No Mass?By Jack L. Stone. Publisher
No Mass?
By Jack L. Stone. Publisher
HAPPY HOLIDAYS!
ere at antenneX,
we are pleased to celebrate our 7th Holiday Season together online with our readers. We
look forward to many more with you, as it is truly a joy to bring this magazine to you,
this one now our 80th monthly issue online.
We are thankful to so many fine writers that have made contributions over the years, and many appear in every issue. They are important, as without them, we could not issue the magazine. Then, to you our loyal readers, without you the magazine would not be possible at all. Some of you date back to our first subscribers in 1988—others have been with us since early 1977 when we first launched this version on the Internet. It is heartwarming to see such a high percentage of subscription renewals each and every year, an indication that we have an interesting and successful journal —Happy Holidays to you all….!
THINGS CHANGE
Every year at antenneX brings some sort of change as we search for new ways to
improve and better communicate with readers and provide ways for our 60,000+ global
readers from 186 countries to conveniently communicate with each other. Sometimes an
overhaul is called for and old customs are replaced with new ones. Such was the case with
our 25 discussion forums that accumulated over the years.
During mid-year 2003, we decided the discussion forums had served their purpose well, but it was time for a change to something better. That replacement was the launch of the antenna-discussion mail list where our readers (subscribers or not) could join and exchange ideas via this classic Majordomo mail management system. Initially, this was a regular posting list for individual threads along with a digest list of the daily messages.
Then, we were urged to also provide a web-based archive
of the messages by date and by thread. This too was done and now the combined memberships
of all three resources are fast approaching 1000. And, in the short period of just a few
months, some 1500 messages have accumulated covering a wide variety of antenna subjects
from theory to how to make them and make them work better.
A LIKEABLE THREAD
As one example of the “fun” and the learning experience enjoyed on the list, I
picked a single thread about “radiation” I especially would like to share. In
fact, it is too interesting and important not to share. It is a question that surely
enters the mind of those dealing with antennas at one time or another, but I wonder if we
really know the answer yet? If not, there remains much that can be done about the design
of antennas.
Although the thread is from an open forum, I only use Initials or abbreviations of the persons in the exchange, except for myself). Only very minor edits made. Those who have a subscription to the discussion lists or the archives will recognize these, but there are many thousands more who have not joined up yet and have missed a valuable resource. I hope you enjoy it as much as I did:
| From: Jack L. Stone Most who deal with EM+antennas are probably familiar with the following definition of a photon: "....The quantum of electromagnetic energy, generally regarded as a discrete particle having zero mass, no electric charge, and an indefinitely long lifetime...." So, I ask an age-old question: "How does the photon without mass or electric charge, leap from the antenna...??? What makes it want to? " I seem to recall this has yet to be explained.... Jack L. Stone |
| From: Michael EV Jack, Here are a couple of ideas without a huge amount of technical jargon that might be considered for the question you presented? Not one to quibble with words, it is my understanding that electromagnetic energy has a strange dual nature to it. Visible electromagnetic energy, light, for instance, exhibits itself both as a wave and as photons. There are plenty of places to read about this so I won't say much more about that. This might answer the first puzzle by considering that when we speak of antennas we are considering the "wave" properties of electromagnetic energy not its "photonic" properties although if one studies optics there are many parallels to transmission lines and antennas that we have in the "wave domain". I spend a lot of time analyzing problems involving electromagnetic compatibility and sometimes one in that discipline has to make "anti-antennas" out of "antennas", i.e. you do not want something to radiate! One of the primary ways to do that other than reduce power input is to mismatch the impedance between the circuit and its antenna from free space. This inhibits energy transfer between the source and the free space. In making good antennas, we would want to improve that power transfer by constructing a "transformer" (if you will allow me that analogy) to couple the energy from the source to free space. So as you might guess, I really view antennas as a very special transformer that couples energy from a circuit in such a way that it allows it to more effectively couple to free space. So why would the energy want to leave in the first place? Anywhere we see concentrations of energy, we see energy dispersal. It would seem that this is an action of something called "entropy" (a result of the second law of Thermodynamics) that merely says that eventually all energy will be evenly distributed through the universe. Concentrations of energy therefore will search for ways to disperse... one way or another. This is a pretty simplistic explanation and not meant
to be exhaustive but perhaps it covers the question well enough for one to dig in and more
precisely define it. |
| From: JRJ Hi Michael and Jack, May I
just add a word (or two)? |
| JRJ: You took the words right out
of my mouth. I was just about to ask about how this all fits into the near/far field,
i.e., how does it know how far to "leap?" Here is an offlist discussion DJJ and I were having on this issue and his reply to me: Jack L. Stone wrote: Well, in the near field, the Physicists tell me words like "virtual photons". The idea is that, because photons are quanta, they obey the Heisenberg uncertainty principle that says the uncertainty in energy times the uncertainty in time = 6.63E-34 Joules/Hz. So, a photon can "leap out" from the
antenna structure for a little while, by "borrowing energy", provided it
"leaps back" before the accountants do the books. Thus, in the region near the
antenna, there can be a great many "virtual photons" making up the near field. |
| From: RW Jack, It is interesting to note that as frequency increases it becomes increasingly possible to identify the signature of individual photons. At light, X-ray, and gamma ray frequencies individual photons are often measured. At radio frequencies energies of individual photons are so small that measurement of individual "quanta" are seemingly impossible and thus it is necessary to measure masses of photons ejected from antennas. These masses of photons appear to have combined wave characteristics but they are still the same h*nu photons just doing their "thing" together. I will be very interested to see what some of the very interesting people on
the discussion net will have to say. I am
sure that someone will be able to make it all outstandingly crystal clear! |
| From: LJP According to the dictionary: "the quantum of the electromagnetic field that manifests itself by absorption or emission only in multiple quantum units of energy E = hn, where h is Planck's constant and n is the frequency of the electromagnetic wave; a unique massless particle that carries the electromagnetic force." But
this is at rest. The photon does have mass at
the speed of light and it can be measured using the laws concerning momentum. An example is the ability to move vanes placed in
a vacuum, also, the capabilities of the laser to punch holes, etc. |
| From: KM Jack, > "How does the photon without mass or electric charge, leap from the antenna...??? > What makes it want to? " There is a somewhat nonscientific question that must first be answered. Namely, what constitutes an explanation? 1. A possible classical explanation: Antennas contain time-dependent currents, which imply that it contains accelerating electric charges. The electromagnetic fields of accelerating charges include "pieces" that we call radiation = field waves that propagate away from the radiating charges. If we add just a bit of quantum mechanics to the above description, we would say that the radiated waves consist of photons. Bottom line: photons leap from the antenna because the antenna radiates. [Recall that a wonderful interactive computer simulation of the fields of accelerating charges can be found at http://c-band.kek.jp/ This gives, for me, an excellent geometrical demonstration of "why" accelerated charges radiate.] Maybe you will think that explanation 1 is not really an explanation... 2. One might seek a full-blown quantum explanation. This will be rather abstract. In brief, electric charges couple to photons whenever the charges make a transition from one velocity state to another. The laws of quantum electrodynamics specify the details. Bottom line: charges radiate photons because that's the way the universe works. No matter how many details are filled in, this may not be the kind of explanation you are looking for. 3. Therefore, I have previously advocated to readers of the List that they might wish to learn a bit about a "semiclassical" description of radiation. I submitted a long email to the List about this on 7/2/2003. Bottom line: a moving charge drags along with it a cloud of "virtual" photons. If the charge is shaken (accelerated), some/all of the virtual photons break free of the charge and become "real" photons = the quanta of the radiated fields. It's probably clear that I find this to be the best
explanation -- but your email may be evidence that it doesn't provide the kind of answer
that you are looking for. |
| From: DJJ Jack, My feeling is that photons can't go far in the amount of time set by the uncertainty principle. What we have in an antenna excited by a single carrier frequency... monochromatic radiation...is a continuous stream of photons, and so the flow of energy is granular and is not a constant number of Joules per second. Statistically, if there are N photons per second going to make up the radiated power flow, then the fluctuations will be about sqrt(N) per second. If you try to localize a photon to some particular point in space, you will have an uncertainty in wavelength and therefore frequency and energy. So we have to ask, for this uncertainty in energy, what is the Heisenberg uncertainty in time, and how far can the virtual photon afford to stray from home base in that time at the velocity of light..... DJJ |
| From: EM Hello all, I seem to have missed some recent discussion concerning radiation about which there seems to be an ongoing discussion (I've not included here any of the message that came in just today that brought this to my attention to save space). In any case, I checked my e-mails and find that apparently the last time I submitted anything about this topic was more than three years ago (sic: on another list). At that time a number of us had a fairly lively discussion going on about radiation physics. The purpose of this short note is to mention an article that Jerry Burke and I published a little while ago in the ACES Journal on this topic. It is "E. K. Miller and G. J. Burke (2001), 'A Multi-Perspective Examination of the Physics of Electromagnetic Radiation,' Applied Computational Electromagnetics Society Journal, Vol. 16, No. 3, pp. 190-201." Among the items discussed there is the E-field "kink" model, and both a frequency- and a time-domain version of something that I developed in late 1999 which I call FARS (Farfield Analysis of Radiation Sources). More recently I presented some results based on the time-average Poynting vector along wire objects that seems to offer some promise concerning radiation [E. K. Miller (2002), 3A Poynting-Vector Approach to Determine Where Radiation Originates from the Surface of a Perfect Conductor,2 National Radio Science Meeting, Boulder, CO, January 9-12, p. 74.]. I should mention also that Joe Jahoda had put me in touch with the 1942 article by Schelkunoff and Feldman, and the results they derive there agree essentially with FARS for a sinusoidal current filament. But FARS is based entirely on the far field while their work uses the near field. I could provide .pdf files of some of this work to
anyone who might be interested. Maybe I'm
fooling myself but I think I'm getting a bit of a handle on some of the issues involved,
which are currently being written in a draft article.
Perhaps I should add that charge acceleration does play a central role in my
thinking about this. |
| Dear EM Also, some Poynting vector distributions round several different antennas were published in the 1970s by Meinke and/or Landstorfer in NTG Fachberichte, which looked interesting and convincing. We have also produced streamline diagrams of the time-averaged PV in a microwave reflector antenna, which shows streamlines emerging from the feedhorn, then bending round and outwards without touching the reflector. The time-averaged PV can be shown to be solenoidal everywhere on and around
an antenna, except in the power source or load, and the proof is based on E.J* being zero
in free space and also on a source/sink-free conducting surface. |
| Dear List, A clarification. In free space, a perfect vacuum, where there are no electrons or charged particles, the current density J is necessarily zero everywhere. On a perfect conductor surface, E is at right angles to the surface but any currents flowing have to be parallel to the surface. In the first case J=0 so E.J* is trivially 0. Therefore the divergence of the Poynting Vector S is zero except at sources and loads. That is what AB means by the term "solenoidal". What that also means is that only the source (in the
throat of the horn) can throw out energy. It completely demolishes the PVS arguments. |
If there are more diversified thoughts about the above subject of radiation and what causes the photon to launch itself from the antenna, please don't hesitate to let me know jack@antennex.com . More submissions in the form of articles would be welcomed.
Indeed the above discussion is not the first time that subject has been debated, nor will it be the last time. There have been many other subjects equally as interesting about other theories, building antennas, especially loops of all kinds which ties right back to some degree to the above discussion when one tries to pin down the properties of a magnetic loop and how those "loop" photons *may* dance to a different tune.
Then, there are those requests for help which are usually answered within minutes from some part of the globe. I am unaware of any question that has remained unanswered for long among this polite and friendly group. As an example, as I write this article, a question came in about the effect of a nearby AM on an MFJ-259B Analyzer while trying to measure a 160 sloper. Literally, within 5 minutes from an opposite side of the country, an answer was posted stating first-hand experience with that issue. Now, that's antenna discussion in the best form—sharing information in real-time!
EMAIL or AMESS?
While on the subject of emails, during previous columns, I have touched lightly
on how I make use of the built-in handy features of my email program to help organize my
emails. I'm primarily referring to "filters" which are in most if not all email
programs. Email filters are indispensable in organizing and wading through incoming
emails. Anyone not using email filters or haven't discovered their use are not realizing
the benefits of a mighty powerful tool on their computer. For example, are you downloading
all of your emails into a single "InBox" within your email program? If you only
receive a few emails, perhaps that is fine, but if you feel swamped with emails, then
filters are your answer for making life easier.
First, your Inbox should be divided into several logical separate Inboxes based on repetitive types or categories of emails received. In my own case, my main workstation uses four Eudora-3.0+ programs, a Eudora-5.2 program, MS Outlook Express and MS Outlook2000, or seven email programs running for different purposes to receive messages of different types. Within each, the Inbox is divided into several Inboxes to receive and organize my emails during the download process. This allows me to perform a "triage" on my emails to attend to the most urgent ones down to the less important.
Next, all of the programs allow for the creation of Inboxes and then provide methods of setting up filters to direct the emails into those separate boxes. The methods for Eudora differ from Outlook but give the same result. Outlook even provides a "wizard" that uses an example message to set up the filter. Eudora is a little more manual, but not difficult.
The really nifty thing about the filters is that they allow you to choose how to identify those repetitive messages so they may be directed into the proper box. You may use the "From", the "To", the "Subject" or almost any other constant string in the header as a basis of identity. Below is a screenshot of one of my Eudora-3.0+ program setups with the various "Inboxes" shown on the left side. The filter setup is found in the "Tools" menus at the top:
As can be seen from the above example, there are 20 Inboxes, plus a regular "In" box and a "Trash" box, essentially making for 22 "Inboxes" because I can and do set up filters that send any SPAM or other emails I don't want directly to the Trash box so I don't have to bother with them at all. As shown, I still have a "Spam" Inbox, but that is for questionable ones that I look at Sender/Subject before deletion. Thus, one can imagine the mess I would have if all of the 21 categories were only downloaded into a single InBox. In my case, perhaps only 3 or 4 messages actually wind up in the default "In" box that came with the program.
Next, I pick the most urgent Inbox by clicking on the box in the left frame which reveals the messages contained in the right frame. Then, I merely scan the subjects and sender to see which of those I want to actually spend time to open, read and perhaps respond if one is required. Any others are deleted. BTW, none of the reader emails are deleted as they are counted among the most important. They arrive in a different email program dedicated to readers and reader business.
GREAT FOR MAIL LISTS
Note that some of the boxes are for some of the various mail lists to which I belong. As
some may know a mail list, especially a large one, can generate several dozen or even
hundreds of emails daily. This is where the filters really come in handy. Again, this
allows me to scan the messages mainly by subject and pick only the ones of interest to
read and perhaps join in on the thread. The rest can be selected and deleted with little
effort. No doubt if all of those were delivered and mixed in with all my other emails in a
single Inbox, it would be an overwhelming task to isolate and read the mixture of emails.
But, applying the use of filters can make separating and reading your emails a breeze!
Hope this has been helpful!
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IN THIS ISSUE
This month is our 80th online issue! We again include many fine articles by our great writing team. Now, allow me now to introduce this month's line-up of content:
THE DECEMBER 2003 ONLINE ISSUE NO. 80 CONTENTS:
OUR MONTHLY COLUMNS (plus this one by yours truly):
FEATURE ARTICLES IN THE LIBRARY:
The
64-(Euro-)Dollar Question |
| U.S. amateur operators have access to the 6-meter (50-54-MHz) band. However, they do not have access to a small band open to UK hams: the 4-meter (70-70.5-MHz) band. Only some Region 1 countries share that middle ground between 6 and 2 meters. UK amateur also generally have smaller plots on which to erect antenna farms. Very often, a chimney-supported mast is the only available antenna support. Hence, multi-band antennas for small spaces are always popular reading (and building) projects. |
Lab Notes: Loop Surface Area Revisited |
| Last month I investigated the effect of changing the surface area of the wires in a loop antenna by adding more and more wires, all the same length. This month I looked at the effect of changing the surface area, but doing it with wires of different lengths. |
Modeling
of the Pfeiffer 2-Element |
| This article first illustrates the polygon antenna configuration and then relates to the usual family of triangles associated with polygon configurations. But the Pfeiffer Quad antenna configuration includes linear loading in the form of stub inserts and therefore has to use a defined and related polygon family of triangles to derive the various x, y, and z model coordinate positions -- at least for a refined approach without too many approximations. |
THE
"ANTAP" APARTMENT ANTENNA |
| There is a big demand in the USA for an HF Apartment-sized Antenna that could continuously tune in the range of frequencies from 3-30 MHz. Local and regional regulations often prohibit the use of exterior antennas. Many of the dwellings are built with wood, which is a not a bad insulating material when dry. Many homes have in the highest part of the house as an apartment or an attic where Hams want to put their antennas. However attic apartment space is often limited. This article describes the development of an antenna suitable for this purposes called ANTAP (ANTenna for APartments). |
A
NEW DIGITAL WORLD: THE "CIAO RADIO" PROJECT |
| The world of Ham Radio Hardware, mostly an analog environment, is progressively becoming digital. The one exception has always been antennas. However, even in antenna design, digital technology has emerged to provide a helping hand. Witness, for example, the use of computers to simulate and evaluate antenna designs. But how about a new digital software package that provides digital signal processing and provides an exciting new tool for evaluating antenna performance? This article will review some of the more interesting (to antenna experimenters) aspects of this software design. |
What
is a Loop Antenna? |
| There are Loops of all kinds and descriptions: Magnetic, non-magnetic, octagon, round, square, rectangle, quadrangle, folded, 3-Dimensional, etc., etc. And they are made from all types of materials, aluminum, copper, jointed, non-jointed, hollow tube, solids, hard-line, cable, speaker wire, etc., etc. Indeed a great deal of designing and experimenting has occurred and David attempts to sort through all of this and define a true loop. as he sees it. |
Well, there you have it, folks—thanks for listening and
remember, the reading lamp is always on for you in the reading rooms. If I can be of
further help, I'm just a Stone's Throw! away. December
2003 antenneX Online Issue #80
reGARDS, Jack L. Stone, Publisher jack@antennex.com
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December 31, 2010