Packet Radio

If you’re exposed to ham radio for any length of time you are sure to hear some discussion of packet radio.

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Without going into much detail, we’ll present a big-picture description here.  Just enough for you to have a basic grasp of what’s involved and give you some idea of how it might apply to you.

Packet radio is a generalized term for a digital communication mode where data is sent in bite-sized chunks (packets) via radio.  The transmission and receipt of packet data is largely automated and features data error correction for reliable messaging.

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Packet radio (sometimes shortened to just packet) blends radio and computer technologies together.  Sounds complicated but it really isn’t.  All you need besides your normal ham radio transceiver is a household computer and an interface between the two.  The heart of this interface is a Terminal Node Controller (TNC) which is an intelligent modem that converts text to audio tones and vice versa.

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Packet radio can be used between hams directly in real-time (peer-to-peer or keyboard-to-keyboard) but is more commonly used to send messages that can be retrieved on demand.  This operates more like email or mobile phone text messaging.

Slow data rates (typically 1200 baud) make large messages impractical, so packet messages should be relatively short and not have any large files attached.  120KB is the max message size accepted by some big message servers.  A 4KB message will transfer in 2-2.5 minutes under ideal conditions at 1200 baud.

Particularly useful for emergency communication (EmComm) messages, packet radio is predominately used on VHF radios (more local) but can be sent over HF bands Continue reading

National Simplex Calling Frequency

A national calling frequency in the USA is a radio frequency that is widely accepted and understood to be a place to start communicating with other hams.

This frequency is established for each RF band under the voluntary US band plan and is not regulated by the FCC.  It is routinely monitored by any number of radio amateurs and is likely to result in a response when calling CQ or Mayday or SOS.

The US band plan shows calling frequencies for various modes (CW, SSB, FM, AM, digital) in different bands.  A calling frequency list includes not only the modes but adds specific activities (expeditions, power levels) as commonly practiced.

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For new hams who are likely to get started in local VHF/UHF operation, the national calling frequencies to be concerned with are 2m and 70cm FM simplex (non-repeater).  These are 146.520MHz and 446.000MHz, respectively, and should be included in your radio’s scanned channels.  If you regularly use 1.25m, 33cm and/or 23cm bands, there are national simplex calling frequencies defined per the band plan for you to look up.

Be aware that the national calling frequency for whatever mode and activity is only a place to start communicating.  Protocol and common courtesy require that once contact is established, you move to another frequency (QSY) to leave the calling frequency open for others to use.

The national simplex calling frequency is sort of a universal (within the USA) place to make contact when you are not sure where to start.  It is particularly useful Continue reading

Ham Humor

Amateur radio operators are not all serious business; some of us actually have a sense of Yuma (and fondness for puns).  It may be obscure and occasionally off-color, but some of it is pretty funny.

You can find bits of amateur radio-related humor on various ham websites.

For our part we have created a new Ham Humor page here which contains links and a selection of favorite clean ham radio humor which will grow as new material is discovered.  You can always access this page from the NewHams.info site menu just below the top banner.

Antenna Gain

Newer amateur radio operators may read or hear some discussion of antenna gain.  The gist of it usually involves how much stronger signals are with a particular type of antenna.

This concept of antenna gain can be confusing or misleading to new hams because it sort of suggests that some antennas actually amplify received or transmitted RF signals.  Not so.

Like the decibel (dB) antenna ‘gain’ is always relative.  So when we speak of antenna gain it refers to a performance improvement compared to a different type of antenna.

More commonly, gain is used to compare highly directional antennas (beams, dishes) to monopoles or dipoles.

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While antenna gain usually emphasizes directivity it may also be used to compare two similar types with different characteristics, as efficiency is another contributing factor.  For example, we can observe and measure the relative gain of a stubby “rubber duck” handheld radio antenna (pathetic) vs. a 5/8-wave whip (much better) even though they are both vertical monopoles with the same directivity.

The two types of antennas usually referenced against are isotropic and the simple dipole.  When measuring performance of other antennas, they will often be compared to one of these two.

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If the gain impovement is relative to the theoretical isotropic antenna, the units should specify the gain as dBi.  If measured against a dipole antenna, the gain should indicate dBd.  Any other comparisons should mention the reference antenna in the text.

Some good references for antenna gain are given below: Continue reading

Mic Fright and Your First Contact

Mic fright is a general term for anxiety leading to freezing, choking or hesitating when speaking into a microphone (mic).  The psychological response of worrying about saying the right thing to an audience large or small is very natural and expected.

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Mic fright or shyness is a reality in public speaking, stage performance and similar situations.  Of course, it’s an important topic to new amateur radio operators so let’s provide some perspective and encouragement here.

Making that first voice contact over the radio can be an anxious moment for many new hams.  This can also carry over into the first several radio contacts where you worry about saying the right thing and following the rules.

First off, don’t let the “rules” make you nervous.  It mainly comes down to proper identification which means giving your call sign every 10 minutes during an exchange and at the end of your last transmission.  That’s pretty easy to remember.

Second, every ham was a newbie once and remembers what it was like not knowing exactly what they were doing.  Most will be patient and helpful, giving coaching and gentle reminders along the way as needed.

For general phone (voice) contacts, there are no real procedures and formalities to worry about; it’s more conversational, much like a phone call.  While radio amateurs often use jargon, abbreviation and technical terms (see our Ham-Speak topic), this is not mandatory.  Hopefully that takes some of the pressure off to make you more relaxed for your first few contacts.

A starting point for getting on the air the first time is to listen in on the local (VHF/UHF) repeaters and HF SSB bands for a few hours to learn what people say and how they say it.  If you follow these examples you are almost certain to be successful when transmitting on your radio.

An excellent way to get past mic fright and performance anxiety is to ease into it with Continue reading

dB, or not dB…

…what was the question?

Whether ’tis nobler in the mind to understand dB or just plod along wondering what the heck other hams, publications and spec sheets are talking about is up to you.  With all due respect to Shakespeare’s Hamlet, decibels (dB) are a frequent subject in ham radio.  All three US license class exams have questions involving dB in their pools.

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Hams new and old don’t have to be technical experts but all should at least be familiar with the decibel.  To that end we will give a simplified explanation here.

Decibels (dB) are a convenient and standardized way of measuring a change or difference between two conditions.  In audio,  radio work and electronics in general, we are often dealing with very large or very small numbers and the difference between them can be many digits long.  To make the numbers more manageable, expressing ratios of large and small values is better done using a non-linear logarithmic scale.  Logarithms are based on orders of magnitude (10,100,1000,10000… and 1/10, 1/100, 1/1000, 1/10000…).

The human ear responds to sound logarithmically so decibels are a natural fit to measuring sound levels.  Similarly, radio work behaves non-linearly in some ways so the logarithmic approach works well here.  We’re stuck with dBs, like it or not.  In amateur radio the dB is commonly used in context of amplification, feedline loss, antenna gain, filter bandwidth and RF signal strength.

Technically the decibel is a ratio between one state and another; it’s not an absolute measurement, it’s relative.  Always ask, dB relative to what?, because this is a ctitical factor.

More practically it often comes down to the amount of amplification or attenuation.  In amateur radio it almost always involves power changes so we will focus on this aspect.  Decibels can also apply to other units such as voltage but this gets a little more complicated and not as widely used in ham radio.

A power ratio is simply comparing two Continue reading

RF Connector Types

The plug that is used for terminating cables between the receiver, transmitter or transceiver and the antenna is generally referred to as the RF connector because it carries the Radio Frequency signal to/from the equipment.

In addition to mating the radio to the antenna via a transmission line (usually a coaxial cable) it may also used on RF test equipment (antenna analyzer, power and SWR meters, spectrum analyzer) and dummy loads.  All hams should be familiar with different RF connectors so we’ll give a brief high-level description here.

Good news!  There are only four common types of RF connector used in ham radio:


PL-259

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By far the most common RF connector, the PL-259 is used to connect most all modern HF transceivers and VHF/UHF mobile rigs to the antenna.  The PL designation stands for plug and the 259 is an old US Signal Corps assignment.  It has a male center pin and female thread.

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The mating  receptacle found on the radios and equipment is known as a SO-239.  SO for socket, it features a female center receptacle and has male threads.

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The PL-259 and SO-239 combination (details here) is frequently referred to as a “UHF connector” although this designation comes from the 1930s when UHF was considered anything above 30MHz.  It has performance limitations above 100MHz so other connector types are more suitable for true UHF use.

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N-type Continue reading