October 1956 Popular Electronics
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Carl and Jerry found the appearance and construction of 2400
megacycle transmitters and receivers to be quite odd compared
to the equipment they were used to dealing with. It's sometimes
hard to believe such an attitude of wonder when our world today
is utterly filled with wireless devices operating in the 2.4 GHz
ISM band. Author John T. Frye could never have imagined
that such a reality would would exist half a century after his
story of the pair of teenage electronics sleuths. Unlike our
postage stamp size integrated assemblies that cost a few dollars,
they speak of "special ultra-high-frequency 'light-house' tubes
with a cavity resonator clamped on top of them." Back to the
story, though... Did you know that police were using radar guns
as far back as 1963?
Carl & Jerry: Abetting or Not?
By John T. Frye
Carl and Jerry were preparing to go on one of their electronic
safaris. Equipment to be taken along was spread out on the workbench
of their basement laboratory, and Jerry was carefully dividing
it into two piles.
First he placed a 75-meter transceiver in each pile. These
were followed by identical small dish-type reflector antennas
and small collapsing tripod mounts to support them. Then he
placed a small power supply in the pile next to him and a larger
and much heavier combination power supply and modulator in the
pile Carl was to carry .
Finally, two small chassis, each carrying what seemed to
be a weird-shaped bit of brass plumbing clamped around the top
of a metal tube, were divided among the growing stacks of equipment.
The two chassis were not exactly alike for, in addition to the
unusual appearing tubes, one of them also had a conventional
miniature glass tube mounted on it.
"These things look like they'd suck eggs," was Carl's disparaging
remark as he examined the unusual pieces of equipment. "I've
seen some odd-ball transmitters and receivers in my day, but
these things are ridiculous."
"At 2400 megacycles, you can't expect conventional-looking
transmitters and receivers," Jerry pointed out. "A wavelength
at that frequency is only 12.5 centimeters long - or approximately
4.92 inches. Compare that with about 260 feet for a wavelength
on 80 meters."
"What are these things that look like tubes crossed with
"Those are special ultra-high-frequency 'light-house' tubes
with a cavity resonator clamped on top of them. The one-tube
job is the transmitter, while the other is the receiver - a
superregenerative type with a separately quenched oscillator.
The transmitter only puts out a maximum of a quarter of a watt,
but these reflector-type antennas should give us enough gain
to cover that quarter mile between Uncle Walt's and his neighbor
up the highway."
"Why have we got to lug all this stuff clear out there? Why
can't we just test it around here?"
"Because that's the closest place I know of where we can
get a clear shot across that distance with absolutely nothing
in the way, and where we can have power for our rigs at both
ends. Uncle Walt lives right on a curve in the highway, and
you can look from his front porch straight up the pavement to
Mr. Arthur's porch. I'll operate the transmitter at Uncle Walt's,
and you can work the receiver at Mr. Arthur's."
"What do we need the transceivers for, anyway?"
"We'll probably have to do a lot of adjusting of antenna
direction, frequency, etc., to get maximum signal strength.
Since we'll only have one transmitter and one receiver on the
ultra-high frequency, we can only talk one way after we establish
contact. Being able to talk back and forth on seventy-five while
making adjustments will help a lot."
"Okay; so let's get going," Carl said; and he quickly exchanged
the heavy power supply in his pile for the light one in Jerry's
while the latter's back was turned.
The two boys loaded the equipment into the handlebar baskets
they strapped on their bicycles only for occasions like this,
(Ordinarily such accessories were considered "too sissy.") Carried
along by their youthful enthusiasm, it required but a few minutes
for them to pedal out to the farm of Jerry's Uncle Walter Bishop.
Carl helped Jerry set up the transmitter and connect it to the
power supply and modulator. The little dish-type antenna and
reflector was perched on its tripod, and a short coaxial line
ran down to the output fitting on the side of the cavity resonator.
Next, both boys rode on down the narrow path from the highway
to Mr. Arthur's and set up the receiver on his porch. When Jerry
was sure the receiver was working correctly, he took off the
earphones and reached over and let them snap shut on Carl's
head with a resounding "plop."
"Guess we're ready," he announced. "Use a single phone over
one ear and leave the other free for use with the transceiver.
The instant you .hear my voice on the u.h.f. receiver, yell
at me on the hand-held unit, for it, will mean that I have the
transmitting antenna pointed nearly at you. That beam will be
very narrow, and we'll have to aim it right on the nose. Once
we make contact, we can go ahead and align both transmitter
and receiver antennas perfectly, checking back and forth with
the transceivers; and then you can carefully tune the receiver
to the exact transmitter frequency."
"I can?" Carl questioned sarcastically.
"With what? I see nothing that looks like a tuning knob on
this plumber's nightmare."
"You tune the receiver by turning this little screw right
here on top of the cavity resonator with this long fiber screwdriver,"
Jerry explained; "and move it only a fraction of a turn at a
Having delivered this bit of advice, he hopped back on his
bicycle and was soon at his uncle's place. After switching on
the high-frequency transmitter, he pulled out the telescoping
antenna of the war-surplus transceiver, which automatically
turned it on. Holding the case so that the earphone was at his
ear and the microphone in front of his lips, he pushed the transmit-receive
switch covered with a waterproof rubber pouch on the side of
"How do you read, W9EGV? This is W9CFI," he said.
"Loud and clear, W9CFI, from W9EGV," was the prompt answer.
"Okay; I'm going to start shooting at you, If you hear me,
yell plenty loud, for I'll have to set the handie-talkie down
on the floor while I'm fiddling with the antenna."
"Roger. Let's see if you can spray me with some of that u.h.f."
Jerry began carefully aiming the reflector at the porch of the
white house up the road. For several seconds nothing happened,
and then he heard a faint cry from the earphone of the handle-talkie
sitting beside him. "Hold it!" Carl said; you're knocking down
the hiss in the receiver."
"Can you hear me?" Jerry asked into the microphone connected
to the modulator of the u.h.f. transmitter.
"Sure can," came the answer; "Wups! You cut out for a minute,
but it's okay again now."
As Carl said this, Jerry noticed a large black car with two
men in it pull off the highway onto the path just next to his
uncle's house. It was when this car had passed through the u.h.f.
beam that Carl said the signal cut out momentarily. Jerry concluded
the men had stopped to examine a map or something, and he and
.Carl went ahead with their experimenting.
It was not until two more cars pulled up opposite the first
one that Jerry took more careful notice. One of the cars that
just stopped was an ancient Model A Ford truck loaded with late-in-the-season
watermelons. The. driver was a little weazened man with a sharply-pointed
white goatee; and from the way he popped from the cab and began
waving his arms about, he was obviously quite excited about
something. The unmistakable appearance of the other car, a state
police patrol, gave a possible clue to the cause of his agitation.
"Hey, Carl,"· Jerry said into the mike, "you'd better come
on down here and see what gives. Looks like it may get interesting."
Collapsing the antenna of the handle-talkie to shut it off,
Jerry hurriedly left without thinking to shut off the u.h.f.
transmitter. He had barely reached the parked cars before Carl
came pumping up on his bicycle.
"I tell you," the little man was shouting, "that you and
your fancy radar gadget are all wrong. You can't possibly drive
that bucket-of-bolts sixty-five."
"Take it easy, Pop," the big state trooper behind the wheel
of the black car said good-humoredly. "This thing doesn't make
mistakes. It said you were hitting sixty-five when you passed,
and that's what you were doing. So we radioed ahead for Jim
to stop you."
"You and your fancy radar gadget are all wrong," the man
with the goatee was shouting. "You can't possibly drive that
"Tell you what I'm gonna do," the man with the goatee offered.
"If anyone of the three of you can drive that Model A a mile
over forty-five miles per hour, I'll give it to you and throw
in the load of watermelons to boot!"
"Old Timer, you've got yourself a deal," the youthful trooper
named Jim said, as he slid out of his patrol car. "I always
did want to drive one of those old cars my old man still insists
is 'the best car Henry ever built.' If you got sixty-five out
of that iron, so can I. I'll go back up the road a piece and
come on by with the thing wide open so you boys can get a reading
He got into the truck, and went off up the highway with the
Do you know how that radar thing works?" Carl whispered to
"Sure. So would you if you had read the article about it
in the May, 1956, issue of Popular Electronics. It depends on
the Doppler effect."
"I remember that from physics. It's an apparent change in
frequency of a signal emanating from a moving source as observed
from a fixed position."
"Fine," said Jerry. "That's exactly right. The most common
example is the apparent change in the pitch of a train whistle
as it passes. When it's coming toward you, the pitch seems to
increase; but as the train moves away, the pitch lowers. When
the train is moving rapidly toward you, the sound waves are
sort of bunched together and the pitch of the signal striking
the ear is increased. When the whistle is moving away, the sound
waves are stretched out, and the pitch seems lower. The radar
gadget sends out a beam of u.h.f. signal that strikes the moving
car and is reflected back to a receiver housed in the same unit
with the transmitter.
"This reflected signal is mixed with the signal direct from
the transmitter," Jerry continued, "and the difference between
their frequencies is read by an audio frequency meter. The difference
in frequency between the transmitted signal and the reflected
signal depends directly on how fast the car reflecting the signal
is moving. The faster it moves, the greater is the difference.
At 100 miles per hour, the reflected signal will be shifted
731 cycles from the transmitter frequency of 2455 megacycles.
Speeds below 100 miles per hour produce less shift. The audio
frequency meter is calibrated in miles per hour for direct reading
"But where is the radar gadget?" "Probably in the trunk of
the black car.
You can see the meter there on top of the dash. The signal
is sent out and received back through a camouflaged hole in
the metal lid of the trunk. All this car has to do is park along
the highway and take speed readings. When a 'live prospect'
shoots past, the radar car radios to a patrol car waiting about
a mile down the highway, and he picks up the speeder. Well,
here comes the truck; let's go over and see what kind of a reading
The boys moved over to the black car and watched the meter
on the dash as the truck went spluttering by. The pointer rose
sluggishly to a reading of thirty-five miles per hour.
"That's all that crate will do," Jim announced, as he drove
back and parked the truck. "I had my foot clear down in the
fan. My old man must have rocks in his head if he thinks that's
a good car."
"I don't get it," the radar operator behind the wheel said
to the other. "This thing never was wrong before. I still say
we give the old gentleman a ticket - hey!" he broke off, "look
at the meter."
Sure enough, the meter on the dash was jumping crazily about.
Jerry's glance went from it to his Aunt Enid busily sweeping
the immaculate front porch. (As every woman knows, a broom is
a wonderful excuse for staying within earshot and eyesight of
any interesting event!) As her broom nudged the coaxial cable,
the dish antenna wobbled back and forth.
"Watch that meter a moment while I do something up on the
porch," Jerry suggested to the men in the car. Running to the
u.h.f. transmitter, he swept the invisible beam from the antenna
back and forth across the trunk of the black car.
"That's what's doing it!" one of the men called. "What you
got up there anyway?"
Carl and Jerry explained that the transmitter they were using
was supposed to be in the 2300-2450 mc. ham band, but, that
since they had no extremely accurate frequency-measuring equipment
at this frequency, the transmitter had drifted down very close
to the 2455-mc. frequency of the radar transmitter. The difference
in frequency was just enough to give a good reading on the speed
"Well, that's one for the book," the man behind the wheel
said, tearing up the speeding ticket he had started to write.
"Of all the places we had to set up our operation, we had to
pick this one directly in the path of your beam. Pop, I'm sorry
for all the hard time we've given you."
"That's all right; young man; we're all wrong at one time
or another," the little man with the goatee said pleasantly;
"but I feel I owe these boys a favor. How about giving you a
lift back to town if you're ready to go? You can put your bikes
The boys promptly took him up on the offer, and soon they
were chugging down the road. After they had gone about a mile,
the little old man took a cautious look in his rear-view mirror,
then reached over to the right side of the dash and gave a shiny
knob there a practiced turn counterclockwise. Instantly the
popping motor smoothed out and the truck plunged forward on
"These young whipper-snappers don't savvy a combination choke
and carburetor control any more than a redskin used to savvy
the hindsight on a rifle," the old fellow said with a cackling
laugh. "Fact is, most of the young ones don't know what a hand-choke
is, let alone a .dash-mounted carburetor control. When I saw
that patrol car take out after me, I just leaned over and cut
Betsy's gas down until she would barely run. That's why the
officer could only get thirty-five out of her. Shucks, with
her Fronty head and special camshaft, she'll hit seventy-five
without a bit of trouble."
Carl and Jerry made no comment. When the old man let them
out at their homes, he insisted that each accept a large watermelon.
As he drove off, Carl turned to his pal and said slowly:
"Jer, I feel kind of funny. I'm not at all sure but that
we helped defeat 'due process of law' today."
"Neither am I. On the other hand, maybe our transmitter did
get into the act. We'll never know. Let's go in and eat watermelon
while we brood about it!"
Carl & Jerry: Their Complete Adventures is now available. "From
1954 through 1964, Popular Electronics published 119 adventures of Carl Anderson and Jerry Bishop, 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
- Electronic Eraser,
- Electronic Trap, March
- Geniuses at Work, June
- Eeeeelectricity!, November
- Anchors Aweigh, July
- Bosco Has His Day,
- The Hand of Selene,
- Feedback, May 1956
- Abetting or Not?, October
- Electronic Beach
Buggy, September 1956
- Extra Sensory
Perception, December 1956
- Trapped in a Chimney,
- Command Performance,
Education, July 1963
- Treachery of Judas, July
- The Sucker, May 1963
- Stereotaped New
Year, January 1963
- The Snow Machine, December
Education, July 1963
- Slow Motion for
Quick Action, April 1963
- Sonar Sleuthing, August
- TV Antennas, August 1955
- Succoring a Soroban,
- "All's Fair --", September
- Operation Worm Warming,
- The Blubber Banisher,
- The Sparkling Light, May
- Pure Research Rewarded,
- A Hot Idea, March 1960
- The Hot Dog Case, December
- A New Company is Launched,
- Under the Mistletoe,
- Electronic Eraser,
- "BBI", May 1959
- Ultrasonic Sound Waves,
- The River Sniffer, July
- Ham Radio, April 1955
- El Torero Electronico,
- Wired Wireless, January
- Electronic Shadow,
- Elementary Induction,
- He Went That-a-Way,
- Electronic Detective,
- Aiding an Instinct,
- Two Detectors, February
- Tussle with a Tachometer,
- Therry and the Pirates,
- The Crazy Clock Caper,
Posted June 18, 2015