The hours of folly are measur'd
by the clock; but of wisdom, no clock can measure.
William Blake (1757-1827)
Otherwise known as "The Test of Time"
Antennas and Propagation
By Jack L. Stone, Publisher
Marcel De Cancks long-running series on propagation and propagation software is now available in 3 volumes (with a fourth to appear in the future) on CD-ROM for those who wish to study in detail both the phenomena and their prediction. That is a milestone for antenneX. Now lets add to this note L. B. Cebiks equally long-running series on antenna modeling, the first 4 volumes of which are also available on CD-ROM. NEC and MININEC software are capable of predicting antenna performance for a wide range of designs.
So far, these remarks look like an advertisement. However, lets turn a little corner by noting that both authors are very careful to note along the way just where the computer predictions hit their limits. Recent discussions of reciprocity within the discussion group are a reminder of two facts. First, antenna modeling presumes transmit-receive reciprocity of antenna radiation and receiving patterns. Second, propagation software can show us vividly that the HF paths between antennas are anything but reciprocal. Indeed, it is a marvel that the paths are sufficiently coincident to yield 2-way communications. (Short-wave broadcasters have an easier time with predictions, since they only need to worry about the path in one direction.)
The interface between the two types of software is somewhat tenuous. Propagation software most often makes use of type-13 VOACAP files that we may derive from antenna models. We may even point a directional antennas pattern on the heading of a specified target that we may be analyzing. Thus, it appears that for best accuracy, the propagation software user only needs an adequate model of his antenna. But two problems show up at this point. First, few amateurs have accurate models of the antennas they actually use. Instead, they tend to use stock models, and most of these are far from precise representations of the antenna in use. As well, stock models rarely use the actual height above ground or the ground quality experienced by the person seeking propagation predictions.
The second problem is that models presume a homogenous flat terrain in all directions. I recently heard of an amateur station located within a few hundred feet of a coastline and over 100 above the water line. He showed an interest in obtaining from his propagation software the most precise predictions possible for his unique location. Lets assume that he has already made a list of the great circle paths in which he is interested. On the seaward side of his antenna position, each path shows a different distance to salt water, which has different consequences for his radiation pattern before it seriously interacts with propagation phenomena. For each seaward path on his list, he may need a new model or type-13 file, and this requirement applies to each frequency band in which he has an interest. All of this, of course, assumes that he has overcome the first problem of being able to model accurately the antennas that he is actually using.
The last month or two has seen some interesting propagation. Despite the generally low sun spot count, the 6-meter amateur band has shown some remarkable openings this year. The openings have revealed another facet of the interface between antenna performance and propagation. One very active west-coast station recently finished construction of a 6-element Yagi. He lives near enough to equally active operators who have reported that they cannot hear many of the stations the first station is hearingand workingeven though they are using longer Yagis with more elements. For the sake of these notes, lets assume that terrain is not the source of difference. If propagation is the same for the stations involved, what could be at the heart of the difference? Lets consider the age of the antennas.
ANTENNAS DON'T DIE, THEY JUST FADE
The new antenna has the freshest set of connections among elements and other antenna parts. As well, all of the insulating materials are as clean as they will ever be. In contrast, most of the other antennas have lived in our grungy atmosphere for a considerable period. Grunge accumulates slowly, working its way between metal-to-metal contacts and coating insulating materials. Coaxial cables gradually change characteristics as they undergo seasonal variations. These factors work their evil slowly so that an operator does not notice changes in performance over time. It is likely that few of the other operators have given their antennas the required semi-annual (or at least annual) maintenance checks and cleaning that they deserve to perform to specification. The most accurate type-13 files become inaccurate if we do not preserve the performance of the antennas that they represent.
Another aspect of antenna aging is less evident but equally influential. Only within the last decade or so have antenna manufacturers begun to use more standardized methods of presenting performance data. In the same period, a number of makers have updated their designs. The latest designs tend to have cleaner patterns than in past decades as we gradually learned that squeezing the most gain out of the least aluminum may not yield the best overall performance. If a pattern is filled with side lobes, a common characteristic of Yagis with too few elements, then a simple propagation analysis in the forward direction may not be sufficient to show receiving conditions that may result from incoming noise along the side-lobe directions.
The interface between an antenna model and propagation calculations thus depends on the user (whether a group or an individual) achieving a high level of input precision. The actual antenna must be up to the standards of the model, if a VOACAP type-13 file is to be accurate. To the degree possible, the model should reflect the antenna location as it relates to each path of interest, and the antenna itself should be in like-new condition, with no false hopes bred by now-ancient ways of presenting gain or developing patterns.
Even UHF (GHz) antennas are subject to intervening objects, and too often antenna installers neglect an important fact of life: antennas have beamwidth in both horizontal and vertical planes. Often we hear of difficult installations between urban locations for point-to-point data transfers. The antennas have plenty of gain for the direct path. Unfortunately, that path is not a simple straight line. Hence, side and lower buildings can introduce reflections that complicate positioning. There is an old rule of thumb that the wider the beamwidth, the easier it is to aim an antenna. However, the rule has a corollary: the wider the beamwidth, the more likely are unwanted reflective and refractive paths to interfere with performance.
BE MASTER OF YOUR DOMAIN
These notes are reminders that even when you have mastered both modeling and propagation software, you work is not done. You must also master to the degree possible the physical factors that make up the communications situation. Some of these factors are readily (if inconveniently) handled, such as regular antenna maintenance. Others lie outside our control, and for them we must compensate. Still others belong to Mother Nature herself, and with these we must live. Although we have seen much in recent times on what global warming is doing to the troposphere, it remains unclear how much these changes may affect ionospheric propagation.
Whatever Happened to the commercial CFA?
It has been years since I did any update on the long saga of the commercial broadcast CFA's ups and downs. Still, I get inquiries wondering whatever happened to the CFA, or at least the commercial version. At one time, they were springing up like weeds on several sides of the globe. Then one by one, each of those broadcast CFAs outside of Egypt were reported as dismal failures, falling far short of the operating claims by the promoters. This includes Germany, Australia, Italy, Brazil, Isle of Man, UK and China.
As everyone may remember, we left off waiting for overdue results from the test CFA in the UK. It was far behind the original schedule, plagued with delays and then a squabble over the rights to the CFA erupted between the UK test group and at least one of the co-inventors. The CFA "story" itself was interesting to follow up to the point when the word "attorneys" popped up which meant a rapid departure from a discussion purely about antenna technology itself. Of course the extended hostilities in the middle east has only served to add to the woes for the CFA.
The last sale we know about was the one to China and no further sales have been reported to us of late. In various previous monthly columns of mine, any newsworthy news was reported as CFA updates, but those ceased with the negative outcome of the test CFA in IoM. The only remaining bit of news is about the installation in China.
Perhaps, though, the following will bring us more up to date and fill in some of the gaps missed earlier about the "story" of the CFA, its inception, its spread about the globe and its plight. Moreover, it's the year of the 20th anniversary since the CFA was patented.
CFAs were invented at the Robert Gordon Institute (now University)
in the Scottish city of Aberdeen, by staff member Maurice Hately GM3HAT
(Hately) and his PhD student Fathi Kabbary (Kabbary). The
invention was patented in 1986. From the start, CFAs were on sale to the ham fraternity
from a business run by Maurice and advertised in Radcom, the Radio Society of
Great Britains monthly magazine. It is not known how many were sold in this manner,
but there were several letters to the magazine from hams who thought their CFAs were a
good answer to the problem of radiating in limited space, and also from others who
questioned the theory and construction of the antenna. A lively debate took place in the
"letters" pages of Wireless World, a longstanding UK magazine that addressed
theoretical topics in a way that most popular magazines did not. The number of
amateur-radio CFA owners who expressed dissatisfaction with their CFAs was understood to
The debates continued briskly during the 1990s when CFA production shifted to Cairo, Egypt, with the appearance of Kabbary Antenna Technology (KAT). At the same time, the product was repositioned to appeal to commercial radio stations in the broadcasting and communications sectors. This decision seems to result from the greatly increased unit price that such products can attract but the decision also attracted criticism and evaluation from a wider range of professional engineers, who almost unanimously reached the conclusion that the published theory did not stand up to any detailed examination and that perhaps these antennas might not perform as well as claimed. One reader has described the difference between ham and commercial use depends on the very different amounts of energy used. For broadcasting, high radiation-efficiency is needed, while for ham use such might not be the top requirement.
Sales of the CFA to broadcasting companies took off in the late 1990s with a few orders, but for some reason no practical results were ever published by anyone who could be described as an independent source. Finally, in 2000, a CFA was commissioned by CFA Inc. to be installed near the English town of Shifnal, about 20 miles north-west of Birmingham. The results were to be produced at the American NAB Conference in the summer of 2001, but, when the conference came along, no results were produced, and despite a promise of results at the same conference a year later, no results were produced yet again. Meanwhile reports surfaced of a dispute between CFA Inc. and the other parties to the Shifnal CFA, with a report that a progress payment of $40,000 had not been made at the time agreed. No reason was ever discovered, but non-performance remains a strong supposition.
A British antenna engineer, called to Shifnal to assist with the installation, reported that he took an impedance bridge and network analyzer to site to assist Kabbary and son. He had just 3 inductors and 4 capacitors to quadrature feed and match his antenna. He had no test equipment, leads or connectors. He had no means of adjustment, i.e. no variable capacitors, or anything to tap on to the inductor turns. After 16 hours of work, the antenna was matched to 50+j0 ohms and Kabbary left the site.
The same UK engineer returned alone the following week and discovered a hidden thick wire inside one of the 4-foot tall standoff insulators, connecting the upper radiating cylinder to the elevated ground plane, and other strange things. It was never possible to power-up the 250 W transmitter provided at the site, which was intended to operate on 972 kHz.
We also know that two other UK engineers, Professor Underhill and Dr Jefferies, visited the site. They radiated power from the antenna, and measured a radiation efficiency of 17%. Nothing else has come into the public domain about the Shifnal antenna, and it remains something of a mystery. No results were ever presented at NAB conferences.
MEANWHILE IN EGYPT
Since CFAs were manufactured in Egypt, readers might expect that several would be installed there, and this is indeed true. antenneX readership have had first-hand experience told of CFAs at Tanta and Alexandria. The first of these provided good signal reports and must be acknowledged as the only successful CFA to date with a gain similar to a quarter-wave monopole. The fact that this antenna sits on the roof of the 2-story transmitter building, which is clad in metal strips in a square 8" grid, is thought to show that the building is radiating as much as the CFA because it doubles the height of the CFA. But, at Alexandria the CFA was found to be well below any reasonable radiation efficiency for broadcasting.
An antenneX expedition to Egypt was put together in 2001 involving specialists from several countries to join forces and equipment to thoroughly examine the CFA in Tanta. It never took place because it was found to be impossible to make practical arrangements with Kabbary. One portion of this multi-country team was a large broadcast management company from South Africa and potentially a very good customer for Kabbary.
CFAs were also sold in Australia, Brazil and Germany, all for the medium-wave broadcast market. The Australian one, at Sydney, and the ones in Brazil, were closely monitored by an antenneX reader, who says that Kabbary was in the habit of picking out one unusually high field-strength reading from a days results as proof the antenna was working: at crunch time, he would say that the CFA would need further expensive modification that the station would not possibly pay for. In Brazil, for instance, to make its CFA work it was recommended that the whole 225 sq. m. structure be raised another 4 meters. Our reader advised the Brazilians: he does not want you to raise the platform, he wants to tell the world that the CFA did not work because the customer would not raise it.
The Sydney CFA was eventually set to work with the D-plate taken away and thus, "D-CFA'd." Hence, as a short, fat monopole it radiated its signal for a while until removed and taken to the scrap yard when the tower block it was installed on was demolished.
The CFA in Germany was built at Kiel for a commercial station, Power-612. The engineer in charge was at first very upbeat about his new antenna, but later became uncommunicative and refused to answer questions. The station went off the air at about the same time and the CFA was laid to rest.
Another CFA was installed in San Remo, Italy and this one appears to have lasted some time. Field strength measurements were published showing that reasonable radiation efficiency was being achieved, and the antenna remained during a change of management at the station, but eventually the antenna was taken off the air in May 2004, according to local sources, for radiation efficiency 6 dB below the requirement. When asked, Kabbary reported to me that residential construction encroachments and a metal fence enclosure diminished the performance.
According to the KAT website, the latest CFA to be installed was in Nanjing, China, in 2002. We know more about this latest installment because an appeal was made to antenneX from China in June 2003 that said: I am in such a bad situation with CFA and I need your help in finding the truth. The company owner who bought the CFA said that we have paid more than 80% of the payment according to the agreement and after two times of complete failure of attempts to make it work, no promises in finding solutions has come true. We have spent more than 100,000 USD and basically have a pile of waste metal and no solution.
In an effort to help, I dispatched a copy of the Chinese plea for help to every CFA expert I could think of. In all fairness, I also sent copies to Kabbary and Hately.
In fairness, below is an unabridged copy I received of a reply from Kabbary to China:
Date: Tue 6.10.2003 4:03 AM
From: Dr. KABBARY
To: Yinong Zhao
Cc: Huang Xiao Ge; Jack L. Stone; John Belrose; Maurce Hatley
Dear Mr. Zhao
Because of SARS, I cannot go to China to complete the CFA of Nanjing. This message was sent weeks ago to Mr. Stone and others. When it become normal, sure the CFA of Nanjing will work. Flights from Egypt to Beijing assumed to start in July, if SARS was under control. Adding to the fact that we hope to receive from Nanjing radio a confirmation letter that they agree to stop their tower antennas during CFA impedance measurements, the close towers and other 100 kw antennas, province antenna.
I have received from your project manager the attached letter confirming to stop the transmitters to do CFA setting up the CFA, but this did not happen during my last visit to the site adding to your confirmation that you have not sent that letter to stop transmitters, while I have found and was sent from your partner Mr. Xiaoge to me with a copy for you, as attached on 24th Nov. 2002.
I would complete this project if you have stopped transmitters during my last visit, I was expecting you assistance to solve these important problem, but you were away in Finland while I was in China!
The delay of the project is now clear caused by Nanjing radio through you, because you could not stop transmitters as promised in their attached letter, so it is clear and fair and is very important to provide us by the needed confirmation letter from your Radio department of Nanjing to show they will stop the stations 15 hours, (day time is preferred than sky waves from other far stations on night time) divided into three days within a week time to do the needed antenna setting up and field measurement needed to control the radiation angle and gain on the ground, on these bases we can easily get the CFA working well, after SARS period which is almost under control.
Please, I hope to hear from you soon to avoid more delay of the project
Again from China in April 2004, he said: Kabbary has done nothing to improve the CFA in Nanjin beside telling how successful the project is. He required to stop all other transmission on the site before his CFA would work. This is not possible. We are doing nothing about the CFA. We are currently looking for anyone who wants to pay even 50% of the original cost and we will be very happy to ship the CFA to him or her.
antenneX has not been able to find any more CFAs actively
operating broadcasting, apart from a few in Egypt. It appears that the Nanjing CFA was the
last one to be ordered and installed and in the last three years no other ones have been
ordered to our knowledge.
One last CFA had remained planned to be built put on the air some time in the future. This is one intended for a new long-wave commercial music station operated from the Isle of Man between England and Ireland, claiming to cover the entire British Isles and some nearby coastal areas in a number of European countries. This stations web site provided news updates, but unfortunately these seem to have trickled to a halt in recent times and nothing appears to have happened for many months.
More definitely, the two IMIB web-sites www.longwaveradio.com and www.iomib.com are apparently closed and IMIB director and operating executive, Paul Rusling, has resigned stating, "I resigned from the project because (a) my board colleagues would not accept funding offers and I could see the project going nowhere without sufficient funding, and (b) I needed to pursue other business, including broadcasting, interests elsewhere." It looks as though the Isle of Man project has also fallen after many, many years of incredible effort and funding.
The experts say, all measurements made by Kabbary and others are doubtful for the following reasons: almost all CFAs are mounted on top of buildings where the building had at least a partial metal skin. Almost all CFA measurements were made at radio transmitting sites, where extensive ground wire systems existed. In at least one case, the measurement inspectors were denied access to the phasing and matching cabinet. In at least one case a hidden ground cable was discovered. In general, all performances have been narrow-band.
MORE FROM A NEW BOOK
R.C.Hansen (counted among our early readers) has authored a new book on Electrically Small Antennas published by John Wiley. Hansen has PhD and DEng degrees and is a member of the National Academy of Engineering, as well as being a fellow of the IEEE and also of the IEE.
Hansen's book has a section on "Pathological Antennas." He says claims on these antennas typically have performance characteristics that violate the physical laws we work under. The first in line in this section is the crossed-field antenna.
Hansens book goes on to say: The basic 'theory' which we all know is described, and then he describes measurements that show that, unlike the inventors' claims, the wave impedance in the vicinity of the electrode is much greater than 377 ohms.
He also quotes a result by J.B.Hatfield (of Hatfield and Dawson) that essential says for a typical CFA to maintain the ratio if E to H of 377 ohms, the D plates would require an RF voltage of more than a megavolt. "Kabbary and Hately apparently do not understand that both the H plates and the E cylinders produce near-fields, that the impedance of these near-fields is not 377 ohms, and that it varies with distance."
DR OR MR?
Was a PhD ever awarded to Kabbary? antenneX has seen a 1991 letter from the British Council for National Academic Awards instructing Robert Gordon Institute that the thesis had failed its examination on its second submission and that resubmission would not be allowed. Further, the University itself states that they did not award a PhD to Kabbary. Maurice Hately continues to describe Kabbary as his PhD student and has directly referred to him as Dr. in some correspondence. Then, most of all, emails from Kabbary were shown as from "Dr. Kabbary"and all of that seemed enough verification for me, at least in those previous reports several years ago.
With all due respect, Kabbary may hold a PhD from another University. I did send an email to Kabbary about this but never received an affirmation or denial on the issue. Moreover, antenneX has published several papers for him that included the title of Dr and no editing correction was ever made in his final reviews prior to publication. I only bring this up because, for years, many of us have referred to Kabbary as "Dr. Kabbary" and we would not want to mislead anyone such has troubled me as we also made more than one effort to confirm this title in the interest of fact-checking for this journal. Needless to say, the possession of such a title would add credence to his theories for many and could affect judgment.
Indeed, the CFA appears to have had a checkered history with no installation outside Egypt remaining on the air for any extended period. In its 20-year history it has not earned much praise from anyone in the industry. Is this the end of this controversial device? At least for now, this marks the end of any updates we have.
VISIT THE GUEST ROOMS
The relentless attacks on our web site by pirates and the like has made it necessary to add more security to protect our material against such piracy. It's only fair that we know who enters the House of antenneX, so our guests will need to provide some minimal information in the process of obtaining a login. This includes using your real active email address without which a login cannot be received. Do not confuse this login with a paid subscription login. They are not the same and your subscriber login will NOT work in the Guest Room areas. Of course, you may choose to create your own login to the Guest Rooms using the same login as your subscription, if the system will accept it.
Along with the continuing fight against spam/virii junk, protecting our material and valuable bandwidth against piracy takes up a great amount of our timetime we can't really spare. The Internet is simply not the friendly neighborhood it used to be in the "old days" and more and more security must be installed to counteract these intruders. Thus, we have made the access to the Guest Rooms as automatic as possible for you to manage your own login.
In view of the above, we have overhauled the nine free and open-access sections that have always been wide open to all of our friends throughout the many years antenneX has been online. But, we must change with the times as the need dictates. I don't think the Internet will become more friendly in the near future and logins are becoming the rule rather than the exception. To repeat, most would like to know who they invite into their house. The same applies at the House of antenneX. It's really worth the effort!
This list pertains to those sections with free access now in our new Guest Rooms we have built and fully operating:
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We have activated a new login system for access to the above guest rooms and, the login can be totally managed by our guests. Above is a graphic of what you see as a login page to the new consolidated area, "antenneX Guest Rooms." This new page for logins is at this location now and available for your use:
Get you login all setup now at this URL:
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As a result of this new programming, you will be able to obtain your own login, change it to update your info, change your password and delete membership if & when you desire without our help. Of course, the bottom link on the new page provides help if you still need it.
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The new Antenna Discussion List is a infinite fountain of ideas making it a great "watering hole" for exchange of ideas, questions and answers on a wide range of antenna-related subjects. You will be in good company along with some of the brightest minds available. Were else would you have such free access to this level of expert advice? To participate or just read along on some very interesting subjects each month with 2000+ members from all around the globe, you are welcome to join us:
You are encouraged to contribute your thoughts on various subjects to a worldwide audience.
AN INVITATION TO CONTRIBUTORS
antenneX thrives on the contributions of antenna experimenters, ranging from the informal home shop construction project to the theoretical investigation of basic antenna, feedline, and propagation phenomena. Over the years, we have published articles on the use of new or newly adapted materials, known antennas adapted to new circumstances, modifications of antenna structures, basic explorations of both common and unusual antennas, antenna modeling exercises, design improvements, antenna matching techniques from both a physical and mathematical perspective, evaluations of mini-antennas and their underlying theory of operation, new and patentable designs, propagation tutorials, and.... The list goes on, since no antenna-related topic is irrelevant to the readers of antenneX.
At the same time, antenneX has experienced continuous growth in its readershipfor which we are appreciative. However, all readers can help us do even better. How? By submitting an article every now and then based on your current antenna work that may be useful at any level to other readers.
Among the engineering and researching readers, there are
undoubtedly a number of unclassified and non-proprietary findings that antenneX
readers would like to know. Among the practical antenna designers, there are ideas, tests,
and numerous other practical findings to benefit our readers. Antenna builders very likely
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If you are uncertain about whether your ideas merit an article, please feel free to send an outline to the general editor/publishers at firstname.lastname@example.org . Do not feel that you must be ready to be a regular submitter to write for antenneX, because we welcome the individual contribution as much as monthly articles. As well, do not believe that the slots in each issue are already spoken forwe shall always make room for a worthy article.
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IN THIS ISSUE
We again include many fine articles by our great writing team from around the globe. Now, allow me to introduce this month's line-up of content:
OUR MONTHLY COLUMNS (plus this one you are reading by yours truly):
FEATURE ARTICLES IN THE LIBRARY:
|Every step along our path through traveling-wave antennas has led us to new heights of gain per unit of wire length (as measured in wavelengths)--and to narrower beamwidths. The final steps take us to the pinnacle of long-wire development: the rhombic antenna. (We should note that there are some "fishbone" designs that may be able to achieve more gain per acre of ground than the designs with which we are working. However, these antennas use a quite different design and require at least 2 to 4 wavelengths of wires per wavelength of forward antenna dimension. We shall not cover them here. However, the ARRL Antenna Book chapter and the Laport volume, both cited in the short list of references, cover the basics of these designs.)|
Great Displacement Current Debate
says: The existence of displacement current has been a hot topic on the Antenna Discussion
List for the past several months, at least. Now Ive read some of the authorities
cited and done some analysis of the examples discussed. The main body of this article
presents a review and discussion of the topic, based mainly on John Roches paper.
Two appendices give the mathematics of the constant-speed charge example and the capacitor
example. A third appendix gives a critique of Bill Millers booklet on his theory of
Bill says: First I want to thank Doug Miron for the time and effort that he invested. Unfortunately, it appears that he did not understand the nature of my proposition. To the extent that this is due to my own inability to communicate a complex subject, I accept a portion of the responsibility. HOWEVER, if the reviewer does not understand the subject matter, does not request clarification, and thus makes assumptions that are incorrect, it is solely the reviewers responsibility. Second, the entire subject of Displacement Current, and my thesis, is based on my allegation that in the absence of charges Displacement Current is NOT responsible for the magnetic field that is associated with it. If the reviewer (or you, the reader) is satisfied with the concept of a virgin birth of magnetic fields via Displacement Current, then my proposition no matter how sound (or fragile) will be nonsense!
Meter Antenna System Impedance Matching
|I have been using the W7FG 8010 meter antenna system for approximately two months and purchased it primarily because I did not wish to construct a length of 600 Ohm transmission line. The W7FG 8010-meter antenna system includes an integral 600-Ohm length of transmission line without any solder connections at its apex. I decided to cut the transmission line to fit with my location restrictions. The length of the line became 51.7 feet. Since the line and antenna leg lengths are not optimum, varied impedance matching at the line source point is present. Then, various matching schemes can be selected.|
A Sensible Explanation of Displacement Current
|Bill says: The key ingredient to Maxwells equations is Displacement Current. This term, as taught by most textbooks and undergraduate Electromagnetic Theory courses, leads directly to the generation of a magnetic (H) field without the intervention of electrical charges. However, despite 140 years of trying, there is no concrete evidence to support this contention. Nevertheless, the absence of this term would mean that among other things radio waves would not exist!|
and EH Antennas
ongoing challenge in electrical engineering is the design of antennas whose size is small
compared to the broadcast wavelength. One difficulty is that the radiation resistance of a
small antenna is small compared to that of the typical transmission lines that feed the
antenna so that the power in the feed line is reflected off the antenna rather than
The radiation resistance of an antenna that emits dipole radiation is proportional to the square of the peak (electric or magnetic) dipole moment of the antenna. This dipole moment is roughly the product of the peak charge times the length of the antenna in the case of the linear (electric) antenna and is the product of the peak current times the area of the antenna in the case of the loop (magnetic) antenna. Hence, it is hard to increase the radiation of small linear or loop antennas by altering their shapes. We will discuss this dilemma with two devices in mind: The CFA and the EHA.
New NCDXF/IARU Beacon Monitoring Program
Part 1 of this review, we examined a number of basic elements within the Faros program, an
automatic NCDXF IARU beacon-monitoring program. Intended for Radio Amateurs, SWL
listeners, and HF communication engineers, the program has many useful and practical
Part 1 reviewed the programs prerequisites, which included a modern receiver, an up-to-date computer, and a continuous high-speed Internet connection. We examined the main menu and looked at the necessary steps to configure the program to our location. We also examined in detail how to set up the clock inputs in order to make full use of the full capabilities of Faros. Even if the network is too slow for precise UTC tracking and the signal delay cannot be measured accurately, the program can still run, detect beacons, and measure the SNR value and the QSB index. The illustrations included review the main menu options of most concern to the new user.
In this second part of the review, we shall begin by looking at the User Interface. Then we can look more intensively at how the program displays results and creates a history of beacon reception.
Well, there you have it, folksthanks 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.-30-
Best reGARDS, Jack L. Stone, Publisher
August 2006 antenneX Online Issue #112
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