Dummy Load

AF5NP Dummy, Heat Sink, Impedance, Load, Resistor, Test/Testing

Radio amateurs should be familiar with the term dummy load, which is a RF-friendly substitute for an antenna when testing a transmitter or piece of equipment such as a Watt meter.

Dummy1   Dummy2   Dummy3

A dummy load is somewhat generic, also having industrial and commercial uses.  As applied in ham radio, it electrically simulates an antenna to allow a transmitter to be tested without radiating radio waves, typically at 50Ω to match transmitter output impedance.

T7C01-2018

Dummy loads are rather simple—  just a big resistor and some way to dissipate heat, all in a package that must be non-reactive, meaning it provides insignificant capacitance and inductance.

T7C12-2018

Why must a dummy load be non-inductive?  Because of impedance (practically speaking, AC resistance), which increases with frequency based on the formula of inductive reactance XL=2πfL.

XL

Most common power resistors are wire-wound, which have significant inductance.  So RF dummy loads must use resistors with little or no inductance.

As an example, this four-resistor series combination using common Dale metal-clad resistors measures 49.4Ω at 0Hz (DC).  Sounds like a perfect dummy load, right?

DSCN4385

Unfortunately  it also has Continue reading →

Flat Ground Strap

AF5NP Conductor, Ground, Impedance, Reactance, RF, Safety, Strap, Wire

Ever wonder why RF grounds should be flat straps and not regular wires?

This is because ordinary wires are not good conductors at frequencies higher than 50-60Hz. This complicates wiring and bonding requirements.

Impedance (effectively, AC resistance) of a conductor increases with frequency and length due to inductive reactance.  The higher the frequency, the greater the impedance.

XL

All conductors have some measurable inductance, and it doesn’t take much to yield significant impedance.  At KHz or MHz frequencies, long round wires might present hundreds or even thousands of Ohms impedance; not suitable for grounding.

A good ground has less than one ohm impedance.  This is a genuine safety issue.

G4C05-2015

Since inductive reactance increases with frequency and length, safety grounds and module bonds need to be something other than long round wires when radio frequencies are involved.

When high frequency grounding is required, use short, wide, and flat conductive straps.  The high aspect ratio minimizes electrical inductance vs. a round wire, as does a short conductor.  This lowers the ground wire’s impedance at higher frequencies.

T4A08-2018

So now you know.  Keep it flat and short (KIFS is a lousy acronym).

It’s not just a suggestion; this one might just bite you if you don’t heed the guideline!

Impedance

AF5NP Impedance, Reactance, Resistance

Impedance is an important subject in amateur radio so we want to spend a little time discussing it here.  Several topics on this site will involve impedance so it’s good to have this basic concept well understood.

In ham radio work we deal with impedance in transmission lines, antennas, transmitter outputs, receiver inputs, microphones, speakers, headphones, and other devices.  Impedance matters everywhere a signal couples to something different.

Basic resistance (R) is what opposes current in a DC circuit, and all components have measurable resistance.

T6A01-2018

But things get more complicated in AC circuits.  Capacitors and inductors (coils) oppose change.  This includes alternating current, a characteristic of audio, video and radio frequencies.   The properties of capacitance and inductance have well-defined opposition to AC which varies by signal frequency.

G5A02-2015

All components have measurable capacitance and inductance so there is always some reactance (X) in a circuit.  There are two flavors of reactance: capacitive and inductive.  Interestingly, they respond oppositely to signal frequency.  Inductive reactance (XL) goes up with frequency while capacitive reactance (XC) goes down.

When you add the constant resistance in a circuit to the capacitive and inductive reactance, the result is impedance (Z=R+jX).  In broad terms, it can be considered “AC resistance”, which is legitimate when we don’t care about the complex phase angle part of the equation.  Resistance plus reactance equals impedance (Z).

T5C12-2018

Like DC resistance, impedance (AC resistance) is measured in ohms.

T5C13-2018

OK so far?  Click on the many hyperlinks in this article for more detail, along with helpful links below.  Don’t worry, you only need to grasp the basics here; high-level math is not necessary for a working knowledge of impedance.

Now that you know what impedance is, the next important thing to understand is that when an AC signal interfaces with a new circuit, the impedances should match.

When impedance of a source (ZS) equals the load impedance (ZL), the best possible signal coupling occurs. Conversely, when impedances are not the same, signals couple poorly.

G5A07-2015

The maximum power-transfer theorem says that to transfer the maximum amount of power from a source to a load, the load impedance should match the source impedance (ZS=ZL).

G5A08-2015

Good examples of impedance matching are: audio amplifier output to speaker (8Ω); transceiver RF circuits to antenna feed line (50Ω); microphone to audio input (2000Ω).

Impedance matching can be accomplished by Continue reading →

QSL

AF5NP ARRL, Card, Contact, eQSL, Etiquette, Green Stamps, IRC, Log, LoTW, QSL, QSO

The final courtesy of a radio contact is acknowledgement of the QSO (radio contact).

g2c09

QSL is an old brevity code meaning, “I acknowledge receipt”.  Back in the early 1900s when passing messages was a main function of amateur radio (whence the Amateur Radio Relay League or ARRL), the term QSL made a lot of sense.  Today you may hear a ham speak or write QSL to let you know they received something.

The term QSL now more commonly means to confirm a radio contact.  Early on this was done mainly with postcards.

5nk

Some hams still do send out QSL cards, or send them in reply or if requested.  Collecting cards is a fun aspect of ham radio.  Many cards are interesting or unique.

Besides tradition,  a sense of satisfaction, and general fun, QSO confirmation in the form of valid QSL is a basic requirement for most operating awards.  This may not matter to you but many other hams are eager for your QSL, particularly if they are requesting one.

All hams should provide some form of QSL for all contacts except for routine local ones.  Information in the QSL should include the station call signs, date and time (UTC), band/frequency, mode, signal report, and sender’s location details. Good logging is essential for this and a QSL function is often supported by computer logging utilities.

You can determine how to exchange QSLs with a particular station from their QRZ profile if they have one set up (most active hams do).

Details about QSL cards are given further below.  Mailing cards can get expensive.  While the cost of printing the cards is not so bad, postage adds up, particularly when sending internationally.  Bureau (BURO) services to send/receive cards internationally reduces cost somewhat but is still pricey and response time is generally slow (months to years).  Alternate methods of  providing a QSL have arisen out of the need for keeping costs down.

Non-card QSLs are all electronic in nature, exchanged via internet connection in some manner.  We will briefly mention three here.  You can search for others Continue reading →

Don’t Be a Lid

AF5NP Amateur Radio, Citizens Band (CB), Lid, Operator, Police/Law Enforcement, Prohibited, Voice

“Lid” is ham-speak to denote a poor operator; one who is inept at the practice of the radio amateur art.  It is someone with very poor operating technique, a newbie or an experienced ham that acts like a neophyte. This old term likely originated from the days of wired telegraphy.

A previous post entitled, What Can I Say?,  presented more don’ts than dos, which was appropriate considering the topic.  This is a good time to review it.

In addition to those prohibitions, we’ll expand on the topic and add a few more things a good ham doesn’t do, assuming you don’t want to be known as a lid.  Most are things a good ham should avoid saying.  In fact, this article was originally entitled, What Should I Not Say?

There are some bad habits certain hams need to break, mainly because it demonstrates ignorance and carelessness.  Other amateurs may not take you seriously if you practice these things.  Numerous ham websites list pet peeves containing these bad practices (a few are linked below).

Some liddish behavior is understandable or excusable in a brand new ham but habits form quickly.  These are generally frowned upon and the perpetrator may find themselves publicly shamed (in a hammy context).  Don’t let it happen to you!

Here is a short list of things a ham should not do:

  • Use of CB lingo and police/public safety codes.  “10-4″,”what’s your 20?”, and “breaker” are particularly egregious.
  • Checking into a net or answering a CQ without identifying phonetically.  But once you are acknowledged you should ID without phonetics.
  • Partial phonetics is also bad form (e.g., KG5-alpha-bravo-charlie).
  • Talking too far from or directly into the mic.  See our microphone technique topic.
  • Using the term “broadcasting”.  Hams never, ever broadcast; they transmit.  The word broadcast has a very particular meaning to the FCC.

T1D10-2018

  • Using too much power or audio level (splatter) on digital modes
  • Adding an S to 73.  73 by itself is fine, but pluralizing it (73s or 73’s) is the equivalent of saying “best regardses”, which doesn’t make sense.
  • Calling your small VHF/UHF radio a Handie-Talkie.  HT means handheld transceiver, not Handy Talkie.

This is a handheld transceiver ⇒       zys-ft-60r

This is a Handie-Talkie ⇒  170px-Portable_radio_SCR536     See the difference?

  • Briefly keying your mic on a repeater without ID.  See our topic on Kerchunking.
  • Calling CQ on a VHF/UHF repeater.  If you want to talk to somebody/anybody, simply ID and ask for a QSO.
  • Over-use of Q-codes and other unique ham lingo.  Makes sense in CW work but not on a local VHF net.
  • Saying “over” on a repeater.  The closing squelch and courtesy tone let everybody know that you are done transmitting.

All of these are bad practice; lid-like behavior, although only a few are likely to earn Continue reading →

CQ

AF5NP Contact, CQ, Frequency, QRL, QSY

CQ is ham-speak for “calling any station”.  For all modes— voice, Morse, visual, or digital, it signifies a radio amateur looking to make a contact.

The basic, general CQ means looking for any station to respond.

T2A08-2018

It can be refined (a directed CQ) to be more specific, often a location.  Common examples are out-of-country long distance (CQ DX), a particular prefix, country or state (CQ VT), a contest or event (CQ SOTA), or perhaps a CW specialty such as using a straight key (CQ SKCC).

G2A11-2015

When you hear a station calling CQ, it’s your chance to work them.  Respond by sending their call sign and then your own, much like on a VHF/UHF repeater.

T2A05-2018

If a ham doesn’t hear any activity or anyone calling CQ it could mean the band is dead… or it could be a good opportunity to go fishing for a contact by calling CQ.  New hams should get some experience with every new mode before calling CQ themselves.

When calling CQ , make sure that you are permitted to operate on the frequency you have chosen (and keep away from band edges).  Also make sure that the frequency is not in use.  Do not assume that if you hear quiet at a valid frequency that it is free; it could be that another ham is listening to a station you can’t hear.

T2A12-2018

Always check if a frequency is in use before calling CQ.  The proper way to do this is to simply ask by voice with your ID (phone), or send the Morse prosign QRL? with your call (CW mode).

G2B06-2015

If someone else is working that frequency, they will let you know.  Move to another frequency (QSY) should you receive a response to QRL.

T2B08-2018

If nobody replies to your QRL, go ahead with your CQ.  There is no official CQ protocol but there are many suggestions out there.  Continue reading →

Your Grid Square

AF5NP Grid Square, Location, QTH

If you are active on HF or non-repeater VHF/UHF frequencies, you should know your operational grid square when making contacts.  Many hams need to know your exact location for logging and awards purposes.  The grid square system was adopted by the IARU for specifying amateur radio station location in a relatively small area.

T8C05-2018

The planet is divided up into 32,400 grid squares roughly 100mi wide by 70mi high (in continental USA) per the Maidenhead Locator System.  More detail here.

Basically, our planet is divided into 18×18=324 fields identified by two letters (AA-RR)
Each field is 20° longitude (east-west) and and 10° latitude (north-south). The first letter represents longitude and the second latitude as shown below.

Maidenhead fields

Each field is sub-divided into 10×10=100 squares starting again in the southwest counting north in columns of tens and shifting east for the next ten.

If you look carefully at field IO above (encompassing most of the UK and Ireland), you can see this refined grid.  It looks like this in a more geodetic (less flat) view:

 

maidenhead field IO

Here you can clearly see square 00, lower left and 99, upper right with the other 98 squares everywhere in between.

This combination of field plus square gives us the basic grid square system.  It follows the specific format as shown below.

Maidenhead detail

Of interest to most readers of this site, the continental United States (CONUS) is Continue reading →