chapter 17c ancient modulation and other topics (continued)

Chapter 17C,

CRYSTAL SETS TO SIDEBAND

© Frank W. Harris 2022, REV 16

Chapter 17C

MISCELLANEOUS ELECTRONIC PROJECTS &

TOPICS

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CLASS D AUDIO AMPLIFIERS

By Frank Harris, KØIYE

Big hi-fi sound, high efficiency, low voltage

Class D amplifiers chop an analog sinewave signal into a pulse-width-modulated

stream of rectangular pulses. In other words, the density of high frequency (400 KHz)

rectangular pulses varies with time and represents the amplitude of the wavy simple

analog signal. When applied to audio amplification, a chopped series of high frequency

square pulses can drive a 4 ohm loudspeaker with surprisingly good fidelity. Because the

amplifier output only has two states, the highest voltage and zero voltage, there is no time

spent half on and half off. Consequently there is little power dissipated in the chip. A

tiny chip can deliver big power, 1 to 3 watts or more. And it does all this with just 5 volts

or less.

Why you might want to use one, ... or not

Suppose you are building a small, portable battery-powered receiver to go with

your QRP transmitter and want to use 6 or 9 volt batteries. If you look at the data sheets

for the good old LM388 or LM386 analog amplifiers, you’ll see they are rated to work

from 5 to 15 volts. If you are listening with sensitive earphones, a low voltage supply

will work well. On the other hand, if you want audio that’s both Hi-Fi and LOUD, then

you’ll discover you need big voltage to go with your 4 inch or larger speaker. Yes, low

voltage can be loud with analog chips using just 5 volts but the distortion is intolerable.

It is theoretically possible to use op-amps and comparators to build your own

Class D audio amplifier. But when you diagram what has to be done, you quickly

discover that you would need a huge array of components, a big circuit board and lots of

trial and error. Class D amplifiers are the reason other people's tiny cellphones can be so

annoying - they're both loud AND hi-fi and they accomplish this with tiny low voltage

batteries.

EMI – digital hash in your receiver

If you’ve ever home-built a sensitive ham receiver, you probably discovered that

a pulse-width-modulated (PWM) regulated power supply or even a simple digital display,

will make noise in your receiver that destroyed much of the sensitivity you worked so

hard to achieve. The class D audio chips I used, Maxim MAX9719 and MAX9759, have

“spread spectrum” PWM systems to reduce EMI. Moreover, you have your choice of 3

Chapter 17C,

different sample frequencies that supposedly make it less likely that the hash will appear

inside your desired ham band. Unfortunately, the wires from this board up to my speaker

radiated VHF RF noise like crazy. Since my project needed to work around VHF hand-

helds, I was relieved to discover that I could silence the racket by stringing several large

ferrite beads on the speaker and battery wires. Unfortunately, the noise was still

unacceptable for use around my HF receiver. Sure, I could still hear the hams over the

hiss, but that’s not good enough. Oh, well. At least Class D worked for my immediate

application.

And now more bad news

Modern chips are often surface mount and really tiny. Even surface mount ICs

with projecting leads are becoming scarce. The tool is the 1.5 mm wide tip of a wood

carving gouge used to cut the pads.

You have probably already noticed that the modern world does not want us to

build cool stuff in our basements. The complexity is bad enough. But modern surface

mount is providing the coup-de-grace to homebrewers like us. In the old days, chips

came in DIP packages with big pins. They have 0.1 inch spacing that we can plug into

sockets. Even the early surface mounts weren’t impossible to solder. Yes, 0.050”

spacing was a little tight, but the leads stuck out from the body of the chip and most of us

figured out ways of soldering them. For example, you can buy tiny adapter circuit boards

to accept the “SO” surface mount chips. The periphery of the little board has pads big

enough to accept reasonable sized wires. I’ve even managed to successfully solder SOs

with 0.020” spacing onto the little boards.

Today many of the new chips aren’t available in DIPs or even SOs. When I

ordered my Class D amplifiers, I studied the 5 or 6 versions of surface mount and ordered

the biggest one. It had no leads that stuck out, but the contacts were at least on the

periphery of the tiny squares and I hoped I could solder wires to those.

I was shocked when I opened the package and found tiny, square black flakes 4

mm on a side. Using a microscope, I could read the labels on the chips. Yes, those were

the “big” versions I had ordered. Sure glad I didn’t get the little ones! The 16 contacts

were positioned around the circumference of the chip, but they were just metallic dots.

My first reaction was that the project was over. But then I thought, These chips are too

cheap to bother sending them back. I might as well have a go at it.

How to solder chips you can barely see

First you must give up caffeine and booze. If you have benign familial tremor

Chapter 17C,

like some members of my family, I’m sorry, you’re already screwed. I talked about this

at the local ham club meeting and I was told that the professional way to solder surface

mount is using low temperature solder available in a paste. The paste is applied to the

circuit board using a syringe with an extremely fine needle. The chip is then lowered

onto its pads and heated with a heat gun. I haven’t tried this, but because of the small

size, it isn’t going to be easy, fine gauge needle or not.

Sharpen your soldering tip and set the temperature to 600 degrees. I use 24 gauge

solder and stripped wire-wrap wire to make the connections. Bring your iron in radially

as shown and solder quickly before you fry the chip.

Even if I had the solder paste and needle applicator, I would still need the PC

board with the tiny traces and pads. I use two methods of making PC boards. For big

DIP chips I use perf- boards with pre-drilled holes spaced on 0.1" centers. RF circuits

need real printed-style circuit boards to reduce lead inductance. I make crude but

effective PC boards using a fine wood gouge to carve off the copper between the traces. I

start by gluing the chip down to the PC board with 5 minute Epoxy. Tiny hand-held

gouges intended for wood carving are hard to find. I bought mine from

www.TraditionalWoodworker.com. “Two Cherries” brand, micro-carving tools are the

smallest I’ve found. They have cupped ends as small as 1mm. However, a 1/8” (3mm)

V-parting gouge can be made to work.

Next, you’ll need a really fine-tipped, temperature controlled soldering iron. I use

a Weller model WES51. I filed the tip to make it as sharp as possible. Also, the solder

needs to be the thinnest you can find. I use 0.022” (24 gauge) diameter solder. I use

stripped wire-wrap wire, about 30 gauge, to contact the chip pads. I solder the easy end

of the jumper first onto the big pads and then bend the tiny wire down into position over

the tiny dot. You have to solder each contact as swiftly and deftly as possible. You

might want to practice before you ruin too many chips. The higher the temperature, the

easier it is to make the contact, but that makes it more likely you’ll kill the chip – a bit of

a dilemma there. 600 degrees seems to be a workable compromise.

My class D amplifier board

Chapter 17C,

Here’s the final product installed in my talking meter project. I like to seal those

delicate wires on the chip with a drop of clear epoxy. It is interesting that over half the

sound I get out of my box depends on the resonance chamber behind the speaker. That

empty space in the speaker cabinet isn’t poor planning - it’s vital. One of my major

challenges in this project was making it loud enough. But the first time it was used on a

practice mission, my teammates demanded that I install a volume control. Success!

In summary, I was totally amazed that I was able to make this work. Who says

we old guys have lost the touch? It rarely hurts to try.

**********************************************************************

HOMEBREW ELECTROLYTIC CAPACITORS

Ashish Derhgawen, KG7YKU, loves to experiment. Like me, he likes primitive

electronics he can actually understand. Ashish's day job is programming smart watches,

so you can't accuse him of being a Luddite. He builds crude crystal sets and spark gaps

as a kind of vacation. Primitive homebuilding is different from modern electronics.

Modern homebrewers buy mysterious modules with multi-pin connectors and download

arcane blocks of undocumented code off the internet. Modern homebrewing reminds me

of Harry Potter. Magic and modern electronics have value because they accomplish

miracles that can't be done any other way. How are you fixed for bezoars, boomslang

skin and Arduino boards?

Ashish and his friend Ray Kampmeier have been experimenting with home-made

electrolytic capacitors. As we all know, a capacitor can be any two conductors separated

by an insulator. Electrolytic capacitors have very high capacitance because the insulator

between the two plates is not a sheet of plastic or mica that separates the conductors.

Instead, it is a layer of oxide on the surface of the aluminum (or tantalum) that is only a

few molecules thick. The water solution serves as the opposite "plate" and obviously the

Chapter 17C,

water is in extremely intimate contact with the oxide layer.

Ashish began with a glass jar filled with water saturated with bicarbonate of soda

- NaHCO3. He could have used ordinary salt, but NaCl is an acid anhydride and the

aluminum foil plates in his capacitor would quickly corrode. His first capacitor was just

a pair of foil strips dangling in a solution. After oxidizing it with a 9 volt source, it

measured 40 μF! Next he took two layers of foil, separated them with paper toweling and

rolled them up like a scroll. After curing for several hours he measured 700 μF. He soon

discovered he could vary the capacitance by sliding the "scroll" in and out of the bicarb

solution.

I was intrigued and repeated his experiment: If you wish to try it, mix a saturated

solution of bicarabonate of soda, NaHCO3. Bicarb dissolves faster if you microwave the

solution. Next insert your foil strips. If you want a BIG CAPACITOR, roll up a pair of

long foil strips separated by paper towel, as shown below.

The towel prevents the strips from shorting together. When dry, my rolled up capacitor

measured 0.000965 μF, i.e. 965 pF. Immersing in bicarb and curing at 45 volts increased

this to 120 μF - 124,000 times more capacitance. Commercial electrolytics have

electrolyte that clearly isn't bicarb. To check this out, apply reverse polarity voltage to a

commercial aluminum electrolytic cap. Bang! You'll have a jet of really stinky steam in

your face.

Oxidizing the plates

The aluminum must be oxidized with electric current to generate the critical inter-

electrode insulation. The oxide forms on the positive plate. I used a lab power supply

with 3 separate outputs. I hooked all 3 together to give me a voltage source that I could

vary from zero up to 45 volts. When I first turned it on, it drew hundreds of milliamperes

current but quickly dropped down to under 10 mA. During this period, thousands of tiny

bubbles appeared on the foil and rose to the surface of the solution. I assume they are

hydrogen and oxygen from the breakdown of water. When the current drops to a low

value, like the 3.1 mA shown below, you can tap on the glass and many of the bubbles

Chapter 17C,

sticking to the foil will be knocked loose. When you do this, more foil is exposed and the

current rises briefly.

When the current stopped changing below 2 mA, I connected the capacitor to my

capacitance meter and measured 7.7 μFarad. I was puzzled until I remembered that

Ashish cured his capacitor with 9 volts DC. When I cured mine with 5 times more

voltage, 45 volts, I got a thicker insulating oxide and about 1/5 the capacitance. Even the

arithmetic makes sense!

I repeated the experiment starting over with fresh aluminum foil and using 9 volts

DC. By the way, I noticed that there's no visible change in the surface of oxidized

aluminum. Curing with 9 volts DC takes many times longer to get the leakage current

down to around 1 mA. Sure enough, the resulting capacitor tested 42 μFarad.

Breakdown voltage?

I abruptly connected my 9 volt capacitor to 45 volts. As expected, it drew huge

currents but it didn't really "fail." It just began to cure to the higher voltage. Maybe this

is what commercial electrolytics are doing when they blow. There is very little fluid in a

commercial capacitor. The big current produces big heat and it only takes a moment to

turn the electrolyte into steam. If you put reverse voltage on an electrolytic, it first breaks

down the oxide and then tries to reform the oxide in the opposite direction. Of course,

Chapter 17C,

when the electrolyte vaporizes, the capacitance vanishes too. I suspect that the specified

"working voltage" of commercial aluminum electrolytics is primarily describing the

oxidizing voltage used to cure them. The limit to this technology seems to be the leakage

current. If I could put 10KV DC on one of these, it would probably continue to draw

kilowatts of power for months, assuming the electrolyte could somehow not boil away.

Electrolytic caps need strong alkaline solutions

I made a big rolled capacitor like Ashish's. I cured it with 45 volts and it got as

high as 120 μF. However, it was still drawing a few milliamperes of current, so I left it

overnight. By morning the positive electrode had corroded away, just like the positive

terminal of an old car battery. Obviously I had an insufficient bicarb concentration to

protect the positive terminal. According to my pH paper, saturated bicarb only has a pH

of 8. However bicarb has considerable buffer capacity which is why our blood uses it to

maintain a pH of 7.4. Years ago I was interested in generating hydrogen using electric

hydrolysis - the electric break down of water. I read that commercial equipment uses

sodium or potassium hydroxide as the electrolyte. I assumed that strong alkali has some

catalyst function for generating hydrogen. No, it just keeps the positive electrode from

corroding!

Ray left their 700 μF cap sitting on his desk unconnected. The last time he

checked, the capacitance had risen to 10,000 μF - oops! My 42 μF cap has risen to 1000

μF. Apparently the oxide is slowly dissolving away. This raises the capacitance but

lowers the working voltage. And that explains why the electrolyte in real capacitors

consists of some strange chemical brew instead of simple water or bicarb. According to

Wikipedia, a common "wet" electrolyte for aluminum caps is a mixture of ethylene-

glycol (anti-freeze) and "borax solution," presumably boric acid. Perhaps the boron

forms a complex oxide that doesn't dissipate? Until a stable oxide is mastered, these

homemade caps are neither permanent nor practical. In any case, I won't be making my

own electrolytic capacitors for my homebrew projects. However, this experiment was

certainly entertaining and educational.

*********************************************************************

A BUTTERFLY HATCHING ALERT

Homebrewing isn't just for ham radio

One of the best reasons for building your own electronics is when you can't buy

the gadget you'd like to have. I have always been fascinated by butterflies and moths.

They are garden flowers in motion. Over the last 60 years I have watched big animals,

like deer, elk, moose, bears, foxes and coyotes become common in my county, even

routine. In contrast most small creatures, like toads, frogs, porcupines, lizards, snakes

and butterflies are becoming rare. In this pattern of big creatures thriving and the small

ones vanishing, the most common colorful butterfly in my yard today is the 6" wide,

yellow, Two-Tailed Swallowtail. This is North America's largest butterfly! I'll bet

hardly anyone has noticed that the similar, smaller Western Tiger Swallowtail has

become scarce. OK, the most common butterfly has always been the little white cabbage

butterflies and in my yard, they still are.

Chapter 17C,

Raising butterflies and moths

If you find caterpillars dining in your garden, rather than squashing or spraying

them, I suggest raising them to adults. Like you, I make an effort to eradicate tomato

worms and tent caterpillars. Unfortunately, they seem to be exceptions to the extinction

pattern. On the other hand, the giant tomato worm metamorphoses into an enormous,

dark gray sphinx moth. It zooms into and out of our tomato patches so fast we rarely see

them. If you were interested, you could attach an electronic monitor, watch them emerge

from their cocoons and pump up their wings.

This circuit uses some basic electronics that perhaps modern hams haven't seen.

The idea is to place thin, bare, twisted 30 Ga. wires on each cocoon or chrysalis so that,

when the insect emerges in the spring, the circuit will be broken and the alarm will sound.

I used a 4001 CMOS quad NOR logic gate triggered by a 1 megohm pull-down. Unlike

simpler circuits, CMOS draws very little idling current so the alarm can wait for months

for the creature to emerge without exhausting the battery. There are two oscillators. One

makes the basic raucous tone and the second slower oscillator keys it on and off to make

an insistent beeping.

Each of the two oscillator circuits consist of two digital inverters in series. The

"NOR gates," also known as NOT OR gates, on the right have their inputs wired together

so they simply invert the binary logic on their inputs. That is, a zero volt input produces

a +9 volt output. The beeper is turned ON or OFF by the monitor wires connected to the

cocoon. The beauty of the NOR gates is that ON can be when the twisted wires separate.

Most switching circuits that turn something ON work by initiating current flow, rather

than stopping it.

Whenever the connection between the two wires is broken, the switching input

goes low and the left hand inverter outputs go high. The high +9 volt input charges the

capacitors through the 43K ohm resistors. When the capacitor voltage charges through

the trigger threshold voltage, both inverters abruptly change state. Now the capacitors

Chapter 17C,

discharge through the same 43K resistors toward zero volts until the inverters switch

again.

My favorite lepidoptera is the Cecropia silk moth. The adults are about 6 inches

wide and, until recently, they were common in our city. Cecropia caterpillars are mostly

green and resemble tomato worms. When ready to pupate they are big, 3 or 4 inches

long, but have yellow feet and pretty yellow, blue and red tubercles on their backs. In

contrast, the tomato worms are plain green with small white and black spots.

If you find such a caterpillar on your apple tree or lilac bushes, you're in business.

No, the Cecropias will NOT eat your tomatoes. Cut off the twig with the caterpillar and

place the twig in a small container of water to keep the leaves fresh. I use old fashioned

film cans with holes punched in the top. I insert the twig of leaves into the film can.

Keep your caterpillars in a large cage or fishbowl. They will often crawl away if they run

out of fresh leaves or when they are ready to pupate. I cover the top of a fishbowl with a

thin gauze to prevent escape, but admit fresh air.

Chapter 17C,

Here are two freshly hatched cecropias next to their cocoons. Notice the thin

blue, wire-wrap, 30 gauge wires on the cocoons. The loosely woven cocoon silk allows

the wires to be woven into the cocoon surface. Mounting the wire switch across the top

where the moths emerge is easy. If you have several cocoons, you can wire them in

series. When your moth hatches, the moths with the big bushy antennas (multi-element

Yagis) are the males. The antennas are "noses" for finding females. The males will leave

your yard as soon as it gets dark. The female antennas are thin with short hairs. If you

have a female, like the one shown below on the left, put her outside on the food plant.

She will stay there and wait for a male. When night comes, a male will find her and they

will mate all the following day. At nightfall they will both depart. The male will find

another female and the female will fly off to lay her eggs on other lilac or apple leaves.

The female always leaves a few eggs on the food plant right where they mated.

Save the tiny, tan colored eggs. A pin is shown for scale. In a couple weeks they will

hatch into miniscule black caterpillars.

Chapter 17C,

My wife and I raised Cecropias like this for 5 years! We even evolved a variant that was

much more red than usual. A red male is shown on the right, above. The normal color is

amber-orange, like the female on the left. Our Cecropia dynasty ended the year that all

our caterpillars turned out to be males. Sigh. We have also raised Io moths, fritillary

butterflies and Black Swallowtails. Fun!

*************************************************************ELECTROCARDIOGRAMS FOR HAMS

Heavy exercise is good for oldsters - in brief doses

When I go to a ham club meeting, 80% of the guys in the room are retired. A

downside of old age is that doctors always assume we have heart disease. Sadly, they are

often correct.

We are constantly told to EXERCISE! Good advice, but it can be overdone. I live

in a city full of hip people who just moved here from California and often over-exert. A

local old guy, Lennard Zinn et al, helped write a book called "Haywire Heart," by Zinn,

Case and Mandrola MD. The book was inspired by Zinn's experience with elderly,

macho-man bike-riding. Riding a bike 20 miles 3 times a week is usually good for

normal folks, but Zinn was speed-riding up mountains nearly EVERY DAY. One day

he stopped to rest half way up our local mountain and noticed his heart rate was 218 beats

per minute instead of the usual 155. He continued his usual Olympian-wanna-be,

extreme training, but he noticed strange "flopping fish" heart sensations. It was a few

days before his doctors finally convinced him he was on the verge of dying. The lesson

Chapter 17C,

for healthy old folks is that we must allow a day or more of rest between extreme bike

rides or heavy exercise. Without rest, the heart muscle becomes scarred. After years of

abuse, heart contractions become chaotic and result in arrhythmias.

Defend yourself from enthusiastic doctors

Doctors seem casual about inflicting draconian diagnostic procedures such as

coronary angiograms. The good news about angiograms, is that, if you have a healthy

heart and don't need an angiogram, the risk is minor. But if you actually need an

angiogram, the risk of a serious complication from the test is 1% to 2.5%. Ouch. Also,

angiograms poke catheters into your heart and cost about $10,000.

A few years ago I climbed a mountain the day before my annual Medicare

physical - a bad idea. Consequently my electrocardiogram (ECG) changed from previous

years. The T-wave in lead III was inverted from my previous ECGs. I'm a healthy guy.

I do heavy exercise 3 times a week. My serum lipids are like a young guy. Because of

the ECG change, my family doc wanted a cardiac ultrasound and a treadmill test. That

sounded interesting, so I went to the cardiology clinic.

I didn't meet any cardiologists, but the technicians were competent, friendly ladies

who answered my questions. I thought it was odd that they insisted I run for several

minutes at a heart rate of 150 beats/minute. My normal maximum continuous rate is

about 135. Other people have higher or lower maximum continuous heart rates. But for

me, 150 was real stress. I assumed maximum stress was their goal. Most important, I'm

an asthmatic, but they never asked. I wasn't told any results that day, but soon received

two letters from actual cardiologists. One simply said, "Normal cardiac ultrasound." The

other just said, "Stress test suggests coronary heart disease. Recommend angiogram,"

and nothing more.

I refused, but didn't ignore the warning. I decided to do my own research, but I

needed an ECG. I quickly learned that buying an ECG, or even ECG electrodes, requires

a current physician license! Ironically, assault rifles are available to any adult. I decided

to make my own ECG. Good old Google listed lots of ECG articles.

The ECG waveform

This trace is the normal ECG for lead II, the voltage between the patient's right

arm and left leg. Lead II is typically seen on defibrillators or patient monitors. The little

heart voltage pulse groups for each contraction are named, left to right, P,Q,R,S and T.

Chapter 17C,

Lead III, measures the voltage from left arm to left leg. Other people can be different,

but for me, lead III is the lowest voltage view of the heart and the above trace is normal.

The voltages of the anterior and posterior sides of the heart tend to cancel in this view so

the waveform pulses are the smallest. If there is any change in the heart muscle - e.g.,

damage - for me, it will be most obvious in lead III.

The above lead III trace shows the same view 2 hours after a climbing a mountain. The

S-wave is larger but most alarming, the little T-wave is now negative. This suggests

fatigue, low oxygen or heart damage. Amplitude changes occur in other views, but the

display would have to be precisely calibrated in volts and measured to demonstrate taller

or shorter pulses.

Display devices

The output from the ECG circuitry is a tiny, low frequency voltage that must be

graphed to be useful. An ordinary oscilloscope scans too fast. If the scan were slowed

down sufficiently, it would just show a dot creeping across the screen. There would be

no way to display the entire waveform pattern. The classic ECG display is a mechanical

strip chart recorder that prints out the track on paper. I used a storage oscilloscope which

has a high persistence glowing phosphor that preserves the track made by the moving dot.

I photographed the screen with a digital camera, as demonstrated above. The trace could

also be recorded and displayed by a computer. There are computer analog interfaces and

programs to simulate an oscilloscope, but I've never used them.

ECG design

Chapter 17C,

My first ECG is shown above. Clinical ECGs usually attach ten electrodes to the

body. One electrode goes on each arm and each leg. The right leg electrode is used for

noise canceling feedback. Six more electrodes are placed across the front of the chest.

The electrode voltages are always measured in pairs. The goal is to monitor the tiny

heart muscle voltages from all sides. A normal heart has consistent, predictable voltage

levels from each view. If one side of the heart is weaker or stronger than normal, the

heart waveform will be increased or diminished in that view.

I found this first design on line. It is an "instrumentation amplifier" made out of

ordinary op-amps, so I used my usual LM324 quadruple op-amp. This design has noise

canceling feedback but lacks the stability of a precision instrumentation amplifier. Also,

it had no electrode switching so it could only record one "heart view" at a time. It

worked, but the output sometimes "locked up." In other words, the output went to the

positive or negative supply voltages and stayed there. Since it wasn't very practical, I

won't bore you with the schematic. My next attempt used a real, integrated circuit

instrumentation amplifier.

Instrumentation amplifiers

An instrumentation amplifier is basically a "difference amplifier" that amplifies

the difference in voltage between two tiny voltage signals. It isn't as versatile as an op-

amp but performs this one application very well. Tiny voltage signals are always plagued

with noise so an "Ins-amp" is designed to cancel out any voltage that is common to both

input lines. That is, "Ins-amps" have high Common Mode Rejection (CMR). The

diagram below shows a representative Ins-amp made from 3 op-amps. Assume that the

whole circuit is powered by two voltages with respect to ground, for example +9 volts

and -9 volts. "Ground" is the voltage half-way between +9 volts and -9 volts.

Chapter 17C,

The differential amplifier output stage, A3, is easy to understand. Any voltage

difference between the two A3 inputs is enlarged and delivered to Vout. The input buffer

op-amps, A1 and A2, are more abstract. They independently amplify the difference

between 2 voltage inputs which are referenced to ground. Normally an op-amp amplifier

has one input connected to the signal and the other input referenced to ground. As seen

above, instead of a fixed negative ground reference, the reference is a resistor, R1,

floating between the two negative inputs. Both A1 and A2 are referenced via R1 to the

input signals of both op-amps. Any voltage on both A1 and A2 inputs will bias the other

input the same amount and the same polarity. Although it isn't obvious, the result is that

signals common to both A1 and A2 inputs will cancel out. Ideally, this would eliminate

all random voltage noise present on the patient's body.

It is easy to see why any imbalance - unequal resistors or amplifiers - between the

A1 and A2 amplifiers could lead to a remaining error voltage between the inputs of A3.

A quad-op-amp chip will have four op-amps that are virtually identical. However, the

external resistors on A1 and A2 are likely to be slightly different, even if you manually

select them. As you may remember, an op-amp such as A3, will change its output

voltage until feedback through R4 causes the input voltages to become identical. If the

A3 output voltage can't compensate for a large voltage across R1, the A3 output will

remain stuck at either +9 or -9 volts.

Noise suppression feedback

The beauty of using an integrated circuit "Ins-Amp" like the 1NA126 is that the

internal amplifiers and resistors are perfectly matched so that the noise canceling

(common mode rejection - CMR ) is very high. Unfortunately ECG signals are too tiny

even for this advantage. Random low frequency noise and 60 Hz pick up from nearby

lights, etc. remain a severe problem. 60 Hz pick up can be minimized by turning off line

cords near the patient, but even more canceling is needed.

An average body reference voltage can be obtained by tapping into the outputs of

Chapter 17C,

A1 and A2 above using high resistances like 33KΩ. These two signals are combined -

added - by connecting them to the input of an inverting op-amp amplifier. The output

from this amplifier represents an up-side-down version of the average common mode

noise from A1 and A2.

Active feedback

Then they do something really clever: They apply this inverted noise signal to the

right leg electrode using active feedback to the patient's body. That is, they broadcast

the signal into the patient's body. The gain of the inverting amplifier is tuned for

minimum noise on the final output. Finally, the displayed output from A3 also goes

through a 0.5 Hz to 150 Hz band pass filter to further limit noise. See the final diagram

below:

Still another "average body voltage" can be obtained by tapping each of three

main input electrodes with a 330K ohm resistor. This voltage is used as a reference for

another "angle" for viewing the heart. On the right side of the diagram above are listed

all the standard "voltage views" of the heart. The ones starting with "a" use this average

Chapter 17C,

voltage as a reference.

My ECG works exactly as diagrammed above. Later I built another

instrumentation amplifier project and it was totally dead using a similar circuit. The

difficulty was that the input pins, 2 and 3, needed high resistance DC paths to Vref, pin 5.

100K resistors worked OK. I connected Vref pin 5 to ground, but the Vref ground

connection didn't seem to matter.

I found the above ECG design on the internet. This filter has a large 10 μFd

output capacitor which charges and discharges slowly. Consequently, the scope must be

set to display DC, not AC. On AC, it turns the T-wave into a sinewave which, if it were

a real ECG heart voltage, is called "Wellen's warning." Wellen's warning means you're

about to have a massive heart attack and die.

Electrodes

Classic ECG electrodes are silver metal with a contact gel containing

silver/chloride salt. They act like little batteries that charge and discharge slowly and

correct for the drifting DC zero volt baseline. Since I couldn't buy them or figure out

how to make some, I used large, reusable TENs electrodes. Ordinary citizens are allowed

to buy these for pain relief. They are long strips of carbon filled plastic coated with

aluminum. They are about 5 inches long and 1.5 inches wide. They have a Jello-like

sticky, adhesive on the carbon side. I wrap an electrode around each wrist and one on

each thigh. These electrodes aren't ideal and I had to hold very still while the trace was

being recorded. The 6 chest electrode readings produce big, dramatic signals, much like

lead II. However, they didn't help me detect heart fatigue.

Minimizing heart stress

When I was in the Air Force, they taught us to pressure breathe. We inhaled

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oxygen from the face mask, then contracted our chest muscles to compress the gas,

thereby raising the partial pressure of the oxygen. This also works while hiking. Instead

of simply panting - exhaling rapidly - the heart receives more oxygen if we hold our

breath for a moment and bear down on our chests to compress the air in the lungs. By

pressure breathing I could climb the same mountain and have a normal ECG the next day.

Regardless of a normal ECG, I no longer do heavy exercise two days in a row.

If you're reading this book, you enjoy building things as much as I do. Aside

from learning how to protect myself from heart arrhythmias and cardiologists, I got a

kick out of doing the R & D. When I showed my ECGs to my family physician, she

pronounced them, "Brilliant!" A couple years later she talked me into getting a coronary

calcification scan. This is a non-invasive, cheap, special cat-scan. It showed zero

calcification in coronary arteries and confirmed my optimism. I'm not immune to old

man diseases, but clogged arteries don't seem to be an immediate threat. Amaze your

doctor with your own ECG research!

************************************************************

SOLDER SMOKE

A solution to a problem I hope you never have

I spend a lot of time home-building electronic gadgets. This means hundreds of

hours leaning over a bench soldering wires. For decades I have noticed that solder smoke

bothers my asthma. After many hours of soldering, I was always aware that I was more

congested than when I started. It was no big deal ... until recently.

One summer I quit using the asthma steroid inhaler because they kept raising the

price 10% every time I refilled the prescription. Not using inhalers was my personal

protest. Much to my amazement, during 6 weeks without any inhaler, my asthma kept

improving! Soon I was running continuously again and contemplating trying our local

10K citizens' race. I hadn't run like that in years. Then the forest fire smoke from

Oregon arrived and I was worse than when I started. I returned to using the inhaler and at

least improved my asthma back to where it had been the year before. A couple months

later smoke from my soldering iron suddenly became extremely irritating. Ten minutes

of soldering and I was having an asthma attack, just like the bad old days.

We hams are inventors, or at least most of us dream of inventing something really

cool. I felt sorry for myself for a couple days, then I had an inspiration: I found my old

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swimming snorkel and positioned the breathing tube over my shoulder. Now I can

breathe the air from my backside which is not directly in the path of the rising solder

smoke. Voila! With the snorkel I can solder for hours. So long as I can't smell the

solder smoke, it doesn't effect me. If I get really desperate, I can always duct tape the

snorkel to a garden hose and breathe in air from the garden and exhale through my nose.

I hear the air is really clean in Patagonia. Maybe I should move down there.

In summary, don't surrender to old age ailments and drug-dispensing doctors

without a fight! Doctors rarely have your disease and usually know very little about the

simple things you could do to ease your symptoms. They typically assume the worst and

treat you accordingly. Engage your inventor brains!

************************************************************************

Becoming a Real Inventor Breakthroughs in your basement, just like the pioneers of old

Many start up companies begin with hobbiests or engineers building prototypes

in their basements or garages. Hewlett-Packard began that way and I'm sure the list is

quite long. All of us who have done any homebrewing probably have dreamed of

inventing something really cool and important. It would be truly satisfying if our

inventions could become part of our everyday technology.

Imagine the pride you would feel when you are old and retired, if you suddenly

find your invention at work out in the real world. Maybe you encounter it for sale in a

store or perhaps it's being used in your grandchildrens' school or your doctor's office. To

people who don't know you, by then you will probably be just another boring old person.

But you will know that YOU have improved the world in some little way. Maybe you'll

be lucky and launch a big improvement in the quality of all our lives.

In the 1970s I worked for Valleylab, a medical electronics company. I designed

electrosurgical generators. These are typically 50 to 400 watt, 200 KHz RF power

sources that cut and cauterize tissue. A few years ago my adult son had a bicycle

accident. Because of his injury he wasn't yet allowed to drive, so I drove him to his

doctor's appointment. The nurse put us in a treatment room to wait for the doctor.

Standing in the corner of the room was a brand new Valleylab generator. I examined it

closely. I picked up the disposable return electrode package. The electrode was 5 by 7

inches. Another company had invented the disposable electrode before Valleylab, so the

disposable electrode I designed was not the first on the market. But our competitor's

electrode was too small and sometimes burned patients. I used my own skin for testing

and determined that a good tradeoff between safety, cost, size and shape was 5 by 7

inches. I handed the modern electrode to my son. "Well, here it is! This is the legacy of

my career." 40 years after my few hours of experimentation, 5 by 7 inches has become a

world standard. Then I noticed that the generator had a separate low-impedance, bipolar

output labeled "Dessication." By golly, that was also my doing. Amazing! I have

changed the world!

Forget about fame and fortune

Money and fame are hard to achieve for an inventor. The real world doesn't

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work that way. Long established corporations are run by fellows who crave money and

status. People who enjoy soldering wires hardly ever sit on the board of directors. Even

worse, directors often have no interest in what the corporation actually does for a living.

Some years ago when General Motors Corporation was failing, the top executives were

so disinterested in automobiles, they were commuting to and from the office in

chauffeured limousines! Would YOU like to spend your life sitting in boardrooms

bickering over money surrounded by fellows whose only motivations are greed and

inferiority complexes? Learn to accept this sad reality. Just because you made millions

for the boardroom guys doesn't mean they are going to share it with you.

Your inventing will be much more satisfying if you don't expect money and fame.

Remember that the board room guys are cursed with "the money disease" and we aren't.

Most of them deserve to be mocked, pitied or on a psychiatrist's couch. If we allow

ourselves to become angry and resentful, it only hurts us, not them. If we think about it,

we only need enough wealth for food, shelter, healthcare, retirement and education for

our kids. Fortunately engineers are scarce enough that the boardroom money addicts will

(nearly) always pay you enough to achieve those goals.

Recognizing a new principle that might lead to a invention

Ground breaking inventions in radio were achieved by Hertz and Marconi, the

triode amplifier by DeForrest, the super-regenerative receiver and FM modulation by

Armstrong, and many, many more. At first these inventions appear to have appeared out

of the blue with no precedent. On close examination virtually all inventions have a

precedent that demonstrated the basic principle of the invention. The inventor took the

observation seriously and put it to work. The people who make the initial observations

often don't appreciate what they see and do not investigate the phenomena.

Most people have no real interest in how anything works. They are only

interested in what technology can do for them. On the other hand, UFOs, ghosts and

other paranormal phenomena are interesting to practically everyone, including me. I

routinely read opinions that integrated circuits, composite materials, exotic metal alloys,

superconductors and many more inventions "must have been reverse-engineered from the

Roswell crashed flying saucer." No ... Sorry. It isn't that exciting. If you look closely,

you will discover that all those amazing developments evolved one step at a time. They

are the work of thousands of hard-working, dumb humans - in other words, guys just like

us.

The corporate inventor

The easiest way to invent something that makes its way into the real world is to

become a engineer and work for a corporation. The good news is that if you are an

engineer working for a healthy, stable company, you will invent new technologies. That

is, or should be, the essence of engineering. The bad news is that the scope of your

inventive genius will nearly always be tightly confined to the immediate needs of your

employer. The chance to do long range, truly innovative R&D for a corporation is rare.

This means that your inventions and your patents are going to be about little things - a

new circuit that does the same old function using cheaper parts, a more precise

measurement, better battery life, etc. By the time I was retired, I had over a dozen little

patents with my name listed among my co-inventors. I had long since stopped taking the

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initiative to apply for more. Since these little innovations are trivial in the great scheme

of history, why did I need my name on more of them?

Of all the patents with my name listed, only one of them was for what I would call

a novel invention. It was a way to "tune" a nerve stimulator so that it could selectively

stimulate different classes of nerve fibers. The 4 classes of nerves are fast twitch muscle,

slow twitch muscle, sensory nerves and autonomic nerves. The invention took advantage

of the refractory period of each class of nerve to resonate the nerve with the stimulating

current pulses - kinda like radio!

Evolution of a novel invention

The origin of tuned nerve stimulation illustrates the tortuous path to a truly novel

invention. It began when I was hired by a nerve stimulator company. I was studying

their existing products to get up to speed on the technology. Their muscle stimulator

used a biphasic current pulse pair applied through a pair of electrodes. A positive, 250

microsecond rectangular pulse was followed by a delay, then a negative 250 microsecond

current pulse. The delay interval was 120 microseconds. I asked the engineer who

designed it why there was a delay and why he picked 120 microseconds. "Oh, it works a

little better with that interval. I got a slightly stronger muscle contraction with 120

microseconds. It isn't a big deal, don't worry about it."

Instead of ignoring it, I took the big step toward a novel invention. I asked myself,

"What's special about 120 microseconds?" Since I knew a little about nerve conduction, I

knew that the refractory period (recovery delay) of fast muscle nerve fibers is around 100

microseconds. I suspected that 120 microseconds had something to do with tuning the

refractory period. But because I was a typical engineer, I had other mundane assignments

and deadlines. I didn't have the time to build a test prototype and explore the

phenomenon. Unless, of course, I wanted to do it on my own time. If I had been a gung-

ho inventor, I could have quit the company, explored the phenomenon in my basement

and started my own company. I wasn't that brave, industrious ... or reckless.

The CEO inventor

The stimulator company I worked for was Staodyn. It was founded by an

engineer, Tom Thompson. Tom's company illustrates a typical way many novel

inventions are launched: The engineer works day and night in his basement making a

new product, original enough to be worthy of starting a new company. He first applies

for a patent on his novel invention. That usually costs many thousands of dollars.

Patenting inventions is expensive and time consuming. Then he visits dozens of banks

and investors to raise money to start his business. If he is a terrific salesman, he manages

to get the funding to launch a company.

New products are a risky nuisance

Why is recruiting investors so hard? The reality is that, if the proposed product

is truly new, the men in the three piece suits won't understand it and won't see any value

in it. There are only two people who are interested in a new invention ... the inventor

and the fellow who wants to buy one. For everyone else the new product is a big risk

and upsets the routine. The manufacturing department must re-tool and stock new parts.

Quality control must come up with new quality assurance methods and they must be sure

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the finished product adheres to government and international safety standards. Most

critically, the marketing department must figure out how to sell it. The marketing

department is especially difficult to convince because marketing directors and field

salesmen almost never understand or relate to anything new. If you ask marketing guys

what new product they would like, they will always tell you that they want you to copy

the successful product of some competitor.

The natural aversion to anything new

My all-time favorite story about this aversion to new inventions happened to

Alexander Graham Bell, the inventor of the telephone. Bell wanted to see his phone used

for intercity communication. Bell went to all five of the existing telegraph companies.

They already had suitable wires strung all around the country. All five companies told

him that they didn't want the telegraph operators talking to each other because "they

wouldn't write the telegrams down verbatim." Bell had to start his own company and

string his own wires.

Buzz word investors

Occasionally there are brief periods when start-up funding is easy to obtain. All

the inventor/entrepreneur has to do is label his invention or company name with the latest

buzz word. In the 1880s silver mines in the western United States were the hot

investment. Silver mining was a solid, but SMALL, growing industry. But the investors

dumped so much money into silver mining, that unprofitable, foolish mines were dug all

over the West. The few mines with rich ore were often wastefully developed in a vain

attempt to deliver as much silver as Wall Street expected. In the late 1920s airplanes

were the fad and investors dumped money into airlines and airplane manufacturers. In

the 1950s any company with "tron" in its name or in its product attracted investors.

During the 1990s virtually any "dot-com" stock attracted investors. Most of the "dot-

coms" produced a service or entertainment, but few of them bothered to figure out a way

to make money. The few successful dot-com companies were the ones with realistic

business plans.

Bait and switch inventing

Sometimes an engineer can use buzz words to manipulate his company into

manufacturing a new product. In the nerve stimulator business there was a period in the

1990s when "microcurrent" placebo stimulators were the latest fad in physical therapy.

"Microcurrents" were comparable to transcutaneous nerve stimulators (TENS) for pain,

but the pulses were so tiny ("micro") that, so far as I could determine, they stimulated

nothing and did nothing. They were analogous to sniffing an aspirin bottle for a

headache. Yes, you might inhale a molecule or two, but would that help your headache?

Useless medical devices are supposed to be illegal according the Medical Device Act of

1976, but the American FDA was too dumb or disinterested to notice. "Microcurrents"

were approved by the FDA as just another TENS. Real TENS deliver big pulses,

stimulate nerves and are an effective treatment.

The marketing guys at Staodyn pressured me to develop a "microcurrent." We

engineers came up with a solution: Pulsed DC stimulators have been a highly effective

wound healing treatment for over 100 years. Unfortunately they were so misused and

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misunderstood that they quickly fell into disrepute. Except for a few niche applications,

to this day they have never fully recovered from a reputation of quackery. During the

microcurrent era our company was working with doctors using pulsed DC to heal a wide

variety of chronic wounds that are difficult or impossible to heal any other way - severed

nerves, bed sores, severe sprains, non-union fractures, severe arthritis, gangrene and even

baldness! We hoped to see this modality turned into a universally recognized treatment.

Seriously, if ordinary folks could be trained to use it competently, there should

be a pulsed DC stimulator in every medicine cabinet. The average DC current for the

widely spaced, tall, brief pulses is typically about 300 microamperes DC. Well, that

sounded like "microcurrent" to me! The marketing guys bought our story and our "DC

microcurrent" stimulator was a great success. It succeeded, not because of the buzz

word, but because it actually worked. It had worked for 70 years for the few therapists

who had stubbornly used it in spite of its quackery reputation. Our first big customers

were ALL of the national football and basketball teams, plus the US Olympic team.

Michael Jordan gave us a free endorsement on ABC TV. After 20 years you could still

buy a "SporTX," the marketing name for it.

Pulsed DC still isn't widely used today because of the sophistication needed to

know how and when to use pulsed DC. Also, the successive companies that bought out

Staodyn were only interested in "third party reimbursement" and stopped educating their

customers on how to use pulsed DC. Education was always the missing ingredient for

successful pulsed DC. If you use the wrong polarity, it makes the injury worse, not

better. As usual, the board room and marketing guys were oblivious and eliminated the

education. Modern operation manuals for pulsed DC stimulators say something like,

"Your health care provider will explain how to apply this unit."

The life of a CEO/Inventor

The bad news about an inventor starting a company is that the new CEO must

work day and night, hire employees, go to trade shows, revisit the bankers, worry about

quality control and government regulations and try to make a profit. The worst result is

that he now has no time for his true love - making stuff! He even has to hire engineers

to do the fun part for him.

The start up phase of a new company is brutal. Tom Thompson spent so much

time working to launch Staodyn, his health failed. Another successful start-up guy I

know was literally never at home and ended up divorced. The lesson I learned was that

starting your own company is usually destructive to your health and family. Also, after

all that pain, the typical start-up usually goes bankrupt.

If you succeed, you will probably be rich, but now you are no longer an

engineer. My friend Tom Thompson passed through all those phases. Once Staodyn was

well established, he did something rare: Instead of retiring to the boardroom or the golf

course, he hired an experienced CEO to run the company and went back to engineering.

He set up his own lab in the factory and looked for new projects to work on. He asked

me if I had any R&D ideas and I told him about my nerve refractory stimulation theory.

He jumped on it and made it work.

Tom discovered that using brief pulses, like 50 microseconds or narrower, made

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the tuning effect much more dramatic and selective. He discovered that autonomic nerve

pain fibers were best blocked with a 450 microseconds delay. There was also an

optimum time interval (frequency) for repeating the pulse pair, 4,500 microseconds. We

turned this into a successful pain reduction product. It worked for patients with severe,

chronic back pain for whom ordinary (TENS) stimulators were not effective. This

eventually turned into two new products covered by a bunch of patents. Nearly everyone

in the engineering department had their names on one or more of the patents, reflecting

their individual contributions - the plastic enclosure, the imbedded software, the circuitry,

the electrodes, etc. This is as it should be. 20 years later our resonant nerve stimulator

was still on the market. I hope everyone else involved in its development got the same

thrill out of it that I did.

The rarity of the sole inventor

The contented inventor accepts the reality that practically all inventions include

contributions from other people. Being "the sole inventor" is difficult and barely

possible. Virtually all inventions are based on the chance observations and technology of

others. But that's OK. Being part of a successful team is highly satisfying. No one guy

can "invent" a moon rocket.

The CEO dictator inventor

Elon Musk and Steve Jobs are examples of modern inventors who achieved

"their" best inventions after they became CEOs. CEO inventors like this don't do the

work themselves. They just imagine the products and demand that their engineers create

the new idea. Successful leaders like this use harsh discipline and impossible deadlines.

"You there, engineer! Invent warp drive by Friday!" It is quite exciting to work for such

a boss, but it's exhausting. Working day and night, trying to do what is barely possible

gets old, really fast.

I worked for a such a man for two years. He continually wanted new gadgets.

He would ask, "What is the absolute soonest you can have it working? Can we try it out

on Saturday?" Like a fool, I always answered truthfully. In retrospect, it was a great

adventure and I wouldn't have missed it. However, it cost me varicose veins simply from

lack of exercise - and I was only 22 years old! If I had been 45, I probably would have

had a heart attack as well. After I was reassigned to a more relaxed boss, the painful

veins quickly healed.

The other corporate route to novel inventions - desperation

Long established corporations occasionally make a serious effort to manufacture

a novel, risky, new product. This happens in spite of all the barriers. Why? Because the

corporation is usually just a few months away from bankruptcy and a new product is their

only salvation. This is the same situation as the start-up entrepreneur who must get his

product selling well before he runs out of investment money.

Patenting new inventions

A hundred years ago the inventor was required to submit a working example or a

model of the invention to the patent office. As you can imagine, this requirement quickly

became impractical as tons of samples of steam engines, model blast furnaces, and grain

combines began to arrive at the patent office. Today the patent office in Washington DC

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is decorated with display cases filled with some of the wonderful old submissions. These

days we are just required to write a list of claims of what we believe we have invented.

Then we must explain in detail how the invention works. Finally, we should discuss "the

prior art" patents that are similar to our invention and why they do not interfere with our

claims.

We are not required to prove that our invention works and the patent office

doesn't do on-site inspections to be sure the device exists. However, if we patent

something we have never actually built, we will almost certainly make mistakes in the

description or claims. These errors will surely come back to bite us when the competition

describes our mistakes in their patent applications.

Formerly, we were expected to keep dated, signed notebooks in which our

inventions were described and "witnessed and understood" by a fellow engineer. During

patent disputes these notebooks were brought to court to prove exactly when the idea for

the invention first dawned. Today, I have read that the courts simply base the rights to a

contested patent on whose patent application was filed first with the patent office.

However, if the product has been for sale or described in public for over a year, it is too

late for anyone to patent the concept.

What is patentable

First of all, having an idea, such as "invent a ray gun that cures cancer," is not an

invention. You can't patent a dream. Surprisingly, you can't patent a principle. If you

discover a new principle or fundamental truth about physics or biology, you can't get

exclusive rights to it with a patent. Until recently at least, all US patents were written to

patent the application of a principle, not the principle itself. As an example, if you

discover a way to generate anti-gravity, you can only patent the means to generate anti-

gravity, not the principle you exploited. Other people are free to build their own anti-

gravity machines using the same principle. However, they must use a "completely

different" way to implement the principle.

As a result, a well-written patent exploiting a new principle will attempt to list

all the ways in which the same invention could be implemented. Perhaps the invention

could be redesigned with hydraulics, mechanical levers, pulleys, electric motors, jets of

air, etc. The patent attorney will try to list all these approaches leaving the details vague.

Of course, it must be "obvious to the experienced practitioner" that these other

approaches will work. In that way you don't have to explain the fine points of versions

you haven't actually built. Only the methods actually used in the real product are

described in detail. These fine points are explained in subordinate claims. Sometimes

key details are left out of the patent application, such as the exact operating temperature,

pressure or certain measurements. This is done to insure that a copycat can not simply

make his own version without at least doing a little R&D.

Sadly, in America at least, the patent system has become muddied and tangled

by predatory lawyers, scientifically ignorant courts and corporate "patent trolls." The

trolls constantly apply for patents for copycat inventions that simply do not deserve to be

called "novel." For instance, a troll shouldn't be allowed to patent an automobile that

drives north. The courts, who don't know the difference between a parsec and a pascal,

often rule against your patent and allow the thieves to continue selling your invention. In

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another example, agricultural and medical companies have succeeded in patenting DNA

sequences found in nature. Yes, it was a lot of work to determine those sequences, but it

was Mother Nature that invented them, not Corporation X. The corporations should be

patenting the methods they used to determine and apply this knowledge, not the DNA

sequence itself.

Patent attorneys have entered into the larceny by establishing a rigid

grammatical structure that each new patent is supposed to follow. In other words, each

sentence of each paragraph of a claim is literally diagrammed into nouns, verbs and

objects, just as you were taught to do in high school English class. The subject must go

here stating "this," the verb must follow there explaining "that" and so on. I once

watched a team of lawyers destroy and invalidate one of my company's patents, simply

because the grammar didn't follow the "standard sentence structure" formulas. Yes, you

can fight this silliness in court, but the years and fortunes spent on lawyers may not be

worth the effort. While the litigation drags on, the outlaw company is happily selling the

illegal product. If by some miracle the court does rule against the trespassers, they

usually award "triple damages," three times the money earned by the criminals.

By now you are probably beginning to see why fortune and fame are unlikely for

inventors who simply like to make things. Let the greedy guys pretend they are

important. When you find your invention working out in the world, you will know that

YOU are the person who improved our quality of life, not the crooks and bureaucrats.

While we're on the subject, try to invent things that improve our lives, not

endanger them. On the 50th anniversary of the AK-47 Kalashnikov rifle, Mr.

Kalashnikov was interviewed. He said he wished he had invented a lawn mower.

Patenting as a way of preserving your work

One company I worked for had a large budget for obtaining patents. When I

developed prototypes demonstrating potential new products or features, I always

presented them to the marketing and the executive departments. Of course they had little

or no interest. The innovations were new, risky and their competitors weren't already

selling them. Curiously, although they didn't pay attention to what I was patenting, they

always framed the patent certificates and decorated the corporate boardroom with them.

Even though the ideas were vetoed, I had managed to preserve them for posterity.

I once worked for a start-up diathermy company that was strapped for money. I

invented a way to shrink the diameter of microwave waveguides. The usual way to do

this was to fill the waveguide with super-expensive, high-dielectric-constant, low-power-

loss, plastic foam. I used cheap internal metal baffles to achieve the same effect but

without losing energy by heating the foam. Since it was a novel innovation, I tried to

patent it. The executives vetoed my patent application because they couldn't afford the

expense. A year after the product had been on the market, it was beginning to sell. The

CEO asked me, "Don't we have a patent on that?" Sorry, it's too late. He didn't realize

that after one year he had already donated the invention to the world.

Discovering and exploiting new physical phenomena

The most dramatic inventions happen when the inventor can discover and exploit

an entirely new physical or biological principle. If nobody else knows about the

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phenomenon, any application of that phenomenon is going to be completely original.

Unfortunately, as civilization advances, it becomes increasingly difficult and expensive to

investigate new frontiers. Lots of undiscovered phenomena surely exist. But if you need

a 100 mile diameter, trillion-dollar particle accelerator to find them, you won't discover

these principles in your basement.

My favorite personal invention

Of all the stuff I invented, my favorite didn't become the product I had hoped for

and I didn't patent it. However, it was a great adventure and I had a rare opportunity in

modern world. I was close to being "the sole inventor" and I was blessed to stumble

across a truly new physical/ biological principle. Well, it was new to nearly everyone

else on Earth.

Most general interest scientific magazines have small mini-articles in addition to

their big, feature articles. In 1984 Scientific American had a short note about the

submarine "Alvin" being recovered after sinking in the Atlantic Ocean. The sub had

sunk in a storm when the waves swamped the open hatch while the crew was climbing

out. It sank in 9,000 foot deep water and it took nine months to find and recover. The

article mentioned that the bologna sandwiches on board were soggy, but remarkably

fresh. Even the lettuce was still crisp and bright green. The author suggested that

immersion in low oxygen, cold water was responsible for the preservation.

That explanation didn't sound sufficient to me. Could the high pressure of the

water at that depth be at least partly responsible? At 9,000 feet down, the ambient

pressure is 4,000 pounds/square inch. I knew that high pressure could be obtained in a

lab by screwing a bolt into a fluid filled cavity. Since water doesn't compress and has no

where to go, extreme pressures can easily be reached if the test chamber doesn't burst. To

shorten the story, I took time off from work and built a tiny pressure chamber that

allowed me to reach 12,000 psi. I bought a commercial pressure sensor that would read

pressures up to 5,000 psi. I discovered that ordinary carbon composition resistors

decrease their resistance linearly from 0 to 5,000 psi. Extrapolating that straight line

allowed me to measure, or at least estimate, 12,000 psi. I discovered I could preserve

fresh, pink hamburger for one month at room temperature at 12,000 psi. It was as though

it had been in the freezer for a month. When the test conditions were repeated without

the pressure, the hamburger turned grey and foul within 3 days. After the pressure on the

hamburger was released, it spoiled just as quickly as the un-pressurized samples. I had

demonstrated that bacteria were inhibited by high pressure.

I had hoped I could use high pressure to preserve blood and organs for transplant.

These biologics are destroyed by freezing and their deterioration is only slowed by non-

freezing refrigeration. High pressure might have been an important medical advance.

Maybe I could put astronauts into "stasis" for interstellar journeys! I was getting ahead

of myself on the last one. I soon discovered that tissues with cells larger than bacteria

were quickly and irreversibly killed by high pressure. It was useless for blood and organ

preservation. Darn! It still might be useful for room temperature storage of vaccines that

normally need refrigeration. Vaccines are isolated protein molecules, not complex living

cells. Vaccines may not be as fragile as living cells. However, the high pressure

containers would be expensive and probably bulky or heavy. Also, the containers would

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need built-in sensors, (possibly the carbon composition resistors), to monitor the high

pressure.

Without investing big dollars and lots of time, I could go no further. I had my

patent attorney do a search on the techniques I had discovered. There was only one

relevant Australian patent. The inventor had discovered high pressure bacterial

suppression a few years before me. Curiously, he didn't claim any application for this

principle or describe how to achieve or measure high pressure. His "patent" read like a

scholarly microbiology paper. It was not a patent as we Americans understand them.

If I had pressed on with the research and invested in super-high pressure

equipment, eventually I would have learned that pressures of 50,000 to 100,000 psi can

also kill bacteria, viruses and fungal spores. After a short time, the pressure is released

all the bacteria are stone dead. Today equipment like that is used to sterilize fruit juice!

The pressure-sterilized juice more closely resembles fresh fruit juice than juice that has

been boiled for sterilization. The Odwalla company made national news with a batch of

juice that had not reached the needed pressure and still had living bacteria. Oops. A

recall was needed to round up the spoiled juice.

The bottom line of homebrewing and inventing

In summary, homebuilding and inventing is great fun. It is the adventure of

inventing that is most of your reward. If the world takes notice and adopts your work,

that is icing on the cake. The good news is that, no matter how far technology may

progress, it will always be possible to put parts together in new ways to create novel

inventions in your basement or at your job. The bad news is that discovering new

physics or new biology in your basement becomes harder every year and is rapidly

leaving the reach of basement experimenters.

Even reproducing hundred year old inventions in your basement can be extremely

difficult. After my experiments in Chapter 4, I thought it would be fun to build my own

vacuum tubes. I quickly found that constructing the tubes, making thorium cathodes,

generating the required vacuum and sealing them was not easy or cheap. I found a

website authored by a French fellow who described his homebrew vacuum tubes. It

turned out he had a real vacuum tube factory in his basement, complete with micro -

welders, tiny lathes, a sophisticated vacuum pump, glass blowing, molding equipment

and more. In short, he owned tens of thousands of dollars worth of equipment. My wife

would love that.

If you get lucky and invent something truly new, just put it on your personal

website and give it to the world - kinda like this book! If it has value, the world will

slowly notice and some corporation might even patent it. The important issues are that

you had fun developing it and your gift to the world will be appreciated. For me, that is

enough. As my ancient grandmother used to advise me, "Enjoy each day!"

chapter 17c ancient modulation and other topics (continued)

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