XPost: rec.radio.amateur.moderated

KB6NU's Ham Radio Blog

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Amateur radio in the news: VOA museum a historical marvel,

Posted: 23 Jan 2022 09:00 AM PST https://www.kb6nu.com/amateur-radio-in-the-news-voa-museum-a-historical-marvel/?utm_source=feedburner&utm_medium=email

Voice heard round the world: Voice of America museum near Cincinnati a historical marvel
The 250 kW Collins transmitter is one of the things youll see when you
visit the VOA Museum.

WEST CHESTER, Ohio — Imagine, if you will, a voice so strong that it shakes the very foundations of global tyranny.
In the early days of World War II, a group of Americans, including
President Franklin Roosevelt, actor and director John Houseman and
Cincinnati entrepreneur Powell Crosley Jr. imagined such a voice, one that could counter Nazi propaganda in Hitler’s own backyard.
They named it The Voice of America.
read more

I got to visit this museum the last time I went to the Dayton Hamvention.
If you ever get to Dayton, make sure this is on your list of things to doDan


From the Austin (MN) Daily Herald.
Ask a Trooper: Ham radio license allows for scanner




Question: I have a friend who drives around with a scanner in his vehicle.
He says because he has a ham radio license it’s legal, is that true?

Answer: Your friend is correct. Peace officers, the State Patrol, and
people with an amateur radio license issued by the Federal Communications Commission are allowed to have a scanner in their vehicle. Emergency
response personnel are also allowed to use scanners if they’re employed or authorized by the federal government, the state, or a political subdivision
to provide fire suppression, police protection, emergency medical services,
or emergency activities relating to health and safety and in compliance
with the requirements of the state statute.


People not authorized to use a scanner could be found guilty of a
misdemeanor. Second and subsequent offenses are gross misdemeanors.

People using such devices while committing or attempting to commit a felony could be convicted of a felony.

You can avoid a ticket — and a crash — if you simply buckle up, drive at safe speeds, pay attention, and always drive sober.  Help us drive
Minnesota Toward Zero Deaths. If you have any questions concerning traffic related laws or issues in Minnesota send your questions to Sgt. Troy Christianson – Minnesota State Patrol at 2900 48th Street NW, Rochester MN 55901-5848 or reach at, [email protected]).


From the Georgetown (CA) Gazette
Radio to the rescue



As the most recent series of storms showed, power and communications infrastructure can be vulnerable, resulting in extended outages. Many El Dorado County (CA) residents not only lost power during these storms but
also vital phone and internet services failed and residents could not reach 911. In areas where heavy snow fell residents were cut off or trapped at
home and did not know how or where to obtain vital help or supplies. Even
the 24/7 emergency telephone outside the Georgetown Fire Department’s Volcanoville fire station went dead due to downed power and telephone lines.

Since 2019 the El Dorado County Amateur Radio Club has implemented
neighborhood radio watch programs throughout El Dorado County.
read more








The post Amateur radio in the news: VOA museum a historical marvel,
appeared first on KB6NUs Ham Radio Blog.


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2022 No Nonsense Technician Class License Study Guide: Antennas and feed
lines

Posted: 22 Jan 2022 07:25 AM PST https://www.kb6nu.com/2022-no-nonsense-technician-class-license-study-guide-antennas-and-feed-lines/?utm_source=feedburner&utm_medium=email

Antennas and feed lines
Antenna types
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. Because half-wave dipole antennas
can be quite long—a 40m half-wave dipole antenna, for example, is about 66 feet long—they are normally mounted horizontally between two vertical supports.

T9A03

Which of the following describes a simple dipole oriented parallel to
Earths surface?

A. A ground-wave antenna

B. A horizontally polarized antenna

C. A travelling-wave antenna

D. A vertically polarized antenna
When putting up a dipole antenna, you should consider the orientation of
the antenna because it radiates better in some directions than others.

T9A10

In which direction does a half-wave dipole antenna radiate the strongest signal?

A. Equally in all directions

B. Off the ends of the antenna

C. In the direction of the feed line

D. Broadside to the antenna
So, for example, if you live in Kansas, you might want to orient the
antenna so that the wire runs north to south. The antenna will then radiate best east and west, meaning that you’ll be able to cover most of the U.S.
The length of a dipole antenna is actually about 5% shorter than the value
that you would calculate using the formula wavelength (m) = 300 / frequency (MHz). The reason for this is that there will be some stray capacitance
between the wire and the ground and other objects near the antenna. Let’s take a look at an example.

T9A09

What is the approximate length, in inches, of a half-wavelength 6 meter
dipole antenna?

A. 6

B. 50

C. 112

D. 236
Here’s how to make this calculation. One half wavelength is 3 m. 3 m x 39.4 in/m = 118.2 inches. Since the length of the antenna is about 5% shorter
than this calculated value, the approximate length of the antenna will be
118.2 inches x 0.95, or about 112 inches.
Once you have built a dipole antenna, chances are it wont be resonant on
the frequency you want. To tune the antenna, you need to determine its
resonant frequency and then make it longer or shorter. To decrease the
resonant frequency of an antenna, you lengthen it, because the wavelength
is longer. Conversely, to increase the resonant frequency, you shorten the antenna.

T9A05

Which of the following increases the resonant frequency of a dipole antenna?

A. Lengthening it

B. Inserting coils in series with radiating wires

C. Shortening it

D. Adding capacitive loading to the ends of the radiating wires
The final length will depend on the height at which you mount the antenna
and any trees or buildings that are nearby.
Perhaps the second-most popular type of amateur radio antenna is the quarter-wave vertical antenna. The radiator of a vertical antenna is
mounted perpendicular to the Earth. This makes it vertically-polarized,
because the electric field will have the same orientation as the antenna’s radiator.
Like the half-wave dipole antenna, the length of a quarter-wave vertical antenna will be about 5% shorter than the calculated quarter wavelength.

T9A08

What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?

A. 112

B. 50

C. 19

D. 12
The wavelength of a 146 MHz radio wave is approximately 2 m. One quarter of
a wavelength is therefore 0.5 m. 0.5 m x 39.4 in/m = 19.7 in. 19.7 in x
0.95 ≈ 19 in.
Because full-size, half-wave or quarter-wave HF antennas can be very long,
many amateurs use a technique called “loading” to shorten them. You can use either inductors or capacitors to load an antenna, but the most common way
is to use an inductor. In either case, loading an antenna makes it seem electrically longer to a signal at the antenna feed point.

T9A02

Which of the following describes a type of antenna loading?

A. Electrically lengthening by inserting inductors in radiating elements

B. Inserting a resistor in the radiating portion of the antenna to make it resonant

C. Installing a spring in the base of a mobile vertical antenna to make it
more flexible

D. Strengthening the radiating elements of a beam antenna to better resist
wind damage
While this technique does allow you to shorten an antenna, the shortened antenna will not be as efficient as a full-size antenna.
Many amateurs use directional or beam antennas. Beam antennas concentrate
the power that is applied to them in onedirection, thereby increasing the signal strength in that direction, when compared to a reference antenna,
such as a dipole antenna. We call this increase in signal strength antenna gain. There are many different types of beam antennas, including the Yagi,
the quad, and the dish antenna.

T9A01

What is a beam antenna?

A. An antenna built from aluminum I-beams

B. An omnidirectional antenna invented by Clarence Beam

C. An antenna that concentrates signals in one direction

D. An antenna that reverses the phase of received signals

T9A11

What is antenna gain?

A. The additional power that is added to the transmitter power

B. The additional power that is required in the antenna when transmitting
on a higher frequency

C. The increase in signal strength in a specified direction compared to a reference antenna

D. The increase in impedance on receive or transmit compared to a reference antenna

T9A06

Which of the following types of antenna offers the greatest gain?

A. 5/8 wave vertical

B. Isotropic

C. J pole

D. Yagi
Most handheld VHF and UHF transceivers come with short, flexible antennas called “rubber duck” antennas. These antennas use inductive loading to make them shorter than a full-sized antenna. Loading them like this makes them
less efficient than a full-sized quarter-wavelength vertical antenna.

T9A04

What is a disadvantage of the short, flexible antenna supplied with most handheld radio transceivers, compared to a full-sized quarter-wave antenna?

A. It has low efficiency

B. It transmits only circularly polarized signals

C. It is mechanically fragile

D. All these choices are correct
This disadvantage is compounded if you try to use a handheld VHF
transceiver inside a vehicle. The shielding effect of the vehicle’s metal frame will prevent some of your signal from getting outside the vehicle and block some of the signal from a repeater or other station from reaching the antenna inside the vehicle.

T9A07

What is a disadvantage of using a handheld VHF transceiver with a flexible antenna inside a vehicle?

A. Signal strength is reduced due to the shielding effect of the vehicle

B. The bandwidth of the antenna will decrease, increasing SWR

C. The SWR might decrease, decreasing the signal strength

D. All these choices are correct
A better option is to use an externally-mounted antenna. A popular choice
for an externally-mounted mobile antenna is the 5/8-wavelength vertical antenna. One reason that it is a popular choice, is that it has more gain
than a 1/4-wavelength antenna.

T9A12

What is an advantage of a 5/8 wavelength whip antenna for VHF or UHF mobile service?

A. It has more gain than a 1/4-wavelength antenna

B. It radiates at a very high angle

C. It eliminates distortion caused by reflected signals

D. It has 10 times the power gain of a 1/4 wavelength whip


Feed lines and connectors
Feed lines connect radios to antennas. There are many different types of
feed lines, including coaxial cable, ladder line, twin lead, and open-wire
feed line, but coaxial cable is the most common type.

T9B03

Why is coaxial cable the most common feed line for amateur radio antenna systems?

A. It is easy to use and requires few special installation considerations

B. It has less loss than any other type of feed line

C. It can handle more power than any other type of feed line

D. It is less expensive than any other type of feed line
Perhaps the most important consideration when choosing a feed line is the impedance of the feed line. In general, you should match the impedance of
the feed line to the output impedance of the transmitter and the input impedance of the antenna.

T5C12

What is impedance?

A. The opposition to AC current flow

B. The inverse of resistance

C. The Q or Quality Factor of a component

D. The power handling capability of a component

T5C05

What is the unit of impedance?

A. The volt

B. The ampere

C. The coulomb

D. The ohm
Most amateur radio transmitters have an output impedance of 50 ohms, and
most antennas have an input impedance close to 50 ohms. Because this is the case, most coaxial cable used in amateur radio stations has an impedance of
50 ohms.

T9B02

What is the most common impedance of coaxial cables used in amateur radio?

A. 8 ohms

B. 50 ohms

C. 600 ohms

D. 12 ohms
RG-58 and RG-213 are two types of coaxial cable often used in amateur radio stations. Both have an impedance of 50 ohms.
Despite being the most popular type of feedline for amateur radio stations, coaxial cable does have some disadvantages. One of them is that it may be
lossy at high frequencies. Some coax cable types have more loss than others.

T9B05

What happens as the frequency of a signal in coaxial cable is increased?

A. The characteristic impedance decreases

B. The loss decreases

C. The characteristic impedance increases

D. The loss increases

T9B10

What is the electrical difference between RG-58 and RG-213 coaxial cable?

A. There is no significant difference between the two types

B. RG-58 cable has two shields

C. RG-213 cable has less loss at a given frequency

D. RG-58 cable can handle higher power levels
In general, the smaller the diameter of the coaxial cable, the higher the losses will be at higher frequencies. And, the longer the feed line, the
higher the losses. So, for example, using RG-58 coax as the feed line for
an 80 m dipole might be just fine, but you don’t want to use 50 feet of
RG-58 to connect your 440 MHz FM transceiver to an antenna on your roof or
on a tower.
Even RG-213 coaxial cable is not really the best choice for use at VHF and
UHF frequencies. Most repeaters, for example, use air-insulated hard line coaxial cable for the feed line.

T9B11

Which of the following types of feed line has the lowest loss at VHF and
UHF?

A. 50-ohm flexible coax

B. Multi-conductor unbalanced cable

C. Air-insulated hardline

D. 75-ohm flexible coax
Many other factors, including water intrusion, high SWR, and multiple connectors in line can cause losses in a coaxial feed line.

T9B08

Which of the following is a source of loss in coaxial feed line?

A. Water intrusion into coaxial connectors

B. High SWR

C. Multiple connectors in the line

D. All these choices are correct
Moisture contamination not only causes higher feed line losses. If not addressed, it can also cause coaxial cables to fail.

T7C09

Which of the following causes failure of coaxial cables?

A. Moisture contamination

B. Solder flux contamination

C. Rapid fluctuation in transmitter output power

D. Operation at 100% duty cycle for an extended period
One way that moisture enters a cable is via cracks in the cable’s outer jacket caused by ultraviolet light.

T7C10

Why should the outer jacket of coaxial cable be resistant to ultraviolet
light?

A. Ultraviolet resistant jackets prevent harmonic radiation

B. Ultraviolet light can increase losses in the cable’s jacket

C. Ultraviolet and RF signals can mix, causing interference

D. Ultraviolet light can damage the jacket and allow water to enter the
cable
Air-insulated hard line is also susceptible to moisture problems.

T7C11

What is a disadvantage of air core coaxial cable when compared to foam or
solid dielectric types?

A. It has more loss per foot

B. It cannot be used for VHF or UHF antennas

C. It requires special techniques to prevent moisture in the cable

D. It cannot be used at below freezing temperatures
PL-259 connectors are the most common type of connectors used on coaxial
cables in amateur radio stations.

T9B07

Which of the following is true of PL-259 type coax connectors?

A. They are preferred for microwave operation

B. They are watertight

C. They are commonly used at HF and VHF frequencies

D. They are a bayonet-type connector
One problem with PL-259 connectors is that they are not the most suitable connector when operating at higher frequencies. Type N connectors are a
much better choice for UHF frequencies.

T9B06

Which of the following RF connector types is most suitable for frequencies above 400 MHz?

A. UHF (PL-259/SO-239)

B. Type N

C. RS-213

D. DB-25
Coaxial cable connectors can be a real pain to install properly and are a frequent cause of failure. When installing a feed line, make sure that your coaxial connectors are crimped or soldered properly and that they make
solid connections with one another.

T9B09

What can cause erratic changes in SWR?

A. Local thunderstorm

B. Loose connection in the antenna or feed line

C. Over-modulation

D. Overload from a strong local station


Standing wave ratio and antenna measurements
Standing wave ratio, or SWR, is a term you’ll often hear when talking about antennas and feed lines. It is a measure of how well a load, such as an antenna, is matched to a transmission line. When we say that an antenna is matched to a transmission line, we mean that the impedance of the
transmission line is equal to the impedance of the antenna. If you measure
the SWR of a perfectly-matched antenna system, the SWR meter will read 1:1.
The higher the SWR reading, the greater the mismatch between the antenna
and the transmission line.

T9B12

What is standing wave ratio (SWR)?

A. A measure of how well a load is matched to a transmission line

B. The ratio of amplifier power output to input

C. The transmitter efficiency ratio

D. An indication of the quality of your station’s ground connection

T7C04

What reading on an SWR meter indicates a perfect impedance match between
the antenna and the feed line?

A. 50:50

B. Zero

C. 1:1

D. Full Scale

T7C06

What does an SWR reading of 4:1 indicate?

A. Loss of -4 dB

B. Good impedance match

C. Gain of +4 dB

D. Impedance mismatch
When the feed line impedance matches the antenna input impedance, the SWR
will be low. Low SWR on a coaxial cable feed line is a good thing because
when the feed line impedance matches the antenna input impedance, signal
losses are low, meaning that the antenna will radiate more power.

T9B01

What is a benefit of low SWR?

A. Reduced television interference

B. Reduced signal loss

C. Less antenna wear

D. All these choices are correct
The bigger the mismatch is between the feed line and the load, the higher
the SWR will be. The higher the SWR, the more power is lost in the feed
line. Power converted into heat is not radiated by the antenna, meaning
your radiated signal will be weaker.

T7C07

What happens to power lost in a feed line?

A. It increases the SWR

B. It is radiated as harmonics

C. It is converted into heat

D. It distorts the signal
Most amateur radio transceivers today will reduce output power if the
antenna system SWR is high. The reason for this is to protect the radio
from being damaged by reflected power.

T7C05

Why do most solid-state transmitters reduce output power as SWR increases beyond a certain level?

A. To protect the output amplifier transistors

B. To comply with FCC rules on spectral purity

C. Because power supplies cannot supply enough current at high SWR

D. To lower the SWR on the transmission line
An SWR meter is not the only way to measure SWR. You can also measure SWR
with a directional wattmeter.

T7C08

Which instrument can be used to determine SWR?

A. Voltmeter

B. Ohmmeter

C. Iambic pentameter

D. Directional wattmeter
When using a directional wattmeter, you first measure the forward power,
then the reflected power, and using those two values, calculate the SWR. Another test instrument that you can use to measure the SWR of an antenna system is the antenna analyzer. The SWR of an antenna system will be 1:1 at
the resonant frequency.

T7C02

Which of the following is used to determine if an antenna is resonant at
the desired operating frequency?

A. A VTVM

B. An antenna analyzer

C. A Q meter

D. A frequency counter
Some antenna analyzers will also let you measure capacitive reactance and inductive reactance, and also be used as an RF signal generator. These capabilities may be useful in applications other than antenna analysis.
If an antennas impedance is not 50 ohms, the impedance at the transmitter
end of a feed line will not be 50 ohms. Dont worry, though. You can use a device called an antenna tuner or antenna coupler to transform the
impedance from whatever it happens to be to 50 ohms. We call this process impedance matching.

T9B04

What is the major function of an antenna tuner (antenna coupler)?

A. It matches the antenna system impedance to the transceivers output
impedance

B. It helps a receiver automatically tune in weak stations

C. It allows an antenna to be used on both transmit and receive

D. It automatically selects the proper antenna for the frequency band being used
In addition to instruments that make antenna measurements, its helpful to
have an instrument that can simulate an antenna. Thats the purpose of a
dummy load. Basically, a dummy load is just a big 50 Ω resistor that
provides a known impedance to the transmitter and converts the transmitter output power into heat so that it does not get radiated. If a transmitter operates normally when a dummy load is connected to it, you can be
reasonably sure that your transmitter is good.

T7C01

What is the primary purpose of a dummy load?

A. To prevent transmitting signals over the air when making tests

B. To prevent over-modulation of a transmitter

C. To improve the efficiency of an antenna

D. To improve the signal-to-noise ratio of a receiver

T7C03 (B)

What does a dummy load consist of?

A. A high-gain amplifier and a TR switch

B. A non-inductive resistor mounted on a heat sink

C. A low-voltage power supply and a DC relay

D. A 50-ohm reactance used to terminate a transmission line


The post 2022 No Nonsense Technician Class License Study Guide: Antennas
and feed lines appeared first on KB6NUs Ham Radio Blog.


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Trade magazine articles: Op amps, microcontroller measures frequency and period, antenna basics

Posted: 22 Jan 2022 06:25 AM PST https://www.kb6nu.com/trade-magazine-articles-op-amps-microcontroller-measures-frequency-and-period-antenna-basics/?utm_source=feedburner&utm_medium=email


All three articles in this post are from Electronic Design.Dan




Op Amps for Linear Designs: Back to the Basics
Op amps are the basic building blocks for much of linear circuit design.
You probably learned about them in college and even designed some products containing an op amp.  As an electronic engineer, you will at some point in your career probably need to design a linear circuit.








If you’re not an advanced linear or analog circuit designer, perhaps the
best way to fulfill your linear design needs is to use an op amp. These ICs
are widely available, inexpensive, and can be configured in hundreds if not thousands of ways to satisfy most linear requirements. Here’s a summary and update on these versatile devices..more












Microcontroller Efficiently Measures Frequency and Period












When you need to take accurate timing measurements in hardware without overloading a microcontroller, the signal measurement timer module (SMT) in
the Microchip16F1619 PIC microcontrolleris perfectly suitable for this application. The SMT module captures features of a signal such as Period
and Frequency, among others. This design measures input frequency signals within the range of 8 Hz to 10 MHz, and Period signals within the range of
0.1 µs to 125 ms..more











Welcome To Antennas 101












Antennas are much more than simple devices connected to every radio.
They’re the transducers that convert the voltage from a transmitter into a radio signal. And they pick radio signals out of the air and convert them
into a voltage for recovery in a receiver.

Typically taken for granted and left for the last minute in a design,
antennas are nonetheless critical for establishing and maintaining a
reliable radio connection. They may look complex and enigmatic to most engineers, especially EEs working with wireless applications for the first time—not to mention that they come in a seemingly infinite variety of sizes and shapes. However, a brief review of the essentials can help allay any
design worries.more







The post Trade magazine articles: Op amps, microcontroller measures
frequency and period, antenna basics appeared first on KB6NUs Ham Radio
Blog.

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