March 1960 Popular Electronics
of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Popular Electronics was published from October 1954 through April 1985. All copyrights (if any) are hereby acknowledged.
That John T. Frye
was a great short story writer is a given truism based on his decades-long production of the Carl & Jerry series
in Popular Electronics. It is easy to look over the fact that he also had artistic skills as well as evidenced by
the pencil drawings that accompanied each installment. In this episode, our two electronics hobbyists build a
resistor anemometer to measure wind speed from within their basement workshop. In the usually storyline style, one
boy gives a lesson in circuit design while the other (also the reader) is the attentive student.
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Carl & Jerry: A Hot Idea
By John T Frye
The buffeting March wind spanked Carl with the slamming basement
door as he stepped into the electronic laboratory of his friend, Jerry:
The latter was sitting with his head encased in a pair of muff-type
earphones connected to an amplifier with a variable frequency audio
oscillator working into its input. As Carl looked at his chum aimlessly
adjusting the frequency of the oscillator and the gain of the amplifier,
he decided there was something about Jerry's appearance that was not
right. There was a certain lackluster look about his eyes, and his round
face looked fatter than ever - but in a sort of lopsided way.
"Guess I'm the one guy in ten for whom it won't work," Jerry said
with a lugubrious sigh as he shut off the equipment and removed the
"What won't work, and what's the matter with your face? It looks
twice as big as it ought to."
"The 'audio anesthetic' won't work for me. I've got an infected wisdom
tooth that's killing me, and I have an appointment with the dentist
in an hour. But the other day I read that a Boston dentist discovered
that music or random noise put into earphones worn by a patient killed
the pain of dental work in 90% of 2000 cases tested. The patient adjusts
the sound level with a gain control in his lap until the sound blocks
out the pain sensation. A company in Rochester is already in production
on the device. I was trying to see if I could kill the pain of my toothache
with various frequencies from the audio generator, but I couldn't."
"That thing must work on a variation of the 'mule skinner' principle,"
Carl said. "You know a veteran mule skinner always took the ear of a
mean mule between his teeth and bit down hard while he was putting on
the bridle. The idea was that while the mule was thinking about how
much his ear hurt he couldn't think about kicking or biting the mule
skinner. With the audio anesthetic, while the mind is concentrating
on the sound it ignores the pain. Your trouble is that in fooling around
with ham radio, etc., you've trained yourself to be a little smarter
than the mule. You can listen and still be thinking about your aching
tooth at the same time. Well, I better scram and let you go to the dentist."
"Oh, no, you don't!" Jerry exclaimed.
"I've a little chore for you to perform while I'm gone; and I just
know you wouldn't refuse your poor, pain-wracked buddy."
"Depends on what my poor, pain-wracked, scheming buddy has in mind."
"All I want you to do is mount this thermistor anemometer out on
the garage and run this cable from it back into the lab."
"You know," Carl said thoughtfully, "I don't think you've got a toothache
at all. You've just dislocated your jaw on one of those big words you're
so fond of. What the heck is a 'Mistermometer'?"
"I said a 'thermistor anemometer.' As you know, or should know, an
anemometer is a device for, measuring wind velocity. This one is intended
to do so by the use of thermistors. A 'thermistor' is a resistor whose
resistance changes, in a nonlinear fashion, incidentally, with a change
in temperature. The temperature affecting the resistance may arise externally
or it may come from current flowing through the thermistor. In the case
of these thermistors you see on the bench, an increase from -60 to plus
150 degrees centigrade will cause the resistance to fall from about
2000 ohms to one ohm."
"That sounds dandy for measuring temperature, but I don't see how
they can be used to measure wind velocity."
"Keep listening and you will."
"I've arranged two matched thermistors and two resistors - one variable
- in a bridge circuit," Jerry explained as he sketched the familiar
diamond-shaped bridge circuit. "These two top legs are the thermistors;
the two bottom legs are the resistors. Here's a battery in series with
a switch connected between the common junction of the two thermistors
up here and the common junction of the two resistors at the bottom.
A d.c. meter connects from this left-hand thermistor-resistor junction
across to the right-hand thermistor-resistor junction.
"Now, when the variable resistor is properly adjusted to equal the
fixed resistor, the battery current divides equally between the left
and right sides of the bridge. Since the same current flows through
each thermistor, any resistance change in one is duplicated by the resistance
change in the other, and the bridge stays in balance. Voltage drop along
the two sides is identical, and no current flows through the meter."
"How do you know the thermistors in your bridge are matched?"
"Because I matched 'em. I put the bridge in the freezer where the
temperature is below zero and then put it in that light-bulb-heated
oven and brought the temperature up to 150 degrees. I kept repeating
this test with different combinations of thermistors until I found two
that would go through the temperature swing with practically no indication
of current through the meter at any point. You satisfied?"
"Yep, but how does the thing measure wind velocity?"
"As you can see, one thermistor is mounted inside this aluminum can
with tiny holes in the top and bottom to permit outside air to filter
very slowly through. The other thermistor is mounted out in the open
so wind can blow around it freely. When battery current flows through
both thermistors, heating them, the heat is lost to the surrounding
air. In a dead calm, the heat lost by the enclosed thermistor and the
heat lost by the one outside in absolutely still air will be the same
and no reading will show on the meter.
"However, when a wind is blowing, the heat from the exposed thermistor
will be carried away; the harder the wind blows, the faster heat is
lost. Heat lost by the enclosed thermistor in its artificial calm will
remain the same. The wind-cooled thermistor will stay high in resistance
while its hotter buddy inside the can will go lower in resistance,.
unbalancing the bridge and permitting current to flow through the meter.
All we have to do is to calibrate this current-indicating meter in terms
of wind miles per hour and we have a remote-indicating anemometer with
no moving parts."
"I suppose. this little wooden umbrella-shaped canopy is to keep
the sun and rain from influencing the reading."
"Right. Actually the whole thing is pretty crude, but I want to put
it up for a while and see how much rain and sun does affect it. This
variable March weather is ideal for making such a study. Will you put
"Oh, I reckon," Carl said gruffly. "Quit stalling and get to the
Actually Carl was as eager as his friend to tryout the new gadget,
and he lost no time after Jerry had gone. It took but a few moments
to fasten the device securely to the garage gable and to run the four-wire
TV antenna rotor cable back into the basement through a casement window.
There he connected two of the wires to the battery-and-switch combination,
and the other two were connected to the milliammeter. When the switch
was thrown, the meter indicated up-scale; and Carl was fascinated by
the way the meter reading kept step with the roar of the March wind
outside. He was still watching the meter when Jerry came in the door.
"You're still kind of fat in the face," Carl remarked critically,
"but you look better. Could he save the tooth?"
"He can if he wants to; I left it with him," Jerry replied breezily.
"He yanked it out, and it didn't hurt a bit."
"Just wait until that dope starts dying out," Carl said with the
voice of experience. "Your gadget is working fine, Jer. Watch how the
meter pointer moves up every time the wind bends the tops of those trees
through the window there - hey, that's funny," he broke off. "It was
working swell, but look at the crazy way it's behaving now."
The meter was acting strangely. No longer did the pointer keep step
with the roar of the wind. First it bobbed up and down the scale erratically
and then began backing off scale below zero. Finally it settled firmly
against the left-hand stop and refused to budge until Carl opened the
switch; then it came to rest on zero.
"Something's gone wrong out there. You stay here and watch the meter
while I go have a look," Carl suggested.
He had hardly reached the top of the outside basement stairs when
he began shouting; "Call the fire department! Call the fire department!
Kreuger's barn across the alley is on fire, and is it ever going!"
Jerry rushed upstairs and called the fire department, and then he
ran out in the back yard. By this time the old two-story frame barn
across the alley was a mass of flames; and blazing shingles were sailing
all around. Long tongues of flame reached across and licked at Jerry's
The fire department came roaring up and started playing water on
the burning barn and the other buildings nearby, but the fire was not
put under control until it had burned the high tension wires overhead
"Boys, that was close," the fire chief said to Carl and Jerry. "If
the thing had had ten minutes more start with this wind, that whole
row of garages could easily have gone. It certainly is a good thing
you spotted it when you did. How did you happen to see it?"
"Well, we were kind of tipped off by a sort of fire detector we had
installed on our garage roof," Jerry explained lamely. He knew from
bitter experience the difficulty of trying to describe the working of
electronic equipment to people without an electronic background.
"Actually it's not hard to figure what happened," he said to Carl
after the chief had gone and the two boys were walking back to their
laboratory. "The wind was blowing right from the fire toward our garage.
When a tongue of flame would lick over and slu-u-urp that exposed thermistor,
the can would protect the enclosed thermistor from the quick increase
in temperature. As a result, the exposed thermistor got hotter than
the enclosed one, and this made the meter read backward."
Jer, old buddy," Carl said as he laid an affectionate arm across
his friend's shoulders, "the thing I like about you as an inventor is
that you always invent something. Of course, you may set out to invent
a thermistor anemometer and end up with a jim-dandy fire detector; but,
by golly, you come up with something! Man, you're the most!"
"Thanks, pal - I think!" Jerry answered as he grinned crookedly up
with his still swollen face at his friend.
Jerry: Their Complete Adventures is now available. "From 1954 through 1964, Popular
Electronics published 119 adventures of Carl and Jerry, two teen boys with a passion for electronics
and a knack for getting into and out of trouble with haywire lashups built in Jerry's basement.
Better still, the boys explained how it all worked, and in doing so, launched countless young people
into careers in science and technology. Now, for the first time ever, the full run of Carl and Jerry
yarns by John T. Frye are available again, in five authorized anthologies that include the full
text and all illustrations."
Carl & Jerry Episodes on RF Cafe
|- Trapped in a Chimney - January
- Command Performance - November
- Extracurricular Education,
- Treachery of Judas,
- The Sucker, May 1963
Stereotaped New Year, January 1963
- The Snow
Extracurricular Education, July 1963
He Went That-a-Way,
Electronic Detective, February 1958
- Aiding an
Instinct, December 1962
- Succoring a
Soroban, March 1963
- Slow Motion
for Quick Action, April 1963
Sonar Sleuthing, August
- TV Antennas,
- The Hot Dog
Case, December 1954
A New Company is Launched,
the Mistletoe, December 1958
|- "All's Fair --", September 1963
- Operation Worm Warming, May
- The Crazy Clock Caper, October
- Two Detectors,
Tussle with a Tachometer, July 1960
- Therry and the
Pirates, April 1961
- The Sparkling
Research Rewarded, June 1962
Hot Idea, March 1960
Eraser, August 1962
- "BBI", May 1959
Ultrasonic Sound Waves, July 1955
- The River Sniffer,
- Ham Radio, April
- El Torero Electronico,
- Wired Wireless,
Shadow, September 1957
Posted May 29, 2014