Free Ham Radio Technician II Questions And Answers — Questions and Answers

Question 1: What mathematical formula should be used to determine the power lost by a series linear voltage regulator?

Input voltage multiplied by input current
Input voltage divided by output current
Voltage difference from input to out multiplied by output current (Correct answer)
Output voltage multiplied by output current

Correct answer: Voltage difference from input to out multiplied by output current

A series linear voltage regulator dissipates excess power as heat. The power lost (P_loss) is calculated by multiplying the voltage drop across the series pass element by the current flowing through it. Since the output current (I_out) is essentially the same as the current through the series element, and the voltage drop is the difference between the input voltage (V_in) and the output voltage (V_out), the formula is P_loss = (V_in - V_out) * I_out.

Question 2: When during the day does transequatorial propagation work best?

Morning
Noon
Afternoon or early evening (Correct answer)
Late at night

Correct answer: Afternoon or early evening

Transequatorial propagation (TEP) is a type of ionospheric propagation that occurs across the magnetic equator, typically on VHF bands. It is most common during the afternoon and early evening hours, particularly around the equinoxes. During these times, the F2 layer of the ionosphere is strongly ionized and exhibits specific characteristics that allow signals to 'duct' across the equator, enabling long-distance contacts.

Question 3: Where are the rectangular coordinates for the impedance of a pure resistance plotted?

On the vertical axis
On a line through the origin, slanted at 45 degrees
On a horizontal axis
On the horizontal axis (Correct answer)

Correct answer: On the horizontal axis

On a Smith chart, the horizontal axis (often called the r-axis) represents purely resistive impedances. Points located on this axis have zero reactance, meaning the impedance is entirely resistive. Moving along this axis from left to right corresponds to increasing resistance, with the center of the chart representing the characteristic impedance (pure resistance).

Question 4: Which of the following best depicts how a receiving filter might block signals coming from an adjacent channel?

Passband ripple
Phase response
Shape factor (Correct answer)
Noise factor

Correct answer: Shape factor

The shape factor of a filter describes how steep its skirts are, indicating how quickly its attenuation increases outside the passband. A lower shape factor signifies a sharper, more selective filter. A good shape factor is crucial for a receiving filter to effectively block strong signals from adjacent channels while allowing the desired signal to pass through with minimal interference, thus improving receiver selectivity.

Question 5: Which of the following carrier frequencies is prohibited for LSB AFSK transmissions on the RTTY 17-meter band and the 18.068–18.110 MHz data segment?

18.068 MHz (Correct answer)
18.100 MHz
18.107 MHz
18.110 MHz

Correct answer: 18.068 MHz

The 17-meter RTTY/data segment is 18.068–18.110 MHz. For LSB (Lower Sideband) transmissions, the signal occupies frequencies below the carrier. If the carrier is set to 18.068 MHz, the entire signal would extend below the lower band edge, violating band plan rules. To operate legally, the carrier frequency must be sufficiently above the lower band edge so that the entire sideband remains within the allocated segment.

Question 6: How can the noise produced by a car alternator be reduced in both conducted and radiated forms?

By installing filter capacitors in series with the DC power lead and a blocking capacitor in the field lead
By installing a noise suppression resistor and a blocking capacitor in both leads
By installing a high-pass filter in series with the radio's power lead and a low-pass filter in parallel with the field lead
By connecting the radio's power leads directly to the battery and installing coaxial capacitors in line with the alternator leads (Correct answer)

Correct answer: By connecting the radio's power leads directly to the battery and installing coaxial capacitors in line with the alternator leads

To reduce car alternator noise, it's best to address both conducted and radiated components. Connecting the radio's power leads directly to the battery provides the cleanest DC power source, bypassing other noisy vehicle electronics. Installing coaxial capacitors or other appropriate filters in line with the alternator leads directly at the source helps suppress both conducted and radiated noise, preventing it from reaching the radio.

Question 7: When the line is open at the other end, what impedance does a 1/4-wavelength transmission line present to a generator?

The same as the characteristic impedance of the line
The same as the input impedance to the generator
Very high impedance
Very low impedance (Correct answer)

Correct answer: Very low impedance

A quarter-wavelength transmission line acts as an impedance transformer. When it is open-circuited at one end, it presents a very high impedance at that end. Due to its quarter-wave length, it transforms this very high impedance into a very low impedance at the input end. This property is fundamental in antenna matching networks and for creating resonant stubs.

Question 8: What is the phase connection between a series resonant circuit's resonance voltage and current?

The current leads the voltage by 90 degrees
The voltage leads the current by 90 degrees
The voltage and current are in phase (Correct answer)
The voltage and current are 180 degrees out of phase

Correct answer: The voltage and current are in phase

At resonance in a series RLC circuit, the inductive reactance (XL) and capacitive reactance (XC) are equal in magnitude and cancel each other out. This leaves only the resistance (R) to oppose the current flow. In a purely resistive circuit, the voltage and current are always in phase. Therefore, at resonance, the total impedance is purely resistive, and the voltage across the circuit and the current flowing through it are in phase.

Question 9: What occurs as the length of a long, unterminated wire antenna increases in terms of its radiation pattern?

The lobes become more perpendicular to the wire
The lobes align more in the direction of the wire (Correct answer)
The vertical angle increases
The vertical angle increases

Correct answer: The lobes align more in the direction of the wire

As a long, unterminated wire antenna increases in length, its radiation pattern tends to align more closely with the direction of the wire. This means the primary lobes of radiation become more pronounced along the axis of the antenna itself. This phenomenon is due to the phase relationships of the currents along the longer wire, leading to constructive interference in directions parallel to the wire and destructive interference perpendicular to it.

Question 10: What is the normalization procedure in relation to a Smith chart?

Reassigning resistance values with regard to the reactance axis
Reassigning reactance values with regard to the resistance axis
Reassigning impedance values with regard to the prime center (Correct answer)
Reassigning prime center with regard to the reactance axis

Correct answer: Reassigning impedance values with regard to the prime center

Normalization in the context of a Smith chart involves reassigning impedance values relative to the prime center of the chart. This process typically means dividing the actual impedance (Z) by the characteristic impedance (Z0) of the transmission line, resulting in a normalized impedance (z = Z/Z0). This allows a single Smith chart to be used for any characteristic impedance, simplifying calculations for matching networks and transmission line analysis.

Question 11: To employ a hairpin matching system, how must the driving element of an antenna be tuned?

The driven element reactance must be inductive
The driven element reactance must be capacitive (Correct answer)
The driven element resonance must be lower than the operating frequency
The driven element radiation resistance must be higher than the characteristic impedance of the transmission line

Correct answer: The driven element reactance must be capacitive

To employ a hairpin matching system, the driven element of the antenna must be tuned to present a capacitive reactance. A hairpin match is essentially a shorted stub that adds inductive reactance in parallel with the antenna's feedpoint. By making the antenna slightly shorter than resonance (thus capacitive), the inductive reactance of the hairpin stub can cancel out this capacitance, bringing the antenna to resonance and transforming its impedance to a desired resistive value.

Question 12: Which of the following geopolitical definitions best fits "Line A"?

A line roughly parallel to and west of the U.S. Atlantic coastline
A line roughly parallel to and south of the border between the U.S. and Canada (Correct answer)
A line roughly parallel to and north of the border between the U.S. and Mexico
A line roughly parallel to and east of the U.S. Pacific coastline

Correct answer: A line roughly parallel to and south of the border between the U.S. and Canada

"Line A" is a geopolitical definition used in amateur radio regulations, specifically referring to a line roughly parallel to and south of the border between the U.S. and Canada. This line defines an area where amateur radio operations, particularly those involving high power or certain frequencies, may have specific restrictions to prevent interference with Canadian radio services. It helps manage spectrum usage near the international border.

Question 13: An isotropic antenna is what?

A grounded antenna used to measure Earth conductivity
A horizontally polarized antenna used to compare Yagi antennas
A theoretical, omnidirectional antenna used as a reference for antenna gain (Correct answer)
A spacecraft antenna used to direct signals toward Earth

Correct answer: A theoretical, omnidirectional antenna used as a reference for antenna gain

An isotropic antenna is a theoretical, omnidirectional antenna that radiates power equally in all directions, forming a perfect spherical radiation pattern. It does not exist in reality but serves as a crucial reference point for measuring and comparing the gain of real-world antennas. Antenna gain values, such as dBi (decibels relative to isotropic), express how much more power a directional antenna radiates in a specific direction compared to an isotropic antenna.

Question 14: In a fast-scan (NTSC) television system, how frequently are new frames transmitted?

30 (Correct answer)
60
90
90

Correct answer: 30

In a fast-scan (NTSC) television system, new frames are transmitted at a rate of 30 frames per second. This standard frame rate, combined with interlaced scanning (where two fields make up one frame), creates the illusion of smooth motion on the screen. While the field rate is 60 fields per second, it takes two fields to constitute a complete frame, resulting in 30 distinct frames per second.

Question 15: What is the main benefit of an inductor with a toroidal core rather than a solenoidal core?

Toroidal cores confine most of the magnetic field within the core material (Correct answer)
It is simpler to connect the magnetic energy into other components using toroidal cores.
Toroidal cores make it easier to transfer magnetic energy into other parts.
Toroidal cores have lower Q characteristics

Correct answer: Toroidal cores confine most of the magnetic field within the core material

The main benefit of an inductor with a toroidal core, compared to a solenoidal core, is its superior ability to confine most of the magnetic field within the core material. The donut shape of the toroidal core ensures that the magnetic flux lines remain largely within the core, minimizing external electromagnetic interference (EMI) and reducing coupling with nearby components. This results in a more efficient and predictable inductor.

Question 16: How is a complicated impedance converted to a resistive impedance by an impedance-matching circuit?

It introduces negative resistance to cancel the resistive part of impedance
It introduces transconductance to cancel the reactive part of impedance
It cancels the reactive part of the impedance and changes the resistive part to a desired value (Correct answer)
Reactive currents are dissipated in matched resistances

Correct answer: It cancels the reactive part of the impedance and changes the resistive part to a desired value

An impedance-matching circuit converts a complicated impedance to a desired resistive impedance by performing two key functions. First, it cancels out the reactive (inductive or capacitive) part of the impedance, bringing the circuit to resonance. Second, it transforms the remaining resistive part to a specific value, typically 50 ohms, to match the characteristic impedance of the transmission line for maximum power transfer and minimum Standing Wave Ratio (SWR).

Free Ham Radio Technician II Questions And Answers

What mathematical formula should be used to determine the power lost by a series linear voltage regulator?