2014 Tech study guide: antenna types, polarization

Three questions were added to this section, the question on antenna loading and two on mobile antenna installation. I think these are good changes…Dan

The most common, and perhaps the simplest, antenna is the half-wave dipole antenna. As the name suggests, it measures close to one half wavelength from one end of the antenna to the other. A simple dipole mounted so the conductor is parallel to the Earth’s surface is a horizontally polarized antenna. (T9A03) The direction that radiation is strongest from a half-wave dipole antenna in free space is broadside to the antenna. (T9A10)

The length of a dipole antenna is actually about 5% shorter than the value that you would calculate using the formula wavelength in meters equals 300 divided by frequency in megahertz. The reason for this is that the velocity of a radio wave through wire is lower than the velocity of the wave in free space. Consequently, the approximate length of a 6 meter 1/2-wavelength wire dipole antenna is 112 inches. (T9A09) To make a dipole antenna resonant on a higher frequency, you would shorten it. (T9A05)

Perhaps the second-most popular type of amateur radio antenna is the quarter-wave vertical antenna. For vertical antennas, the electric field is perpendicular to the Earth. (T9A02) This makes them vertically-polarized antennas. The approximate length of a quarter-wavelength vertical antenna for 146 MHz is 19 inches. (T9A08)

Because HF antennas can be very long, many amateurs use a technique called “loading” to shorten them. Loading, when referring to an antenna, means inserting an inductor in the radiating portion of the antenna to make it electrically longer. (T9A14)

Another popular type of antenna is the beam antenna. A beam antenna is an antenna that concentrates signals in one direction. (T9A01) The quad, Yagi, and dish antennas are directional antennas. (T9A06) The gain of an antenna is the increase in signal strength in a specified direction when compared to a reference antenna. (T9A11)

Most hand-held VHF and UHF transceivers come with what’s called a “rubber duck” antenna. A disadvantage of the “rubber duck” antenna supplied with most handheld radio transceivers is that it does not transmit or receive as effectively as a full-sized antenna. (T9A04) A good reason not to use a “rubber duck” antenna inside your car is that signals can be significantly weaker than when it is outside of the vehicle. (T9A07)

A better option is to use an externally-mounted antenna. VHF or UHF mobile antennas are often mounted in the center of the vehicle roof because a roof mounted antenna normally provides the most uniform radiation pattern. (T9A13) Many mobile installations use a 5/8-wavelength vertical antenna. One reason to use a properly mounted 5/8 wavelength antenna for VHF or UHF mobile service is that it offers a lower angle of radiation and more gain than a 1/4 wavelength antenna and usually provides improved coverage. (T9A12)

2014 Tech study guide: schematics and components (part 4)

My study guide covers the questions in T6C and T6D of the question pool in four separate sections. Overall, the question pool committee added several questions to T6C and T6D. In this section, T6D12 is an added question…Dan

There are many different types of components in modern radio equipment. Below, we will describe the types of components you will need to know about to pass the Technician Class license examination.

A relay is a switch controlled by an electromagnet. (T6D02)

Meters are devices used to indicate many different values. For example, a meter can be used to display signal strength on a numeric scale. (T6D04) Meters are also used to indicate the output voltage of a power supply, the output power of a transmitter, and many other parameters.

Integrated circuit is the name of a device that combines several semiconductors and other components into one package. (T6D09) Integrated circuits may perform either analog or digital functions. One type of analog integrated circuit that is very common is the voltage regulator. A regulator is the type of circuit that controls the amount of voltage from a power supply. (T6D05)

An LED is commonly used as a visual indicator. (T6D07) LED is short for light-emitting diode. They come in a variety of colors.

When connecting electronic assemblies together, we often use cables with one or more conductors. Some of those conductors may have a shield around them that is connected to ground. A common reason to use shielded wire is to prevent coupling of unwanted signals to or from the wire. (T6D12)

2014 Tech study guide: schematics and components (part 3)

T3

My study guide covers the questions in T6C and T6D of the question pool in four separate sections. Overall, the question pool committee added several questions to T6C and T6D. In this section, T6D11 is an added question…Dan

The circuit shown in Figure T3 is the output circuit of a transmitter. Component 3 in figure T3 is a variable inductor. (T6C10)

There are two variable capacitors in this circuit—component 2 and the unlabeled component. A capacitor is used together with an inductor to make a tuned circuit. (T6D08)

Component 4 in figure T3 is an antenna. (T6C11)

An inductor and a capacitor connected in series or parallel to form a filter is a simple resonant or tuned circuit. (T6D11) When the capacitor and inductor are connected in series, the circuit has a very low impedance at the resonant frequency. When the capacitor and inductor are connected in parallel, the circuit has a very high impedance at the resonant frequency.

2014 Tech study guide: schematics and components (part 2)

My study guide covers the questions in T6C and T6D of the question pool in four separate sections. Overall, the question pool committee added several questions to T6C and T6D, but in part 2 below, all of the questions and answers are the same as in the 2010 question pool…Dan

The circuit shown in Figure T2 is a simple power supply. Component 2 is a fuse.

T2

Component 3 in figure T2 represents a single-pole single-throw switch. (T6D03) It turns the power supply on and off.

Component 4 in figure T2 is a transformer. (T6C09) A transformer is commonly used to change 120V AC house current to a lower AC voltage for other uses. (T6D06)

A rectifier changes an alternating current into a varying direct current signal. (T6D01) Component 5 in Figure T2 is a rectifier diode.

Component 6 in figure T2 is a capacitor. (T6C06) It is a filter capacitor, whose function is to help filter out the 60 Hz component of the rectified AC.

Component 8 in figure T2 is a light emitting diode. (T6C07). It is a pilot light, serving to alert a user when the power supply is on.

Component 9 in figure T2  is a variable resistor. (T6C08) Its purpose is to limit the output current of the supply.

2014 Tech study guide: schematics and components (part 1)

My study guide covers the questions in T6C and T6D of the question pool in four separate sections. Overall, the question pool committee added several questions to T6C and T6D, but in part 1 below, all of the questions and answers are the same as in the 2010 question pool…Dan

Schematic symbols is the name for standardized representations of components in an electrical wiring diagram. (T6C01) The symbols on an electrical circuit schematic diagram represent electrical components. (T6C12) The way components are interconnected is accurately represented in electrical circuit schematic diagrams. (T6C13) T1 Figure T1 is a schematic diagram of a simple circuit that turns on a lamp when a positive voltage is applied to the input. Component 1 in figure T1 is a resistor. (T6C02) Its function is to limit the input current.

Component 2 in figure T1 is a transistor. (T6C03) Its function is to switch the current through the lamp on and off. The function of component 2 in Figure T1 is to control the flow of current. (T6D10)

Component 3 in figure T1 is the lamp. (T6C04) Component 4 in figure T1 is a battery. (T6C05) This battery supplies the current that lights the lamp.

2014 Tech study guide: math for electronics

Below is the “Math for electronics” section of the 2014 edition of the No-Nonsense Technician Class License Study Guide. As always, comments welcome…Dan

When dealing with electrical parameters, such as voltage, resistance, current, and power, we use a set of prefixes to denote various orders of magnitude:

  • milli- is the prefix we use to denote 1 one-thousandth of a quantity. A milliampere, for example, is 1 one-thousandth of an ampere, or .001 A. Often, the letter m is used instead of the prefix milli-. 1 milliampere is, therefore, 1 mA.
  • micro- is the prefix we use to denote 1 millionth of a quantity. A microvolt, for example, is 1 millionth of a volt, or .000001 V. Often you will see the Greek letter mu, or μ, to denote the prefix micro-. 1 microvolt is, therefore, 1 μV.
  • pico- is the prefix we use to denote 1 trillionth of a quantity. A picovolt is 1 trillionth of a volt, or .000001 μV.
  • kilo- is the prefix we use to denote 1 thousand of a quantity. A kilovolt, for example, is 1000 volts. Often, the letter k is used instead of the prefix kilo-. 1 kilovolt is, therefore, 1 kV.
  • mega- is the prefix we use to denote 1 million of a quantity. A megahertz, for example, is 1 million Hertz. The unit of frequency is the Hertz. (T5C05) It is equal to one cycle per second. Often, the letter M is used instead of the prefix mega-. 1 megahertz is, therefore, 1 MHz.

Here are some examples:

  • 1,500 milliamperes is 1.5 amperes. (T5B01)
  • Another way to specify a radio signal frequency of 1,500,000 hertz is 1500 kHz.
    (T5B02)
  • One thousand volts are equal to one kilovolt. (T5B03)
  • One one-millionth of a volt is equal to one microvolt. (T5B04)
  • If an ammeter calibrated in amperes is used to measure a 3000-milliampere current,
    the reading it would show would be 3 amperes. (T5B06)
  • If a frequency readout calibrated in megahertz shows a reading of 3.525 MHz, it would
    show 3525 kHz if it were calibrated in kilohertz. (T5B07)
  • 1 microfarad is 1,000,000 picofarads. (T5B08) (Farad is the unit for capacitance.)
  • 28.400 MHz is equal to 28,400 kHz. (T5B12)
  • If a frequency readout shows a reading of 2425 MHz, the frequency in GHz is 2.425 GHz. (T5B13)

When dealing with ratios—especially power ratios—we often use decibels (dB). The reason for this is that the decibel scale is a logarithmic scale, meaning that we can talk about large ratios with relatively small numbers. At this point, you don’t need to know the formula used to calculate the ratio in dB, but keep in mind the following values:

  • 3 dB is the approximate amount of change, measured in decibels (dB), of a power increase from 5 watts to 10 watts. (T5B09) This is a ratio of 2 to 1.
  • -6 dB is the approximate amount of change, measured in decibels (dB), of a power decrease from 12 watts to 3 watts. (T5B10) This is a ratio of 4 to 1.
  • 10 dB is the approximate amount of change (actually it is the EXACT amount of change), measured in decibels (dB), of a power increase from 20 watts to 200 watts. (T5B11) This is a ratio of 10 to 1.

Should amateur radio operators know how to use the Internet?

My No-Nonsense Technician Class License Study Guide is available for free here on KB6NU.Com

My No-Nonsense Technician Class License Study Guide is available for free here on KB6NU.Com

Often, I get requests from hams teaching courses to print a number of copies of my No-Nonsense Technician Class Amateur Radio License Study  Guide. I normally reply that individuals are free to download and print the study guide if they like, but that I don’t usually give permission to print out many copies. There are a couple of reasons for this, the main one being that when individuals each download their own copies, I get a better indication of how many are actually using it.

Sometimes, they’ll come back and say that the reason they’re asking for permission to print copies is that some of the students aren’t very Internet-savvy, and that they may not know how to get on my website and download the study guide. That, of course, begs the question, “Should amateur radio operators know how to use the Internet?”

The NCVEC question pool committee obviously thinks so. There are a number of questions on the test about IRLP and EchoLink, both of which use the Voice Over Internet Protocol (VOIP) to allow communications over the Internet.

Don’t get me wrong. I love it that folks want to use my study guide, and I will continue to make it free for as long as I continue to produce it. It seems to me, however, that knowing how to use the Internet is now a basic skill that every ham should have. That being the case, I’m going to continue to ask that teachers that want to use my study have their students download it from my website and not print copies for them.

Transforming impedances: Question G5C07

In the last two weeks, I’ve received e-mails from two readers of The No-Nonsense General-Class License Study Guide. Both questioned my explanation of how transformers transform impedance. I wrote:

Transformers are also used to transform impedances. The impedance ratio is also related to the turns ratio, but the transformation is equal to the square of the turns ratio. The turns ratio of a transformer used to match an audio amplifier having a 600-ohm output impedance to a speaker having a 4-ohm impedance is 12.2 to 1. (G5C07)

Doug wrote, “The only way I can reproduce the calculation is by taking the square root of the turns ratio.” His comment made me see where my explanation could be a bit misleading. I wrote back:

Think about it this way. An impedance transformation can go either way. When transforming from a higher impedance to a lower impedance, you divide by the square root of the turns ratio. When transforming a lower impedance to a higher impedance, you multiply by the square of the turns ratio. In either case, the impedance ratio is “related” to the square of the turns ratio.

I love getting feedback from my readers. Feedback like this helps me improve my study guides. If you have used one of my study guides, and have a comment or question about any of the material, please feel free to contact me.

ARRL instructor’s newsletter sports new name, look

Radio Waves

It’s been a long time coming—more than two and a half years, in fact—but the ARRL has finally published another issue of the newsletter for  instructors and teachers. It’s now called Radio Waves, and the October 2013 issue contains articles on:

  • teaching amateur radio in elementary school,
  • the new band chart of Tech-only privileges,
  • an exam-prep game modeled on the game show Jeopardy,
  • the upcoming 2014 update to the Technician Class question pool, and
  • 2013 licensing statistics.

Unfortunately, the majority of the issue is devoted to the ARRL’s Education and Technology Program, which sponsors programs for classroom teachers. I may be missing something here, but while I think that these are useful programs, they have little value for instructors teaching amateur radio classes.

At any rate, let’s hope that it doesn’t take the ARRL another two and a half years before they publish another issue of this newsletter.

Thanks to all my customers

extra-class-cover-375x500When I sign into the admin section of my website, I get a summary of how well sales of my No-Nonsense Extra Class License Study Guide are going.  Here are the numbers from the last quarter.

  • July 2013 – 32
  • August 2013 – 39
  • September 2013 – 37

Over the past year, by quarter, I’ve sold the following number of copies:

  • Jul 2013 – Oct 2013 – 112
  • Mar 2013 – Jul 2013 – 115
  • Dec 2012 – Mar 2013 – 133
  • Oct 2012 – Dec 2012 – 73

These are just the sales made from my site, and don’t include the sales on Amazon or Barnes&Noble.

I would just like to thank you all for buying my books. It’s been very gratifying to me to be able to help so many hams get and upgrade their licenses. Please pass the word about my study guides if you found them at all useful.

Looking to the future, the Technician Class question pool will be updated in 2014. You can be sure that I will be updating my study guide well in advance the July 1 switchover date. My goal is to have it available by mid-May 2014 and bring some copies with me to Dayton.