The New Photonic Communications

by Raymond “Woody” Woodward K3VSA

North Carolina ARRL Public Information Officer

A directed beam of light from a 3 Watt red Luxeon LED at a distance of almost fifteen miles, easily stands out against the lights of Salt Lake City, Utah.   (Credit Photo: Clint Turner KA7OEI, copyright, used with permission)

 

Since the beginning of wireless, Amateur Radio operators have shown an insatiable curiosity to explore and populate the high frontiers of the electromagnetic spectrum.  Many years ago, hams were relegated to the “shortwaves,” thought to be worthless, and they discovered that those frequencies allowed for worldwide contacts. A few years later, hams colonized the VHF and UHF frequencies and found them to be ideal for reliable local communication.

This technological wanderlust of ours may be happening again, perhaps encouraged by the Federal Communications Commission in the US, which, along with many other members of the International Telecommunications Union, has opened the frequencies above 300GHz to licensed Amateur Radio use. Small groups of hams, some in Australia, New Zealand, Tasmania and France, as well as here in the US, are experimenting with lightwaves as a communications medium.

There is some historical precedent for this. The first “wireless” electronic communication of the human voice was done in 1880, not by radio, but over Alexander Graham Bell’s “Photophone.” This device used a mirror vibrating in accord with the sender’s speech to modulate a beam of sunlight, which was detected at the other end by a selenium cell attached to a battery and an earphone.

Obviously, Bell’s invention wouldn’t help much if someone had to make a call at night, but the recent blossoming of Light Emitting Diode (LED) technology is enabling hams today to shoot a beam of concentrated light over many miles of “line of sight” territory.  Because the thin beam of laser light is degraded by scintillation (“twinkling”) when propagated through a lot of atmosphere, LEDs are actually a superior transmitting tool.

Sensitive photodiode circuits behind inexpensive Fresnel lens concentrators or off-theshelf telescopes serve to receive the light and retrieve the message. How sensitive can they be? Yves Garnier, F1AVY, detected harmonics of power line frequencies in terrestrial street lighting reflected from the surface of the moon during a recent lunar eclipse. Rye Gewalt, N9LCJ, reported that output “spikes” from a photodiode receiver board he was working on were the result of the board seeing lightning strikes from a thunderstorm many miles away. Neither of these events was producing enough light to be visible to the naked eye.

For a good look at some actual hardware being used right now, Clint Turner’s (KA7OEI) website, “Optical Through-The-Air Communications” …   (http://modulatedlight.org/optical_comms/optical_index.html), offers about the best introduction to the subject that can be found on the ‘net. At least one Amateur Radio club is being formed specifically to explore this new frontier. The “Carolina Flashers Photonics Group” (http://www.carolinaflashers.org), a group of hams headquartered in North Carolina, will soon be chartered and at work to help see how far this technology might be developed.

A new satellite for Radio Amateurs

December of 2009 brought a nice present to radio amateurs around the world. The Chinese “Hope-1″ satellite carries a series of interesting and easy to use VHF/UHF transponders.
AMSAT-NA formally designated the new satellite as Hope OSCAR 68, or HO-68.
 
Hope-1 (or Xi Wang-1) is developed by CANSAT and is a so-called micro-satellite with educational purposes. It includes both a linear (SSB) transponder as well as a strong and sensitive FM repeater. This repeater can be used for regular voice contacts as well as digital communication with the
on-board BBS. Status of the satellite is continuously transmitted via a CW beacon at 435.790 MHz.
All uplinks to the satellite are in the 145 MHz band, and all downlinks in the 435 MHz band.

Satellite operators around the world got immediately enthusiastic as the satellite proved to be easy to operate. Due to its relative high orbit the ‘footprint’ is larger as for most other amateur radio satellites. Already in the first days after launch reports of contacts across the oceans became available.

This 2 minute video features the launch of the satellite and its various modes of operation, including its CW beacon, the FM repeater and the linear (SSB) transponder:

More information (including status) can be found at the CAMSAT (AMSAT China) Hope-1 website: http://www.camsat.cn/

ANDE-2 Experiments and Amateur Radio

by Henk Hamoen, PA3GUO, The Netherlands

 

Very often I find it difficult to explain to ‘outsiders’ what “HAM” radio is all about. Therefore I have released a short video on YouTube about the recent ANDE-2 experiments and how Radio Amateurs world-wide contributed to this mission;

 

When I was a young kid I watched the first Space Shuttle flight on TV, a fantastic, scientific event, happening far away, on the other side of the world. Many years later, licensed Radio Amateurs are given opportunities to engage directly in space-experiments. It’s a thrill to be involved!

 

Atmospheric Neutral Density Experiment – 2 (ANDE-2) consists of two micro satellites launched from the Shuttle payload bay on July 30th 2009, that will measure the density and composition of the Low Earth Orbit (LEO) atmosphere while being tracked from the ground.  Data will be used to better predict the movements and decay of objects in orbit.

 

Originally designed as passive payloads, both satellites were turned into research projects of various participating high schools and universities.  Radio Amateurs participated in the program as they acquired all satellite data transmitted via radio.

 

Featured in the video are the launch and deploy from STS-127, as well as reception and decoding of the satellite’s radio signals (‘telemetry’) received from space by a team of licensed Radio Amateurs around the world.

 

 

Naval Research Laboratory information on the ANDE-2 program:

https://goby.nrl.navy.mil/ANDE/Main.html

 

NASA information on the ANDE-2 launch:

http://www.nasa.gov/mission_pages/station/science/experiments/ANDE-2.html 

 

Henk Hamoen, PA3GUO, The Netherlands

http://www.pa3guo.com

 

Compass-1

by Henk Hamoen, PA3GUO, The Netherlands

 

COMPASS-1 is the first CubeSat of the Aachen University of Applied Sciences in Germany. It is a 10×10x10 cm³ cubic satellite with a mass of less than 1 kilogram! The original mission purpose was to let everyone take and download pictures of the earth from the unique view of a satellite in orbit.

Daily download of satellite data is delegated to a team of licensed radio amateurs around the world, and is coordinated by Mike Rupprecht, DK3WN. Satellites systems information, like battery condition and temperatures, are monitored and provided to the University of Aachen. This includes downloading of pictures from the experimental camera system.

In this video it’s demonstrated how satellite data (telemetry) is downloaded using 1k2 AFSK modulation. Radio amateurs use computer controlled antenna systems to ‘follow’ the satellite while it travels through space. Computers compensate for ‘Doppler’ effect on the transmit (command) and receive (telemetry) frequencies. Data decoding and telemetry processing is also fully automated by software developed by radio amateurs.

 

 

University of Aachen, Germany, Compass-1 project:

http://www.raumfahrt.fh-aachen.de/information.htm

 

Sounds from Space: APRS via the ISS

by Henk Hamoen, PA3GUO, The Netherlands

 

Did you know you can actually see with your naked eye the International Space Station (ISS) when it passes over your home? During passes when it is dark outside, early morning or late in the evening, the ISS itself is still in sunlight, and you can see it in the sky as a moving star.

 

It’s really fascinating to watch the ISS. But there’s even more. You can listen to the ISS as well. At a frequency of 145.825 MHz FM, licensed radio amateurs use dedicated equipment onboard the ISS for short message services, also called APRS. In very short packets of around 2 seconds (it’s digital communication), they can broadcast a message via the ISS to everyone in the ‘footprint’ (that is everyone that could ‘see’ the ISS at that very moment).

 

This same radio equipment is also used for voice contacts between astronauts and radio amateurs, as well as for daily for school contacts, when students ask astronauts onboard the ISS questions about their stay in space.

 

This video shows the ISS passing over the Netherlands (Europe) as a bright, moving star. You hear the bursts of digital communication and see them decoded on screen. LA4FPA (Norway), G6HMS (United Kingdom), IW9FRA (Italy), ON7DS (Belgium), YO8RBY (Romania), PA3GUO (Netherlands), OE1CWJ (Austria), UA1CAS (Russia) and SP9TTX (Poland) were active during this pass with their stations.

 

 

For NASA information on the amateur radio equipment, go to:

http://spaceflight.nasa.gov/station/reference/radio/

 

 

Henk Hamoen, PA3GUO, The Netherlands

http://www.pa3guo.com

 

Want to bone up on wireless tech? Try ham radio

http://www.computerworld.com/s/article/9139771

 

For 40 years, Computerworld has been the leading source of technology news and information for IT influencers worldwide. Computerworld’s award-winning Web site (Computerworld.com), weekly publication, focused conference series and custom research form the hub of the world’s largest global IT media network.  So it is quite a commendation when they published the October 2009 article

Want to bone up on wireless tech?

Try ham radio

Abundant spectrum resources and an engaged research community are drawing wireless experimenters back into a hobby that many had forgotten.

 

By John Edwards

October 29, 2009

 

See the article at http://www.computerworld.com/s/article/9139771

Amateur Radio and Computers – a natural match.

HP website story at:  www.hp.com/go/hamradiostory.

 

HP's website

“VE2DXY” is an Amateur Radio contesting team.   2009 “core team” members are Bill Ballantine K3FMQ, Andy Vavra KD3RF/VE2DXY, Irwin Darack KD3TB, Sebastien Jean VE2GTZ and Ken Nicely N3PSJ.  Information about them and past DXpeditions (taking Amateur Radio into unusual and often wilderness areas) is available at  http://www.wix.com/andyvavra/VE2DXY

They have done mini-DXpeditions into Canada for 6 years as a “Field Day” type exercise and go beyond the 50 degrees north parallel.  They carry all of their equipment 1,000 miles to set-up and operate radio stations for the duration of the contest, then dismantle and return home. 

In 2009, their ham radio efforts were selected by HP for a feature on the “HP in Real Life” website highlighting the real-life integration of Amateur Radio technology and HP computers. The VE2DXY team’s use of HP products in Amateur Radio applications was a key factor to the story at www.hp.com/go/hamradiostory.

Radio amateurs have been mixing the capabilities of computers and radios into new applications and technologies for decades.  In the rapid fire exchanges of radio contesting, computers are used to record contacts made, information about radio propagation and find frequencies which will give the best chances of contacting other rare stations.  Blending GPS systems, computers and Amateur Radio allows remote tracking and position reporting.  (See section on APRS at http://wedothatradio.wordpress.com/2008/04/14/aprs/  ) 

Video from a past DXpedition is at http://www.youtube.com/watch?v=rg_AKj_UMnY

Rock & Roll meets Ham and Radio

Bob Heil is a ham, K9EID.  He’s also the premier person in sounding good for many musicians.   His Amateur Radio experience has taken him into the Rock & Roll Hall of Fame. 

How?

Well….watch this!

About this website

The Amateur Radio Service frequency bands are the place on the usable radio spectrum where you as an individual can develop and experiment with wireless communications. Hams not only can make and modify their own equipment, but can create whole new ways to do things.

Discrete-Method Signal Analysis

 

 An Introduction to the The Fifth Pillar for Amateur Radio

 

William E. Sabin, WØIYH

 

 At the Dayton Hamvention in May 2008, ARRL President Joel Harrison, W5ZN, announced the formation of a Fifth Pillar for amateur radio, combined with the in-existence Four Pillars (Public Service, Advocacy, Education and Membership). The purpose of the new Pillar is to encourage and enhance math, science and engineering appreciation and skills. Individuals who are interested in and involved with, at various levels, the rapidly expanding modern-age technology developments in electronic hardware and software are the intended audience. This applies in particular for us as it pertains to the art and science of Amateur radio communications, not only at the “black box” and “operating” levels, all of which are very important, but equally important at the math, science, analysis and design levels.

 

This concept was encouraged by Dave Sumner, K1ZZ, in the August 2008 QST Editorial. QEX and other ARRL Technical staff members are very active in advancing the Fifth Pillar ideas. The new ARRL website wedothat-radio.org is dedicated to this effort. Traditional (“legacy”) methods are also respected, as they should be.

 

Many national governments, including the USA, are deeply concerned with inadequate awareness and education by the general public in the fields of math and science. Many nations are ahead in this respect. The Fifth Pillar effort is dedicated to adding to the improvements in deficiencies of this kind. This brief and simple example article is also dedicated to this effort.

A Modern Discrete-Method for Signal Analysis and Design

 

The modern personal home computer, in conjunction with an elegant and sophisticated mathematics calculation program, Mathcad Version 14.0 [Ref. 1], is employed in this brief article at an introductory level that is very user-friendly. This program is used to calculate, process and graph-plot a variety of signal-processing and very many other kinds of math problems. The so-called symbolic math methods {see the Mathcad User Guide, Chapter 13} are also used in modern math computing. This software is an outstanding tutorial tool for the advancement of the engineer’s and student’s math skills, which is considered to be an important goal in today’s advanced technology environment.

 

The signals and their analyses can be in the time domain or the frequency domain, and they can be linear in nature or non-linear. Signals, before and after processing, can be switched back and forth easily between time domain and frequency domain. A complete Mathcad 14.0 program, with perpetual usage, is attached to the new book Discrete-Signal Analysis and Design [Ref. 2].  This is a special and very generous Mathcad promotional offer by the PTC company.  The User Guide that is on the compact disk can be placed on the Desktop as an icon.

 

Example: A three-tone distortion simulation. [Ref 3.]

  A typical discrete-signal processing example will help to illustrate just a few of the basic ideas of Mathcad usage in the practical world of electronic design. This and similar examples can also be further explored with circuit simulation programs such as Multisim (student edition) by National Instruments (http://www.ni.com/academic/multisimse.htm) using accurate models of I.C.’s, transistors, diodes, tubes and many kinds of passive components. In addition to the three desired tones, a large undesired “out-of-band” signal that contributes to distortion products will be examined.

 

Time domain information can be converted to spectrum results. After modifying the frequency spectrum, for example by introducing a filter or a signal interference or random noise (additive or multiplicative), the modified time domain results can then be obtained. We can also begin with various spectrum shapes that achieve certain desired time-domain results.

  Certain communications waveforms use methods similar to this example, and laboratory test equipment (http://www.ni.com/analysis/) is used to perform discrete-time and discrete-frequency tests automatically. Pseudorandom data error rates can be evaluated.

Analysis of the Example.

 

 

Illustration A & B

Part (A) shows the time-domain input Vsig(n) and part (B) the time-domain output Vout(n) of an amplifying device that is perfectly linear. The device delivers only output signals that are proportional to those at the input, i.e.,Vout(n) = Vsig(n)^1.0 times a voltage gain constant Gv. The signals in Part (A) are at frequencies 4, 7 and 9. Another much smaller input at frequency 29 will be considered a little later. Observe also the DC bias Vdc on the device. This is called the “operating point.”

 

 

 

  Part (C) is the two-sided (positive-frequency and negative frequency) phasor spectrum of the output as calculated by the Discrete Fourier Transform (DFT) of the time-domain output (part B) of the device. Part (D) shows the same actual positive-frequency signals as the input. We get these positive-frequency signals by combining the positive-frequency phasors and the negative-frequency phasors. Chapter 2 of the Sabin book explains how this is done. Also, Chapter 1 discusses phasors vs signals.

  

 Part (E) introduces a nonlinearity, the exponent 1.5, which is often used in text books [see Sabin ch. 2], in the transfer function of the device. This creates distortion products in the form of new frequencies at the output Vout(n) that are not present in the input Vsig(n). In the signal spectrum Vout(k) of part (F) many, but not all, of the nonlinear output products are identified. For example, the term at (k) = 3 is due to the term at (k) = 4 interacting with the term at (k) = 7. The 1.5 exponent also increases the voltage gain, in this particular example, to Gv^1.5. Gv can also be a more complicated time-varying function of (n) such as [Gv(n)]^1.5.

 Another consequence of the nonlinearity is that the spectrum phasors, therefore also the signals, are “complex” and may possibly display items that have a real (Re) part, an imaginary (± j Im) part, a magnitude ( |  | ) and phase angle (Θ) with respect to some “reference” phase such as zero. The graphs of parts (F) and (G) would identify these. Mathcad can be instructed to calculate and plot all of these results.

 In part (G) the interfering “out-of-band” signal at (k) = 29 is greatly increased in amplitude so that distortion terms are emphasized. The ability of a strong out-of-band interferer to corrupt a desired signal spectrum is illustrated. In particular, the spurious product at (k) = 6 stands out. In addition to this large distortion term, there are many smaller distortion products that can degrade the desired weaker signals. Also 4, 7 and 9 are degraded slightly. This is very serious interference that can be difficult and expensive to repair, especially in wideband high-level systems where filtering of strong interfering signals is expensive. A tunable notch filter is sometimes possible for constant interferers, but costly high dynamic range equipment is often indicated. We see this effect in practical environments, for example in HF/VHF/UHF radio. We now see it also mathematically.

Beyond this simplified introduction, a much more complete study would be well-justified. For a closer look at the various related technologies for this and many other topics, visit the new ARRL website www.wedothat-radio.org.

 

Ref 1.

 Mathcad, version 14.0, PTC company, Needham, MA.(http://ptc.com/products/mathcad/)  The Mathcad program is very mature and has a history of fourteen versions in more than 25 years.

 Ref 2.

 Discrete-Signal Analysis and Design, by William E. Sabin, published in January 2008 by www.wiley.com Interscience Division, available from the ARRL Bookstore, item #0140 at http://www.arrl.org/catalog/, search: Sabin.

 Ref 3.

 Sabin, W0IYH. QEX, Nov/Dec 2008 “A Modern Discrete-Method for Signal Analysis and Design” pp 36-38.

 
 

Bill Sabin, W0IYH

About the author:

 

Bill Sabin received the call Sign W9YFA in 1941 in Covington, KY at age 15. This changed to W4YFA in 1946, and to W0IYH in Iowa (Collins Radio Company) in 1964. He holds BSEE and MSEE degrees from the U of Iowa. He retired from the Rockwell Collins Company in Cedar Rapids IA in 1990. He is co-editor of and contributor to, with E.O. Schoenike, three books on Single-Sideband and HF Radio. He is the author of more than 40 technical articles and portions of the ARRL Handbook (1995 to 2009 editions). In 1983 he received the annual ARRL Technical Excellence Award. He is a member of ARRL, Life Senior Member of IEEE, and member of the ARRL DXCC Honor Roll.

 

 

 

Bill Sabin W0IYH,  w.sabin@mchsi.com