Getting Started in Ham Radio, Part 2 – Wavelengths and Watts and
You can also
part one here.
already decided on getting an amateur radio license, and you find
yourself with a few questions. One of the first questions you have
is probably, “What is all this ‘wavelength’ and ‘meter band’ and
‘HF’ stuff?” Or, maybe you wonder what that guy was talking about
when he invited you to “check in to our prepper net down on 80,
we’re at 3850.” Like most pursuits, ham radio uses some specialized
jargon. Let’s try to clear up a few of the basics.
all this crap?”
Ham radio operates
on certain segments of radio frequencies, or bands. Just like AM
radio is found between 540 and 1710 kHz, and FM radio is found between
87 and 108 MHz, ham radio has its own sections of bandwidth to occupy.
These bands are generally referred to using the approximate physical
wavelength of the radio waves. For instance, the “80-meter band”
runs from 3.500 MHz to 4.000 MHz (3500 to 4000 kHz), as 80 meters
is the approximate physical wavelength of a radio wave at those
frequencies. Likewise, anything from 28.000 MHz to 29.700 MHz is
considered the “10-meter band,” and so on. Remember, these are approximations,
as wavelengths change with every change in frequency. The “band
plan” designations just make it easier to group them together.
If you know
the frequency and want to calculate the approximate wavelength,
there’s an easy formula to get a fast-and-dirty result. Just take
300 divided by the frequency in MHz. For example, using this formula
with 146.5 MHz, we come up with a result of 300/146.5 = 2.047. Correspondingly,
146.5 MHz is found in the 2-meter band. Another one, 14.150 MHz,
would be 300/14.150 = 21.20. That means that 14.150 falls in the
in ham radio are referred to in either megahertz (MHz) or kilohertz
(kHz). 1000 kHz = 1 MHz. You might hear somebody referring to a
contact they made on 40 meters at either “seven point two” or at
“seventy-two hundred.” That’s just two ways of saying the same thing.
7.2 MHz = 7200 kHz. Using our previous formula, 300/7.2 = 41.66,
so that frequency is in the 40 meter band.
So, when that
guy earlier asked you to join a discussion net “down on 80 at 3850,”
you now know that if you tune in to 3.850 MHz on the 80-meter band,
that’s where you’ll find him. Pretty easy!
list of frequencies”
For those of
you who are old enough, do you remember your old TV set that had
separate dials for VHF and UHF? Those terms stand for Very High
Frequency and Ultra High Frequency, and while your TV shows now
come via cable or satellite, VHF and UHF, along with HF (High Frequency),
are still terms you encounter every day in ham radio.
are frequencies both above and below, the three most common in ham
radio are HF, VHF and UHF. Ham radio HF starts at 1.8 MHz (just
above AM broadcast frequencies) and goes the whole way up to 30
MHz, and includes the 160-, 80-, 60-, 40-, 30-, 20-, 17-, 15-, 12-
and 10-meter bands. This is the frequency range that you’ll sometimes
hear referred to as “shortwave.” Ham radio VHF starts at 50 MHz
and goes up through 300 MHz, and includes the 6-, 2- and 1.25-meter
bands. FM broadcast radio (87 MHz-108 MHz) falls in the middle of
this segment. Ham radio UHF frequencies start at 300 MHz and run
the whole way up to 3000 MHz, and you’ll find most users on the
70-cm and 33-cm bands. Great, so… what’s the difference?
The short answer
to that question is “distance.” The HF bands are generally more
geared towards long-distance communication, while the VHF and UHF
bands are for more local communication. For example, in an SHTF
situation, most of your communication with the outside world would
be on the HF frequencies, and for local operations the hams in your
group would likely be using handheld or mobile VHF radios to communicate
with each other. Those rules aren’t written in stone – you
can talk to someone just a few miles away on HF, and if conditions
are right you can get out pretty far on VHF, but generally, lower
frequencies = longer potential communication distance. For a person
holding a technician license, most of your operating will be on
VHF and UHF, where you have full privileges. Technicians have some
very limited voice privileges on 10-meter HF, but other than that,
if you’re a Technician who wants to use HF, you’re mostly limited
to morse code. But, if you have your Tech license and you’ve read
this far, you’re probably already chomping at the bit to upgrade
to General and then Extra Class, which will open up the whole world
of HF frequencies for you!
formulas you need to know”
One of the
hardest thing for an aspiring ham to learn, particularly one without
any electronics experience, is Ohm’s Law. While it might make your
eyes glaze over just like high school algebra, it’s actually a very
simple formula that you’ll need to understand whenever you’re building
or troubleshooting something. It’s also required reading for taking
your amateur radio test! There are many formulas that are part of
Ohm’s Law, but these are the basics you’ll need to know to get started.
electronics text will tell you that volts are electric potential,
amperes are current, ohms are resistance and watts are power, but
what does that really mean? As a kid, I was taught to think of it
like plumbing: Volts are the water in the pipe, amperes are the
water flow, ohms are the size of the pipe and watts are how much
water you get out of the spigot. Lots of water, high flow rate and
a large pipe will give you a lot of water in your bucket, while
less water, low flow and a small pipe will give you a lot less.
works in much the same way (just don’t mix the two together!). Put
more volts or current in the wire (more water or higher flow in
the pipe), and you’ll get more out of the other end. Higher resistance
(a smaller pipe) will let through less power than lower resistance.
The chart above shows the easy way to calculate these figures.
let’s say you have a 12 volt power source, and you want to generate
2 amps of power. How much resistance will you need in your circuit?
As the chart shows, resistance = volts / amps. 12 / 2 = 6, so you’ll
need 6 ohms of resistance in your circuit. So, you’ve got your 12
volts at 2 amps, but how many watts of power is that giving you.
Power = volts x amps, so 12 volts x 2 amps = 24 watts. Easy! These
two basic charts will get you started with most of what you need
to know in your ham radio projects.
If you haven’t
gotten your Technician license yet, now’s the time to get started.
If you have, well, now’s the time to upgrade to General and then
to Extra Class! The same resources available for Technician study
are also available for General and Extra, so with a little bit of
effort, you’ll have no problem at all. In my first entry we talked
about licensing, and this time we went over some basics, so next
time, let’s start getting some equipment together and then we can
get radio active!
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