Epistle to the Old Man
"Throwing the works to my bottle." Any idea what
that means? Neither did I. "You went out just like a Swedish match in a Kansas hurricane..." Ever heard that saying? Neither
had I. I never knew Swedish matches had a reputation for easily going out. I never knew the swedes made matches. Evidently
the tech jargon in 1935 was a bit different than today. This story from QST will introduce you to many new terms with a
fairly short read.
The guy in the story looks a lot like the Ham in the 2013 Field Day patch (sans specs).
Beauty and the Bad Board
This latest installment of EDN's Tales
from the Cube series. In it, author
Mainwaring describes his ingenious process for emergency testing assembled and ready to ship product for a bad inductor.
It involved building an EM simulation model for the test
implement and then qualifying it with a Kappa analysis inductor. The action saved his company significant embarrassment.
Technology for Their Support
WOKEN specializes in microwave/RF coaxial connectors, cables, cable
assemblies, microwave/RF antennas and RF accessories. With the experienced R&D engineers & technicians, active marketing
staff, up-to-date production equipment and measuring instruments, WOKEN designs its own RF / microwave products for meeting
all kinds of requirements demanded by its customers at communication markets.
There's an App for That
Bosch has been at the forefront in
automobile navigation automation for many years.
They developed some of the first systems for keeping cars in lines of traffic without the driver needing to constantly apply
brakes or step on the gas (or battery) pedal. You can find lots of cool videos on their work. This video shows a new system
for automatically parking a car via a smartphone app. I'm sure somewhere there is a group of lawyers just salivating at
the prospect of lawsuits when someone gets her legs pinned between cars in the process. Maybe it will just be a smashed
bicycle, or flattened puppy, but you know they can't wait for an opportunity.
Microstrip Lines and Slotlines
This quiz is based on the information
presented in Microstrip Lines and Slotlines,
by Ramesh Garg, Inder Bahl, and Maurizio Bozzi. The book was graciously provided by
Artech House. As with many books used for quizzes, this
one will eventually be made available as prize for the RF Cafe
monthly book drawing.
quizzes are also good fodder for selecting interview questions for applicants
and for brushing up on the basics if you are the interviewee.
SP4T Absorptive Switch
PMI Model No.
is an absorptive, single pole, four throw solid-state switch that operates over the 100 MHz to 2.0 GHz frequency
range. The insertion loss is less than 3dB and offers port to port isolation of over 50 dB. The switching speed is
25 nsec maximum and the rise and fall times are less than 10 nsec. The control is via four independent TTL lines
with Logic "0" being the low-loss state and Logic "1" being the isolation state. This switch operates on ±5 VDC
for Used Test Equipment
Mr. Richard Barker, of Kitmondo, wrote to request a listing on my
Test Equipment (new & used) vendor resource page.
Kitmondo is based in the UK and is "an online marketplace where buyers and sellers of used business and industrial equipment
can find each other and trade safely." They currently have many pieces of
TE and individual RF components like amplifiers
Crowdfunding is a scheme whereby inventors and other types of startup individuals and groups pitch their plan to the public and solicit
payment of funds with the promise of certain goods or services when and if the monetary goal is met or exceeded. If, for
instance, I wanted to develop new RF system planning software and needed, say, $100,000 to produce a beta version, I might
promise $50 donors ('investors') a specially designed T-shirt, $100 donors an early beta for evaluation and discount on
first release, and $500 donors a full release version.
Inc magazine had
as their June edition theme leadership. If nothing else, the collection of articles proved the old adage about opinions
being like ***holes - everybody has one. There were some worthwhile tidbits, though, like this quote from Captcha co-founder
Luis Von Ahn: "Competition
among investors is good. If you are talking to one big VC and wind up talking to another, they will find out. How much that
matters is insane."
Xcvr to Optimize RF
DP1203 Series radio-only
RF transceiver module is designed for the wireless transmission of digital data at data rates of up to 152.3 kbps.
Operating in the 433, 868 and 915 MHz license-free ISM frequency bands, this module series is ideal for applications
that require full-control of the radio channels and configuration, without having to go through the effort and expense of
a discrete RF design. The module has a maximum output power of +15 dBm and a receiver sensitivity of –111 dBm.
This gives the module a typical line of sight range of 2 to 3 miles at the maximum output power with typical monopole whip
antennas, depending on frequency.
for June 14, 2013
Take a break and let this week's
engineering-themed crossword puzzle
be a Father's Day present to yourself. All the words are pulled from a hand-built list of terms, names, and abbreviations
that have only to do with science, mathematics, and engineering. If you want a crossword with names of movie stars and obscure
countries, try the local newspaper. If you want to exercise your nerd knowledge, this is the one for you.
Data from Tech Companies
Here is an interesting chart from Reuters
that shows which countries have the
highest rate of collecting data from tech companies. Google, Microsoft, Skype, and Twitter are evidently
the top suppliers of personal data. I'm guessing the U.S. is at the top at least partially because the tech companies are
based in the U.S. and therefore the FBI, NSA,
IRS, DHS, and other 3-letter agencies are able to exert the most influence. Of course what is not shown are countries
that make no pretense of granting citizens a right of personal privacy such as Russia, China, Saudi Arabia, Venezuela, and
other Communist regimes. Our government exploits a populace that actually expects privacy because the Constitution mandates
it. They don't need to heed no stinking Constitution.
The word 'transformer' in
the title for this article does not refer to a mutual inductance transformer, but an impedance transformer for
lines to antennas (or anything else for that matter). Author T.A. Gadwa gives examples of impedance-matching circuits
both for when the antenna impedance is lower than the characteristic impedance of the transmission line and when the antenna
impedance is higher than that of the feed line. "L," "pi," and a couple other circuit configurations are covered.
Capacitors & Dopey Design
In the latest adventure
of Sherlock Ohms, Mr. Frank Karkota tells of his experience with a used
digital satellite receiver for reception of
free-to-air (FTA) programs. "The receiver worked great, and I mapped hundreds of television and radio stations on the various
satellites. Later, some of the stations disappeared. Then, more started disappearing, until I couldn't find any stations.
Since my analog receiver still worked, I concluded that the digital receiver had failed. I opened the receiver and found
that in one corner was the RF section, another corner had the digital section, and the other side housed the power supply..."
Solutions for Connected Home
Solutions today announced that it is partnering with SMC Networks, a leading customer premise equipment manufacturer for
multi-service operators (MSOs), to develop wireless connectivity solutions for security, monitoring and automation (SMA)
applications in the emerging connected home market. SMC is utilizing Skyworks' wireless networking and
ZigBee® front-end solutions for security
sensors, smoke alarms, motion detectors and touch pads. “SMC is joining forces with Skyworks to deliver innovative solutions
for the connected home,” said Max Brogi, vice president of product management at SMC Networks.
Korea & Japan Agendas
AWR, the innovation
leader in high-frequency EDA software, has finalized the agendas and opened registration for the summer
AWR Design Forums (ADF) 2013 being held in
Seoul, Korea on Monday, July 8th and
Tokyo, Japan on Friday, July 12th. The
ADF is a free and open event where designers of microwave and RF circuits and systems such as MMICs, RF PCBs, and LTE communication
systems can network, share useful information and resources pertinent to high-frequency design, and collaborate on industry
issues and trends.
If terms like 'magnetostriction,' mu-metal,' and 'D-ring'
arouse your technostimulus receptors, then this
quiz on magnetics should be just what you've been waiting for. It appeared in a 1962 edition of Popular
electronics, but the principles therein have not changed since then. I must admit that I had never given thought to the
orientation in which bar magnets should be stored when in close proximity to each other.
High-Frequency Integrated Circuits,
by Rosin Voinigescu. A transistor-level, design-intensive overview of high speed and high frequency monolithic integrated
circuits for wireless and broadband systems
from 2 GHz to 200 GHz, this comprehensive text covers high-speed, RF, mm-wave, and optical fibre circuits using
nanoscale CMOS, SiGe BiCMOS, and III-V technologies. Step-by-step design methodologies, end-of chapter problems, and practical
simulation and design projects are provided, making this an ideal resource for senior undergraduate and graduate courses
in circuit design. With an emphasis on device-circuit topology interaction and optimization, it gives circuit designers
and students alike an in-depth understanding of device structures and process limitations affecting circuit performance.
This book is the subject to
RF Cafe Quiz #49.
Microwave for Their Support
Wenteq provides a wide range of high
quality RF and microwave products with quick delivery time
at very competitive low prices. Their products include coaxial connectors and adapters, circulators, isolators, low noise
amplifiers, power amplifiers, broadband amplifiers, terminations and more, covering the frequency range of 100 MHz
to 110 GHz.
Started June 11, 2013
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moment and vote in this poll. No sign-in-required. Results are displayed automatically. Thanks!
I/Q Up & Downconverters
Hittite Microwave has launched several new,
highly integrated I/Q upconverter and downconverter products which cover the licensed 38 GHz and 42 GHz bands
in microwave radios for cellular backhaul radio links. The
HMC6787ALC5A and the
HMC6146BLC5A are GaAs MMIC I/Q
variable gain upconverters which form a competitive and cost-effective microwave radio transmitter solution which has been
designed to meet or exceed all of the performance criteria required for modern high capacity QAM microwave radios. The
HMC6787ALC5A operates from 37
to 40 GHz and provides a small signal conversion gain of 10 dB with 17 dBc of sideband rejection, and 13
dB of gain control.
of Simple Math
Many people were reluctant to
approach the theoretical aspect of electronics as it applied to circuit design and analysis, QST
(the ARRL's monthly publication) included equations and explanations in many of their project building articles.
Occasionally, an article was published that dealt specifically with how to use simple mathematics for
In the July 1944 edition is the third installation of at least a four-part tutorial that covers resistance and reactance,
amplifier biasing oscillators, feedback circuits, etc. I do not have Part I from the May 1944 edition or Part IV
from the August 1944 edition, but if you want to send me those editions, I'll be glad to scan and post them.
NSA's PRISM program has been in the headlines lately because of its omnipotent, omnipresent
purpose of recording every possible form of electronic communication into, out of, and within the U.S. Per the Constitution's
"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures,
shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly
describing the place to be searched, and the persons or things to be seized." What part of that is difficult to understand?
If such blatant disregard for the law is deemed necessary to protect the country, why didn't it prevent the Benghazi, Ft.
Hood, and Boston Marathon terrorist attacks? The government had ample info on record about all three but ignored it for
political correctness reasons. Surely they knew the Benghazi attack was not due to "an offensive video" prior to selling
the lie to the public. Yet, when it comes to targeting specific political groups, the IRS seems to know all it needs to
manipulate national elections. Think you're safe from PRISM, et al, since
you've done nothing wrong? Watch who you offend - if not today then tomorrow when control changes hands.
Linx Technologies, a developer
and manufacturer of wireless products such as radio frequency
RF modules, announces a distribution agreement with
Corporation, a global electronics distributor with a strong presence worldwide that provides catalog distribution catering
to design engineers, engineering students, research labs and Original Equipment Manufacturers. DComponents Corporation will
sell and support Linx modules, connectors and Antenna Factor antennas.
Here is a quick
course on how to point antennas for over-the-horizon (DX) reception, and, if you also happen
to have a license to transmit, for broadcasting. It covers how to determine the shortest
straight-line path by stretching a string around a globe (remember those spherical
maps that used to be a mainstay of every household and schoolroom?) and using a protractor
(a what?) to get the angle. Author Edward Noll uses a simple 1/2-wave dipole antenna radiation pattern as an example
of how directivity is affected by frequency (relative to the fundamental).
is only useful to the point where resolution is limited by the wavelength of light representing the object under observation.
Astronomer William Dawes first provided a means of quantification based on an ability to visually resolve closely spaced
stars. Known as the Dawes Limit, a value of 4.56/D arc seconds was empirically determined (D is aperture of instrument in
inches). A theoretical upper limit to magnification of any optical system with perfect optics is around 2,000. The
electron microscope removed that resolving limit by shooting a stream of electrons with radii much less
than the wavelength of visible light, and measuring its reflection. Images are necessarily in 'false color' because we cannot
perceive the real wavelength/color of the surface revealed by the electron beam.
Winner Bogdan V. !!!
Each month I select someone to receive
a free book from those provided by Artech House or Cambridge
University Press. They are often books I have used to create quizzes.
How to enter? Either buy one of my inexpensive software offerings or send me an e-mail. This month's winner, Bogdan V., selected Introduction to
RF Design Using EM Simulators (Artech House), by Hiroaki and Yoshie
Kogure, and James Rautio. "Richly illustrated, this resource provides novice engineers and engineering students with a solid
introduction to the use of EM simulation in RF design. This book describes exactly how microwave and high-speed digital
circuits operate, offering practitioners clear troubleshooting guidance for their work with these circuits. DVD is included."
"That's one of the reasons
we can't sell a telecom switch in most countries, for instance." -
Enderle, principal analyst at the Enderle Group, on news of NSA's ubiquitous
program that coerces companies into complying with demands for user data. (what a difference 5 years makes - video)
Crossword for June 9, 2013
Every Sunday I create an
engineering-themed crossword puzzle
using a word list that I personally created and added to during over a decade of making puzzles. All of the words are related
to engineering, science, mathematics, chemistry, astronomy, etc. There are no numbnut clues about movie stars or clothing
On-the-Fly Alignment Data
Pinpoint Laser Systems has
introduced a new and improved data accessory named “Pinpoint Capture™” for the popular
Microgage industrial measuring and alignment system. Pinpoint Capture™ allows operators to quickly grab measurement
readings, on the fly, from as many as four remote laser receivers to analyze the alignment and performance of their production
machinery and industrial equipment. The software is a powerful, Windows-based application that quickly records incoming
readings, displays results and enables added control.
Calibrated noise diodes are fairly inexpensive
these days and are widely used for measuring noise figure of systems and for generating specific signal-to-noise ratios
when testing receiver performance. This article from a 1967 edition of QST describes a method for using a
'hot resistor,' aka 'monode,'
as a noise reference source. When the temperature (T) and the resistance (R) is known, a noise power can be calculated with
a precision limited by the precision of the T and R measurements. The tungsten filament of a pilot lamp is used as the resistor.
Unless I have just forgotten, I never remember seeing the
math term Ff (pronounced "eff-sub-eff")
prior to the other night while reading an article on dark matter. Now that I know, I'll be sure to use it in my writing
somewhere. Highlight the following text to see what it stands for if you don't already know. "Ff = Fudge factor"
for Their Ongoing Support
Established in 1979, Reactel is an industry leader in the design and manufacture of
RF and microwave filters, diplexers, and sub-assemblies. They offer
a line of filters covering DC-50 GHz. The latest in CAD/CAM methods and equipment in all design and manufacturing processes
are used along with a machine shop complete using CNCs, which gives the ability to produce long production runs quickly
and economically. The testing department is equipped with the latest in Agilent network analyzers offering quick, dependable,
and accurate measurements.
Gives Semiconductors a "Trip"
I have no idea why this
quiz is titled what it is. LSI stands for "Large Scale Integration" and is generally applied to integrated circuits, not
discrete components. The quiz's creator has come up with 17 questions, only the first of which has anything to do with LSI
circuits. The other 16 are on topics like capacitor plate spacing,
magnetorestrictive material, and coaxial cable. I realize that LSI attempts to minimize the number of
external components necessary by absorbing them into the IC, but I'm just not sure what that has to do with whether a submarine
can communication via SHF while submerged.
Automotive Design Wins
Skyworks Solutions today announced that an increasing number of its products are enabling
telematics and infotainment systems in the automotive market. Telematics
is the term used to describe the integrated use of computers and electronic technology in automobiles for wireless communication
applications such as cell phones, the Internet and GPS receivers. Skyworks' industry-leading SOI switching technology is
already being utilized by global car manufacturers for seamless low noise and broadband handoffs between audio, Blu-ray/DVD,
navigation, cell phone and vehicle security display inputs.
With today being the 69th anniversary (June
6, 1944) of the D-Day invasion of Normandy on the coast of France, I thought posting this advertisement by
Hallicrafters from the
July 1944 edition of QST would be apropos. This issue of the magazine probably arrived in ARRL member's mailboxes within
a few weeks of the miraculously successful invasion of Omaha Beach, Utah Beach, Gold Beach, Juno Beach, and Sword Beach.
When you consider that in those days - and also not so long ago for that matter - the lead time for going to the printing
presses was measured in months, the fact that this ad made the final cut for the next month's issue
(July) is noteworthy. Hence, I duly make note.
Each month the IEEE JobSite sends out an e-mail with a few helpful hints and stories
regarding job hunting. Even though the stock market is soaring,
employment is not, so you can probably use any help available to find a new job - whether you are currently employed or
Mastering the Art of Giving a Job Reference
How Veteran HR Professionals Really Feel about Job Seekers from Millennial Generation
- 1 in 10
Young People Losing out on Jobs Because of Pics and Comments on Social Media
LNAs at MTT-S 2013
Skyworks Solutions today unveiled a portfolio of LNAs that provide best-in-class
noise figure, a critical component to boosting weak incoming signals for today's 4G wireless infrastructure as well as diverse
broad market systems including GPS, broadband, military and satellite communications. OEMs can now leverage a single
Skyworks LNA to address all cellular, ISM and military bands, enabling unconditional stability and simple band specific
external matching across a wide voltage range.
The mere sight
of a Nixie tube evokes passion and nostalgia in the hearts and minds of vintage electronics aficionados. For
the uninitiated, Nixie tubes were one of the most successful early numeric display formats. They had wire filaments shaped
in the form of numerals 0 through 9, stacked front-to-back inside a vacuum tube enclosure. Rather than the filament
(wire) doing the glowing, the neon gas (plus traces of others)
fluoresces (glows) in the vicinity of the wire. 7-segment LED displays had not yet hit the
commercial market when this story was published in 1970, so even though the numeric display uses vacuum tubes
(Nixie) the power supply, counter, and display driver circuits use semiconductors rather than
of CMOS Operational Amplifiers, by Rasoul Dehghani. CMOS op amps are one of the most important building blocks
in many of today s integrated circuits.
This cutting-edge volume provides you with an analytical method for designing CMOS Op Amp circuits, placing emphasis on
the practical aspects of the design process. This unique book takes an in-depth look at CMOS differential amplifiers, explaining
how they are the main part of all Op Amps. Complete chapters dedicated to the critical issues of CMOS output stages, fully
differential Op Amps, and CMOS reference generators.
PA Modules at IMS 2013
NuWaves Engineering is exhibiting its high
performance, miniaturized RF products and is also introducing and demonstrating the latest product entry to the
line of small, lightweight, and power-efficient RF PA modules – an S- & C-band power amplifier – at the 2013 IMS hosted
by the MTT-S. The NuPower™ S- & C-band PA joins a growing line of high-performance RF PA modules that cover VHF,
UHF, L-band, S-band, and C-band frequencies in miniature and ruggedized packages as small as 1.3 cubic inches. The PA accepts
delivers at least 15 watts of saturated power across 2500-6000 MHz.
the R&D Lab Anymore
Headlines are filled every day with new, radical
applications for the rapidly advancing 3D printer phenomenon.
3D-printed prototypes for developmental
models have been around for a few years now, but the paradigm is changing to include finished products. Just as you can
send a file for a printed circuit board that you design to a vendor for rapid turn-around fabrication, you can now ship
a 3D CAD file to companies that will print your object.
Gears, enclosures, statues, even wearable
clothing can be turned out as single or multiple components for assembly. Last week a story appeared about a
airway being used to save a baby's life. Available material media and step resolution is not yet advanced enough to
make a metal ball bearing, but it will get there. The May 2013 edition of
Smithsonian magazine has a good article on the state of the art.
to 6120 MHz VCO
Z-Communications announces a new RoHS compliant
VCO model V950ME36-LF in the C-band.
This octave tuning VCO operates at 5120 to 6120 MHz with a tuning voltage range of 0 to 22 Vdc and provides better
than 1.1:1 tuning linearity. This high performance VCO features a spectrally clean signal of -87 dBc/Hz @ 100 kHz
offset and a typical tuning sensitivity of 51 MHz/V. The V950ME36-LF is designed to deliver 0 dBm of output power
into a 50 Ω load while operating off a 5 Vdc supply and drawing typically 22 mA of current.
The Boy Scouts of America was formed in 1910
in conjunction with The Boy Scouts Association in the UK. Per their 2007 website statement, "The aim of the Association
is to promote the development of young people in achieving their full physical, intellectual, social and spiritual potential,
as individuals, as responsible citizens and as members of their local, national and international communities." Part of
being a Boy Scout is earning merit badges by performing certain community services and by demonstrating proficiency at defined
tasks. Radio proficiency is one such merit badge. In order to earn the
Radio merit badge, along with
certain other projects the Boy Scout must participate in either Amateur Radio, Broadcast Radio, or Shortwave Listening...
for Helping Deliver RF Cafe
designs and manufactures solid state broadband linear RF power amplifiers
for commercial, military, medical and industrial applications. RF amplifiers range 10 kHz to 3 GHz in frequency
and power levels exceeding 1 kW.
Standard products can be quickly modified to your specific requirements. Full custom
requests are welcome. Our team of RF Engineers have over 20 years in the field and are dedicated to providing the best in
value, performance and reliability.
Started June 3, 2013
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Variable/Step Attenuator Line
Kete Microwave announces a line of
RF variable/step attenuators that can be used to
adjust the power signal level continuously or by step within certain frequency range. They can also to adjust the test system's
power as inset attenuator. Attenuation ranges from 0 to 120 dB with step sizes as small as 1 dB are available
at frequencies up to 3 GHz. Power handling of 2 W to 30 W, with N, SMA or BNC connectors. These parts
can work at operating
IRS Guidelines Are Out
2016 could be the first year of crippling
health care insurance costs, but major changes
begin next year. Per the Department of the Treasury's new document, "Shared Responsibility Payment for Not Maintaining
Minimum Essential Coverage," the 'Affordable' health care act is projecting the following mandatory plans for all people
(see page 56 for examples): Single w/no dependents = $5,000, Married w/dependents = $20,000.
Those numbers are straight from the IRS document. Your employer pays it or passes some or all of it on to you. Low income
and Illegals (both strong voting bases) will pay nothing or else get subsidies. You cannot
opt out. Remember, the IRS is in charge of collection. Redistribution and reparations are here, folks. Whom should we who
will be paying the bill thank for this - anyone you know?
Security Training Complete
entire RF Cafe staff (that would be Melanie and me) are required to undergo firearms proficiency
training twice per year. We just completed the spring 2013 qualification. Included are 380, 9mm, and .38 special handguns,
and a 20GA shotgun and brand spanking new 30-30 lever action from Henry Repeating Arms. The 30-30 is like what was used
to win and tame the wild west. The first 5 rounds for both of us at 50 yds. clustered within an 6 in. diameter - sans scope.
When I make decisions
on what and how to post on RF Cafe, part of my strategy is to not do what I hate about other websites.
Three annoyances are at the top of my list:
* Audio playing automatically
without my permission (I try
never to link to pages that
initiate audio automatically)
* Full-page ads with or without
a countdown timer
* Short articles being broken
into multiple pages just to
get you to click more
You will know RF Cafe is under different management the day you see any of those things happen here.
"We rely on our early customers
to identify issues like this for us." - Fisker Automotive representative to IEEE
John Voelcker during demo drive when the $106k Karma electric car put itself to sleep while recovering from a fault. Now
that's bad karma.
Might Interest You
Every month I peruse our industry's leading magazines for good articles that cover topics pertinent to they typical RF
Cafe visitor. Here are a few of the latest.
- Design Solution for
Achieving the Lowest
Possible Receiver Noise
(I worked with these
two guys a while back)
- A Topsy-Turvy World
(state of defense)
- Aerospace & Defense
- Crystal Oscillators –
Identifying Emission Sources
and Propagating Structures
L networks are probably the most common
types of impedance matching
networks not just for antennas, but for a relatively narrowband load. Determining the required values for the network
is relatively simple using well-established equations. Knowing how to use a Smith Chart makes the job even easier. This
article from a 1966 edition of QST presents the equation approach. If you have access to the May 2013 edition of
QST, there is a complimentary article on L networks that uses the free Smith Chart cross-platform Java software called
SimSmith. If you want to do a little complex number math, try the 1966 approach.
for T/R Switching Applications
Inc. has introduced a miniature 0402 PIN diode for attenuator and transmit / receive switching applications. The
SMP1302-040LF is a small form factor,
low profile, discrete surface mount technology packaged solution that is ideal for the handset, WLAN, CATV/Satcom, land
mobile radio and infrastructure markets. This diode offers very low insertion loss, good isolation, low inductance
and fast switching in a very small package.
Every Sunday I create a
crossword puzzle using a
word list that I personally created and added to during over a decade of making puzzles. All of the words are related to
engineering, science, mathematics, chemistry, astronomy, etc. There are no numbnut clues about movie stars or clothing designers.