Loop de Loop

INTRODUCTION

he antenneX News Announcement Releases have been especially busy of late with so many interesting antenna-related developments emerging—not only in terms of new books and modeling software, but in terms of promising progress made in the area of compact antenna technology sprouting up at a fast clip. Indeed, these new entries of compacts are promising wide band and high efficiency, and the best part is that the theory can be explained in scientific terminology so that they may be easily subjected to scrutiny against the developer claims. Even so, let's follow these new upstarts and see how well they really work. Let’s review a summary of some of those new antennas, all of which have emerged into the spotlight within just the past 3-4 months:

The 3-D Folded Loop:
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In late June 2003, we made the following announcement:

The Cube-C Loop:
cubec.jpg (25185 bytes)

In the August 2003 issue of antenneX, we published an article about one the first of FOUR more new Compact Loops— the Cube-C developed by the team of Dan Handelsman of New York and Claudio Re of Italy. That article described a new 40-meter antenna design that is compact with a dimension of 1/20 wl/side or smaller. It has the following characteristics:

In the Part 2 article about the Cube-C published on September 1, the author provided dimensions and values of capacitance that enables the duplication of this antenna for any frequency range of interest.

As I recall, the answer to his question was that it is pretty close to linear, except for the compensation needed for “skin effect” produced by the larger surface mass.

The ADR Loop:
adr.jpg (18145 bytes)

In September 2003, we announced the new "ADR" Loop. The ADR is an acronym for Asymmetrical Double Rectangle since this new innovative antenna is composed of two concatenated loops. The first article about the ADR compact appears in this October 2003 Issue #78 of antenneX. A picture of one of the ADR test units adorns the front cover of this new issue.

Claudio Re of Italy constructed a 30 cm diameter ADR-loop of 22 mm copper tubing and tested it at 50 MHz. Its gain was found to be -1 dBi. Dan Handelsman of New York measured the gain of a 50 cm copper loop of 18.5 mm diameter at 28 MHz and the tuning and bandwidth of a 1.3 m loop over 21 to 7 MHz. At 28 MHz, the gain was found to be 0 dBi.

The gain measurements and the tuning measurements were all reasonably close to the values predicted by NEC. As with compact loops in general, the gain and impedance measurements are in close concordance with those generated by NEC. Dan says NEC has no problems in modeling the performance of such loops.

The developers state that the ADR is not a replacement for the Cube-C, but each have different advantages that gives folks a wider variety of compacts to choose from depending on needs.

This newest development of compact Loops is yet another joint effort of Dan Handelsman of New York, USA and Claudio Re of Italy. There will be follow-up articles about the Cube-C and the ADR so that one and all can duplicate them and try each one. Also, these will be followed by the disclosure of the Cube-L and the Cube-E compact loops — two more interesting designs by this International team of inventor/developers.

Claudio says he has filed his patents for the Cube-L and Cube-E in Europe so far with more patent filings yet to be completed. After that, he will be able to go public with his articles about these two more versions of a cube loop.

What Do Experts Say?
Several independent experts on different sides of the globe are said to conclude that various calculations of the efficiency of the C-Cube at various frequencies are quite in agreement. And, also the ADR-loop is the same antenna but with a smaller overall loop size than the Cube-C. So, based on this expert feedback, the developers believe its theoretical foundations appear to be firmly grounded.

On expert studied the ADR-loop model at the same time that he was doing field-strength measurements on other loops and the upshot was that Dan's loop would be more efficient by a factor related to the losses of any additional matching network—with 3 dB being the LOWEST additional loss in the matching network. He expected matching losses to be higher than that but could not quantify them.

Dan's article this month on the ADR concluded in the article that the ADR loop, in the field, would have a 3 dB advantage compared to a comparable simple loop. Dan believes that conclusion is conservative.

Further, Dan's conclusion, based on expert feedback work is that matching losses of ordinary loops will increase with smaller relative loop size and that the ADR-loop's efficiency advantage will improve under those circumstances. Dan says he is not claiming greater gain differences although the studies have shown that the ADR-loop is far better than a simple loop.

Based on the progress reported over past months, it appears that these new Loops have the lead at the moment in the search for an efficient compact antenna. The “test of time” has begun to tick and we shall know soon how well these devices stand up to that test. I for one am not as uneasy about the usual concerns of the radiating lead line “factor” as these developers are well aware of that trap. Also, it appears other clinical steps have been taken to isolate from the “coupling trap” too.

Yes, it seems a great deal of progress has been achieved, but if all proves to be as claimed, we have a very good start and some choices of compacts for confined spaces that can be used until something better comes along. The more folks that experiment with these new concepts, the more we will know about them—independent of any commercial motivation.

Public Service Announcements
Recently, we have dispatched a couple of specific warnings about the recent floods of some really nasty viruses and/or worms that accompany emails. We do this because we are well positioned to send out early warnings about these intruders to thousands on our announcement mail list and we figure if we can “neutralize” even one virus/worm from infecting a computer, we have provided a good thing in the way of a public service. While that may sound insignificant, a single infected PC can infect hundreds if not thousands of others as it compounds itself and spreads much like an organic virus. But, just think if we can neutralize hundreds or thousands of these electronic bacteria by spreading the word ahead of it.

And, it is a good idea to pay close attention when forewarned, because the bad guys have become even cleverer about disguising the existence of their malicious missiles among the emails within your Inbox. Unless your mail server catches them first, you WILL get them! Even if your mail server has scanners/filters in place, they may not get them all—so, be on your guard at all times.

Those running Windows and using a version of “Outlook” are especially vulnerable. This is so because of being the largest “target” for such things. For example, 94% of our readers use Windows with the remaining 6% spread over 6-7 other operating systems. MACs are second to Windows at only 1.5% followed by Linux as third at only 1%. The rest are miniscule. The 94% doesn’t translate into 94% using Outlook, but it’s a good indicator of the broadest market for spammers and viral attacks.

Now, for those who didn’t receive our recent warnings about viral attacks, let me repeat them here. Further, you should take note that each warning contains a link to screenshot so that folks can safely see what to watch for and how to better identify them should they land in your email Inbox. The graphics typically include the body of the malicious message and examples of the links to executables they want you to launch to infect your machine.

I have placed a small copy of a sample screengrab of the SoBig virus to the right. By the "arrows" you will notice we have analyzed and highlighted what to look for when, not if you get some of these. The same thing is provided below on the more recent flood of "Fake Microsoft" worms being spread. For a larger more legible view of these, just click on the links provided here.

The Fake Microsoft Worm:
ms_fake.gif (17363 bytes)

Just short of a month later on September 19, 2003, we announced another massive attack:

As one can see from that last one, it was actually masquerading as being from Microsoft, playing upon any paranoia created by the others making worldwide news about shutting down hundreds or thousands of servers and PCs. The radio & TV news was already reporting that anti-virus patches were being made available by Microsoft, but were hard to get because even the MS servers were loaded down with traffic attempting to get the patches. So, taking advantage of the hysteria, the bad guys sent out millions of new emails with viruses claiming to be from Microsoft containing the real patches—of course, none was true. MS is not in the habit of sending out unsolicited patches. In the past 15 years. I don't remember ever receiving an unsolicited patch from Microsoft. Personally, I go to the MS website for updates—only.

Here on our UNIX mail server, we quickly put up some new “nets” and were catching most if not all of these new intruders before they could be delivered to our user email accounts. Thousands were being snagged within each 24-hour period. In “netting” these we probably helped to avoid thousands of PCs from becoming infected. Modifying our various intruder blocks/filters/nets is almost a daily job.

This last flood of viruses is waning, but there will be more to come on that we can bet for certain. We’ll keep sounding the alarms by way of our announcement mailing list, so if you see on of our warnings, it’s a good idea to take a close look because if you use a PC, the alert is meant for you and not just the other guy!

If you are not on our News Announcement List and want to be notified of such important things and other breaking news, just subscribe here.
http://www.antennex.com/subscribe.htm

COMING UP
In exchanging so many emails with folks, it has become apparent to me that many may not be using an excellent and very powerful feature on their email programs—the filters. Next month, I will explain the use of filters and how to set them up on those who use Outlook and/or Eudora. However, if you use some other email program, the setup should be similar. This information will help many organize the incoming emails more easily. If you aren't already using filters, you are missing out on a hugely useful feature! This type of information is provided as another service to our readers because email is an important part of our relationship.

Notes on a Long-Boom General Coverage LPDA
By L.B. Cebik, W4RNL

In a recent article, "Notes on HF General Coverage LPDAs Using 30-35' Booms," LB explored the design factors involved in obtaining smooth general coverage from 14-30 MHz from a relatively short-boom array. In this exercise, LB explores the same goal, but to employ a much longer boom to obtain a gain level average at least 1.5 dB higher than we could get from the shorter boom. The boom lengths involved in the new exercise fall in the 55-60 foot range.

LAB NOTES: More Data on the Tri-Band Dipole
By Joel C. Hungerford, KB1EGI

Last month, Joel designed and tested an integrated loading structure that tunes a 20-meter dipole to 40 meters and two frequencies in 80 meters. This month he fabricated a second integrated structure of loading coils and capacitance hats for the other end of the dipole, mounted both on the ends of the 20 meter antennas and then spent a lot of time unscrambling the data as it tuned up. Tuning it up was tricky because there were four tuned circuits operating at 80 meters, two at 40 meters, and a hidden participant in the experiment: the length of the feed line. It was easy to tune the wrong hat by mistake and change part of the antenna that had been completed, or to tune a hat way off frequency because one didn’t recognize it was above, not below, the correct frequency. The learning continues!

An Antenna System Design Approach
By Fred M. Griffee, N4FG

Through his years of experimenting, Fred has tried various approaches to antenna systems design. Finally, he came up with an approach that comes closer to predicting the final design before the installation is started. Fred's approach to an antenna system design does not use costly test equipment but uses available programs including one written by myself, and other available support tools such as NEC-Win Plus and Mathcad.

The ADR Compact Loop
By Dan Handelsman, N2DT and Claudio Re, I1RFQ

The ADR is an acronym for Asymmetrical Double Rectangle since this new innovative antenna is composed of two concatenated loops. The first article about the ADR compact appears in this October 2003 Issue #78 of antenneX. The gain measurements and the tuning measurements were all reasonably close to the values predicted by NEC. As with compact loops in general, the gain and impedance measurements are in close concordance with those generated by NEC. NEC has no problems in modeling the performance of such loops. The developers state that the ADR is not a replacement for their Cube-C, but each have different advantages that gives folks a wider variety of compacts to choose from.

Determining Frequencies Without a Counter
Doug Flory ~ WB6BCN

Before the introduction of affordable high accuracy frequency counters Hams had to devise other methods to make sure they didn’t transmit out of band. None of the older methods offered the speed and accuracy we have with the instruments of today. In many cases, early Hams used crystal-controlled transmitters. This way they knew within a KHz or two where they were transmitting. Usually they were much closer than that, but they really had no way to be 100% sure they were they were even as close as 100 HZ of the frequency marked on the crystal. Most of the problem stemmed from the fact that tube circuits had a large amount of drift during warm up and crystals drift in frequency with temperature change. So, how was it done?

The MicroVert Analyzed - Part 2
Matching, Impedance & Gain Measurements
By Claudio Re, I1RFQ

In Part 1 of this series on the MicroVert we discussed the modeling predictions. In this Part 2, we shall see how the antenna measures up to the predictions. For every different configuration of the MicroVert, a set of three different measurements was made:
1) Return Loss measurement
2) Impedance measurements with results plotted on a Smith Chart
3) Gain measurements
The different configurations of the MicroVert were:
1) MicroVert with vertical counterpoise in open space in the test range
2) MicroVert with horizontal counterpoise in open space in the test range
3) MicroVert with horizontal counterpoise mounted on the ground
4) MicroVert with horizontal counterpoise situated under a metallic shield of 1 x 3 m
5) MicroVert with horizontal counterpoise on the roof of a car that is 4.5 m long
Another configuration was tested in the same way: a short loaded monopole with open counterpoise coaxial to the cable horizontally along the roof of a car 4.5 m long. The length of the monopole was the same as that of the MicroVert upper section.

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. October 2003 antenneX Online Issue #78
reGARDS, Jack L. Stone, Publisher jack@antennex.com