(aka Grid Dip Oscillators)
Grid dip meters, aka grid dip oscillators
(GDO in this article), are extremely useful for determining
when a circuit is functioning at resonance. In the words of Sherlock Holmes, "It
is simplicity in itself" the way a GDO operates. The grid dip oscillator emits power
at a calibrated frequency which is absorbed (or not) to a degree depending on how
close to resonance the external circuit under test is to that frequency. The nice
thing about this type of instrument is that it does not need a wired or other type
of physical connection to the circuit. Of course modern day GDOs do not use vacuum
tubes with grids that register relative current levels as an indication of resonance,
but the nomenclature has persisted
...
Converter for Multiple Apps
Skyworks-Step-down-Converter-Auto-Power-Industrial-Medical-3-13-2015.htm" >
Skyworks introduces a
step-down, DC-DC converter for automotive, distributed power,
industrial, and medical applications. The 28 V, 3 A, non-synchronous SKY87608-11-577LF
is also applicable for general purpose, point-of-load, 16 V, 20 V, and 28 V voltage
regulators. The converter offers prime thermal performance and space savings in
addition to addressing the green-power initiative in the non-portable markets. The
competitively priced high-performance solution comes in a SOP-8L, EP, 5 x 6 x 1.55
Skyworks-Step-down-Converter-Auto-Power-Industrial-Medical-3-13-2015.htm" ...
Radio Wave Curvature
Early investigations into RF signal atmospheric
'ducting' was reported in this 1956-era article in Popular Electronics. Ducting effects were first noticed during World War II when
Nazi broadcasts from occupied Paris were received occasionally in London. Scientists
discovered that a small change in the humidity of the air near the surface has the
effect of trapping radio waves, a trapping process dubbed "ducting." These waves
are conducted as if they were inside of a metallic waveguide. Research by the U.S.
Army Signal Corps determined a sudden temperature rise of around 50 to 200 feet
above the surface appears
...
from 1963 Electronics World
Research has shown over and over again that
engaging in mental exercise is a good way to stave off senility in old age. Playing
musical instruments, writing software, working
crossword puzzles, and other types of activities that require
logic, physical dexterity, and memory recall are often cited as examples. There
is no guarantee these things will prevent or even delay cerebral atrophy, but why
take a chance? Work this crossword just to make sure. Disclaimer: I am not a doctor
and am not prescribing this challenge as a remedy for potential future imbecility,
daftness, tendency to dodder, mental infirmness, or senescent gray matter accumulation,
nor do I suggest that starting now will reverse
...
R&S SMW200A Creates Signals
for Complex A&D
and 5G Apps
R-S-SMW200A-Modulated-Signals-40-GHz-Complex-AD-5G-3-11-2015.htm" >
Rohde & Schwarz now offers three new options
for its R&S SMW200A high end R-S-SMW200A-Modulated-Signals-40-GHz-Complex-AD-5G-3-11-2015.htm" >vector
signal generator with microwave frequency ranges from 100 kHz to 12.75 GHz, 100
kHz to 31.8 GHz and 100 kHz to 40 GHz. An option covering the range between 100
kHz and 20 GHz has been available since the summer of 2014. The R&S SMW200A
is the only microwave signal generator on the market to combine a baseband generator
and RF generator with fading, AWGN and MIMO capabilities in a single box. As a result,
it supports numerous challenging aerospace and defense and wireless communications
applications R-S-SMW200A-Modulated-Signals-40-GHz-Complex-AD-5G-3-11-2015.htm" ...
Absorptive Notch Filter
KR-Electronics-10-MHz-Bidirectional-Notch-Filter-3-11-2015.htm" >
KR Electronics part number
3230 is a 10 MHz bi-direction KR-Electronics-10-MHz-Bidirectional-Notch-Filter-3-11-2015.htm" >absorptive
notch filter. The filter maintains excellent forward and reverse return loss even
throughout the notch frequency. The filter has a typical 3 dB bandwidth of 1.66
MHz and 60 dB bandwidth of 577 kHz. The filter is supplied with SMA connectors.
Other frequencies and bandwidths are available.
Even
in this age of a prodigious supply of computer programs and mobile device apps
(OK, apps are also computer programs) to calculate circuit
component values and responses, having a cool graph to look at can take a
lot of mystery out of the results. Depending on the sophistication of your software,
calculated values can be unrealizable in real life (size,
power handling, standard values, Q, operational frequency, etc.), or maybe
you have a box full of parts you want to use and the suggested value is not readily
available. In those instances and others, being able to grab a handy-dandy design
chart to see where component values lie with respect to all design parameters, in
this case load impedance, desired
power supply ripple, inductance and
...
for RF Design
Ed Troy, owner
of
Aerospace Consulting, LLC, was kind enough to offer a few of his articles for
posting on RF Cafe. With more than 30 years in the electronics communications design
field, Ed has a lot of valuable knowledge to impart to us mortals ;-) This second
paper discusses why using a less expensive
substrate material for a production printed filter design can
be much more costly in the long run. As the old says goes, a picture
(in this case a screen capture) is worth a thousand
words. He's a highly rated airplane pilot as well, which counts for something in
my book. Stay tuned for others...
Antenna
Tuner w/4:1 Balun
As with most other types of commercial electronics
products, Ham radio equipment is sold by many distributors at prices discounted
below MSRP (manufacturer's suggested retail price).
Manufacturers usually have sales agreements with distributors that they
(the manufacturers) will not offer lower prices for
current products in order to not compete with their distributors. When shopping
for deals, be sure to consider return policies and shipping costs
(inc'l for returns).
Amazon, while sometimes not the lowest posted
price, is very good in customer service and free shipping, often making them my
choice; I buy almost everything online through them. If you plan to buy via Amazon,
please start your shopping with a link from RF Cafe since I make a few ¢ commission
on the sale and it doesn't cost you extra. Thanks.
Resistance of a Ground
For some reason the
subject of
grounding has been very prominent in my reading in the last few
days. The chapter I just finished reading in one of David Herres' books on the
National Electric Code (NEC) covering grounding of commercial and residential
services, an article by H. Ward Silver in QST titled, "Grounding and
Bonding Systems," and now this article by John T. Frye
(of
Carl and Jerry fame) on grounding, makes
for a wealth of knowledge. Mr. Frye takes a unique approach at teaching by exploiting
his gift for story-telling. In this article, electronics repair shop owner Mac give
technician Barney a nice bit of tutelage on what constitutes a good Earth ground
and what does not. In some
...
Airtronics Aquila Sailplane
There are some RF
Cafe visitors who are into model building and operation, so this might be of interest.
Radio control systems these days use a combination of DSSS and FHSS modulation on
the 2.4 GHz ISM band, while the brushless motors and LiPo batteries used are
state-of-the-art. Back in the late 1970s I built an
Aquila sailplane from plans that appeared in
RC Modeler magazine, then I built another Aquila in the early 1980s from
a kit. Both are long gone. About 6 months ago while waxing nostalgic about the Aquila,
I decided to build another, but this time I had the plans enlarged to 105% to get
the wingspan over 100" while not having to change airframe component sizes. This
version has a 0.10 size electric motor for power. I wanted to determine the amount
of down-thrust needed to prevent a nose-high climb prior to final nose shaping and
canopy installation. For this maiden flight, there was about 8°, which was not
enough. It really needs about 12°
…
Blockband Tunable Satellite
Filter
Eagle-Comtronics-Blockband-Tunable-Satellite-Filter-3-10-2015.htm" >
Eagle Comtronics Model
NF-1110-TUNABLE passes the entire satellite block
band from DC to 2500 MHz. The tunable notch filter is preset to a center frequency
of 1110 MHz and tunable ±40 MHz with a passband loss less than
1.0 dB (0.5dB typical). Factory set notch depth
is 15 dB with a 3 dB bandwidth of 3 MHz. Power capability is 1 A
at 20 VDC. Connectors are 75 ohm type “F” female/female and the unit measures
8.5” X 1.75” X 2.5” approx. Unit is designed for indoors use. 30 dB and 40 dB
models also available. For different frequencies, connectors and Eagle-Comtronics-Blockband-Tunable-Satellite-Filter-3-10-2015.htm"
...
"These pulses speed toward the moon at the
fantastic speed of light... through the ionosphere and on into the unknown void
surrounding the earth's atmosphere [emphasis added]."
Hard as it might be to imagine nowadays, in 1946 there was no empirical data regarding
the Earth's upper atmosphere other than the few instrumented sounding rockets that
had been launched for studies. Orbiting man-made communications satellites were
still a decade away when engineers at the Evans Signal Corps Engineering Laboratory
in New Jersey made the first
Earth-Moon-Earth (EME, aka 'moon bounce')
signal bounce using a massive radar and antenna that blasted 10 MW EIRP pulse
at the lunar surface. It was a big deal then; it's no big deal today. Amateur radio
hobbyists routinely conduct EME
...
3 New Filter Designs
anatech-product-update-3-10-2015.htm" >
Anatech Electronics offers the industry's largest
portfolio of high-performance standard and customized RF and microwave filters and
filter-related products for military, commercial, aerospace and defense, and industrial
applications up to 40 GHz. Anatech has released three new filter designs: a
90-1100 MHz connectorized highpass filter, a 100-1250 MHz surface mount
LC lowpass filter, and a 2574 MHz connectorized highpass filter. All can be
ordered directly through their AMCrf web store.
"The explanation for the occurrence
of power amplification in the junction transistor is somewhat less complicated than
is the case with the pint-contact transistor, but it is still too abstruse to attempt
here except to say again that two junction areas interact. A more thorough explanation
calls for the use of the concept of
conduction by 'holes' in addition to conduction by electrons. Holes are places
in the germanium crystal atomic structure where electrons could be but are not.
Although this sounds ridiculous it has considerable foundation in fact. These holes
do enter into the conduction process and behave as if they were positive electrons.
There is no ...
& Books for March
2015
The free
whitepapers,
pamphlets, books, and chapter examples listed here are a small sample of a lot of
new items that are offered for
FREE through TradePub. The publishers make them available to
qualifying people as a promotional campaign for their full line of offerings. You
might want to take a couple minutes to see what's new there. They are all free downloads.
'Q' is an often used term to describe the
electrical 'quality' of a circuit or component, and for the most part anyone engaged
in the conversation (verbally or via reading) understands
the concept. However, having a firm grasp on the technical ramifications is required
if you happen to be a circuit or system designer and need to conform to certain
specifications.
'Q' can be good or bad, depending on your needs. If, for example,
you need a narrowband receiver to reject adjacent signals or you are designing a
high stability and spectrally clean oscillator, then you want all the 'Q' you can
get. On the other hand, if your goal is to receive a spread spectrum signal or generate
white noise across some bandwidth, then a lower 'Q' is what you want. This article
provides a brief look at
...
Environment Now Available
NI-AWR-Design-Environment-New-VersionAvailable-3-9-2015.htm" >
NI
(formerly AWR Corporation) announces the immediate
availability of the 11.03/.04 release of
NI AWR Design Environment™ high-frequency software, inclusive
of Microwave Office, Analog Office, Visual System Simulator™
(VSS), Analyst™ and AXIEM for the design of MMICs,
RF PCBs, RFICs, microwave modules, communication systems, radar systems, antennas
and more. More than 100 improvements, enhancements and user interface changes are
contained within this release NI-AWR-Design-Environment-New-VersionAvailable-3-9-2015.htm"
...
Job Opening Announcements!
If your company has a current opening
for an engineer, technician, manager, salesman, or other relevant position, you
might want to let the appropriate HR people there know that they can have those
job opportunities posted
at no charge on RF Cafe. More than 8,000 of the very type people you are seeking
visit RF Cafe on a typical weekday, so don't miss the opportunity. Only offers from
direct hire employers are accepted - no recruiters. It could be a good way to filter
out a lot of worthless resumes because let's face it, RF Cafe visitors are the kinds
of people you want to hire :-)
Oddly, most of this roundup of
career
and job hunting articles have titles asking questions, as opposed to the typical
counted ones that have '5 ways' to do this or '7 things' not to do. The most interesting
article, IMHO, is Alan Murray's piece on what
Millennials
are looking for in terms of opportunity, stability, situation, etc. Not too surprisingly,
according to Mr. Murray the 'Me' generation seems to be comfortable with big
government programs with its accompanying social program safety nets, and are largely
compliant and willing to be fit into a mold as long as their network of 'friends'
(real-life and online) is not compromised. Be sure
to see the Pew Research Center study that he cites. This situation most likely does
not apply as much to RF Cafe visitors, who are
...
Send Me Your Company's
Press Releases!
Since deciding to discontinue the hosting
of private advertising on RF Cafe, I have had many requests to resume the program.
Serving between 7,000 and 9,000 pages each weekday provides a valuable amount of
exposure to people like you - serious engineers, technicians, students, and hobbyists.
While I do not plan to reconstitute private advertising anytime soon, there remains
a very easy - and FREE - way for you to get your company's products and services
in front of RF Cafe visitors:
Press Releases. If your company makes products that I deem relevant to my readership,
I will gladly post your press release, company news, product announcements, etc.
Please send the information, along with ...
High Power Coaxial
Limiters
Pasternack-Broadband-High-Power-Coaxial-Limiters-3-6-2015.htm" >
Pasternack, a leading manufacturer and supplier
of
RF, microwave and millimeter wave products, debuts
their new broadband, high power coaxial limiters which help protect sensitive low
power RF receivers and other microwave circuits in close proximity to high power
signals. Common applications for these Pasternack-Broadband-High-Power-Coaxial-Limiters-3-6-2015.htm" >RF
limiters include electronic warfare, instrumentation, fiber optic communication
systems, military communications, radar, SATCOM, point-to-point radio, telecom,
data links and R&D. Pasternack's latest release of high power limiters consists
Pasternack-Broadband-High-Power-Coaxial-Limiters-3-6-2015.htm" ...
Crossword Puzzle
This week's
Daylight Saving Time crossword puzzle has a few special words
and clues related to our biannual timekeeping shift. All the rest of the words and
clues are engineering and science related - no movie star names or clothing designers.
in FSW High End Signal
Analyzer
Rohde-Schwarz-Unique-2-GHz-Analysis-BW-High-End-Signal-Analyzer-3-6-2015.htm" >
Rohde & Schwarz is expanding the analysis
bandwidth of its
R&S FSW high end signal and spectrum analyzer
to 2 GHz by introducing the new R&S FSW-B2000 hardware option. This test solution
enables R&D users to demodulate extremely wideband signals and analyze them
in detail. There is no other instrument on the market that combines such a large
analysis bandwidth with a frequency range up to 67 GHz, and it opens up numerous
applications. For example, users can measure the EVM values of communications signals
or the chirp rate on chirped radar systems Rohde-Schwarz-Unique-2-GHz-Analysis-BW-High-End-Signal-Analyzer-3-6-2015.htm"
...
Occurs This Weekend
Twice each year the Earth undergoes the first
of two annual Heaviside step functions in its orbit around the sun. Earth is
the only celestial body known to be subject to such a phenomenon. The Bible says
God stopped the Earth it in its tracks one time, but that is nothing compared to
what truly omnipotent kings, politicians, and bureaucrats have decreed
to occur since the early part of the last century. Those megalomaniacs instituted
Daylight Saving Time here in the U.S. and most other parts of
the world with a scheme which each year causes clocks to be advanced by one hour
near the vernal equinox and to be retarded one hour around the autumnal equinox.
Experts disagree on who was the first person to propose our inconvenient timekeeping
shift; some credit (or blame) a New Zealander named
George
...
Are 'Write-Only' Venues
If you have ever sent me a message via LinkedIn,
Twitter, or Facebook and I have not responded, please know that it is not because
I elected to ignore your message. Rather, it is because I use those three venues
in a 'write-only' manner. My trusty secretary, Melanie, posts the items for me on
LinkedIn,
and then LinkedIn has a feature where it automatically broadcasts the same message
on both Twitter and Facebook. So, I typically do not see or read messages from social
media users. If you want to contact me for any reason, please send an e-mail to
kirtrfc@aol.com. I always respond to e-mails from legitimate senders;
i.e., those not from the widows of Algerian princes or from Chinese aluminum window
blind manufacturers
...
Winner Stephen B. !!!
Congratulations to Stephen B., of Georgetown,
TX, for being selected as one of the February 2015
RF Cafe Book Drawing
winners! Stephen opted to receive
Aviation Security Engineering: A Holistic Approach,
by Rainer Kolle, Alex Tarter (graciously provided by
Artech
House). Two other people have been notified for having been
selected, so check your e-mail if you either bought a
software
item from me or submitted an entry in the month of February.
Troubleshoot an LC Filter
Design
Ed Troy, owner of
Aerospace
Consulting, LLC, was kind enough to offer a few of his articles for posting
on RF Cafe. With more than 30 years in the electronics communications design field,
Ed has a lot of valuable knowledge to impart to us mortals ;-) This first paper
discusses a method for accommodating real-world stray capacitances in the simulation
model for helping to assure first-pass success on LC filter designs. He's a highly
rated airplane pilot as well, which counts for something in my book. Stay tuned
for others
...
Extra Sensory Perception
Carl and Jerry were early adopters of the
near field communications (NFC) craze that is going full-swing today. The often harmlessly
mischievous teenage duo used their combined grasp of modern electronics to pull
off gags on unsuspecting friends... and sometime adversaries. In this episode, a
near-field transmitter and receiver pair is designed to help Carl bedazzle a scientist
who was attempting to disprove the ability to use extrasensory perception
(ESP) to determining what another person was thinking
about. In this case it was detecting which playing card was being displayed on an
overhead projector. Of course Carl didn't really have 'the gift,' but relied on
his co-conspirator, Jerry
...
News reports are full of features about the
wave of
radio controlled (R/C) 'drones'
terrorizing citizens with their often inexperienced pilots navigating their camera-laden
craft to peer into bedroom windows, obtain 'birds-eye' views of sporting events,
and to be a general pain in the posterior to people trying to enjoy their right
to privacy and safety (except, of course, unless it is the
Government choosing to violate them). Incredible advances in radio, navigation,
and sensor systems has facilitated a wide variety of very affordable multirotor
(the correct term, not 'drone') aircraft that can
literally fly themselves. For under $500 you can buy a GPS-guided multirotor that
can be programmed to fly to one or more waypoints and return to the launch location,
with range and flight duration limited
...
Splitter for 2-18 GHz
Werbel-Microwave-4-Way-Splitter-2-18-GHz-3-4-2015.htm" >
Werbel Microwave expands its series of 2-18 GHz
coverage with the new,
model 4PA1000 Werbel-Microwave-4-Way-Splitter-2-18-GHz-3-4-2015.htm" >four-way
SMA splitter. Can be optimized using our trade techniques to meet strict amplitude
and phase balance per customer requirements. High isolation, typically 22 dB
or more between all branches. Great for lab test setups, made in USA.
It was not until 1963 that the International
Committee of Weights and Measures (CIPM) adopted the
cesium clock as the world scientific community's standard time
reference. It boasted an accuracy that kept it within 1.1 parts in 100 billion,
meaning it would not gain or lose more than a second in 3 thousand years. To show
how far technology has advanced since 1963, in April of 2014 the National Institute
of Standards and Technology (NIST) launched a new
atomic clock called NIST-F2 (also cesium-based) to
serve as a new U.S. civilian time and frequency standard. NIST-F2 would neither
gain nor lose one second in about 300 million years - a factor of 10 thousand. According
to the U.S. Navy's official Time.Gov website, the Internet time reported on my computer
was 1 minute and
...
Coaxial Cable Advertisement
Amphenol has been around since 1932, when
founder Arthur Schmitt offered sockets for vacuum tubes. Now headquartered in Wallingford,
CT, the company began life in Chicago, Illinois. Amphenol was a major supplier of
coaxial cable in the days when most of the cable Americans used was produced in
the country. Alpha Wire, Amphenol, Carol Cable (now part
of General Cable), and General Cable are the names that come to mind that
were around in the 1970s when I entered the radio-electronics realm. The radar system
I worked on in the USAF, and all of the defense electronics electronics systems
I worked on as a technician and engineer, used those four brands. Today, of course,
there is a seemingly unlimited number of coaxial cable
...
Your Phone Use?
Terahertz Metrology, by Mira Naftaly. "This
new book describes modern terahertz systems and devices and presents practical techniques
for accurate measurement with an emphasis on evaluating uncertainties and identifying
sources of error. This is the first THz book on the market to address measurement
methodologies and issues - perfect for practitioners and aspiring practitioners
wishing to learn good measurement practice and avoid pitfalls. This book provides
a brief review of different THz systems and devices, followed by chapters detailing
the measurement issues encountered in using each of the main types of THz systems,
and a guide to performing measurements rigorously. Particular attention is given
to evaluating
...
Training with Visual Aids
Long before there was Power Point
(OpenOffice's Impress
is the free equivalent), presentations at training seminars were conducted
using overhead projectors and larger-than-life props of the devices being taught.
The U.S. Navy, during World War II, set up a special facility called the Visual
Aid Model Shop located at
Radio Chicago, Chicago, Illinois. Its charter was to design and
build very large scale models of equipment and tools that service personnel used
while performing their duties. It is kind of funny to look at the sizes of some
of the items, like the 8x size radio chassis assembly shown in this article's main
photograph. As a life-long model builder myself, I would have loved to work in a
shop
...
High Power Circuit Protection
RFMW-SM-Iso-Attenuator-High-Power-Circuit-Protection-3-3-2015.htm" >
RFMW announces design and sales support for the
Iso-Attenuator model
RFSL2308-A30 from
RF Circulator Isolator
(RFCI). RFCI Iso-Attenuators combine protection for active components from distortion
or potentially damaging reflected power with a convenient, attenuated port for monitoring
RF power or providing a feedback loop. The RFSL2308-A30 is capable of handling 1000 W
peak / 200 W average forward power and 100 W CW reverse power into the
on-board, 30 dB attenuator. Spanning 2200 to 2400 MHz, the RFCI RFSL2308-A30
provides >25 dB typical port-to-port isolation RFMW-SM-Iso-Attenuator-High-Power-Circuit-Protection-3-3-2015.htm"
...
- Marshall McLuhana
"Xerography is bringing a reign of terror
into the world of publishing, because it means that every reader can become both
author and publisher." - Marshall McLuhana, 1966, from March 2005
Smithsonian magazine. An unregulated
Internet provided the next step in that freedom. On February 26, 2015, the FCC adopted
"Net Neutrality," giving the Federal government control over
the Internet under the guise of protecting little 'ol you. Be sure to thank the
people you know who voted for the people who passed this. If you think you're being
spied on now, you ain't seen nothin' yet.
Application Note Now Available
NI-AWR-Improve-2nd-Harmonic-Passband-Rejection-Microstrip-Filters-3-2-2015.htm" >
NI (formerly AWR Corporation)
released a new NI AWR Design Environment application note, “Improving the Second-harmonic Pass Band Rejection
of Microstrip Side-coupled Filters.” Because of their low cost and easy manufacturability,
side-coupled filters constructed from printed-circuit board-based microstrip are
widely used throughout the industry. One of the main drawbacks of the side-coupled
filter is its limited rejection of the second harmonic. This application note demonstrates
a solution that mitigates this problem through the introduction of notch-filter
elements that improve the overall rejection of side-coupled filters at the second
harmonic without significantly affecting the filter passband behavior NI-AWR-Improve-2nd-Harmonic-Passband-Rejection-Microstrip-Filters-3-2-2015.htm"
...
Winners Have New Selection
Thanks to Qorvo's Jeff Cameron, Sr. Manager,
Product Marketing, Filter Solution, for providing this very high quality polo /
golf shirt (made by the
Pebble
Beach brand) with a Qorvo company logo embroidered on the front. It is
being offered as a prize selection in the monthly
RF Cafe Book Drawing.
I knew Jeff back in the early / mid 2000s when I worked for RF Micro Devices in
Greensboro, NC. As you probably know, RFMD merged with TriQuint last year and became
Qorvo. Both of
February's winners have been notified, but I haven't heard back yet from either.
The shirt might be gone before the March drawing occurs.
Embedded Hardware/Software
and Mixed Applications
Synergy Microwave currently has an opening for
an Intermediate Engineer: Embedded Hardware/Software and Mixed Applications. A very
exciting opportunity to join a strong engineering team dedicated to developing radio
frequency products for the microwave communication, microwave instrumentation, radar
and defense applications. You will have extremely deep resources and guidance for
modern radio product development using mixed signal and digital radio techniques.
Qualifications include experience in radio frequency applications, modulation algorithms,
signal detection, leveling and control ...
You've Been Missing on RF
Cafe
Are you kidding me ?!?!?! Why in the world
would you WANT to see a
full-screen splash
ad when you visit any website? I absolutely detest those things. When I visit
a website, I want the first thing I am presented with to be the content of the site,
NOT a full-page advertisement with some lame message like, "Please wait
while your page is loading," or "Welcome Screen," or some other annoying and/or
disingenuous text. Do the webmasters really think visitors are stupid enough to
believe that the website's real content is loading behind the advertising screen,
and that they are doing visitors a favor by providing
...
Puzzle for March 1, 2015
I stopped creating the RF Cafe engineering
and science themed crossword puzzles at the end of January in order to test the
interest in them. As of today, on March 1st, I will resume creating them every couple
weeks. It takes up to an hour to make each crossword. Enjoy this
radar engineering themed puzzle.
