Monthly Archives: March 2017

1917 New York Police Wireless Telegraph


A century ago, cops knew Morse Code, as shown by these New York City police officers appearing in the March 1917 issue of Popular Mechanics.

According to the accompanying article, instruction in wireless telegraphy was being given to the officers, and a wireless apparatus had been set up at headquarters. That station worked in conjunction with other stations around the harbor, and also with a number of private wireless stations that had been placed at the service of the police for emergency work.

Motorcycle couriers would carry messages from the wireless stations to district and precinct offices. At press time, the department had eight certified wireless operators, and sixteen more were under instruction.

1957 British “Mini-Max” Transistor Portable


Sixty years ago, it was clear that the transistor was here to stay, and virtually all of the magazines for electronic hobbyists were filling up with construction articles featuring solid-state circuits. More often that not, the project was a transistor radio of some sort. This British example appeared in the March 1957 issue of Radio Constructor magazine.

This set was billed for local reception, but it made up for any lack of sensitivity in the fact that it would provide “loudspeaker” volume. In this case, the speaker was actually originally intended as a headphone element, but the set would put out 40 mW of audio, more than enough to listen to the set without any difficulty.

The set was constructed in a sandwich box cut to size. The author noted that the dimensions given in the construction article were intended for one particular brand of box. So if you want to recreate this set exactly, you’ll need to track down a British “Elevenses Pack” sandwich box. The circuit inside the sandwich box consisted of a diode detector followed by four stages of audio amplification. The set had a built-in loopstick antenna, and would presumably pull in those local stations without an external antenna or ground connection.

The author noted that the industry wasn’t quite ready to supply experimenters with components to construct a small superheterodyne receiver.  Small IF transformers were available, but none of them were in the subminiature category.  Transistors suitable for medium wave were hitting the market in the U.K., but the small transformers needed for a superhet weren’t yet available “comparable to those available in the States.”  But this crystal set with lots of audio amplification would serve the purpose for pulling in the strong local signals, and the hobbyists who built it were undoubtedly the first on their block to own a transistor radio.


Substitute Teaching in Minnesota

No, you don’t need a teaching license!

Among the many hats I wear is that of substitute teacher. Depending on how busy my schedule is with other business, I teach in one of the Twin Cities area districts a few days a week.  For many people, this is an excellent part-time job opportunity to make a few extra dollars, make a difference in the lives of students, and possibly find yourself energized by exposure to their youthful exuberance.  The information on this page explains how to become a substitute teacher in Minnesota, although much of the information will be relevant in other states as well.

The rate of pay for this work varies from district to district, but in Minnesota, typically it is about $140 per day. Depending on the school, the substitute is expected to arrive about a half hour before the students arrive, and typically leaves about the same time as the students. This means that the substitute typically works about seven hours a day, and the afternoon is usually free.  The mathematically astute will realize that this is about $20 per hour, which isn’t too bad on days when I didn’t have anything else scheduled.  There are also frequently half-day assignments available. During the day, the substitute usually has at least one “prep hour” available. During the prep hour, the normal teacher catches up on other work such as preparing lesson plans or grading papers. Since the substitute usually isn’t expected to do such things, this usually results in another hour during the day to catch up on other work. Since there is almost always a telephone and computer with internet access available, this can usually prove to be a productive time.

A person would certainly struggle to pay the bills if substitute teaching were their only source of income. But the schedule is so flexible that subbing can provide a great source of extra income for those who are self-employed or work another job in which they are free during the day.

For me, the main advantages of substitute teaching are:

  • A source of income on days when I’m not working elsewhere.
  • An opportunity to be an “insider” at my children’s own schools.
  • The opportunity to make a real, albeit brief, positive impact on students.

For those who do need the income, it would be possible to work almost every day as a substitute. Jobs are available on an almost daily basis. For those who do not need to work every day, this allows you to be very selective on which jobs you take.

Minnesota Requirements

In Minnesota, anyone with a four-year college degree in any subject can become a substitute teacher. You do not need to have a degree in education. This is because many school districts have a shortage of substitute teachers. In Minnesota, a person with a four-year degree, but without an education degree, and receive a “Two Year, Short-Call Substitute” license.

This license is issued by the Minnesota Department of Education. There is a fee of about $93, and you will need to be fingerprinted as part of the application process. As the name implies, this license is valid for two school years.

Even though you will need to obtain this state license, the starting point is the individual school district where you plan to work. This is because the two-year license is available only to persons teaching in districts where the superintendent has verified that the district is experiencing a hardship in locating fully licensed teachers. As far as I can tell, the license, once issued, is valid statewide. But to get the license in the first place, you will need the signature of a district superintendent verifying that district’s hardship.

Fortunately for you, many districts in Minnesota are experiencing such hardships, and they will be overjoyed to sign off on your license application. In fact, they routinely do this as part of the hiring process.

I have noticed that these “hardships” seem to come and go. For example, the district where I am currently teaching does not currently have this hardship. Therefore, I would not be able to be hired there as a new substitute. However, once I’m in the system, I can keep teaching there. And since they frequently have substitute jobs that go unfilled, I wouldn’t be surprised if they once again declare a hardship and hire new substitutes such as me.

A quick Google search reveals that the following Minnesota school districts are currently hiring subsitutes and are willing to sign the certification so that you can get your license.  So if you live in or near one of these districts, they would be the ideal starting point.

Please note that these districts are the ones that currently publicize on their website that they’re willing to sign your application, and they are the ones I found with a quick Google search. There are undoubtedly many others.  (Some districts might not want to publicize on their website that they’re experiencing a shortage, so a phone call might be productive.)  To find these opportunities, check the district’s website, ask at your children’s school, or call the district. Many other Minnesota districts work with a firm called Teachers On Call, which handles the application process. Many of these districts will probably be willing to hire persons with a limited license as well.

The Hiring Process

When you inquire, you will probably be asked to apply in person. And it’s quite likely that you will be hired on the spot, subject to obtaining your license. You’ll probably walk out with the required form signed by the superintendent, who is happy to learn that his or her chronic substitute shortage is one step closer to being solved. Chances are, the staff at the district will be able to assist you with the process of applying for your license. When you visit the district office, you should plan on being hired that day. Therefore, it’s a good idea to bring along your college transcript, as well as the ID documents (driver’s license and passport or social security card) to complete all of the required forms that day.  When the license is approved, you’ll start getting jobs.

You will get little if any training. Most substitute teachers seem to be hired on a “sink or swim” basis. On your first day on the job, you will simply walk in, announce to the class that you’re their substitute for the day, and then make the best of the situation.

You will be told the mechanics of how you get jobs. Before the internet came into existence, school districts employed a person often known as the “gatekeeper.” This person would report to work at 5:00 AM and wait for teachers to call in sick. When they did, he or she would start calling substitutes to fill the vacancy.

The job function of the “gatekeeper” has now been largely automated. Instead of a human calling you, you will go to a website and/or receive an automated telephone call.  You will see all available positions and be able to select one.  My district, and most others, use a system called AESOP.  If you want to limit yourself to particular schools or grades, you have this option.  But your license allows you to teach any grade level from preschool through adult, and you’ll be given the opportunity to take any available assignment.  Since you don’t have to deal with a human being on the other end of the phone, it is very easy to be selective and take only the “good” jobs.

I currently have the telephone option turned off, and I get jobs strictly by logging in to the website.  I usually have these jobs lined up in advance.  If I were in need of daily work, I would set the alarm clock for 5:00 and wait for the phone to ring, safe in the knowledge that I would be working almost every day.

What the Work is Like

As a substitute teacher, there will be good days and bad days.  Fortunately, however, the good days far outnumber the bad.  And because you can pick your assignments, you never have to worry about going back to the bad classes!  After a while of taking jobs, you will recognize which are the good schools, which are the good teachers, and which are the good classes.  Armed with that knowledge, you can pick and choose and go back only to the good jobs.

Surprisingly, at first, it can be hard to predict which will be the good assignments and which will be the bad ones.  I’ve taught at schools with extremely bad reputations, and often found those assignments to be the most rewarding experiences.  On the other hand, I’ve also taken a few jobs at “good” schools where I don’t plan to go back.  For this reason, the early days of your substitute experience will teach you a few lessons.  But after you’ve figured out where the good jobs are, you’ll have days when you feel guilty about collecting a paycheck for such a fun assignment.

Because of my particular temperament, I  prefer taking jobs in high school, junior high, and occasionally the upper elementary grades.  I know that I wouldn’t be a particularly good kindergarten teacher, so I don’t take those jobs.  Other substitutes are more suited to younger kids and would be horrified at the prospect of teaching high school students.  The nice thing about subbing is that you can pick and choose.

One reason why I prefer high school and middle school is the fact that if I get a bad group of students, I know they’ll be gone in less than an hour.  I can put up with just about anything for an hour.  I rarely have miserable assignments, but it’s nice knowing that if I do, it’s of very short duration.

I have found that the principals, teachers, and all of the staff of the schools where I teach are genuinely happy to see me.  There is indeed a shortage of substitute teachers, and there are times when they need one but don’t get one.  When that happens, the other staff need to work harder.  The regular teachers often need to use their prep hour to cover another class, or the principal or another administrator needs to step in.  So when they see me, they’re happy to know that they don’t have to worry about the class that day.

Most times, the regular teacher leaves lesson plans.  This is often an activity where I need to do little more than hand out the assignment and sit back as the students do the work.  Many substitute teachers are happiest when they discover a lesson plan sitting on the desk.  On the other hand, I tend to enjoy the situations where there is no lesson plan and I’m left to fend for myself.  I consider myself a renaissance man, and I can always come up with something that ties in to what they’ve been studying, whether it’s math, English, social studies, science, or just about any other subject.  It’s my chance to pontificate, and yes, I enjoy showing off to the students that I can do the algebra problem and that, in fact, yes, we do algebra in the “real world” on a regular basis.

The most common question I’m asked about substitute teaching is how well the students behave.  Many adults recall their days as a student, and remember that when a substitute appeared in the room, the class erupted in chaos.

Thankfully, few days end like this. FEMA photo.

Thankfully, few days end like this. FEMA photo.

You will, indeed, experience chaotic situations from time to time as a substitute.  Some students will believe that they can get away with anything with the regular teacher gone, and they will try to do so.  However, by using a bit of common sense and displaying an aura of calm authority, most of these problems can be overcome quite easily.  Occasionally, it’s necessary to kick some student out of the room and refer him to the assistant principal or whoever deals with behavioral issues.  But this is actually quite rare, especially after students realize that you are willing to go to such extreme measures.  Typically, students will do their job with a minimum of prodding.

I’m also frequently asked whether substitutes need to understand the subject matter that they’re supposedly teaching.  The answer to this question is a resounding no.  The expectation is that the substitute will have absolutely no understanding of the subject matter.  If you maintain order for the day, you will be lauded for doing a great job.  You’re not actually expected to impart any knowledge to the students.

Having said that, my favorite part of the job is actually imparting knowledge, or at the very least showing off to the students that I actually understand the material.  So I take pride in explaining the causes of the Civil War on one day, and then applying the quadratic formula the next day.  The students are duly impressed, the teacher is pleasantly surprised to discover that the students actually learned something, and I’m probably requested the next time that teacher is absent.  But this is not the norm.  Normally, if the classroom is still standing at the end of the day, then you have done your job as a substitute, and everyone is happy.  So no, you do not need any particular knowledge of the subject matter in order to substitute teach.  Even if you have no idea what the quadratic formula is, you’ll still do fine teaching math classes.

Even in the worst classes (which are, thankfully, rare), it is clear that most of the students want to learn something.  It’s actually quite gratifying when a student thanks you at the end of class.  The rewards can come at unexpected times.  It’s not unusual to be teaching a history class and have a student ask if you can help with their math.  Occasionally, you’ll see that the student finally “gets it” after struggling with something for quite a while.  I’m not a better teacher than the regular teacher.  But I might bring a different approach that works better for one particular student.

If I haven’t scared you off so far, then I encourage you to become a substitute teacher.  The rules I’ve discussed here apply to Minnesota.  Most other states allow substitute teachers without an education degree.  In fact, some require only a high school diploma.  (Pay in such states, however, seems to be considerably lower than states requiring a four-year degree.)  Each state will have a different set of hoops to jump through.  But most seem to have enough of a shortage of subs that they will assist you in every way possible as you jump through them.

You might get a small amount of training before your first job, but I’ve discovered that experience actually doing the job is much more valuable.  If you want to do some reading before undertaking the job, you might find some of the following books and websites helpful:



MacArthur’s Escape from the Philippines, 1942

Today marks the 75th anniversary of the escape from the Philippines by General Douglas MacArthur, which began on March 11, 1942. He and his forces were surrounded on the Island of Corregidor.

The Japanese invasion had commenced at the same time as the attack on Pearl Harbor. In accordance with American doctrine, Manila was declared an open city. By March, American and Filipino forces had withdrawn to Bataan, with the General’s staff on Corregidor. In February, MacArther had announced that he and his family intended to share the fate of the garrison, but fearing that the General would become a high value prisoner, President Roosevelt ordered him to go to Australia.

MacArthur’s route. Wikipedia image.

MacArthur, his family and staff, travelled through waters patrolled by Japanese warships in PT boats to Mindanao, from which they flew to Australia. President Roosevelt issued a statement on March 17:

I know that every man and woman in the United States admires with me General MacArthur’s determination to fight to the finish with his men in the Philippines. But I also know that every man and woman is in agreement that all important decisions must be made with a view toward the successful termination of the war. Knowing this, I am sure that every American, if faced individually with the question as to where General MacArthur could best serve his country, could come to only one answer

Over the coming weeks, Bataan fell, leading to the Bataan Death March, which began on April 9, in which thousands of Filipino and American POW’s perished.

MacArthur arrived in Melbourne on March 21, where he gave his famous “I shall return” speech:

His Kite Wireless, 1917


A hundred years ago this month, the March 1917 issue of Boys’ Life magazine featured this illustration of a Scout preparing to send his wireless aerial aloft by means of a kite.

The title of the design is “His Kite Wireless,” by prolific illustrator Charles L. Wrenn (1880-1952).

The magazine also carried a two-page photo spread of Boy Scouts as long distance talkers, whether it be by semaphore, telegraph, or wireless.  At the time, varying levels of skill in each were required for Second Class, First Class, and the Signalling Merit Badge.


Kriket Kamel CB Mount, 1977


Most red blooded young amateur radio operators in the 1970’s were quite opposed and appalled by the shenanigans taking place on the CB airwaves. On the other hand, most young male amateur radio operators were quite intrigued by the CB column appearing in Elementary Electronics magazine, “Kathi’s CB Carousel,” authored by Kathi Martin, KGK3916. Undoubtedly, most of them probably wondered what a nice girl like Kathi was doing in a place like eleven meters. (We previously wrote about her in an earlier post.)

Kathi Martin, 1975.

Kathi Martin, 1975.

But she seemed to enjoy the CB lifestyle, and who were we to judge. So we read with interest her articles, such as the one appearing 40 years ago in the March-April 1977 issue, reviewing the latest in anti-theft devices, the Kriket Kamel, Model KC-3085, from the Acoustic Fiber Sound Systems company. It was a “hump mount” (hence the camel moniker) for safely mounting a CB radio on the transmission hump of a vehicle.

Kathi begins by noting that the confounded transmission hump on the floor of the car was about the most useless thing in the world. But thanks to the Kriket Kamel, it made the perfect place to mount the CB. The whole radio could be removed without a trace. Without any tell-tale signs of a CB radio in the car, a thief wouldn’t take a chance by breaking into the trunk and rummaging around for one.

She suggested that to complete the CB-free illusion, there were two options for the antenna. First, you could use a combination CB-AM-FM antenna. Since it looked just like a regular broadcast antenna, the thief wouldn’t have a clue that the car was owned by a CB’er with valuable equipment. Another option would be a trunk mount that could be removed completely to inside the trunk.

An added bonus was that this mounting position provided improved sound, since the Kamel also included a speaker, and the transmission hump allowed it to be mounted perfectly for good car-filling audio.

Kathi  noted that she wasn’t “one of those helpless type females,” but since an eager male friend was hanging around, she let him do the installation job for her. “I figure it does no harm to let the boys demonstrate how clever they can be too–at least once in a while!” The whole operation required just a few minutes to attach two bolts. The power cord was connected to a cigarette lighter plug, which didn’t even require soldering, since Kathi was partial to crimp-on connectors.

To take the radio out of the car and outwit the thieves, it was a simple matter of unplugging the power, unscrewing the antenna connection, and putting the entire unit in a safe place.

Due to her relatively common name, attempts to find out more about Kathi Martin on the Internet have largely proven futile. The Editor-in-Chief of Elementary Electronics was Julian Martin, WA2CQL, (also known as Julian M. Sienkiewicz), and it appears that CB Editor Kathi was his daughter. But I haven’t been able to find any more information about her. On the other hand, people Google themselves, and it’s not unlikely that she will eventually be reading this. So I’ll put out a request to her: I suspect you have a lot of fans who wonder what you’ve been up to. So if you’re reading this, please leave a comment below or contact me so that I can get them up to date. If you wish to continue keeping a low profile, I promise to respect that wish and will keep your contact information confidential.

Training Navy Radiomen, 1942

1942Mar8ChiTribNavyRadioOn this day 75 years ago, March 8, 1942, the Chicago Tribune carried this description of the fever pitch at which it was training its radio experts.

It explained how the Navy was cramming a two-year college radio engineering curriculum into three months. Students were housed at the Naval armory where they woke at 5:30, and were in class by 7:00 at the Balaban & Katz television studio at 190 North State Street.  The theater company was the licensee of WBKB-TV, located at 190 North State Street, the present location of WLS-TV.

The men were in class until 11:00, at which time they marched back to the armory to eat, and were back in class at 12:15 until classes ended at 5:00. Lights were out at 9:00, and the Ensign in charge of the program reported that there were no problems with insomnia.

In a few months, the men’s duties would include RADAR, so the UHF expertise of the television engineers running the program were ideal for instruction.

The men’s former occupations were diverse, and included electricians, refrigerator servicemen, farmers, and locomotive firemen. Each was given a preliminary scholastic examination by mail, followed by the regular navy physical examination. Even though the scholastic test was tough, the Navy didn’t care whether the students had any formal education.

Many of the men were married, and many had turned down commissions as officers in the Army , instead opting for the rank of naval radioman, second class. They recognized that the training would be invaluable when they returned to civilian life, especially with the prospect of a future in television.

The men were paid $72 per month, with an additional allowance of $34.50 for dependents. It was noted that the men could live on “nothing a week,” with the exception of cigarettes or extras.

ChicagoRadioSchoolA typical classroom at the school is shown here, courtesy of an article describing this and other Navy radio schools in the November 1942 issue of QST.


End of Wartime Civilian Radio Production

1942Mar8ChiTribWPBOn this day 75 years ago, March 7, 1942, the War Production Board (WPB) ordered that civilian radio production would cease on April 22, as reported in this clipping from the March 8 Chicago Tribune.

As of that date, the entire industry would be on a wartime footing, and the entire industry, with the exception of replacement parts production, would be converted to war production.

A billion dollars worth of war orders were already in the pipeline, and half of that business was to companies making home radio sets. The WPB acknowledged that some unemployment would result as companies switched over to war production, but it was estimated that 95 percent of the conversion would be complete by the end of June.

The board estimated that when the last civilian set rolled off the assembly lines, there would be 60 million sets in operation, with a set in 87% of American homes.

More details of the order can be found at our earlier post.


1947 Portable Phono-Radio


Seventy years ago this month, the March 1947 issue of Popular Science showed how to put together this portable radio phonograph.  It was by no means deluxe, but it was the epitome of portability.  The magazine noted that in most cases, the “portable” terminology meant only that a handle had been slapped onto the cabinet, and the set was still tethered by the need for electrical current.   But in this case, a crank-up phonograph motor and a one-tube battery powered amplifier meant that it was truly portable.

The electronics consisted of a 1D8GT tube powered by two batteries, a 1.5 volt cell for the filaments, and two 67.5 volt batteries providing 135 volts B+, although it noted that it would work with as little as 90 volts.

The magazine noted that the spring motor should be set to 80, which would result in it running at the desired 78 RPM with a record on the platter.

The radio was simply a crystal set with a fixed crystal, which could be switched in place of the phonograph’s pickup cartridge.  While the radio strength was not great, it would serve to pull in local stations, especially with an external antenna and ground of some sort.


Underground Dutch WW2 Radio Receivers

Another collection of clandestine Dutch radios.

Another collection of clandestine Dutch radios.

Clandestine radio concealed in book.

Clandestine radio concealed in book.

When the Nazis invaded the Netherlands, they didn’t want to deal with the possibility of the Dutch tuning in foreign radio broadcasts. So in the spring of 1942, they simply confiscated all radio receivers.

Undaunted, Dutch radio enthusiasts simply went underground and constructed sets to listen to the BBC and Radio Boston to learn how the war was going. A number of interesting radios were described in the March 1947 issue of Radio Craft, in an article by one Mr. J. Maquerinck, who described sets built by himself and others.

The simplest, or course, was the venerable crystal1947MarRadioCraft3 set, such as the one shown here, constructed by one of the author’s friends. This set pulled in England quite well and was constructed in a wooden box. When the friend wanted to listen, he opened the box, hooked up an antenna and ground, and tuned in the BBC.

Another friend, who had in his possession a vacuum tube, constructed the simple one-tube set1947MarRadioCraft4 shown here. This friend had no variable capacitor, but the coil wound on an iron core provided adequate selectivity, and was sensitive enough to pull in England.

1947MarRadioCraft1The author himself wanted to avoid the complication of an external antenna, which could be seen. He was fortunate enough to own a dual tube, which he was able to use in the circuit shown here as RF amplfier, grid-leak detector, and audio amplifier. To conceal the set, he hollowed out his telephone and built it inside the phone cabinet. His finger served as enough of an antenna to pull in the BBC on 200 kHz. The telephone’s ground connection served as the radio’s ground.

To avoid detection, he had the phone set up so that the dial had to be turned to 7 to power up the radio. As an added precaution, he placed above the radio the sign shown here, meaning “Take care, don’t use. Defective!” He noted that the loss of the telephone wasn’t much of a loss, since it had been out of order most of the time anyway.


This “real radio-telephone” was never discovered. In September 1944, the civilian population of the author’s town was evacuated. When he returned, everything else in the house had been stolen, but the receiver remained.  I guess even Nazis were afraid of messing with the telephone company’s equipment.

The author was evacuated to the town of Aalten, population 10,000. The owner of the home in which the author resided had not previously owned a radio, but the town’s serviceman constructed a regenerative which used plug-in coils, one for 200 kHz and the other for 1000 kHz. The 200 kHz frequency was used to tune in the BBC, and 1000 kHz was the frequency of a station in a part of Holland that had already been liberated.

For another look at clandestine radio receivers used during the war, see our prior post on radios in occupied Guernsey.

Radio concealed in camera, constructed by of , Holland.

Radio concealed in camera, constructed by F.M. Leopold of Eindhoven , Holland.