HAM’S LIFE

Do you know anyone who is interested in
becoming a ham and needs some study material?
I have just updated my ham radio class blog at http://hamslife2.blogspot.com . 

I will be teaching a class using the basic
format found in these ten lessons.  The
class will be held at the Colusa County Sheriff’s office in Colusa, California.  The classes will be every Saturday starting
on September 11, 2010 going through October 30, 2010.  The time will be 9 AM to 12 noon. 

One of the fun parts of operating this blog is being able to answer emails from readers who have questions.  Two areas of questions that frequently come up are, “Should I get a ham radio or a CB radio?” and, “Can my teenager get a ham license?”  Frequently these questions come together.

The first question is impossible for me to answer but I try to give some guideline that will hopefully help.  Reading my post on the difference between ham radio and CB radio (http://hamslife.com/?p=24) might help in making the decision.  One big consideration is are you willing to study and take a test to get on the air?  If not then ham radio is out but that does not necessarily mean CB is in for you. 

The second question is easy to answer.  There is no age limit in the United States on who may hold an amateur radio license.  Some countries do have limits and if you are not in the United States of America and do have age restrictions please leave a comment so if others in your country reads this they can know about the restriction.  Children 8 years old and younger have passed the test and received their ham radio license. 

Now let me bring the two questions together and ask, should a child or teen be on the amateur or the CB radio frequencies?

Some young children who obtain their ham radio license do not yet have the social skills or interest that is needed to effectively use their acquisition.  If they are pushed by a ham parent to get the license it could have a negative result as they get older.  My wife and I raised six children; three of them got their ham license before leaving home and one got her license after she was married.  None of my children currently have valid amateur radio licenses.  Maybe I was guilty of pushing.

While my children were allowed to listen to and, when licensed, operate on the ham bands they were not allowed to listen to nor operate on the CB band. 

Citizen Band radio was authorized to provide an inexpensive short range business radio communications service for the general public.  A license, though no test was involved, was required.  From the beginning there were people who abused the system and in the early 1970 the whole CB operation got so out of hand that the FCC could not enforce the regulations so for the most part if the operators were not bothering anyone outside the CB frequencies the FCC just ignored it.  Obscene language became the norm.  Drug dealers and prostitutes found they could use CB to their advantage in selling their illegal traffic. 

Ham radio operators have a history of trying to keep illegal operations off the ham bands.  So while I can not say it does not happen I can say it is rare. 

It is my personal opinion that children and teens should not be subjected to the Citizen Band service.  When it comes to children and teens acquiring their ham license and using the ham bands it needs to be remembered that each one is an individual and thus different.  I know hams who have been hams for many years who got their license as teens and some even younger. 

When we hear the word “LOG” without context we may think of a fallen tree with all its limbs removed ready to be cut into lumber, or for some of us older hams we might think of a book where we were once required to keep a record of every transmission we made. In the case of the question in the title the word log is short for “Logarithms.”

While teaching my General Class Amateur Radio class an old bugaboo came back and bit me. When expressing power gain we refer to it in decibels and to calculate decibels we use log and antilog. You can get your General Class license without understanding logs especially today when questions and answers can be memorized but I believe most hams would like to understand what the question and answer means not just 10 is the answer to this question if it is asked. I was able to obtain a First Class Radiotelephone License without understanding logarithms. It was not that I did not want to know it was just I could not find anyone who either could or would explain the concept to me.

When I finally took a course in electronics where logs were explained I was surprised how simple they were but how difficult they are to explain. Over the next few days I am going to use this blog as a forum to try to explain what and whys of logarithms.

The first part of understanding logs is the understanding powers of tens. Most of the readers of this blogs probably already understand the power of tens but because of the connection that is where we will start today.

The powers of ten is a way we use to express large numbers without having to write out a long line of zeros. We might speak of the speed of a radio wave as 300,000,000 meters per second but we can also say it is 3X10⁸ meaning 3 times 10 times 10 eight times or 3 with 8 zeros following; so 10⁰ =1, 10¹ = 10, 10² = 100, and 10³ = 1000.

Maybe an easy way to understand is when speaking of the square of a number it means a number multiplied by itself (2X2=4) and when speaking of the cube of a number it is a number times itself and then times itself again (2X2X2=8). When a formula tells us to square a number is uses a superscript 2 after the number (2²=4) and to cube a number the superscript 3 is used (2³=8). Knowing this and applying this knowledge to powers of 10 it can be seen that 10²=100 and 10³=1,000. 10¹ would naturally follow down to equal 10 and 10⁰ will equal 1.

The numbers considered above are all Integral numbers or whole numbers. The powers of ten also work with non-integral numbers or numbers which are factions of whole numbers. In the figure 2.2 we see that 2 is the integral number and .2 or ²/₁₀ is the non-integral number. Sense 10⁰ is equal to 1 a minus superscript number or power indicator is used to make up the non-integral numbers. ¹/₁₀ or .1 would be written 10^-1 which shows the number is one number over from the decimal point. 10^-2 (pronounced as ten to the minus two) is equal to .01 and down it goes.

The powers of ten numbers make up the Characteristic numbers of logarithms. This is fine if you are going to calculate power increase of 10, 100, 1,000, 10,000 and so on but more needs to be known when it comes to calculating other numbers such as 5, 15, 25, or any other number not included in the previous pattern. So more on using logarithms will be covered tomorrow’s post.

Log 10,000 = log 10⁴ = 4 (that is, the log of 10,000 it 4)

Log 1,000 = log 10³ = 3 (that is, the log of 10,000 it 3)

Log 100 = log 10² = 2 (that is, the log of 10,000 it 2)

Log 10 = log 10¹ = 1 (that is, the log of 10,000 it 1)

Log 1 = log 10⁰ = 0 (that is, the log of 10,000 it 0)

Log .1= log 10^-1 = -1 (that is, the log of .1 it -1)

Log .01= log 10^-2 = -2 (that is, the log of .01 it -2)

Log .001= log 10^-3 = -3 (that is, the log of .001 it -3)

Log .0001= log 10^-4 = -4 (that is, the log of .0001 it -4)

While preparing for Friday night’s ham class I noticed that questions G1A07 and G1A09 have some very interesting detractors.

Question G1A07 reads, “Which of the following frequencies is within the General class portion of the 75 meter phone band?” and the detractors are “A. 1875 kHz,” “B. 3750 kHz,” “C. 3900 kHz,” and “D. 4005 kHz.” The correct answer is C (300,000/3900 = 76.92).

Question G1A09 reads: “Which of the following frequencies is within the General Class portion of the 80 meter band?” and the detractors are “A. 1855 kHz,” “B. 2560 kHz,” “C. 3560 kHz,” and “D. 3650 kHz.” The correct answer is C (300,000/3,560 = 84.27)

Usually when we speak of the 80 meters band and the 75 meters band we are referring to the CW portion being 80 meters and the phone portion of that band being 75 meters but if we refer to the over all band we call it the 80 meter band. 3,750 KHz is equal to 80 meters (300,000/80 = 3,750). 4,000 KHz is equal to 75 meters (300,000/75 = 4,000). Considering the overall 80 meter band goes from 3,500 KHz to 4,000 KHz 3,750 KHz is in the exact center of that band. The phone portion of that band is from 3,600 KHz to 4,000 KHz.

If you are not careful it would appear there are two correct answers given to each of these questions.

Should 3,750 KHz and 3,650 be considered 80 meter or 75 meter band? They are both in the phone band and a 3,750 KHz signal is 80 meters long thus a 3,650 KHz signal is even longer then 80 meters. The point is it doesn’t make any difference when it comes to these two questions because the questions clearly say “within the General class portion…” and neither of those frequencies are in the General class section of the band. An Extra class license is required to operate on 3,650 KHz and either an Extra class or Advanced class license is required to use 3,750 KHz.

If you are preparing to take your amateur radio exam let me give you a little tip. Carefully read the question and all the answers. If there are two answers that appear to be correct and there is not an option to include two answers then try to see why one is wrong. If a detractor saying “all answers are correct” make sure all are correct and if one is wrong then two will be wrong. It is important to know why incorrect detractors are wrong as well as why the correct detractor right to prevent marking the wrong answer.

While preparing to teach my class this week I came across question G1E4 in the question pool. Question G1E4 says, “Which of the following conditions require an amateur radio station to take specific steps to avoid harmful interference to other users or facilities?” and the answer is, “All of these answers are correct”. One of those above answers is, “When a station is transmitting spread spectrum emissions”.

When preparing to teach a class I try to anticipate questions so I can be prepared to give an answer. I could anticipate the question “what is spread spectrum emission?” This is a new term to me so I started to research and found most of the sites about spread spectrum emission start out with the assumption the reader already knows what it is.

One thing I ran into while researching this is an amplifier known as a “Class D” amplifier. I have written on classes A, AB, B, and C amplifiers but not on D because though I had heard the term many years ago I was given wrong information. I was told that a “Class D” amplifier was a DC amplifier and thus nothing more then an electronically controlled switch. As I understood at the time it was a vacuum tube or transistor being used as a relay.

Today’s research has revealed to me that a “Class D” amplifier has very high efficiency and good linearity. 90% efficiency is very possible while in a “Class C”, the most efficient of the other four, amplifier that efficiency is only theoretical. It is sometimes thought of as a “digital amplifier” and thus called “Class D”. But the term comes from the normal line of succession of amplifiers. There is the “Class A” amplifier which conducts 100% of the time; The “class B” amplifier which conducts 50% of the time; and the amplifier which fits in between called a “Class AB). Then there is the “Class C” amplifier which is biased well beyond cutoff and thus conducts much less then 50% of the time, typically 10 to 20%. The letters A,B, and C are already used so it is logical that the next amplifier in order would be D.

While the “Class D” amplifier is very efficient it has problems with spurious radiation and that is why it is not widely used. I am not going to try to explain its operation for two reasons. One I am still trying to understand it and two I am not experienced enough yet at adding photos in my blog to insert the diagrams into the post that are needed to explain its operation. If you would like to know more Google “Class D Amplifier.”

Class Photo

Three eager students are starting their journey from Technician class to General class amateur radio operators. Willing to attend class every Friday night, endure the homework assignments these students informed me they do not want to just learn to pass the exam they want to learn the subject and that is exciting because that is the only way I will teach a class.

It is teacher’s privilege to choose the text and I chose the ARRL General Class License Manual. I chose this book because it is not just a Q&A manual but it is l written in a text format with the answers to the questions included so the reader is learning the subject material surrounding the questions. It has little blue boxes on the side of the page which tells the student to stop, go to the back of the book and see if they can answer the questions which was included in the text they just read. The Q&A portion in the back of the book has the answers along the outside edge of the page so they can be covered up by a piece of paper on which the answer choices can be written then by holding the paper next to the page the answers in the book can be easily compared with the answers by the student. This, in my openion, is an excellent manual for class room training and for independent study.

As you look at the photo of the class above you may be wondering, sense there are only three students, why are five pictured. I am standing in the middle and to my left is Ron, an extra class amateur, who joined with us to give me some assistance. I had not expected Ron so it was a pleasant surprise. The class includes Al to my right, Stony in front of Al, and Dan to Stony’s left. I want to thank the young lady from the facility where we are meeting for taking the photo.