Amateur Extra E3A: EME, meteor scatter and wave basics
These are the 14 official questions in group E3A of the 2024–2028 Amateur Extra question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- E3A01Question 1
What is the approximate maximum separation measured along the surface of the Earth between two stations communicating by EME?
- A2,000 miles, if the moon is at perigee
- B2,000 miles, if the moon is at apogee
- C5,000 miles, if the moon is at perigee
- D12,000 miles, if the moon is “visible” by both stations Correct
Why: EME works up to about 12,000 miles if both stations can see the Moon.
- E3A02Question 2
What characterizes libration fading of an EME signal?
- AA slow change in the pitch of the CW signal
- BA fluttery, irregular fading Correct
- CA gradual loss of signal as the sun rises
- DThe returning echo is several hertz lower in frequency than the transmitted signal
Why: Libration fading is fluttery and irregular.
- E3A03Question 3
When scheduling EME contacts, which of these conditions will generally result in the least path loss?
- AWhen the Moon is at perigee Correct
- BWhen the Moon is full
- CWhen the Moon is at apogee
- DWhen the MUF is above 30 MHz
Why: At perigee the Moon is closest, so path loss is lowest.
- E3A04Question 4
In what direction does an electromagnetic wave travel?
- AIt depends on the phase angle of the magnetic field
- BIt travels parallel to the electric and magnetic fields
- CIt depends on the phase angle of the electric field
- DIt travels at a right angle to the electric and magnetic fields Correct
Why: The wave travels at right angles to both fields.
- E3A05Question 5
How are the component fields of an electromagnetic wave oriented?
- AThey are parallel
- BThey are tangential
- CThey are at right angles Correct
- DThey are 90 degrees out of phase
Why: The electric and magnetic fields are at right angles.
- E3A06Question 6
What should be done to continue a long-distance contact when the MUF for that path decreases due to darkness?
- ASwitch to a higher frequency HF band
- BSwitch to a lower frequency HF band Correct
- CChange to an antenna with a higher takeoff angle
- DChange to an antenna with greater beam width
Why: When the MUF drops, switch to a lower band.
- E3A07Question 7
Atmospheric ducts capable of propagating microwave signals often form over what geographic feature?
- AMountain ranges
- BStratocumulus clouds
- CLarge bodies of water Correct
- DNimbus clouds
Why: Microwave ducts often form over large bodies of water.
- E3A08Question 8
When a meteor strikes the Earth’s atmosphere, a linear ionized region is formed at what region of the ionosphere?
- AThe E region Correct
- BThe F1 region
- CThe F2 region
- DThe D region
Why: Meteor trails form in the E region.
- E3A09Question 9
Which of the following frequency ranges is most suited for meteor-scatter communications?
- A1.8 MHz - 1.9 MHz
- B10 MHz - 14 MHz
- C28 MHz - 148 MHz Correct
- D220 MHz - 450 MHz
Why: 28 to 148 MHz suits meteor scatter best.
- E3A10Question 10
What determines the speed of electromagnetic waves through a medium?
- AResistance and reactance
- BEvanescence
- CBirefringence
- DThe index of refraction Correct
Why: A medium's index of refraction sets the wave's speed.
- E3A11Question 11
What is a typical range for tropospheric duct propagation of microwave signals?
- A10 miles to 50 miles
- B100 miles to 300 miles Correct
- C1,200 miles
- D2,500 miles
Why: Microwave tropo ducting typically reaches 100 to 300 miles.
- E3A12Question 12
What is most likely to result in auroral propagation?
- AMeteor showers
- BQuiet geomagnetic conditions
- CSevere geomagnetic storms Correct
- DExtreme low-pressure areas in polar regions
Why: Severe geomagnetic storms bring auroral propagation.
- E3A13Question 13
Which of these emission modes is best for auroral propagation?
- ACW Correct
- BSSB
- CFM
- DRTTY
Why: CW works best through aurora.
- E3A14Question 14
What are circularly polarized electromagnetic waves?
- AWaves with an electric field bent into a circular shape
- BWaves with rotating electric and magnetic fields Correct
- CWaves that circle Earth
- DWaves produced by a loop antenna
Why: Circularly polarized waves have rotating electric and magnetic fields.