivers?
How does the physical size of half-wave dipole antenna change with operating frequency?
What is the advantage of 5/8 wavelength over 1/4 wavelength vertical antennas?
What is the primary purpose of a dummy load?
What type of antennas are the quad, Yagi, and dish?
What is one type of antenna that offers good efficiency when operating mobile and can be easily installed or removed?
What is a good reason not to use a "rubber duck" antenna inside your car?
What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?
What is the approximate length, in inches, of a 6-meter 1/2 wavelength wire dipole antenna?
T9B Propagation, fading, multipath distortion, reflections, radio horizon, terrain blocking, wavelength vs. penetration, antenna orientation.
Why are VHF/UHF signals not normally heard over long distances?
What might be happening when we hear a VHF signal from long distances?
What is the most likely cause of sudden bursts of tones or fragments of different conversations that interfere with VHF or UHF signals?
What is the radio horizon?
What should you do if a station reports that your signals were strong just a moment ago, but now they are weak or distorted?
Why do UHF signals often work better inside of buildings than VHF signals?
What is a good thing to remember when using your hand-held VHF or UHF radio to reach a distant repeater?
What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?
What might be a way to reach a distant repeater if buildings or obstructions are blocking the direct line of sight path?
What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting?
Why do VHF and UHF Radio signals usually travel about a third farther than the visual line of sight distance between 2 stations?
T9C Feedlines types, losses vs. Frequency, SWR concepts, measuring SWR, matching and power transfer, weather protection, feedline failure modes.
What, in general terms, is standing wave ratio (SWR)?
What reading on a SWR meter indicates a perfect impedance match between the antenna and the feed line?
What might be indicated by erratic changes in SWR readings?
What is the SWR value where the protection circuits in most solid-state transmitters begin to reduce transmitter power?
What happens to the power lost in a feed line?
What instrument other than a SWR meter could you use to determine if your feedline and antenna are properly matched?
What is the most common reason for failure of coaxial cables?
Why is it important to have a low SWR in an antenna system that uses coaxial cable feedline?
What can happen to older coaxial cables that are exposed to weather and sunlight for several years?
Why is the outer sheath of most coaxial cables black in color?
What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?
Why is coaxial cable used more often than any other feed line for amateur radio antenna systems?