### Converting Metric Units, A Ham Radio Exam Study Page

Several of the exam questions involve converting metric units from one form to another.  By memorizing what a few unit prefixes mean, these questions become easy.  Look at the table below:

 Prefix Size Multiply/Divide by pico one millionth of a millionth .0000000000001 or 1E-12 micro one millionth .000001 milli one thousandth .001 kilo one thousand 1000 mega one million 1,000,000 giga one billion 1,000,000,000

• a kilohertz is one thousand hertz
• a megahertz is one million hertz
• a milliampere is one one thousandth of an ampere
• a microvolt is one one millionth of a volt
 From To Multiply/Divide By Mega Kilo x1000 Kilo Mega /1000 One milli x1000 milli One /1000 milli micro x1000 One micro /1,000,000 pico micro /1,000,000 mega One x1,000,000

The prefix in front of a unit just tells you how many of those units your talking about.  A few examples:

To convert between prefixes, there are two steps you can follow.  First, convert the original unit to single units, (megahertz to hertz for example), then convert the single units to the second prefix, (hertz to kilohertz for example).  To convert from a bigger unit, (megahertz for example), to a smaller unit, (hertz), multiply the number of the bigger units by the number in the right hand column above for the prefix, so 3.525 megahertz, (MHz), is 3.525 x 1,000,000 = 3,525,000 Hertz, (Hz).  To convert from a smaller unit to a larger unit, divide by the number in the right hand column, so 3,525,000 hertz / 1000 = 3525 kilohertz.

Rules of Thumb
Sometimes it’s simpler to remember a few rules of thumb in the next table.  These will become more familiar to you the more you use them for actual radio operations.

Exam Questions:
186|T|5|B|01|C|How many milliamperes is 1.5 amperes?
A. 15 milliamperes
B. 150 milliamperes
C. 1,500 milliamperes
D. 15,000 milliamperes

187|T|5|B|02|A|What is another way to specify a radio signal frequency of 1,500,000 hertz?
A. 1500 kHz
B. 1500 MHz
C. 15 GHz
D. 150 kHz

188|T|5|B|03|C|How many volts are equal to one kilovolt?
A. One one-thousandth of a volt
B. One hundred volts
C. One thousand volts
D. One million volts

189|T|5|B|04|A|How many volts are equal to one microvolt?
A. One one-millionth of a volt
B. One million volts
C. One thousand kilovolts
D. One one-thousandth of a volt

190|T|5|B|05|B|Which of the following is equivalent to 500 milliwatts?
A. 0.02 watts
B. 0.5 watts
C. 5 watts
D. 50 watts

191|T|5|B|06|C|If an ammeter calibrated in amperes is used to measure a 3000-milliampere current, what reading would it show?
A. 0.003 amperes
B. 0.3 amperes
C. 3 amperes
D. 3,000,000 amperes

192|T|5|B|07|C|If a frequency readout calibrated in megahertz shows a reading of 3.525 MHz, what would it show if it were calibrated in kilohertz?
A. 0.003525 kHz
B. 35.25 kHz
C. 3525 kHz
D. 3,525,000 kHz

### Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems, there seem to be fewer explanations of the procedure for deriving the conversion, so here goes!

What do we actually want?

To convert the Cartesian nabla

to the nabla for another coordinate system, say… cylindrical coordinates.

What we’ll need:

1. The Cartesian Nabla:

2. A set of equations relating the Cartesian coordinates to cylindrical coordinates:

3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system:

How to do it:

Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables.

The chain rule can be used to convert a differential operator in terms of one variable into a series of differential operators in terms of othe…

### Lost Phone

We were incredibly lucky to have both been in university settings when our kids were born.  When No. 1 arrived, we were both still grad students.  Not long after No. 2 arrived, (about 10 days to be exact), mom-person defended her dissertation and gained the appellation prependage Dr.

While there are lots of perks attendant to grad school, not the least of them phenomenal health insurance, that’s not the one that’s come to mind for me just now.  The one I’m most grateful for at the moment with respect to our kids was the opportunities for sheer independence.  Most days, we’d meet for lunch on the quad of whatever university we were hanging out at at the time, (physics research requires a bit of travel), to eat lunch.  During those lunches, the kids could crawl, toddle, or jog off into the distance.  There were no roads, and therefore no cars.  And, I realize now with a certain wistful bliss I had no knowledge of at the time, there were also very few people at hand that new what a baby…

### Lab Book 2014_07_10 More NaI Characterization

Summary: Much more plunking around with the NaI detector and sources today.  A Pb shield was built to eliminate cosmic ray muons as well as potassium 40 radiation from the concreted building.  The spectra are much cleaner, but still don't have the count rates or distinctive peaks that are expected.
New to the experiment?  Scroll to the bottom to see background and get caught up.
Lab Book Threshold for the QVT is currently set at -1.49 volts.  Remember to divide this by 100 to get the actual threshold voltage. A new spectrum recording the lines of all three sources, Cs 137, Co 60, and Sr 90, was started at approximately 10:55. Took data for about an hour.
Started the Cs 137 only spectrum at about 11:55 AM

Here’s the no-source background from yesterday
In comparison, here’s the 3 source spectrum from this morning.

The three source spectrum shows peak structure not exhibited by the background alone. I forgot to take scope pictures of the Cs137 run. I do however, have the printout, and…