B-007 — Radio wave propagation

How signals travel: the ionosphere and its layers, skip, ground wave, sporadic E, and which bands work when.

All 87 questions

• B-007-001-001 What type of wave propagation usually occurs between two nearby VHF transceivers?
• B-007-001-002 What does near vertical incidence sky-wave (NVIS) propagation enable?
• B-007-001-003 When a signal is returned to Earth by the ionosphere, what is this called?
• B-007-001-004 On VHF and higher frequencies, why does the radio horizon extend beyond the visible horizon?
• B-007-001-005 What type of wave is commonly known as sky wave?
• B-007-001-006 What portion of a radio signal is directly affected by the surface of the Earth?
• B-007-001-007 What makes radiocommunication out to 200 km possible at lower HF frequencies during the daytime?
• B-007-001-008 Considering the bands from 160 metres to 6 metres, which band offers the greatest ground-wave propagation distance?
• B-007-001-009 What type of radio wave follows a path from the transmitter to the ionosphere and back to Earth?
• B-007-001-010 Reception of high frequency (HF) radio waves beyond 4000 km is generally made possible by:
• B-007-002-001 What causes the ionosphere to form?
• B-007-002-002 What type of solar radiation is most responsible for ionization in the outer atmosphere?
• B-007-002-003 Which ionospheric region is closest to the Earth?
• B-007-002-004 Which region of the ionosphere is the least useful for long-distance radio-wave propagation?
• B-007-002-005 Which region of the ionosphere separates into two sub-regions in the daytime?
• B-007-002-006 When is the ionosphere most ionized?
• B-007-002-007 When is ionization at a minimum in the ionosphere?
• B-007-002-008 Why is the F2 region mainly responsible for the longest distance radio-wave propagation?
• B-007-002-009 What is the main reason the 160-metre and 80-metre bands tend to be useful only for short-distance communications during daylight hours?
• B-007-002-010 During the day, what two sub-regions appear in the ionosphere?
• B-007-002-011 What is the position of the E region in the ionosphere?
• B-007-003-001 What term describes an area that is too distant for reception of ground waves, but too close for reception of ionospheric waves?
• B-007-003-002 What is the maximum distance along the Earth's surface that is normally covered in one hop using the F2 region?
• B-007-003-003 What is the maximum distance along the Earth's surface that is normally covered in one hop using the E region?
• B-007-003-004 Skip zone is:
• B-007-003-005 The distance to Europe from your location is approximately 5000 km. What type of high frequency (HF) propagation is the most likely to work?
• B-007-003-006 Assuming constant ionosphere region height, how does a higher radiation angle affect skip distance?
• B-007-003-007 On a double-hop path involving the surface of the Earth as a middle point, what phenomenon returns the radio wave to the ionosphere?
• B-007-003-008 Skip distance is the:
• B-007-003-009 Skip is a term associated with signals from the ionosphere. What causes skip?
• B-007-003-010 The skip distance of a sky wave will be greatest when the:
• B-007-003-011 How does an increase in the height of the refracting region affect skip distance?
• B-007-004-001 What effect does the D region of the ionosphere have on lower frequency HF waves in the daytime?
• B-007-004-002 Why can you not hear distant 160-metre and AM broadcast stations during daytime hours?
• B-007-004-003 A radio transmission may follow two or more different paths during propagation, and this may result in phase differences at the receiver. What is the effect at the receiver?
• B-007-004-004 While using a 2-metre hand-held transceiver in an urban setting, you notice that moving less than one metre can severely attenuate your received signal. What is the likely cause?
• B-007-004-005 A transmitted radio signal reaches a receiver by both one-hop and two-hop skip paths. What can small changes in the ionosphere cause?
• B-007-004-006 What can be done to continue HF communications during a sudden ionospheric disturbance (SID)?
• B-007-004-007 On the VHF and UHF bands, the polarization of the receiving antenna in relation to the transmitting antenna is very important, yet on HF bands it is relatively unimportant. Why is that so?
• B-007-004-008 What causes selective fading?
• B-007-004-009 How does the bandwidth of a transmitted signal affect selective fading?
• B-007-004-010 What effect do refraction, reflection and Faraday rotation have on a radio wave?
• B-007-004-011 If a radio transmission follows two or more different paths during propagation, the received signal may degrade due to fading. What other type of degradation can occur?
• B-007-005-001 How do sunspots change the ionization of the atmosphere?
• B-007-005-002 How long is an average sunspot cycle?
• B-007-005-003 What is solar flux?
• B-007-005-004 What is the solar-flux index?
• B-007-005-005 What influences all radiocommunication beyond ground wave or line-of-sight ranges?
• B-007-005-006 What effect of the sun's activity influences ionospheric propagation on a daily basis?
• B-007-005-007 When sunspot numbers are high, how is propagation affected?
• B-007-005-008 All communication frequencies throughout the spectrum are affected in varying degrees by:
• B-007-005-009 Average duration of a solar cycle is:
• B-007-005-010 The ability of the ionosphere to refract high frequency radio signals depends on:
• B-007-005-011 What is the major cause of cyclical changes in HF propagation?
• B-007-006-001 Observatories probe the ionosphere at vertical incidence. What term describes the highest frequency that a region can reflect at the time?
• B-007-006-002 What causes the maximum usable frequency to vary?
• B-007-006-003 What does maximum usable frequency mean?
• B-007-006-004 Why is communication possible between two continents at a frequency above the local critical frequency?
• B-007-006-005 What is one way to determine if the maximum usable frequency (MUF) is high enough to support 28 MHz propagation between your station and western Europe?
• B-007-006-006 What usually happens to radio waves with frequencies below the maximum usable frequency (MUF) when they are sent into the ionosphere?
• B-007-006-007 At what point in the solar cycle does the 20-metre band usually support worldwide propagation during daylight hours?
• B-007-006-008 What happens daily when the solar UV radiation increases?
• B-007-006-009 When is propagation on the 80-metre band generally the LEAST effective?
• B-007-006-010 The optimum working frequency provides the best long-range HF communication. Compared with the maximum usable frequency (MUF), it is usually:
• B-007-006-011 During summer daytime, which bands are the most difficult for communications beyond ground wave?
• B-007-007-001 Which ionospheric region most affects sky-wave propagation on the 6-metre band?
• B-007-007-002 What effect does tropospheric bending have on 2-metre radio waves?
• B-007-007-003 What causes tropospheric ducting of radio waves?
• B-007-007-004 What term describes that portion of a transmitted wave kept close to the Earth's surface due to bending in the atmosphere?
• B-007-007-005 What is a sporadic-E condition?
• B-007-007-006 On which amateur radio band is the extended-distance propagation effect of sporadic-E most often observed?
• B-007-007-007 In the northern hemisphere, in which direction should a directional antenna be pointed to take maximum advantage of auroral propagation?
• B-007-007-008 Where in the ionosphere does auroral activity occur?
• B-007-007-009 Which analog emission mode is the most reliable in auroral propagation?
• B-007-007-010 Excluding enhanced propagation modes, what is the approximate range of normal VHF tropospheric propagation?
• B-007-007-011 What effect is responsible for propagating a VHF signal over 800 km?
• B-007-008-001 What kind of unusual HF propagation allows weak signals from the skip zone to be heard?
• B-007-008-002 If you receive a weak, distorted signal close to the maximum usable frequency, what type of propagation is probably occurring?
• B-007-008-003 What type of VHF/UHF propagation depends upon small variations in density and water-vapour content?
• B-007-008-004 What makes HF scatter signals often sound distorted?
• B-007-008-005 Why are HF scatter signals usually weak?
• B-007-008-006 What type of propagation may allow a weak high frequency (HF) signal to be heard at a distance too far for ground-wave propagation but too near for normal sky-wave propagation?
• B-007-008-007 On the HF bands, when is scatter propagation most likely involved?
• B-007-008-008 Tropospheric scatter frequently explains VHF/UHF communications well beyond the radio horizon. What makes this propagation mode possible?
• B-007-008-009 Meteor scatter is most effective on what band?
• B-007-008-010 What is the effect of scattering on a radio wave?
• B-007-008-011 In which frequency range is meteor scatter most effective for extended-range communication?