CTHA EVALUATIONartpix.jpg (8442 bytes)
by Ben Smith, W4KSY

PROLOGUE
wctha.gif (1443 bytes)ith great curiosity, I read the advertisements from IAS COMMUNICATIONS on the Hawk's Contrawound Helical Toroidal Antenna, which says this on their website:

"The HAWKS Antenna is an antenna that's shaped liked a torus or doughnut. It can be placed on the ground, on a tower, on a boat, or concealed in the fuselage of a plane and operate with equal efficiency. A giant leap forward in radio frequency transmission and reception, the HAWKS Antenna is so effective that it can transmit VHF signals over three times as far as conventional antenna operating at the same input power level. This means that the input power can be dramatically lowered while maintaining the same range. What's more, its lightweight and inexpensive materials give it an impressive edge over the mono-pole and di-pole antenna used today....."

Above is the picture of the device displayed on the website, which shows an enhanced piece of artwork and looks more like a big golden doughnut, or blown up yellow inner tube and pretty sturdy:

orderpix.jpg (6149 bytes)However, in the packet of information sent on request, I received an order form, which contained the picture to the left that more closely represented the product actually shipped. So, I bought it anyway!

When I opened the box and saw this floppy, flimsy hula-hoop covered with a black plastic electrician's tape! I was annoyed to find the covering already had a tear exposing the innards. Clearly, if this device can be torn riding inside a box, surely it can't endure much abuse exposed to the outside elements of heat, cold, rain and wind!

This antenna is a loop three feet (91cm) in diameter and 1-1/2 inches (3.8cm) thick. As noted from the order form, they say the thickness is 2 inches (5cm). BUT, if you used the scale of proportion shown in their rendered golden display picture above, it would have had to be about one foot (30cm) thick instead of just 1-1/2 inches! A pretty big difference from the real thing! Don't make your purchase decision based solely on the website "picture"!

myctha.jpg (19709 bytes)To the right is a photo of what I received. Note, in both photos on the ground and mounted in the tree, I have used some bracing to help keep the device straightened because it is very flimsy and has a tendency to twist. Also, in the tree, notice the drooping.

CTHA CONSTRUCTION
The CTHA is circular. It is made with nine feet of one and five sixteenths PVC Braided Tubing, nine feet long. The ends of the main core are joined with a smaller piece of Braided PVC inserted into the ends of the main core. A PL 259 chassis connector is mounted equidistant from that joining. It is mounted with self-tapping screws into the tubing. The contrawound wrapping is made of two wires with 31 "crossovers" spaced 3-1/2" apart which I believe is supposed to have something to do with generating the electrical fields. It is about number 14, stranded, insulated wire; one black and one red. The red wire connects to the center of the PL259. The black wire is connected to the normally grounded side of the connector with a solder lug. The two wires are wrapped around the tubing in opposite directions and cross at 3-1/2-inch intervals. Where the two wires meet back at the connector they are soldered together. The entire assembly is then wrapped with electrician's plastic tape.

Here's a picture tour of the device's construction described above:

Click Links: >>> | The Whole Thing | Connector | Insides 1 | Insides 2 | Insides 3 |

treemnt.jpg (9038 bytes)The advertisements sounded far out and my first impression, made me think it was a hoax. Then I E-Mailed for an information packet, received it, read it and opined it was just too good to be true. There were no real specifications given. Instead, lots of marketing rhetoric about replacing towers, dipoles, verticals, etc. There were no reliable evaluations available to me. I felt the only way I would ever find out about its performance would be to purchase one of these things and test it myself (after all, it's only money!).

FIRST TESTS
A CTHA was purchased in the early Spring of 1999. The CTHA was taken out of its box, unfolded and quickly hoisted up in the air and tested on 160, 80 and 40 meters. It was also tested with the antenna on the ground, and on my roof. But, yet I thought, the antenna was not given a fair chance to perform since I had not followed the manufacturer's recommended use of 50 feet (15m) of coax and a tuner.

INSPIRED TO TRY MORE TESTS
Because I had expected the CTHA to be unusable and my belief was somewhat substantiated by those early results, I put the CTHA aside and out of my mind. Then someone started the ball rolling on the antenneX Compact Antenna Forum http://www.antennex.com/compact/  I told my friend, K5CNF, Editor of antenneX, that I had a "Hawks" antenna. K5CNF forwarded my E-Mail message to antenneX Publisher, Jack Stone. I immediately received E-Mail from Jack and a number of the writing team members of antenneX urging me to do an evaluation, or ship them the CTHA so they could do it.

Editor's Note: In an abundant effort to tell the full (and fair) story of Ben's experience, this is that October 8, 1999 message of Ben's first reaction to the CTHA before making more extensive tests.

Hello Richard, I have just had an astounding experience and simply had to tell someone about it. I suppose I should wait until I have finished the evaluation, but I have to tell someone that understands, right now!

I had thought that I was about finished with testing and was ready to add in some notes and call it a job. Then it dawned on me that there was mention of operating on the ground! So this afternoon, I took the CTHA down from its test position and put it flat on the ground. With the MFJ Tuner and the Analyzer I was able to get an SWR of 1.5 to 1 at 35 Ohms. The Kachina Autotune brought it down to one to one at fifty ohms. Signals were 5 S Units below the dipole. I had to leave it until about eight thirty this evening.

With the CTHA selected on the Kachina, I stuck my tongue in my cheek and called CQ once and then again...VE3BNO in Ottawa came back. He was an S7 (on the CTHA). He gave me an S5!!! I switched to the dipole, he was 599. He gave me an S9 on the dipole. George said, "I can copy you on the other (CTHA) antenna but stay on the one you are on now." (dipole) George also stated that the band was very quiet at his QTH.

After we signed, I disconnected the CTHA and carefully put the coax back in the grass. I came inside and took a look. There was nothing. No noise, no signals, absolutely nothing. When I reconnected, signals came back. If the transmission line was contributing, it had to have the CTHA connected.

Now I have to try the CTHA ON THE GROUND, on all bands. Then I am going to have to try it on the roof, HORIZONTAL! I suppose I will also test it on the roof of my car. A mobile antenna!

But how about that! I will also put my dipole in the grass and see how that does!!!! Everything works! BUT HOW WELL DOES IT WORK?

Richard, I am copying this to my friends who helped me test on 75 meters.

73 all, Ben

I'LL DO IT!
Well, since I had thrown the box away, it was easier to go ahead and do the evaluation myself, so, I bought a blankety-blank tuner! I feel that evaluations without comparisons made in the real world with real antennas are to be taken with big doses of disbelief. I have found that some performance claims have been made by so-called developers/authors that have never built this device. If one asks to see it, it has been taken down. It's a shame but he never took a photograph. The fact that one works a station two thousand miles away tells me that the antenna and/or feedline are radiating proves nothing unless a real world ben.jpg (5984 bytes)comparison is made. I suffer from a not-so-rare disease called "COMS".

AM I QUALIFIED?
I suppose you could say, at the least, I am certainly a well-qualified consumer of such devices and know how to hook up and operate an antenna. I have been a radio amateur for over sixty years. I have worked in Electronics for sixty-five years. I have worked on everything from crystal sets to sophisticated airborne early warning radar systems and data communications systems. I have been a Field Engineer, Supervisor of a couple hundred Engineers and have marketed communications and radar equipment for a six billion dollar corporation (sold the first RCA contract to NASA). I have also been a consultant to the U. S. Navy for data communications. AND I AM STILL LEARNING EVERYDAY! Foremost: I want to do a good job!

THE EVALUATION BEGINS
Testing was done utilizing the following equipment.
1. Hawks CTHA for Amateur Use
2. MFJ Model 259 HF/VHF SWR Analyzer
3. MFJ Model 969 De Luxe Versatuner
4. Kachina 505 DSP Transceiver (with S-Meter update modification by Kachina)
5. Fifty feet (15m) of Belden 5913 Coax
6. Welz CT-150 Dummy Load
7. Inverted Vee Dipoles at a 20-foot (6m) apex


equip.jpg (39712 bytes)The coax and connectors were tested using the SWR analyzer and the dummy load. Existing dipoles and feedlines were looked over carefully and tested with the Analyzer and dummy load. The first measurements were made with just the 50 feet of coax and the Analyzer. The CTHA measured infinity VSWR with various reactance from 1.9 MHz through all amateur bands until 24.925 MHz where a 4:1 VSWR was measured at 90 Ohms. At 28.7 MHz the CTHA measured 3:1 VSWR at 40 Ohms.

Next, measurements were made using the 50 feet of coax, Antenna Tuner and SWR Analyzer, as recommended by the manufacturer, with the following results:


160 METERS

On 160 meters (1.9 MHz) I nearly wore out the tuner. I could not get close to a reasonable VSWR. It was infinity or close to infinity. No further testing was accomplished on 160 meters. The Antenna is advertised to work from .5 to 50 MHz.

MHz

VSWR
at 50 Ohms

1.9
3.8
7.150
10.125
14.175
18.120
24.926
28.7
Infinity
3:1
2:1
3:1
1:1
1:1
1:1
1:1

Perhaps better VSWR could be obtained on the lower bands with a better tuner/coupler, different feedline lengths, and/or a better operator.

On-the-air tests were accomplished by using the VSWR Analyzer and the Antenna Tuner to get as close to one to one VSWR as possible. The coax was then removed from the VSWR Analyzer and plugged into one of the Kachina's Antenna Ports, leaving the Versatuner in the antenna line. The Kachina was adjusted for about five watts and the Auto Tune in the Kachina energized to attain a one to one VSWR into the Kachina. The various dipoles for comparison were plugged into the other of the two antenna ports. The ports were switched to obtain comparisons making sure that both antennas were one to one. All transmissions were made with one hundred watts.


puter.jpg (36493 bytes)

80 METERS ON THE AIR TESTS
Numerous signals from various distances were compared. The dipole consistently outperformed the CTHA by at least three S Units on receive. Transmissions were made to four other stations, using 100 watts output with 10-dB speech processor compression, with the following results.

Station

Distance
Miles/Km

Signal Strength

Dipole

CTHA

WA4QNO

180/290

5/9+10

S5

W4VOO

40/65

5/9+15

S5

N8FB

100/160

5/9

In Noise

KE4SN

200/320

5/6

Nothing

My 80-meter dipole is twenty feet (6m) high. The CTHA was hanging twenty feet high and oriented in the same direction as the dipole. (Not that it would matter at this frequency and height) I tried very hard to make it perform. The CTHA is a very, very poor performer on 80 meters.

The CTHA was also operated flat on the ground. W4VOO forty miles away gave me an S9+20 dB on the dipole and an S6 on the CTHA. WA4QNO (180 miles distant) Gave me an S9 on the dipole and an " in the noise" on the CTHA.

40 METERS ON-THE-AIR TESTS
Numerous signals were compared on the low end of forty meters. CTHA performance was always inferior to an inverted Vee. Both were twenty feet high. Most of the time, the CTHA was at least two S Units and sometimes as much as 3 S units down from the dipole. These stations were from two hundred to three thousand miles away. The best performance came from PY1GKA, which was at times less than one S Unit down from the inverted Vee. Also, several west coast stations were copied at one S unit down. A W7 in Tacoma, Washington was two S Units down. KA3P, Bob near Pittsburgh, gave me an S9 on the dipole and an S5 on the CTHA.

THE VEHICLE HOOD TEST
There is a press release at the CTHA website about the Dayton Ham convention of May 19, 1998:

May 19 1998
News Release

Successful CTHA Tests Demonstrated at the Dayton, Ohio Ham Convention

IAS Communications, Inc. (OTC BB IASCA) wishes to announce that successful CTHA tests were demonstrated by Larry Hawkes for the ham version of the CTHA at the Dayton Hamvention last week and were very well received.

THE FOLLOWING IS A BRIEF DESCRIPTION OF THE EVENT:

IAS Communications Vice President for Research Larry Hawkes demonstrated the ham version of the Contrawound Toroidal Helical Antenna (CTHA) at the Dayton Hamvention on May 15-17, 1998. This convention is the largest hamfest in the world, with 60-90 thousand attendees annually; the CTHA display generated much interest and was well attended by the visitors. In the demo, a 3-foot diameter CTHA was placed on the hood of a GMAC Suburban, where it was able to send and receive signals. When the CTHA was placed under the truck, it still worked, which impressed audiences and drew inquires from CEOs and presidents of antenna and electronic companies. The demo CHTAs were tuned to 7.2 MHz and 14.213 MHz, thereby replacing dipoles 65- and 33-feet long, respectively. Audience members participated in all of the tests and were also shown high frequency circuit board versions of the CTHA. This demonstration successfully introduced the CTHA to users in the ham frequency range.


ON BEHALF OF THE BOARD OF DIRECTORS

(signed)
John Robertson

President

(Note: I left the spelling of "Hawkes" as reported in the press release rather than change it to "Hawks" that appears elsewhere.)

Well, I also tried that hood test. The CTHA was operated on the hood of a Honda CRV. Signals were generally at least five or six S Units down from the dipole. W1FZY in Athol Massachusetts gave me an S8 to S9 on the dipole. I was an S1 to S2 with the CTHA. Paul said he could copy me on the CTHA but it was only because the band was very quiet.

20 METERS ON-THE-AIR TESTS
A GW3 was the same strength on the CTHA as the dipole. However, he was easier to copy on the CTHA since the noise was not as great. This was an S2 signal with the S Meter bouncing. I could not work the GW3 on either antenna. The noise was really not measurable on either the dipole or the CTHA, but I could hear it!

KD5I in Fort Lauderdale (1300) miles was the same. WB7QQM in Tacoma, WA was one S Unit down on the CTHA. WA6RGV in California was also one S Unit (-6dB) down. A W8 in Michigan, 1000 miles, was also one S-Unit down. An RU3 was the same, but easier to copy on the CTHA. Several times in switching back and forth between antennas the RU3 was better on the CTHA than the dipole. The RU3 stayed on for quite a while and I was able to hook up my five foot magnetic loop for a comparison. My Home Brew Copper Tubing LOOP, five feet in diameter, gamma matched, five feet above ground (allow for personal bias) outperformed both the dipole and the CTHA. I could not hear a G8 on the CTHA-he was S-1 and readable on the dipole. Numerous European stations were two S Units better on the dipole than on the CTHA

A K4 in West Palm Beach (1100 miles) was 3 S units down as received on the CTHA. Transmitting, I was given an S7 on the dipole and an S4 on the CTHA-down 3 S Units (18dB) on the CTHA.

W0TUT in Panama City, Florida, gave me a 579 on the dipole and a 559 on the CTHA. He said there was quite a bit of QSB and "…it is hard to get a reasonably accurate reading, but the CTHA was at least 2 S Units down from the dipole."

17 METERS
K0KNF, Dale in Slater, Missouri; was using 100 watts into a ten-element log periodic on 18.155 MHz. He was 10 dB over S9 on the dipole. On the CTHA he was an S7. Dale gave me an S9 on the dipole and an S5 on the CTHA. He said, "The Little Antenna just can't do the job."
DL3HSC was S4 on the dipole, S zero on the CTHA. Other Europeans were consistently 3 S Units better on the dipole than the CTHA, these included GW4, HB9, ON5, RU, etc.

ON4AJW, Jean in Antwerp, gave me an S8/9 on the dipole and an S3/2 on the CTHA. I received Jean S8 on the dipole and S2 on the CTHA.

15 METERS
SM7EHU, EA3DD, KA7EQU were 3 S Units below the dipole. An EA3 was worked on the dipole with a received 549. He did not hear the CTHA.

10 METERS
Numerous signals were monitored. Nearly all were four S Units below the dipole. Some were five S Units below the dipole. None were better than four S-Units. Europeans, South Americans, West Coast, and Florida were monitored. My antenna on ten meters is an 80-meter dipole, a very poor antenna for ten. I called numerous stations with zero results, using both the dipole and the CTHA. PU2WIF near Sao Paulo was working stateside stations. He was an S6 on the dipole and S2 on the CTHA. I called him at frequent intervals for forty five minutes... (whenever he would QRZ?) …with no results.

It was noticed that most signals were 3 or more S Units down on the CTHA as compared to the dipole. It seemed the CTHA was omni-directional. It was oriented vertically and twenty feet high. In looking at the CTHA up in the air, with the feedline hanging down directly underneath it, made me think: "Perhaps the CTHA is acting like a vertical with the feedline doing the work." My favorite signal generator for testing for directivity is W1AW. It is at least two hundred miles north of me and transmits a good signal into this QTH. It stays on the air long enough to run outside, swing the antenna, run back inside, take measurements, etc. etc. I could see no difference in signal strength with the CTHA oriented directly toward W1AW or at ninety degrees from it. Ferrite chokes were then installed at the antenna, midway (25 feet from the antenna) and at the Versatuner. There was no discernible difference. All other antennas were taken down and the exercise repeated. There was no difference. It appears the CTHA is non-directional when mounted vertically! I don't believe it, but I can't disprove it! I can't prove that the ferrite chokes are working, either. Perhaps that is the problem. I have also looped the coax in a five-turn loop at the CTHA feedpoint. NO DIFFERENCE!

All of the testing had been done with the CTHA twenty feet in the air and oriented vertically. I thought I had better see what would happen if I suspended the CTHA Horizontally. This was done. Listening was accomplished on eighty, forty, fifteen, twenty, and ten meters. The CTHA was always 3 or four S Units below the dipole.

CONCLUSIONS
I feel that the CTHA is a poor antenna. It doesn't even make a good dummy load because of its complex reactance! A dipole costs less, is easy to build, easy to tune (no tuner required), and will outperform it. This is another of those antennas that "works" but not very well. It's like standing a hamstick in a corner of the closet...it works...not well, but it works. If you can only use a closet for an antenna installation then it may be worthwhile.

One hundred and seventy-nine dollars plus shipping (and in some instances the cost of an Antenna Tuner) will buy a lot of wire, insulators and coax. Oh, I almost forgot. "COMS" stand for Crotchety Old Man Syndrome!

By the way, the ICOM 765, shown in the picture with the SWR Analyzer and Versatuner, was not used in the evaluation. It was the one place on my crowded, untidy workbench that I could use to place the other equipment!

Frankly though, I was surprised the CTHA did as well as it did. I will be very pleased to hear from other radio amateurs who have used the CTHA and have on the air comparison data. I will also welcome any critical advice and make good use of it, the next time around.

Editor's Note: Again to be fair, and as at the beginning above about Ben's initial reaction to using the CTHA, here also is Ben's last message after the above more extensive testing.

The CTHA is a very poor performer, BUT I got a charge out of working a couple of guys, one in Ottawa with the CTHA and feedline FLAT IN THE GRASS. Also working W1FZY in Athol, Mass. with the CTHA flat on the hood of an SUV was neat.! One thing for sure, the CTHA is different. 73, Ben

Now, let you the reader be the judge! Would you buy one based on the above experience? It should be remembered that Ben is not just an average consumer. He's pretty qualified to hook up and use an antenna! Compare his background to your own abilities if you are considering a purchase. Plus, we hope to have another review as a follow-up in the next issue of antenneX of this same device which we understand will include a further look at the claims and the patent. In the meantime, we do welcome your comments including anything you may see that may have been missed, especially if you have a CTHA and other (or similar) experiences to report.

Further, it should be noted, again to be fair, more than a half dozen attempts were made to contact the principals of IAS and Mr. Hawks for any comments they would like to make. However, no replies were received from IAS and one brief e-mail exchange between one of antenneX's team writers, Harold Allen, W4MMC and Harold was asked to keep that discussion "off the record". But, Harold also made several attempts by telephone with call-back messages left with the receptionist, but the calls were not returned. The last attempt was as late as October 22, 1999 where Harold waited all day for a call-back. Being a very capable scientist himself, Harold is quite capable of having an informative exchange with the CTHA folks. ~ Editor.

Editor's Note #2: While writing this, we have come across two more companies which appear to make some claim to the CTHA, the "New Revolutionary Antenna". Just how many Patent Holders are out there? Well, here's what the US Patent Office shows:

US5442369: Toroidal antenna
Inventor(s): Van Voorhies; Kurt L. , Morgantown, WV
Smith; James E. , Morgantown, WV
Applicant(s): West Virginia University, Morgantown, WV
Issued/Filed Dates: Aug. 15, 1995 / Dec. 15, 1992 CC
Application Number: US1992000992970
IPC Class: H01Q 011/12;

Abstract: An antenna has windings that are contrawound in segments on a toroid form and that have opposed currents on selected segments. The windings may have a helical pattern, poloidal peripheral pattern or may be constructed from a slotted conductor on the toroid. Poloidal loop winds have a toroid hub on a toroid that has two plates that provides a capacitive feed to the loops, which are selectively connected to one of the plates.

I did not find any reference to the name Hawks, so why is it called it the "Hawks CTHA"? I must admit to being confused about that. We made a Patent search but did not find any under his name.

A company appeared with the same "Revolutionary Antenna" claim as a display ad in the April 1999 issue of QST at an even higher antenna price of $289.95 versus the IAS $179.00 paid by Ben. It not only claims (at least shows on the ad) to have a "Pat. 1997" (no number), but claims the word "Stealth" as a Trademark which I thought had already been spoken for. The website www.nomosno.com/satellite shown on the ad is not found. Nomosno website only shows they sell covers for satellite dishes.

Another company has popped up also claiming the CTHA as their "Revolutionary Antenna" and makes this statement as well: "REVOLUTIONARY NEW ANTENNA RECEIVES TECHNOLOGY INNOVATION AWARD". The company, goes on to say:

Integral Technologies, Inc. ("ITKG-BB") is proud to announce that Aviation Week & Space Technology, , has selected Integral Technologies' newest antenna technology as one of ten winners of its prestigious "Third Annual Technology Innovation Award" in its May 10, 1999 issue.

Integral's Contrawound Toroidal Helical Antenna (CTHA) is currently undergoing intensive study and testing by a number of significant military, government and law enforcement organizations for use in vehicle, ship, and aircraft communications systems as well as GPS and other space-based communications devices plus cellular phones and wireless LANs. Integral's innovations have improved the conventional CTHA performance characteristics in all of these applications.

The CTHA provides significant benefits in both in size, performance, cost and form/factor in a variety of wireless applications from 800 MHz to 2.4 GHz. The CTHA for these wireless applications is realized as a printed circuit pattern occupying an area of less that 2inx2in at 800 MHz and less than 1in x 1in at 1.5 GHz (GPS application). The printed circuit CTHA eliminates the standard dipole antenna, thereby reducing the system cost and enhances the wireless system's reliability.

The CTHA antenna concept has also been developed for applications at HF, VHF, UHF frequencies In mobile field testing the omnidirectional/isotropic CTHA has demonstrated range improvements of up to 300% compared to monopole antennas and from 500 to 700% in helicopter tests. The size of the CTHA antenna is dramatically smaller than conventional antennas in these applications, for example at 150 MHz, the standard dipole antenna is 6 ft long and the CTHA is realized as a ring with a diameter of 7 inches....."

It's interesting to note that Integral Technologies, Inc.'s press release at: http://www.itechfin.com/news/in_051899.html
is dated May 10, 1998 within a few days of the May 19, 1998 press release of the above IAS Communications. It is more interesting to note that none of the three companies give out anything technically of substance and nothing at all is found at the Nomosno company site! That was not a cheap ad in QST! But, at least Integral explains it acquired the RIGHTS to the CTHA through a subsidiary, Emerging Technologies Corporation (ETC) somehow from the actual inventors and had continuing participation with the West Virginia University. This was not verified.

It's beyond the scope of this evaluation to sort out and/or verify the underpinnings of all these companies and their claims. Suffice it to say, all of these claims are certainly confusing at the very least, so, folks, Caveat Emptor! (Let the Buyer Beware!) Again, be sure to check out things carefully if considering a purchase! ~ Editor. -30-

BUY OR BUILD?
One might be better off to consider building one considering you can get all of the components at Home Depot or Lowes or comparable building supply stores in other countries. The inner tube or hula hoop is made from fiberglass reinforced water line used to make short local hook-ups from cut-off valves to faucet assemblies, and the red/black wire seems ordinary. Unlike some sketches from the site, there appears to have been no attempt to make those periodic coils around the hose.

Had they chosen to use something more self-supporting, they might have had the makings of a decent ham radio article on using hardware store materials as the foundation of a small receiving loop--but hardly more. Actually, it is not even contrawound, given the solder job in the middle, but simply a 2-turn loop that might create a 4:1 impedance factor at the coax relative to a single loop. The so-called contra-winding simply sets an average spacing between the wires that is greater than winding them in tandem. So, if you've just got to have a CTHA or want to eXperiment, consider building one!

Print/Save Article

Send mail to webmaster@antennex.com with questions or comments.
Copyright © 1988-2000 All rights reserved worldwide - antenneX©
Last modified: January 02, 2009