dB, or not dB…

AF5NP dB, Decibel

…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

AF5NP BNC, Connector, N-Type, PL-259, RF, SMA

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

220px-uhf_pl_connector     250px-uhf-connector

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 →

How Far Can I Communicate?

AF5NP Antenna, Distance, DX, High Frequency (HF), Signal, VHF/UHF

One of the more interesting questions a new or prospective ham will have is, “how far can I communicate?”  The frustrating answer is, “it depends…” (don’t you hate hearing that?)

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There are many factors involved in the limits to distance of radio communication.  Carrier frequency is the huge one, followed by operating mode, antenna characteristics and transmit power. Time of day, solar activity and the season (spring, summer, autumn, winter) also have a big impact on range.  Natural (thunderstorms, aurora, geologic, cosmic) and man-made (crowded band, power lines, noisy electronics) interference can also limit or disrupt a radio contact.  Also factor in the use of repeaters (terrestrial and space satellites) or reflective objects (structures, moon, meteor showers), plus unusual weather conditions and you have a lot to consider.

Since many hams get started using VHF/UHF radios for local communication, let’s talk about this first.  VHF/UHF radio wave propagation is normally limited to line-of-sight, meaning the antennas at each end must have a clear path between them (no obstructions such as buildings, trees, and particularly, the earth).

3-20 miles is a realistic range for VHF/UHF hand-held radios on the ground, depending mainly on a clear path and relative height of the two parties.  Throw in a repeater with a high antenna and that range extends considerably.  Raising your own antenna up higher Continue reading →

Public Service Events

AF5NP Emergency Communications (EmComm), HT (Handheld Transceiver), Public Service, QST

Are you a new ham who wants to practice radio communication?

Just getting started in amateur radio and want to learn about emergency communications (EmComm)?

Are you a ham who wants to make better use of your hobby?

If you answered yes to any of these, consider helping with a local public service event (PSE). Public Service Events provide an excellent chance to practice your EmComm radio skills.  Not only is it fun and interesting, but you will gain valuable experience in radio communications similar to a real disaster scenario, without the stress and urgency of a life and death situation.

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Ham radio operators are often invited to assist with PSEs to provide primary or supplementary communication.  PSEs typically involve parades, races or large gatherings.  They normally use VHF/UHF radios so you don’t need any fancy equipment or big antennas.

Participants may be stationary  or mobile, depending on the nature of the event.  You may be sitting or standing or walking around.

Because hams supporting a PSE will often use a handheld transceiver (HT) it’s a good idea to have a few recommended HT accessories.  First would be a quality 1/4-wave antenna in place of the poorly-performing factory “rubber duck”.  Second is a spare battery pack for your radio.  Third would be headphone(s).

A must-read for new hams is Continue reading →

Don’t Settle for Just a HT

AF5NP Amateur Radio, Amplifier, Antenna, HT (Handheld Transceiver), Mic (rophone), Rat Tail, Repeater, VHF/UHF, Yagi

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Often a new ham’s first radio is a handheld transceiver (HT).  A HT represents the lowest-cost entry point to amateur radio and is relatively easy to set up and use.  Your first on-air experience as a licensed ham may involve a HT on a local VHF/UHF repeater, and that’s fine.

But don’t settle for just a HT as supplied by the manufacturer for your early ham radio experience.  You are almost certainly going to be frustrated and disappointed at its performance to the point of giving up on ham radio and wondering why all these hams are so enthusiastic about the hobby.

Don Keith N4KC makes this point eloquently  in his ‘HT Trap’ article where he discusses how easily a new ham can get discouraged with amateur radio because of the limitations of a stock HT.  I have observed this as well while helping new hams get set up in a local EmComm organization.

Huge improvements in HT performance or ease of use can be accomplished with three accessories.

First and foremost is the Continue reading →

Change of Address

AF5NP FCC, License, QTH

Have you moved since you got your amateur radio license?  This is a common concern for renters or apartment-dwelling hams and revocation or suspension of your license is the ultimate consequence of failing to notify the FCC.

If you have relocated your QTH from one place to another, or if you have otherwise changed your mailing address, you are obliged to update your postal address with the FCC in the United States.  The FCC needs to know where to reach you by mail for either operator or station license questions or issues.

It’s also common courtesy to other hams who want to send QSL cards or just to know where you are located based on your call sign.

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US Code of Federal Regulations 47 C.F.R Section 97.21 requires you to file timely for an update of the license as necessary to show your correct mailing address, name, club name, license trustee or custodian name. Revocation of your station license or suspension of your operator license may result when correspondence from the FCC is returned as undeliverable because you failed to provide the correct mailing address.

In the US you can update your address online (filing electronically) at Continue reading →

ARRL Membership

AF5NP Amateur Radio, ARRL, Membership, QST

arrl-logo The American Radio Relay League (ARRL) is is the largest membership association of amateur radio enthusiasts in the USA and it represents the interests of hams before federal regulatory bodies, provides technical advice and assistance to amateur radio enthusiasts, supports a number of educational programs and sponsors emergency communications service throughout the country.

The ARRL is the primary representative of amateur radio operators to the US government, lobbying Congress and the Federal Communications Commission on various issues of importance to ham radio.  The ARRL has a significant international membership and influence as well, serving as the secretariat of the International Amateur Radio Union, which performs a similar role internationally, advocating for amateur radio interests before the International Telecommunications Union and the World Administrative Radio Conference.

The ARRL’s underpinnings as Amateur Radio’s witness, partner and forum are defined by five pillars: Public Service, Advocacy, Education, Technology, and Membership.

ARRL’s Vision Statement–  As the national association for Amateur Radio in the United States, ARRL:

  • Supports the awareness and growth of Amateur Radio worldwide;
  • Advocates for meaningful access to radio spectrum;
  • Strives for every member to get involved, get active, and get on the air;
  • Encourages radio experimentation and, through its members, advances radio technology and education; and
  • Organizes and trains volunteers to serve their communities by providing public service and emergency communications.

For all the above reasons it is good to support the ARRL with membership at $49 per year. As a bonus, and for many it is reason alone to be a member, the ARRL publishes the monthly magazine QST.  Each issue is a source of equipment reviews, technical tips, projects, news and many other ham-related topics.

Regular columns address specific interests:

  • Amateur Radio World-  International ham radio news and info
  • Classic/Vintage  Radio- Fun look at older receivers, transmitters and transceivers
  • The Doctor is In-  Authoritative answers to interesting technical questions
  • Eclectic Technology- Discussion on new or unusual technology in ham radio
  • Hands-On Radio- Practical technical discussion of interest to DIY hams
  • Hints & Kinks- Ideas, tips, and related handy suggestions on all things ham
  • How’s DX?-  Long-distance (DX) communication news or issues
  • Public Service- Ham radio for emergency communication and/or events
  • The World Above 50 MHz- Ham radio at VHF and higher frequencies

There’s something for everyone in QST.  A new ham will be exposed to the Continue reading →