C O N T E N T S :

INTRO
SOLAR-TERRESTRIAL DATA
STATION PROFILE
RADIO CLIPS
RADIO TOPICS
PICTURE BOOKS
LINKS

L A T E S T   A D D I T I O N S :

17-10-2011: ENERGIEFLUSS AUF ÜBERTRAGUNGSLEITUNGEN (In German only, RADIO TOPICS)
01-10-2011: CapKey, a PIC-based capacitive sensor paddle (RADIO TOPICS)
16-06-2011: new radio clips, PICTURE BOOKS

WELCOME TO MY RADIO SHACK !

MY SIGNALS ARE DEDICATED TO THE
PHENOMENON
SCIENCE
ART
SPIRIT AND SOUL
OF
RADIO

"Why has this discipline of radio - at one time the very heart of electronic technology - come to the point where people consider it an arcane science ? I have been forced to consider what first attracted me to radio during my formative years. I liked radio because it was aesthetically appealing. I was not nearly as impressed by the capabilities of radio as by the very nature of radio. Radio is great, not because of what it does, but because of what it is. Nobody buys an original Da Vinci painting to cover a hole in the wall. By the same token there are other means of communication that are more efficient than bouncing signals off the ionosphere; but the very fact that we can bounce signals off the ionosphere makes it worth the effort ... Maxwell's equations appeal to the body, soul and spirit. Sine waves are veritable works of art. Antenna radiation patterns are beautiful ... It is incumbent upon radio initiates to convey the mystique and aesthetic aspects of our hobby to newcomers. To fail to do so is to doom our hobby and the radio profession to the status of a lost art."

Eric Nichols, KL7AJ

"Somewhere on a lonely mountaintop on a starry night, or maybe in an apartment on a bustling city block, someone is channeling the whole world onto a mobile device. It's not a phone; it's a shortwave radio ...
Now that the Internet is a fixture in many homes in the United States and Canada, there are few practical reasons to buy a shortwave radio. Thousands of stations that once were available only on the shortwave band are online ...
The contrast is stark: iPods and satellite radios are slim and pocket-sized, while shortwaves are throwbacks, typically as square as a textbook and just as serious looking.
So why bother with shortwave?
It's easy and cheap -- and fun. You can hear and learn things that you would never find even if you work your search engine like a mule. From Swaziland to Paris to Havana, shortwave broadcasters can surprise an adventurous listener more than any MP3 playlist ...
It's also magic. Shortwave radio enthusiasts acknowledge the thrill -- the romance, in a way -- of going out at night and snaring news, music, odd bleeps, religious zealots and other broadcasts from the wild sea of frequencies in the sky.
In aural terms, the Internet wins. Shortwave by nature sounds dirty: Its signals whoosh from clouds of static and are subject to the whims of sunspots and atmospheric disturbances.
But when you hear voices over the noise and squeal, and realize you are hearing Mongolia, live, there is a warmth and a human connection that are hard to find on the Web.
Shortwave also can deliver news faster than you might find it online, and in places where your other devices don't work ..."

Excerpts from
"Shortwave Radio Still Packs an Audible Thrill"
by Robert MacMillan, New York (Reuters), Jan 14, 2009

 

Callsign: DJ5IL

Operator: Karl Fischer (on Earth since 1956, on the air since 1973. Profession: Software Engineer)

Location: Pforzheim (48° 54' N / 8° 42' E), the Gateway to the Black Forest, Germany, Central Europe - 25 Km from the University of Karlsruhe, where in 1886 Heinrich Hertz proved the existence of electromagnetic waves as predicted by Maxwell. Learn what happened to my hometown Pforzheim on February 23, 1945.

Transceivers: Kenwood: TS-590 / TS-50, Ten-Tec: Corsair II / Omni-D  - and some homebrew QRP transceivers

Receivers: RFT EKD300 (vintage, ex GDR), Drake MSR-2 (vintage), Drake 2B (vintage, tubes)

Transmitters: Drake T-4X (vintage, tubes)

Power Amplifiers: Yaesu FL-2100Z (2x "572B" triodes @ 2.4 KV plate voltage, max. 700 W output power)

Antennas: Antenna #1: Tennadyne T6 LPDA (Log Periodic Dipole Array), 6 Elements @ 15m above ground, operable continously from 14 to 30 MHz with SWR<2.   Antenna #2: 18m Vertical Dipole, feedpoint @ 9m above ground + automatic tuner SGC SG-230, operable countinously from 3.5 to 30 MHz (one arm of the dipole is a "Titanex V40" 10m long vertical radiator of aluminium / titanium alloy, the other arm is a 8m long vertical coax section going straight down towards ground).   Antenna #3: Inverted-V dipole for the 80m-band.

Memberships: FOC # 1980, HSC # 842,  DARC, RSGB, ARRL

Preferences: radio telegraphy with straight keys, sideswipers, bugs and electronic keyers --- DX-ing (DXCC entities confirmed: 315) --- rag-chewing in CW and SSB --- radio engineering --- antennas & transmission lines in theory and practice --- study and forecast of ionospheric radio propagation --- vintage radio equipment collection, restoration and operation --- exchange and collection of individually designed QSL cards --- good food --- dry wines --- hiking --- jogging --- cycling --- travelling

Aversions: crocodiles (radio operators with small ears and big mouths) --- contersters who ignore the band plans and legal power limits --- five-nine-nine QSOs --- promised QSLs which never arrive --- eQSL --- DX-cluster --- soft-drinks

DJ5IL, opr. Karl, in February 1974 at the age of 17

In memory of Fritz Hauff, W3NZ cousin of my grandmother, passionate and exceptional radio amateur. This picture shows OM Fritz in his 1950 radio shack in Royersford PA, when he held his first callsign W3GHS.

IT'S A SMALL WORLD! by W3NZ
(from the FOC News Sheet 666, April 2005)

At 2200z on 9 October 2001 I checked 20 meters. Signals from Europe were strong but not plentiful, and in my pet spectrum (14022 - 14030 KHz) the CQ from DJ5IL was outstanding and snappy. I gave my call once and he bounced back to me with flawless CW. "TNX OM for call, you are 599 and my name is Karl, the QTH is Pforzheim, at the north end of the Black Forest. BK".

I said, "Many TNX Karl, you are also solid 599, my name is Fritz. I know the Black Forest well, my mother came from Haiterbach and years ago I had some relatives in Pforzheim. I am not sure of their name, but believe it was Karl Fischer, he was married to my cousin Kaethe Klenk and he had a store selling watches and clocks. Would you know them or of them? BK".

Karl replied. "Solid copy Fritz. My name is Karl Fischer and the store is still in the family. We are related, I am 45 years old and I never knew my grandfather Karl Fischer, he had died before I was born. How about it?".

By that time my mind went almost blank. A good CW operator in the relationship was too much for me to contemplate. We exchanged e-mail addresses and signed.

After I told my wife Jean this story, her eyes opened wide and she said, "It's hard to believe, it is a small world!".

My first experience with radio!
(by W3NZ, from a personal letter)

I was ten years old - back in 1921 when I saw and heard my first radio. It was a home built 3 tube breadbord set.
I was hooked !
It was an adventure for me to build a little crystal set. The big expense was a pair of Siemens earfones and the cotton covered wire for the coil and the aerial. It took a few days before the miracle happened - I heard Stuttgart. Was I ever excited! " Mom, hurry up and listen! " She arrived, I put the earfones over her head. Her cheeks turned white and after a few seconds she hollered: "Get this thing out of this house, it is the work of the devil!" A week later she had a change of mind - after she found out that her preacher also had a
RADIO.
It was the beginning of my life long passion!

Listen to the magic sounds of shortwave radio ! Here you find audio clips of worldwide Amateur Radio, Broadcasting, Utility and Spy Number Stations recorded from my station transceivers and vintage receivers RFT EKD-300, DRAKE MSR-2 and DRAKE 2B. Stop by from time to time for brand new radio recordings ... Click on a station identifier to play the audio clip. Enjoy !

AMATEUR RADIO STATIONS

VU2DK   a well-known voice on the bands: op. Zal, QTH Poona near Bombay / India, here in QSO with DK5EC (op. Karl, QTH Bonn / Germany). 11-02-2011, 11:02 UTC, 21239 KHz, S9, (TS-870 / LPDA).

VK2GND   op. Mark, QTH Hornsby / Australia, pushing 1 KW into two stacked 3-element Yagi antennas, in QSO with VU2XO (op. Patel in India). 10-01-2011, 13:30 UTC, 14273 KHz, S9 (TS-870 / LPDA short path). 

ZL2JBR - qrp test   John asks his QSO partner DL1DH in Germany to reduce power and copies his 1 Watt Signal still perfectly well with S3 in New Zealand, a distance of nearly 20.000 Km - really incredible ! 17-01-2011, 11:10 UTC, 14215 KHz, S9+10dB (TS-870 / LPDA short path). 

ZL2JBR   op. John, QTH Wellington / New Zealand. 21-12-2010, 09:25 UTC, 14215 KHz, S9, (TS-870 / LPDA short path). 

HB9QQ   calling "CQ DX" from Switzerland in CW on the 17m band, with echo signals due to multipath-propagation (... he worked many Japanese stations afterwards). 07-11-2004, 09:10 UTC, 18087KHz.

BROADCASTING STATIONS

"Radio Kitaia"   the Russian program of "China Radio International" CRI. 13-02-2011, 09:00 UTC, 15340 KHz (TS-870 / LPDA). 

China Radio International (CRI)   with echoes caused by multi-path propagation. 20-12-2010, 10:20 UTC, 15440 KHz (TS-870 / LPDA). 

Deutsche Welle (DW)   with strong echoes caused by multi-path propagation. 07-09-2010, 15:30 UTC, 6075 KHz (TS-870 / Vertical).

Voice of Russia   interval signal and anouncement "Hier ist Moskau ..." ("Here is Moscow ...") starting the German programme, 01-06-2004 15:00 UTC 7330 KHz.

AIR India   with a typical music program. 06-Jul-2004, 13:52 UTC, 11585 KHz.

Radio Tashkent   interval signal and announcement, exotic sounds from the capital of Uzbekistan on the Great Silk Road in Central Asia. 07-07-2004, 14:30 UTC, 17775 KHz.

BBC World Service   time signal and announcement. 07-07-2004, 15:00 UTC, 15565 KHz.

UTILITY & SPY NUMBER STATIONS

38702  77026 ...   yes, there are still spy number stations active in CW like this one ! After the automatic transmission of number groups, the operator seems to wait for confirmation by the target station and uses the straight key to ask "QRV ?" ("are you ready ?"). 27-03-2011, 08:17 UTC, 14937 KHz, S9+20dB ! (TS-870 / Vertical). 

"846 846 ..."   Russian spy number station. 12-01-2011, 10:15 UTC, 14280 KHz (TS-870 / LPDA). 

"Echo Zulu India"   spy number station (ENIGMA classification: E10). It is generally believed that MOSSAD (the Israel Intelligence Service) operates these stations, transmitter sites include Israel and their embassies and consulates. E10 is characterized by a female voice repeating a three letter phonetic phrase. This can go for hours before the message is sent, which consists of blocks of phonetic letters. 03-07-2004, 07:00 UTC, 11565 KHz.

"39208 ..."   another spy number station playing xylophone - spooky ! 05-07-2004, 15:10 UTC, 11545 KHz.

 

 
This chapter presents articles, essays and features dealing with technical, operational, regulatotory and historical  aspects of radio. The layout of some of the available PDF files is my reminiscence of the "ham radio" (HR) magazine, which was founded by Skip Tenney, W1NLB, and Jim Fisk, W1HR/W1DTY and published from February 1968 to June 1990. In its time HR was the preeminent technical magazine for amateur radio, it had no peers and to this day published some of the most cutting edge articles in amateur radio history. Feel free to download and circulate any of the material presented here ...

ENERGIEFLUSS AUF ÜBERTRAGUNGSLEITUNGEN     (in German only)

Wohin geht die Leistung, die von einer fehlangepassten Last am Ausgang einer Übertragungsleitung reflektiert wird ? Jahrelang war ich der Ansicht, daß sie am Generator total re-reflektiert wird, so wie es von Walt Maxwell, W2DU, ursprünglich propagiert wurde, und meine Darstellung dieses Modells war hier zu finden. Inzwischen bin ich zu einer anderen Überzeugung gelangt und warum das so ist, wird hier erklärt ...

CapKey    

 
Early sensor-paddles worked with the skin-resistance, which is a widely varying parameter and made two electrodes necessary - in the form of split or meandering paddles or solid paddles and a conductive hand pad. They were very unreliable and no pleasure to operate and that's why they gained a bad reputation. Being a passionate high-speed CW operator, in the late 1990s I had the idea for a sensor-paddle based on the capacitance of the human body to ground, which has a much more settled value of typically around 200 pF. In 2011 I developed CapKey as the latest evolutionary stage of my initial idea. The result is a capacitive sensor-paddle controlled solely by software logic, utilizing one single re-programmable 8-pin PIC microcontroller 12F683 instead of discrete and specialized ICs in a very simple and easy to build circuit ...

SHORT END-FED DIPOLE ANTENNA
 
See my patent paper for a Short End-Fed Dipole Antenna on the servers of  the German Patent Office (patent number DE 103 22 186 B3, granted on 02.12.2004, in German only). It has many advantages over a common center-fed dipole and I encourage all readers to build their own version of my practically proven antenna design for personal non-commercial use. If you do so, please contact me for important notes on the BalUn !

THE CODEPHASER  
 
Add a new dimension of CW perception to your receiver by incorporating this simple audio device for pseudo-stereo reception of radio telegraphy signals. The sound does not seem to originate from the earphones as usual, but from the inside of your head. Multiple CW signals in the receiver passband seem to be spreaded out holding specific positions, while static crashes appear randomly distributed throughout the entire space - a spatial sound sensation with depth and presence that makes CW copy unique ...

I recorded a few moments on the 40m band to demonstrate the effect of the CODEPHASER. Before you listen to the demo, please note that it is absolutely necessary to use stereo headphones - PC loudspeakers definitely don't work !  Don't expect astounding but rather subtle effects, since spatial sound sensations are the normal condition for our auditory system. Close your eyes while listening in order to focus exclusively on the sound. And certainly it will take some time and several listening sessions before you can fully appreciate this new dimension of CW reception. The demo consists of 9 radio clips :

Clip #1 (39 sec.): Sweep across the 40m CW band. The clip starts monaural, after 15 sec. the CODEPHASER is switched in and the signals now appear on the right moving to the left with increasing pitch ...

During the following clips, the CODEPHASER is switched in and out alternately (the switching moment can be identified by a short popping noise):

Clip #2 (18 sec.), Clip #3 (30 sec.), Clip #4 (31 sec.): CW pile-ups. A wide filter is used to enhance the spatial effect. Pay attention especially to G3PHO in the first and F6COW in the last pile-up ...

Clip #5 (16 sec.), Clip #6 (19 sec.), Clip #7 (10 sec.): FSK-signals. Though it makes no sense to listen to them, they sound quite interesting through the CODEPHASER ...

Clip #8 (18 sec.), Clip #9 (18 sec.): SSB-signals.

Please listen now to the CODEPHASER sound demo

MAGNETOSPHERIC DUCT ECHOES

Sometimes, at rare occasions in the night during the winter months and predominantly on the 80m-band, very few radio amateurs are lucky enough to observe a strange and most thrilling phenomenon: they can hear the echoes of their own transmitted signals, delayed by much more time than a trip around the globe would take. Please don't hesitate to download my simple computer program mde.exe which explains Magnetospheric Duct Echoes (MDEs), calculates path lengths and time delays specifically for your location and contains a short bibliography on that topic. This small self-explanatory program (95 KB) is absolutely save to use on any Windows platform and does neither generate nor touch any files on your system. Always keep a recording device attached to your transceiver and ready to go - who knows, maybe you are one of those few lucky radio operators who ever experience these rare echoes ...

THE COOTIE, SIDESWIPER OR DOUBLE SPEED KEY

Being a passionate CW operator, after 35 years of mainly high-speed operation with electronic keyers I felt more and more bored listening to the uniform and impersonal sound of CW signals on the amateur radio bands. That's why in March 2008 I found myself a new challenge: to build and learn to operate a Cootie key. The picture shows my homebrew Cootie  #1. Please note that this is NOT a paddle to operate an electronic keyer, and it is also NOT a semi-automatic key or "Bug" ! In fact, the dots and dashes are both made manually by horizontal movement of the blade. If properly operated, the resulting CW note sounds very distinct, melodic and a little bit corny ... My main key is still electronic ("CMOS Super Keyer II" with a homebrew Sensor-Paddle which works much better than common sensors by utilizing the capacity of the human body instead of the skin resistance). However, operating the Cootie makes a lot more fun, is a most natural way of sending morse code, and learning to master it is a true challenge which took me more than two years. So you can hear me on the air - not always but often - with my sweet sounding Cootie ...

 
HOW THE MICROVERT REALLY WORKS

Extremely small and highly efficient - These two properties of a fictious superantenna sound very attractive, not only to us radio amateurs. Unfortunately, they are physically competing since the smaller the antenna copared to the wavelength, the smaller the radiation resistance. And because in real antenna systems the losses increase with decreasing radiation resistance, efficiency drops with reduction in size. See my detailed analysis of the DL7PE-MicroVert and it's derivatives and learn how the MicoVert really works (in English and in German).

A NEW EQUIVALENT CIRCUIT FOR THE IMPEDANCE OF SHORT RADIATORS

In 1973 the two scientists Friedrich Landstorfer and Hans Heinrich Meinke of the University Munich published a highly interesting article that explains the division of the total antenna capacitance into so-called space capacitance and dead capacitance very clearly both in quality and in quantity on the basis of the time-dependent course of wave detachment in the near field of antennas - a subject which has been intensively addressed by Prof. Dr. Landstorfer with many interesting publications. They show why and how the radiation resistance and as a result also the efficiency are decreasing with shortening of a radiator, why for a rod of uniform diameter that diameter has no influence on the radiation resistance and how constructive measures affect efficiency. Download the German original "Ein neues Ersatzbild für die Impedanz kurzer Strahler" (PDF, 1037 KB) or my English translation "A New Equivalent Circuit for the Impedance of Short Radiators" (PDF, 322 KB).

POYNTING VECTORS

Where on an antenna does radiation come from ? If you are one of those searching minds intrigued by this big question, read the explanation on the Poynting vector and energy flux in electromagnetic wave fields as part of my analysis how the MicoVert really works (in English and in German) and watch my little movies Poynting #1 and Poynting #2. They visualize the electromagnetic energy flow around a dipole transmitting antenna in free space, represented by a Poynting vector field. The movies start to run with normal speed as soon as the picture is completely downloaded. Watch very carefully since it takes time before some most interesting details become obvious ... (Animated GIFs, work only if viewed with a web browser, best resolution: 1024x768).

THE INVENTOR OF THE COMMON-MODE CHOKE

"common-mode choke", "current balun", "Guanella balun" or "1:1 Guanella" are different names for the same device which is widely used in electronic engineering to force balanced RF currents. It is generally claimed that it was invented in 1944 by the Swiss Gustav Guanella - Fact is, however, that this device has been already invented and patented in 1932 (patent #592184) by the German Felix Gerth for the company "C. Lorenz Aktien-Gesellschaft in Berlin-Tempelhof". There is no doubt that it was an ingenious idea by Guanella to use that common-mode choke as the basic building block for his transmission line transformers in later patents, with ports connected in parallel on the low-impedance side and in series on the high-impedance side. But the common-mode choke itself is the true brainchild and invention of Felix Gerth. Here are some translated excerpts from Gerth's patent paper:

"High-frequency engineering utilizes energy transmission lines which are comprised of two parallel conductors carrying high frequency in anti-phase so that their external fields compensate and no radiation is present. If, however, the geometrical lenghts of these energy transmission lines are in the order of a wavelength with external fields being present, it is possible that the conductors also carry in-phase currents in addition to the anti-phase currents. This is the case, for example, in arrangements which are used to feed antennas ... These in-phase currents result in radiation of the energy transmission line ... In order to prevent these drawbacks, it is suggested to include means by which anti-phase currents are allowed to flow unhindered through the parallel conductors whereas in-phase currents are hindered ... an arrangement of coils is inserted which consists of two coils wound into each other in the same sense thus being tightly coupled. The inductivities of the coils cancel for the anti-phase currents from the transmitter so that energy flow in that wanted direction is unhindered. But for the in-phase currents which are induced by emission of the antenna the inductances sum up so that these currents encounter a high resistance and thus are hindered ..."

IEC/CISPR THREATENS RADIO SERVICES

CISPR is the Special International Committee on Radio Interference of the International Electrotechnical Commission IEC with central office in Geneva, Switzerland. It is concerned with the development of standards regarding electromagnetic interference and most of these are adopted by the European Union and many other countries. Disturbance limits for Power Line Telecommunications (PLT) systems are defined by the standard CISPR 22 and its European equivalent EN 55022 entitled "Information technology equipment - Radio disturbance characteristics - Limits and methods of measurement". Read my report describing why and how CISPR and the PLT lobby threaten the Radio Services ...

IEC/CISPR Threatens Radio Services by a Planned 18 dB Relaxation of PLT Disturbance Limits (Part 1)

CISPR Project Team Dominated by PLT Lobby - Rationale Behind Proposed Approach Disproved (Part 2)

To be continued - stay tuned !

EMC

The European Commission considers the protection of radio services from harmful interference caused by electrical aparatus of any kind as embodied within the Constitution an Convention of the International Telecommunication Union (ITU), which represents international law, to be an obstacle to trade and market. With her new directive 2004/108/EC on electromagnetic compatibility (EMC) she tries to grossly cut down the protection of radio services for the benefit of neoliberal political objectives. The German federal ministry for economy and technology (BMWi) even goes one step further - and steps the mark - with it's bill for a new national electromagnetic compatibility act (EMVG), which is an attempt of the subordinate federal regulatory authority for telecommunications (BNetzA) to get rid of her liability for the protection of all radio services. The bill infringes not only the ITU Radio Regulations and thus international law, but also the EMC-Directive of the European Council itself. Here are my comment and petitions on that bill for download (in German only).

QTC DL (in German only)

Mitteilungsblatt für den Amateurfunkdienst - Archiv mit allen Ausgaben zum Download

RADIO STUFF

Yaesu FL-2100Z Linar Power Amplifier  

Tennadyne T6 LPDA (Log Periodic Dipole Array)  

AMATEUR RADIO SERVICE

FOC The First Class CW Operators' Club

WebSDR (Software-Defined Radio receiver) at the University of Twente / Netherlands

ANTENTOP e-magazine devoted to antennas and amateur radio

The Radio Regulations are a binding treaty for all ITU member states

DX Summit monitors amateur radio DX spots, live from the worldwide packet-radio DX cluster

Announced DX Operations by Bill Feidt, NG3K

FUNKAMATEUR is a popular German amateur radio and electronics magazine

IARU (International Amateur Radio Union)

National Amateur Radio Organizations - Please accept my apologies that I cannot list all of them, here are some of the larger ones:

WIA (Wireless Institute of Australia)

LABRE (Liga Brasileira de Radioamadores)

DARC (Deutscher Amateur Radio Club)

REF (Union Francais des Radioamateurs)

RSGB (Radio Society of Great Britain)

ARI (Associazione Radioamatori Italiani)

JARL (Japan Amateur Radio League)

SRR (Soyuz Radiolyubitelei Rossii)

ARRL (American Radio Relay League)

Radio amateurs homepages:

DL1IAO - my friend Stefan von Baltz is a great contester !

DL4YHF - Wolgang Büscher's fantastic audio spectrum analyzer software "Spectrum Lab"

IZ8BLY - Nino Porcino's ham radio software for windows and soundcard

JF1OZL - ingenious electronic circuits for the homebrewer

BROADCASTING SERVICE

"On the Shortwaves" - a great site devoted to the history of shortwave broadcasting

Prime Time Shortwave guide for English shortwave broadcast schedules ...

Hugh's Awesome Shortwave Recordings

Interval Signals Online

IONOSPHERE AND RADIO PROPAGATION

Ionograms from Digisondes around the world

Solar Terrestrial Activity Report by Jan Alvestad

Solar Terrestrial Dispatch by Lutz Schenk

10.7 cm Solar Radio Flux

VOACAP - A free professional HF prediction program, originally developed for the Voice of America (VOA)

SECRET SIGNALS

Simon Mason's site on Secret Signals with a lot of infos, sound-clips and links ...

Learn more about Shortwave Spy Number Stations

SPREAD SPECTRUM

Read the fascinating story The Invention of Secret Electronic Communication: "Hollywood screen siren Hedy Lamarr had read bad-boy composer George Antheil's articles on endocrinology in Esquire magazine and had invited him to meet her at the home of Adrian, the dress designer ... And that, according to the legend, was the origin of all secret electronic communication."

The History of Spread Spectrum Technology

THIS AND THAT ...

Take a Breath of Complexity on the site of Levitated Design & Code. Click on any image and find out what you can do with the mouse - absolutely fantastic !

Richard Feynman was the ultimate physicist and the greatest lecturer of all time ...

 

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