CA_BASIC
Basic - Interference and suppression
Interference and suppression follows the B-007 section of the Canadian question bank.
87
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7
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For regulatory and safety questions, prefer compliant and conservative actions.
For calculations, check units, multipliers, and approximations.
Topic Study Guide
This section focuses on radio wave propagation, covering ionospheric layers, solar activity, skip zones, and signal fading. Understanding how the atmosphere and the sun interact with radio waves is crucial for this topic.
High-Yield Checks
- Ionospheric Layers: The D region is closest to Earth and absorbs lower HF frequencies (like 80m and 160m) during the day. The F region is responsible for long-distance skywave propagation.
- Skip Zone vs. Skip Distance: The skip zone is the "dead space" between the end of the ground wave and the first returning skywave. Skip distance depends on the radiation angle.
- Solar Activity: The solar cycle averages 11 years. Solar flux measures the radio frequency energy emitted by the sun, which directly impacts daily ionospheric propagation.
- Fading and Multipath: Selective fading is caused by phase differences between radio wave components arriving via different paths, which can also cause phase distortion.
Trap Patterns
- Confusing Critical Frequency with MUF. Critical frequency is measured at a vertical (90-degree) incidence, while MUF applies to oblique (inclined) angles for communication between two distant points.
- Misunderstanding daytime HF propagation. Assuming 80m/160m are good for daytime DX, forgetting that the D layer heavily absorbs these frequencies during daylight hours.
- Assuming the skip zone starts right at the antenna. Remember that the ground wave provides local coverage first; the skip zone is the silence gap after the ground wave fades.
Review Steps
- Map out the ionosphere. Draw the D, E, and F layers, noting their altitudes and how they change from day to night.
- Visualize wave paths. Sketch ground waves, line-of-sight (VHF), and sky waves to clearly see where the skip zone occurs.
- Link solar concepts. Connect solar flux, the 11-year cycle, and electromagnetic radiation to their effects on the Maximum Usable Frequency (MUF).
Quick Checks
- Which ionospheric layer is responsible for daytime absorption of 160m and 80m signals?
- What is the average duration of a solar cycle?
- What causes selective fading in a received signal?
- What is the term for the highest frequency that can be reflected when sent straight up into the ionosphere?
Questions in This Topic
Choose Practice ModeB-007-001-001What type of wave propagation usually occurs between two nearby VHF transceivers?B-007-001-002What does near vertical incidence sky-wave (NVIS) propagation enable?B-007-001-003When a signal is returned to Earth by the ionosphere, what is this called?B-007-001-004On VHF and higher frequencies, why does the radio horizon extend beyond the visible horizon?B-007-001-005What type of wave is commonly known as sky wave?B-007-001-006What portion of a radio signal is directly affected by the surface of the Earth?B-007-001-007What makes radiocommunication out to 200 km possible at lower HF frequencies during the daytime?B-007-001-008Considering the bands from 160 metres to 6 metres, which band offers the greatest ground-wave propagation distance?B-007-001-009What type of radio wave follows a path from the transmitter to the ionosphere and back to Earth?B-007-001-010Reception of high frequency (HF) radio waves beyond 4000 km is generally made possible by:B-007-002-001What causes the ionosphere to form?B-007-002-002What type of solar radiation is most responsible for ionization in the outer atmosphere?B-007-002-003Which ionospheric region is closest to the Earth?B-007-002-004Which region of the ionosphere is the least useful for long-distance radio-wave propagation?B-007-002-005Which region of the ionosphere separates into two sub-regions in the daytime?B-007-002-006When is the ionosphere most ionized?B-007-002-007When is ionization at a minimum in the ionosphere?B-007-002-008Why is the F2 region mainly responsible for the longest distance radio-wave propagation?B-007-002-009What is the main reason the 160-metre and 80-metre bands tend to be useful only for short-distance communications during daylight hours?B-007-002-010During the day, what two sub-regions appear in the ionosphere?B-007-002-011What is the position of the E region in the ionosphere?B-007-003-001What term describes an area that is too distant for reception of ground waves, but too close for reception of ionospheric waves?B-007-003-002What is the maximum distance along the Earth's surface that is normally covered in one hop using the F2 region?B-007-003-003What is the maximum distance along the Earth's surface that is normally covered in one hop using the E region?B-007-003-004Skip zone is:B-007-003-005The distance to Europe from your location is approximately 5000 km. What type of high frequency (HF) propagation is the most likely to work?B-007-003-006Assuming constant ionosphere region height, how does a higher radiation angle affect skip distance?B-007-003-007On a double-hop path involving the surface of the Earth as a middle point, what phenomenon returns the radio wave to the ionosphere?B-007-003-008Skip distance is the:B-007-003-009Skip is a term associated with signals from the ionosphere. What causes skip?B-007-003-010The skip distance of a sky wave will be greatest when the:B-007-003-011How does an increase in the height of the refracting region affect skip distance?B-007-004-001What effect does the D region of the ionosphere have on lower frequency HF waves in the daytime?B-007-004-002Why can you not hear distant 160-metre and AM broadcast stations during daytime hours?B-007-004-003A 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-007-004-004While 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-007-004-005A transmitted radio signal reaches a receiver by both one-hop and two-hop skip paths. What can small changes in the ionosphere cause?B-007-004-006What can be done to continue HF communications during a sudden ionospheric disturbance (SID)?B-007-004-007On 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-007-004-008What causes selective fading?B-007-004-009How does the bandwidth of a transmitted signal affect selective fading?B-007-004-010What effect do refraction, reflection and Faraday rotation have on a radio wave?B-007-004-011If 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-007-005-001How do sunspots change the ionization of the atmosphere?B-007-005-002How long is an average sunspot cycle?B-007-005-003What is solar flux?B-007-005-004What is the solar-flux index?B-007-005-005What influences all radiocommunication beyond ground wave or line-of-sight ranges?B-007-005-006What effect of the sun's activity influences ionospheric propagation on a daily basis?B-007-005-007When sunspot numbers are high, how is propagation affected?B-007-005-008All communication frequencies throughout the spectrum are affected in varying degrees by:B-007-005-009Average duration of a solar cycle is:B-007-005-010The ability of the ionosphere to refract high frequency radio signals depends on:B-007-005-011What is the major cause of cyclical changes in HF propagation?B-007-006-001Observatories probe the ionosphere at vertical incidence. What term describes the highest frequency that a region can reflect at the time?B-007-006-002What causes the maximum usable frequency to vary?B-007-006-003What does maximum usable frequency mean?B-007-006-004Why is communication possible between two continents at a frequency above the local critical frequency?B-007-006-005What 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-007-006-006What usually happens to radio waves with frequencies below the maximum usable frequency (MUF) when they are sent into the ionosphere?B-007-006-007At what point in the solar cycle does the 20-metre band usually support worldwide propagation during daylight hours?B-007-006-008What happens daily when the solar UV radiation increases?B-007-006-009When is propagation on the 80-metre band generally the LEAST effective?B-007-006-010The optimum working frequency provides the best long-range HF communication. Compared with the maximum usable frequency (MUF), it is usually:B-007-006-011During summer daytime, which bands are the most difficult for communications beyond ground wave?B-007-007-001Which ionospheric region most affects sky-wave propagation on the 6-metre band?B-007-007-002What effect does tropospheric bending have on 2-metre radio waves?B-007-007-003What causes tropospheric ducting of radio waves?B-007-007-004What term describes that portion of a transmitted wave kept close to the Earth's surface due to bending in the atmosphere?B-007-007-005What is a sporadic-E condition?B-007-007-006On which amateur radio band is the extended-distance propagation effect of sporadic-E most often observed?B-007-007-007In the northern hemisphere, in which direction should a directional antenna be pointed to take maximum advantage of auroral propagation?B-007-007-008Where in the ionosphere does auroral activity occur?B-007-007-009Which analog emission mode is the most reliable in auroral propagation?B-007-007-010Excluding enhanced propagation modes, what is the approximate range of normal VHF tropospheric propagation?B-007-007-011What effect is responsible for propagating a VHF signal over 800 km?B-007-008-001What kind of unusual HF propagation allows weak signals from the skip zone to be heard?B-007-008-002If you receive a weak, distorted signal close to the maximum usable frequency, what type of propagation is probably occurring?B-007-008-003What type of VHF/UHF propagation depends upon small variations in density and water-vapour content?B-007-008-004What makes HF scatter signals often sound distorted?B-007-008-005Why are HF scatter signals usually weak?B-007-008-006What 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-007-008-007On the HF bands, when is scatter propagation most likely involved?B-007-008-008Tropospheric scatter frequently explains VHF/UHF communications well beyond the radio horizon. What makes this propagation mode possible?B-007-008-009Meteor scatter is most effective on what band?B-007-008-010What is the effect of scattering on a radio wave?B-007-008-011In which frequency range is meteor scatter most effective for extended-range communication?