Welcome

Welcome to the NewHams.info site.  Its purpose is to provide training, information and general encouragement to new or prospective amateur radio operators (hams).  Sort of a virtual “Elmer”, as we say.  Experienced hams should find it interesting and useful as well.

Organized in sort of a blog format, post topics are usually small and simple. You can scroll through the posts sequentially or search for key words or click on a category of interest.

The reader can sign up for email notification of new posts by clicking on the Follow button below Categories on the sidebar.

Topics generally cater to USA hams getting started in amateur radio with local VHF/UHF communications.  However, HF band operators and hams in other countries should find something interesting here as well.

You will see US license exam questions and answers in green boxes in various posts to refresh your knowledge.

Voice Modulation- SSB

In the last post we explored voice modulation and learned that AM and FM are the two primary modes.  We also noted that single sideband (SSB), a variant of AM, is the dominant form of voice communication on the ham bands below 50 MHz.   This post will delve into the details of SSB.

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SSB is important because it significantly improves the plain AM signal in both efficiency and bandwidth.

G2A06-2019In context of voice modulation, bandwidth means the range of frequencies the signal occupies.  In general, wider bandwidth means higher audio quality but less efficiency, and vice versa.

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The SSB signal is generated using AM but before it is transmitted the carrier and one sideband are removed.  A diagram of an AM signal helps visualize how it starts:

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SSB transmission reduces the power required (more efficient) and occupies a smaller slice of the RF spectrum (narrower bandwidth, ~3kHz), when compared to AM.

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The transmitter circuitry is essentially AM but adds carrier and sideband filters at nominal cost.  The SSB receiver is more complex and expensive than AM because it must reconstruct the missing (mirror image) sideband to create a full voice signal, as well as replace the carrier with a local signal.

Because it has to recover the opposite sideband the SSB receiver is somewhat sensitive to tuning to make the voice sound normal or natural.  You will find that voices sound quite different in clarity and pitch when tuning around the transmit frequency.   A common reaction to hearing off-tune SSB is that it sounds like a quacking duck.  A great video demonstrating some of the nuances of SSB sound and tuning can be found in the links at the bottom.

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So SSB transmits only one sideband, but which one, you ask?  The answer is either.  When the upper sideband is transmitted and received, the operation is called upper sideband (USB).

USB waveform

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Conversely, when the lower sideband is used, the operation is called lower sideband (LSB).

LSB waveform

G2A02-2019In ham radio either one is legal to use in the phone portion of the band plan but by convention LSB is used below 10MHz, and USB is used above 10MHz (note that Continue reading

Voice Modulation- AM & FM

In the last post we introduced the concept of modulation as one of the five meanings of the term mode.  Voice is the most common and obvious mode of modulation so let’s dive into that a bit as it is one of the basic concepts of amateur radio.  

Modulation is the means to impress information on a radio signal.  It’s how a circuit puts our voice onto the radio signal through a microphone.

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If you are (or were) fortunate enough to receive US Technician license training using the ARRL course book and companion slides you would find some good info as follows:

When information is added to the radio wave, (the carrier) we modulate the wave.
     •Turn the wave on and off (Morse code)
     •Speech or music
     •Data

In the physics of waves there are three characteristics we might control to impart information (three possible modulation methods or modes).

Different modulation techniques vary different properties of the wave to add the information:   amplitude, frequency, or phase.

These three are commonly known as Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).


AM is relatively easy to understand and visualize.  The RF carrier wave is varied in amplitude according to the audio waveform (as from a microphone) to create a modulated signal.

AM Graphic

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Amplitude modulation is commonly used on the familiar AM broadcast band.  It may occasionally be found on lower frequencies in the HF ham bands.  While it used to be the primary mode of voice communication in the early years, very little pure AM is used nowadays in favor of single sideband (SSB), which is a type of AM. 

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SSB is a big and important topic which merits its own write-up so we will post that soon.


FM is less intuitive and harder to visualize than AM.  The RF carrier is varied in frequency according to the audio waveform (as from a microphone) to create a modulated signal.

FM Graphic

Frequency modulation is commonly used on the familiar FM broadcast band and in ham radio above 28MHz for high quality simplex and repeater operation.

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PM is very similar to FM in the way it operates with only a technical difference between the two (integration of the baseband signal).  Here the RF carrier is varied in phase according to the audio waveform, instead of the frequency.

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Despite the terminology, many (most?) FM radios we routinely use for local communications over repeaters use PM circuitry.   The two are effectively equivalent for ham radio use; interesting discussion here and even more detailed one here.


For the ham radio operator, AM and FM are the two main voice modulation modes to understand.  SSB and PM are simply sub-sets or derivations.  This animated graphic is particularly helpful in visualizing AM vs FM:

AM vs FM animation

Useful comparisons between the two (applies equally to broadcast and ham radio):

  • AM has poorer sound quality (narrow bandwidth); FM better quality (wider).
  • AM is prone to noise interference; FM is relatively immune to electrical noise.
  • AM has narrower bandwidth (more efficient) than FM (trade-off with sound quality)
  • AM circuitry is simpler and cheaper than FM
  • With AM, transmitted power level varies with the amplitude of the signal; with FM transmitted power level is constant, regardless how much modulation (deviation) is applied.

In context of voice modulation, bandwidth means the range of frequencies the signal occupies.


Because of these differences in bandwidth and efficiency, AM and FM are generally used on different Continue reading

Mode Madness

In ham radio the term mode has at least five distinct meanings.  It’s confusing for even experienced hams so we’ll try to tame some of this madness.

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If you’re a new ham with a handheld or mobile transceiver to talk on the local repeater, mode doesn’t mean much to you.  Your basic radio has no mode controls because it can only do one thing.  In this case you are operating in voice mode using frequency modulation (FM).  Guess what?  These are the first two—and most important—of the definitions of mode.  These are operating and modulation modes.

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Below we will explore the five different contexts for mode found in US license exam questions:

  • Operating
  • Modulation
  • Propagation
  • Satellite
  • Split

Operating Mode-  The most basic definition of mode; a general category of radio transmission and reception.  There are three or four operating modes, depending on how they are categorized.  The common three are:

  • CW (continuous wave), typically for Morse code (radiotelegraphy)
  • Radiotelephony (phone), a fancy term for voice communications
  • Digital, where data is exchanged over the air, requiring computers or machines to interpret signals

For logging and awards these three categories are CW, Phone, and Digital modes.  The ARRL Logbook of The World (LoTW) adds a fourth category:  Image.  Collectively these 3 or 4 are known as mode Groups.

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Modulation Mode-  Modulation is the means to impress information on a radio signal.  It’s how a circuit puts our voice onto the radio signal through a microphone.  There are different forms (modes) of modulation which can be employed within each basic operating mode.

For example, typical modern HF transceivers support voice modes using AM, FM, and SSB modulation modes.  There are a few flavors of CW and dozens of digital modes (and the list keeps growing).  Just look at that mode group list link above.

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To further complicate matters we now have both traditional analog modulation for phone (voice) signals, and digital voice modulation as well.  Many digital modes simply modulate a SSB waveform using specific tones to represent data characters.  We live in an era where computers and radios are really working together to do amazing things.


Operating and modulation modes are hard to separate.  In fact, they sort of overlap and mash together.  Context of the discussion is key here; often it doesn’t really matter.

These two also play a role in the ITU classification of RF signals.  Refer to Types of Radio Emissions link.  Hams may occasionally log their mode according to this or a similar scheme.

Why do so many operational and modulation modes exist?  It’s largely for historic reasons as technology and electronics have advanced over the years.  In the earliest days of radio, only radiotelegraphy existed. Mode had no meaning as CW was the only possibility.   Then came voice technology and a second operating mode was born.  Going from original AM to SSB,  we then had modulation modes, adding FM as an improvement later.  Digital mode entered the scene after voice once people discovered they could encode audio signals to represent data; computer technology has made the digital mode wildly successful, if less personal, in recent years.  Image modes have been around since the early days of television but here again, computers have made them better and easier.

One other reason for different modes is Continue reading

Generator Use & Safety

Spring is [hopefully] coming soon with expected turbulent weather.  A new hurricane season is also upon us.  Both are liable to cause disruptions to utility electrical power.  Annual ARRL Field Day is also approaching.  Time to think about auxiliary power generators.

Small gasoline-powered generators are relatively common and widely available for emergency or portable electrical power.  It’s a good idea for the prepared homeowner to have one, mainly to keep the fridge/freezer cold during times of sustained power outage.  The savvy radio amateur also recognizes the importance of communications capability in a blackout scenario as well.  Power is needed to make our radios work beyond what limited battery capacity we have, particularly in emergency situations.  Most EmComm groups include generators in their plan and have them on hand.  Not every ham does.

Honda Generator

Consider having a small generator for essential power when the lights are out for hours.  Having a generator is good; knowing how to use it safely is the focus of this topic.  We will look at four related safety considerations:

  1. Carbon Monoxide hazards— CO
  2. Fuel handling and storage (fire)
  3. Generator grounding
  4. Shock hazard

Carbon Monoxide (CO) is the primary hazard with generators, since  CO is produced in the exhaust of all gasoline and natural gas combustion engines. 

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NEVER, ever run a generator inside a dwelling or garage where exhaust can seep into the occupied space.  CO is a colorless and odorless gas which can kill or injure humans and animals.   It can be detected only with chemical or electronic CO detectors; it’s wise to have detectors in every home.

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Always operate a power generator outdoors in a well-ventilated area. Continue reading

Coaxial Cable (Coax)

Because it’s commonly used in radio work, every ham should be familiar with coaxial cable, often simply called coax.

Coaxial cable is most often used between the transceiver (or T/R switch) and antenna.  In this application coax acts as the feed line (AKA transmission line) to carry transmitted and received RF signals between the antenna and radio.  Other types of feed line can be employed but coax is used by many hams because it is easy to work with and readily available.

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Coax  is a type of electrical cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. Most coaxial cables also have an insulating outer sheath or jacket.  The term coaxial comes from the inner conductor and the outer shield sharing a geometric axis.

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To be useful coaxial cable must be terminated with mating RF connectors.  An experienced ham may terminate their own coax; at greater cost they may purchase ready-made and tested assemblies.

coax ca assy  coax ca assy2

A wide variety of coaxial cable and assemblies are available with different characteristics. A quick summary of the important features:

  • Characteristic impedance
  • Signal loss
  • Power capacity
  • Diameter/weight
  • Flexibility
  • Environmental resistance

A seventh important characteristic of coax is velocity factor but that is a more advanced topic of lesser importance so we’ll simply mention it here.

Coaxial cable selection for each installation may be a compromise between features, requirements, and cost. The ham has to factor in what he needs or wants, what is available, and what it costs.


A quick look at these features of coaxial cable: Continue reading

Family Comms Plan

One of the more useful applications of ham radio (beyond the obvious enjoyment of the hobby) is for emergency communications (EmComm).  In times of man-made or natural disaster, mobile phones and internet may be inoperative or unreliable.  In such times ham radio may be the only way to communicate.

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Extend this idea to your loved ones with a family communications plan.  This would involve you, a spouse and/or children. For it to be practical all would need to be hams with at least a Technician class license.

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A family communications plan would be established and written down for all family members to have near their radios.  This would include primary, secondary, and tertiary repeaters in your area.  Also include a simplex frequency and the national call (simplex) frequency in case the repeaters aren’t working or are tied up.

Make sure to test all frequencies between expected locations (home, work, school) with a dry run to discover any interference or lack of coverage.

To help visualize how this might work, let’s say there is a major tornado outbreak that wipes out a large chunk of a mid-sized city one weekday afternoon.  Dad is at work, Mom is at home, and daughter is at school.  Cell phones (voice & text) and internet are not working so none of these people can let each other know where and how they are.  All three members know that the situation is bad so all get on their radios.  Primary and secondary repeaters are busy with dozens of other local hams reporting in damage and trying to reach their families.  Tertiary repeater is open so all three move there.  From his mobile rig Dad reports that he is fine and will make his way home ASAP.  With the base radio Mom reports minor damage with a fence section down.  With her HT Daughter reports that the college is unaffected but has to wait for clearance to leave campus.  All can share updates as needed, and may have to wait their turn on the repeater.

Great idea, but you may have objections.  Let’s address a couple of these:

  1. Getting everybody licensed.  The necessary Tech license is actually pretty easy to obtain.  Five year olds can do it with a little study and coaching.  Not a good excuse.
  2. Cost.  License exam fee is $15 or less.  Many hams already have at least one VHF/UHF FM radio.  Cheap HTs (minimal requirement) can be had for less than $50 each.  Money should not be an excuse.

The licensed family member can train/coach the others to get a license and work on getting more radios.  It may be that they already have multiple radios (base at home, mobile in car, one or two HTs) so all that is needed is establishing the plan and testing it.

Local comms using VHF/UHF is most important in disaster situations but you could extend this beyond line of sight to more regional or national distances using HF equipment.  It gets more complex in this case and practically speaking a General class license would be needed.  Here also non-voice messaging using WinLink may be useful.

An interesting article on a surge in US licensees for EmComm purposes including family members is found here.

SWR

The standing wave ratio (SWR) is an important topic to hams regardless if they are working HF, VHF, UHF or any other frequency range allocated to radio amateurs.  Unfortunately it is technically involved and somewhat complex so is not intuitive or easy for non-technical folks to understand.  We’ll give a simplified explanation of SWR here and give you a basic idea of its significance and how hams relate to it.

The simplest way to think of SWR is as a measure of impedance matching.  Most commonly it is looking at the impedance differences between transceiver, transmission line (more often coaxial cable), and antenna.

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Assuming that all modern radios and cable have 50Ω impedance, the real SWR of interest boils down to the match between the transmission line and antenna.

As we mentioned in a previous post, when impedance of a source equals load impedance the best possible signal coupling occurs. Conversely, when impedances are not the same, signals couple poorly.  This is true of all electronics circuitry involving AC waveforms.

In amateur radio SWR focus is on transceiver to antenna coupling where we want to maximize RF power transfer in both transmit and receive modes.  When impedances do not match, received signals will be weak or non-existent; when transmitting, power will not radiate well from the antenna.  The ideal or “perfect” SWR for best possible transmit/receive coupling is 1:1, meaning a 50Ω radio/transmission line to a 50Ω antenna.

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SWR is simply the ratio of two impedances being measured.  It is commonly expressed in the X:X format and the larger value is always given first, regardless of which side is higher.

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With a 50Ω radio and 50Ω coax cable, a 4:1 SWR could indicate either a 12.5Ω or a 200Ω load (antenna).  Similar examples for 50Ω cable are contained in the General class exam pool:

G9A09-2015G9A10-2015A ham’s main concern with high SWR is significant power reflected back from the load, which stresses the transmitter power amplifier.  While a 1:1 SWR is ideal, practically speaking, 1.5:1 or less is good.  Many modern transceivers automatically reduce transmit power with a SWR greater than 2:1.

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SWR can be measured Continue reading