Kabbary Finds Wave Pockets?
By Jack L. Stone, Publisher
s the saying goes, "there is nothing new under the Universe, we just havent found it yet!" But, once significantly important discoveries are found, careers are made; names as associated permanently with the discovery and Nobel Prizes are awarded in some rare cases. With that said, in this months issue, Dr. Kabbary has presented his paper on a phenomenon that at least bears attention and close scrutiny, whether are not it is truly a new discovery of a significant scale.
During the past couple of years, Dr. Kabbary, a co-inventor of the Crossed-Field Antenna, has been keeping his eye on a phenomenon that he believes he may have discovered accidentally during some 1999 signal measurements and doing some A/B comparisons between an existing mast antenna and the CFA sites.
Using several road signs on the roads leading away from the Tanta broadcast station sites as a constant point of reference for the measurements, Dr. Kabbary found a strange effect on the broadcast signals from the 125-meter high medium-wave broadcast mast. It is an effect he calls wave pockets. At first, we thought perhaps he was talking about signal nulls, but after more information, it was clear this was indeed, not nulls.
I will let Dr. Kabbarys paper speak for itself and will not attempt to cover the specific details in this column, but briefly, these wave pockets were attributed only to mast-type antennas in the Egyptian locale where these tests and observations were made several times over a period of two years since the first discovery. The CFA site near the mast antennas did NOT exhibit this same behavior and Dr. Kabbary thinks it ties in directly to the anti-fading attribute of the CFA. And this is where it gets interesting, indeed! Dr. Kabbary has gathered a substantial amount of data on the wave pockets and the various measurements taken in these A/B comparisons of the CFA to the masts. The data is included in the article in the form of charts, which graphically compare the signals of the mast antennas versus the signals of the CFA. Be sure to take a look at this interesting article, which is available for all to read at Wave Pockets (click here to read).
BUT IS IT REALLY NEW?
If you have ever done much research or worked on what you thought was a really new concept, you have no doubt have experienced disappointments by learning after your great discovery that it was NOT a new idea and it had already been discovered by othersyou just hadnt stumbled across it yet!
The same may or may not apply to the wave pocket discovery as it does bear more scrutiny and by next months issue, we expect to have another article about this subject from one of our GARDS members, Ralph Holland, VK1BRH who has already started his research. In fact, Ralph remembers reading about a similar effect published as far back as 1955 By Frederick Terman in Electonic and Radio Engineering, 4th Edition, McGraw-Hill, circa page 812. Apparently Terman says a similar effect is caused by interference between the direct wave and wave reflected from the ground. Terman also has plots from a distance of 0.5 to 50 miles above a perfect earth and above an actual earth. In that case, those pockets show signal drops between 12 to 30dB below the peak. Further, the effect is more pronounced as the transmitting and receive antenna heights increasenot dissimilar to the observations found by Dr. Kabbary, although his observations found that the distance between wave pockets changed as the antenna height changed. Antenna height also influenced where the wave pockets started in reference to the masts location.
Additionally, Ralph has located a treatise on a similar pocket study in another book Radiowave Propagation Over Ground, MacLean and Wu, Chapman and Hall, 1993. Ralph goes on to say that this reference is found on pages 50-51 and again on pages 111-113. It contains graphs and equations on the subject. This same information should be helpful to Dr. Kabbary in his comparisons to the effects of the wave pockets observed in his own study, however, it is all still too early to conclude whether we are comparing the same phenomena or not. I hope Dr. Kabbary will do a follow-up article after Ralph has had an opportunity to present his article researching the matter more deeply in conjunction with the observations set forth in this months article by Dr. Kabbary. I might add that Dr. Kabbary believes it has more to do with the ionispheric layers than anything on the grounds surface, or more toward the sky wave rather than ground wave.
One can only assume that this has something to do with the matter of propagation and the more we understand about the source of the effects, the better we can make antennas, or at least arrive at proper measurements. Dr. Kabbary feels strong enough about his discovery that, in the final analysis, this discovery just may dictate that a rewrite of the measurement regulations is in order! Dr. Kabbary agrees that before this is absolutely concluded to be some new phenomenon, much more investigation needs to be conducted from other mast antennas at other locations under other environmental conditions.
Certainly, Dr. Kabbarys study will be the first of its kind to observe this wave pocket effect, or lack of effect thereof on the CFAs signal. If the Kabbary observations prove to be correct, the CFA once again bears more investigation as to why its signal is not influenced when all of the medium wave mast antennas, short or tall, experience this wave pocket effect. Is it at least partly because the CFA is just shorter than ALL of the masts? This is one of the first questions to answer among others. At the same time though, we should remain mindful of the CFA's unique near-field signal as reported from earlier measurements by independent engineers.
RALPH WANTS TO KNOW
In his study of this from the CFA side of the issue, Ralph would like to ascertain a description of how high from the ground surface the CFAs are mounted, how big or tall the CFAs are, how big are the buildings and some of the geometry of the surrounding terrain. Of course, some of this can be ascertained from earlier articles in the antenneX archives, especially the article #41 in Archive III Tour of Dr. Kabbary's CFA Broadcast Stations. This article in particular gives the antenna heights and the buildings underneath the CFAs can be extrapolated. About the only thing missing is the amount of power used, but this months article by Dr. Kabbary discusses that too as he describes the transmitters used for both mast and CFA during the A/B tests.
So, stay tuned for the next stage of this investigation as Ralph Holland finishes his closer look at this issue. After that, then perhaps we will learn more about the results reported from Egypt as well.
NEW PROPAGATION COLUMN TO BE LAUNCHED!
Speaking of propagation, I am pleased to announce that a new monthly column will be launched commencing with the April 2002 issue of antenneX. Incidentially, that will be our online issue number 60exactly five years as an online magazine!
The new popagation column will be a regular monthly publication available to one and all to read (about 60,000 monthly now) and will be written by a new addition to our writing team, Marcel H. De Canck, ON5AU who hails from Belgium. Marcel became a member of the UBA, Union Belgium Amateurs, and in 1961 started studying transmitting theory, among other radio subjects. This was shortly after he obtained his call ON5AU in 1960.
Born in 1943, Marcel has been intrigued with the properties of propagation since age 10. Later, he became a member of the UBA Union Belgium Amateurs, a club in Belgium.
Marcel also developed computer and computer programming skills along the way and as a result, he has come up with some very clever and interesting propagation wizards as he refers to them. The columns will be sprinkled with samples of these wizards that the reader will enjoy making use of for their own radio operations. So, this will not be just the ordinary propagation column, as it will be packed with such gems as the wizards made possible by the antenneX online Internet media. The reader will see animations of the propagation examples discussed. If you want to learn more about the subject of propagation, so important to radio operations, antenneX will now help make that possible starting in April 2002just another of the many useful services provided!
LPDA NOTES VOLUME 2 TO BE RELEASED
About six months ago, we released and introduced the LPDA Notes Volume 1 Pure LPDAs by author, L.B. Cebik, W4RNL who is truly an antenna guru in all sense of the word. L. B. Cebik, W4RNL, has written extensively about antennas and antenna modeling (as well as other electronics subjects) in most of the U.S. ham journals, including QST, CQ, Communications Quarterly, QEX, Ham Radio, 73, QRP Quarterly, Radio-Electronics, and QRPp. Besides the continuing series of antenna modeling columns he does for antenneX, he also writes a column for 10-10 News (An-Ten-Ten-nas) and another for Low Down (Antennas From the Ground Up). A life member of ARRL, he serves as both Technical and Educational Advisor. He has been a ham since 1954 and is also a life member of QCWA and of 10-10 International, for which he maintains an extensive web site. He also maintains a web site of his own http://www.cebik.com on which he has placed a large collection of entries from his notebooks. A teacher for over 30 years, he is retired and professor emeritus of philosophy at the University of Tennessee, Knoxville. antenneX is very fortunate, indeed, to have LB as a member of its writing team and author of several books published by the antenneX BookShelf and Modeling Files in the Software section.
The LPDA Notes, Volume 1 has proved to be a very popular book and many have asked about when the Volume 2 will be released. We are pleased to say that it will be released in about 10 days or so, or within the second week of March 2002, which was our original schedule for this book. Volume 2 is entitled Hybrid LPDAs and is expected to be a popular book considering the interests expressed in this type of antenna and the Volume 1 released earlier.
So, keep an eye on the BookShelf in the Shopping Shack for this new book and keep an opening in your personal reference library for this special information about antennas. Well be sending out an announcement to all on our announcement list as well. If you are not already on this list, be sure to sign up as it is a way to keep informed about breaking radio-related news around the globe as well as these new products.
ECONOMICAL ANTENNAS FOR LOW & MEDIUM FREQUENCIES
Talking about "hot sellers!" If you missed our announcement in mid-February 2002 about another new book release with the above title, be sure to check on it at this section in the BookShelf. As the ad page says, low and medium frequencies remain an important part of our interest in antennas, not only for the amateur, but as well for the engineer and technician working in AM broadcast and air and sea navigation.
This new book by Robert C. Wilson, AL7KK combines basic antenna theory and practical knowledge with a focus on Tee and Ell antennas, the most economical antennas for LF and MF. You will learn the fundamentals of good engineering practice that are very useful for HF antenna installations as wellor at least call attention to giving careful consideration to often neglected areas of concern.
Robert is a physicist, engineer, and senior member of IEEE. He spent his career designing and supervising the installation of such antennas. Now retired, he shares with you the wisdom of hard-earned experience as an engineer with hundreds of low and medium frequency antennas to his credit and explains how to build good, effective, simple, low cost, long range antennas. he has been employed by the FAA, Voice of America, Martin-Marietta, Comsat, RCA, and DoD working in 21 countries.
He has handled government and civilian antenna projects in North, Central, and South America. His radio station projects have included Europe, Africa, and Asia. He personally built some of the first U.S. satellites. Mr. Wilson has been on the staff of the University of Colorado and Wyoming. Robert also attended the University of Alaska, Allegheny College, University of Colorado, University of Iowa, Lake Forest College, University of Maryland, and Rockford College. In addition he is a helicopter pilot, a ship radio officer, and a long time radio amateur with the call AL7KK. He now lives with his wife on a remote Alaskan lake. We are pleased and very lucky to count Robert among our team of very knowledgeable authors!
ISLE OF MAN GRANTS LONG WAVE
On February 13, 2002, we received a message from Paul Rusling, CEO of Isle of Man International Broadcasting, plc along with a News Release about the granting of the much sought-after license to broadcast at Isle of Man. In that message, Paul says:
We are pleased to announce that this afternoon, the Hon Phil Braidwood MHK, who is Minister of Home Affairs on the Isle of Man, and as such is also the Chairman of the Communications Commission has signed the full Broadcast Licence for IMIB to commence operations on 279 Long Wave.
A copy of the Press release issued by the Communications Commission at 5pm today is attached.
More details on http://www.longwaveradio.com/News.html
Below is a copy of the News Release as received from Paul (and as received with European-type spelling of the text):
GRANT OF LONG WAVE LICENCE
The Isle of Man Communications Commission has today (13 February 2002) announced the grant of a substantive licence to Isle of Man International Broadcasting plc (IMIB). The licence, under the Broadcasting Act 1993 (of Tynwald), is to enable IMIB to provide a long wave radio service broadcasting on 279 kHz, and will be for a ten-year period.
The service, provisionally called MusicMann 279, will be music led and will target an audience across Britain and Ireland. It is expected to launch towards the end of 2003.
IMIB plans to install the transmission antenna on an offshore platform in Manx waters some 9km northeast of Ramsey, Isle of Man, near the spot Radio Caroline was anchored in the 1960s. Some 50 new jobs, both full and part time, will be created in the town where the studios will be located. As well as its Isle of Man broadcasting licence, IMIB will hold a Wireless Telegraphy licence from the United Kingdom Radiocommunications Agency.
Announcing the grant of the licence, the Chairman of the Communications Commission, the Hon Phil Braidwood, MHK, said The Isle of Man first sought a high power broadcasting frequency four decades ago. IMIB now has the opportunity to demonstrate that the Island is again a vibrant source entertaining radio for the whole of the British Isles. The Director of the Commission, Anthony Hewitt, added It is now nearly 3 years since the selection of IMIB to exploit this opportunity was approved. With planning issues behind them, the way is now clear for IMIB and its backers to get the station on air and to realise its full commercial potential.
As mentioned in earlier columns, Paul still plans to employ use of a CFA for the project. This will indeed be an interesting ptoject to watch and if anyone deserves success based on perserverence, it is most certainly Paul Rusling! We wish Paul continued good luck, as he appears now to be picking up momentum again through this new direction.
NOW WHAT'S THE ISSUE?
This month is our 59th online issue! We again include many fine articles by our great writing team. Allow me now to introduce this month's line-up of content:
THE MARCH 2002 ONLINE ISSUE NO. 59 CONTENTS:
OUR MONTHLY COLUMNS (plus this one by yours truly):
FEATURE ARTICLES IN THE LIBRARY:
80-Meter Wire LPDAs
|Previously for the 80-meter LPDA, the combination of performance-degrading factors in this array strongly suggest that a redesign is in order. In this article, LB explores more adequate arrays for 80 meters. However, each example will presume standard linear elements at right angles to the main array axis. In the course of these notes, we shall look at the question of optimal element size and how to simulate it with a wire array. We shall also examine some limits (and the reasons for those limits) of improving thin wire lower HF arrays with simulated fatter elements.|
LAB NOTES: Understanding the Gieskieng - Part 2
|In the February 2002 issue, Joel described a Gieskieng antenna made with a length of twinlead with the wires shorted together at one end and fed a short distance up the line from the short by connecting the shield of a drive cable to one wire of the twinlead and the center conductor to the other wire of the twinlead through a capacitor or a coil. The capacitor or coil tuned out the effective reactance of the twinlead section to form a purely resistive load on the drive cable at the resonant frequency. This month, Joel examines the possibility of using a second twinlead Gieskieng antenna instead of the coil or capacitor. There is found to be more than first meets the eye with the outcome!|
QRP Expedition Above the Clouds - Part 2
|The UR-QRP Club is made up of members from Russia and the Ukraine. The idea to go to Ancient Crimea for a QRP-expedition has been considered by the members of this QRP-club for quite some time. Finally in May of 2001, the QRP-expedition became a reality. They set other things aside, collected their backpacks, stuffed them with QRP gear and other tourist gear into them and left for the Crimean mountains. This expedition gave them a good chance to visit with the other members of the QRP club, visit ancient places in Crimea and to go to the beautiful, but rugged AI-Petri Mountain in the locale. This is the sencond part in a series of articles by Igor about this exciting QRP-expedition we originally announced in May 2001. In Part 1, the group explained their preparations for the expedition and setup of the rig. This month, they start operating and learn something new about the "cloud effect".|
A NEW VARIABLE TROMBONE CAPACITOR
|Magnetic antennas, specifically for transmission, do need high quality variable capacitors in order to reduce ohmic losses. Magnetic antennas do have a very low radiation resistance, way below one ohm (sometimes only milliohms) which is in direct competition with all ohmic losses of the loop and the capacitor used to tune the antenna to resonance. We therefore need to avoid all lossy contacts such as loose sliding contacts. Once again, Pascal applies his fine craftmanship to make such a capacitor and tells how he did it in this article.|
The LDG Z11 QRP Automatic Antenna Tuner
|In an earlier article Richard reviewed the LDG AT-11 tuner he had purchased, but afterwards he found out that it would not easily fit into his emergency portable antenna bag. It was just too big and even though it tuned every one of the antennas he planned to use for emergency communications, size and power consumption issues raised their heads. So after some more review and about three-tenths of a second consideration, he decided to buy the LDG Z-11 tuner and describes his experience with the unit in this article.|
A Brief Overview of the Zeland Software Suite
|The antenna modeling software packages with which most casual antenna designers and analysts are familiar rely on either NEC or MININEC. However, as we move into the realm of "wireless," we often outrun the ability of either type of core to do the jobs that we need. Software packages aimed at meeting these needs do exist. They are large, complex, and often require special trainingnot to mention lots of trial and error experienceto use effectively. One such program that I recently had the chance to review is Zeland Software's suite. Their software packages offer ever-increasing abilities to create the detailed geometries that close the gap between reality and modelor between model and reality, as you prefer.|
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. March
2002 antenneX Online Issue #59
reGARDS, Jack L. Stone, Publisher email@example.com
Send mail to firstname.lastname@example.org
with questions or comments.
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