1-23. 1-24. 1-25. 1-26. 1-27. 1-28. For    ionospheric    reflection    to occur,    the   ionized   layer   must not   be   thicker   than   how   many wavelengths    of    the    transmitted frequency? 1. One 2. Two 3. Three 4. Four The   ability   of   radio   waves   to turn   sharp   corners   and   bend around   obstacles   is   known   as 1. reflection 2. refraction 3. diffraction 4. waveshaping Which   of   the   following definitions    best    describes    a shadow    zone? 1. The   area   of   complete coverage   at   vlf   frequencies 2. The   area   within   the diameter   of   an   obstruction 3. The   area   ranging   the   height of   the   obstruction 4. The   area   on   the   opposite side   of   the   obstruction,   in line-of-site    from    the transmitter   to   the   receiver What   type   of   fading   occurs   for the   longest   amount   of   time? 1. Phase    shift 2. Absorption 3. Multipath 4. Diffraction Which   of   the   following   are examples   of   multipath   radio wave     transmissions? 1. Groundwaves 2. Ionospheric     refractions 3. Reflection   from   the   earth’s surface 4. All  of  the  above Fading   on   the   majority   of   the ionospheric   circuits   is   a result   of   what   particular   type of   fading? 1. Selective 2. Absorption 3. Multipath 4. Weather IN   ANSWERING   QUESTIONS   1-29   AND   1-30, SELECT   FROM   THE   FOLLOWING   LIST   THE DEFINITION   OF   THE   INDICATED   TERM. A. B. C. D. Two   or   more   receiving antennas   spaced   apart   to produce   a   usable   signal Two   or   more   receiving antennas   of   varying   heights located    together The   use   of   two   separate transmitters    and    receivers on    different    frequencies transmitting    the    same information The   use   of   two   separate transmitters    and    receivers on   the   same   frequency transmitting    the    same information 1-29. Space    diversity. 1.   A 2.   B 3.   C 4.   D 1-30. Frequency    diversity. 1.   A 2.   B 3.   C 4.   D 1-31. A   wide   band   of   frequencies   is transmitted    and    selective fading    occurs. Which   of   the following    statements    best describes   the   effect   of   the fading   on   the   signal? 1. It   affects   various frequencies 2. It   can   cause   changes   in phase    and    amplitude 3. It   can   cause   severe distortion   and   limit   total signal     strength 4. All  of  the  above 1-32. Which   ionospheric   layer   is   most dense   during   the   winter? 1.   E 2.   D 3. F2 4. F1 3