Example questions from the Technican class exam pool

# What type of electrical component consists of two or more conductive surfaces separated by an insulator?*

A. Resistor
B. Potentiometer
C. Oscillator
D. Capacitor

Well, I guess I gave it away in the post title.  Yes, the answer is D. Capacitor.  But what exactly is going on here?

A capacitor is a device that has the “capacity” (get it?) to store energy in an electric field.  It does this by collecting charge on one of two plates, separated by an insulator called a dielectric.  The charge couples with the conductor on the other side and creates an electric field inside the dielectric. (See the image above.)  The most obvious type of this is the typical ceramic disc style capacitor.  It’s easy to visualize the construction that way.  A “rolled” foil regular or electrolytic capacitor is built the same way, except the whole 3-layer construct is rolled into a nice tight package.

Variable Capacitor (http://commons.wikimedia.org/wiki/File:Kombidrehko.jpg)

An “air” variable capacitor (see left) like ones that were used in early radios for tuning, simply use the air in between the fins as the dielectric.

Looking at the other possible answers, though:  A potentiometer is simply a type of variable resistor.  Neither is constructed in this manner.  An oscillator is a type of circuit, not a component therein.

*(This question is taken from the upcoming 2018-2022 Technician pool.  It may not be the same as the 2014-2018 pool.) [T6A05]

## What is the current flowing through a 24-ohm resistor connected across 240 volts? [T5D09]

A. 24,000 amperes
B. 0.1 amperes
C. 10 amperes
D. 216 amperes

Get out your calculators, because this is a cut-and-dried case of needing to use Ohm’s law.

Ohm’s law defines the relationship beteween voltage, current, and resistance in a circuit.  It looks like this:

$V = IR$

Where V is voltage, I is current, and R is resistance.  You might see it with and E for Voltage instead of V.  (Old habits die hard!)

All we need to do is substitute in our known values and then solve this simple equation for the current, like this:

$240 = (I)(24)$

re-arranging, we get:

$I = \frac{240}{24}$

which reduces to:

$I = 10$

and we get our answer, C. 10 amperes.

## Which of the following electronic components can amplify signals? [T6B05]

A. Transistor
B. Variable resistor
C. Electrolytic capacitor
D. Multi-cell battery

The answer is, as luck would have it, A. Transistor.  The transistor is probably the miracle of 20th century technology.  It’s an amplifier, a switch, and so much more.

None of the other components listed have the ability to amplify a signal.

## What is the ability to store energy in an electric field called? [T5C01]

A. Inductance
B. Resistance
C. Tolerance
D. Capacitance

Hate to say it, but this is basically a definition question.  The answer is D. Capacitance.  The easy way to remember this is just think about capacitors, the devices that actually store the electric field.  The next closest answer might be A. Inductance, which is the ability to store energy in a magnetic field, using (wait for it) an inductor.

## If an ammeter calibrated in amperes is used to measure a 3000-milliampere current, what reading would it show? [T5B06]

A. 0.003 amperes
B. 0.3 amperes
C. 3 amperes
D. 3,000,000 amperes

Don’t panic! This is a simple question about unit conversions, nothing more.

Remember your definitions of metric prefixes.  Milli means one one-thousandth, or 0.001.  Therefore, one milliampere is one one-thousandth of an ampere, or amp.  We can just multiply like this (and also remember to bring your calculator with you to the test!)

$3000 x 0.001 = ?$

and our answer is then C. 3 amperes.

## What is the most common repeater frequency offset in the 2 meter band? [T2A01]

A. Plus 500 kHz
B. Plus or minus 600 kHz
C. Minus 500 kHz
D. Only plus 600 kHz

The answer is B. Plus or minus 600 kHz.  Recall that the frequency offset is the difference between the repeater’s input frequency, and its output frequency.  You transmit from your radio on its input frequency, and you will hear the signal on its output frequency.  Whether that input frequency is 600 kHz higher or lower than the output is dependent on where in the 2m band it lies, and the particular whim of the repeater operator.  Some, like D-STAR repeaters, use non-standard offsets.  Some will use different offsets just to be different.

For example, a local repeater’s output frequency is 146.91 MHz, and its input is 146.31Mhz.  A difference of .6 Mhz, or 600 kHz.

In any case the accepted standard 2m offset is 600 kHz.

## Where should an in-line SWR meter be connected to monitor the standing wave ratio of the station antenna system? [T4A05]

A. In series with the feed line, between the transmitter and antenna
B. In series with the station’s ground
C. In parallel with the push-to-talk line and the antenna
D. In series with the power supply cable, as close as possible to the radio

OK, lets put on our “common sense” caps and come up with the answer.  A lot of times the exam questions are like this, painfully obvious.  If you’re not ready for them, they can throw you off.

In series with the station’s ground? Why would you do that? It doesn’t even make sense. Neither does in parallel with the PTT line and the antenna. How would you even wire that up?  In series with the power supply cable? The only meter you would want there, is a DC ammeter, to measure the current going into your radio.

Therefore, the answer is A. In series with the feed line, between the transmitter and the antenna.  The SWR or Standing Wave Ratio meter shows how much of your signal is being reflected back from the antenna.  The only way you will know this, is by placing the meter in the signal path from your radio to your antenna.

## Which of these components can be used as an electronic switch or amplifier? [T6B03]

A. Oscillator
B. Potentiometer
C. Transistor
D. Voltmeter

Piece of cake this one is….  Lets go through the false answers first, just to make sure.

A. Oscillator.  By definition, an oscillator simply takes a signal and, well, oscillates it.  on/off, high/low, whatever.  While definitely important in radio (you can’t get an alternating waveform without one) you can’t really make a switch out of one.  It is possible to use an oscillator as an amplifier.  It’s how vacuum tube radios get the work done (and that’s our first clue!)

B. Potentiometer.  A potentiometer is nothing more than an adjustable value resistor.  While it may have a switch built into it, such as an on/off/volume switch combination, a potentiometer by itself doesn’t make a particularly good switch.  I suppose you could use it as one, by increasing a signal via the “pot” up to or below a given “cutoff” value…. but that’s a bit of a stretch.

D. Voltmeter.  A voltmeter simply measures the voltage across a given circuit or component.  Nothing more.  It’s quite impossible to use one as a switch.  (I think!)

So all that remains is C. Transistor.  A transistor is a solid state device that toggles between states depending on an external input.  By placing (for example) a 5V load on a transistor you can essentially “flip the switch,” and removing the voltage will turn it off again.

## What causes spin fading when referring to satellite signals? [T8B09]

A. Circular polarized noise interference radiated from the sun
B. Rotation of the satellite and its antennas
C. Doppler shift of the received signal
D. Interfering signals within the satellite uplink band

It occurs because the satellite is not “fixed” in position during its orbit.  It’s tumbling end-over-end as it makes its pass.  Therefore, the antenna is always moving.

I suppose you could say we’ve just provided our answer, also.  B. Rotation of the satellite and its antennas.  Interfering signals won’t exhibit “fading” characteristics.  Doppler shift will be observed, but it manifests as a slight change in the signal frequency, depending on if the satellite is moving towards you or away from you.  And answer A. Circular(ly) polarized noise interference radiated from the sun just doesn’t make much sense at all.