VE3SQB ANTENNA DESIGN PROGRAMS EN82NE
Antenna Design Programs--With surface mount technology and microcircuitry, most hams no longer build their own equipment. One area that is still open to amateurs is in antenna building. For a hundred years the amateurs have made more breakthroughs in antenna design than the professionals. We do not know all the rules so we go ahead and build the antennas anyways, Some work, some don't. We are still looking for that PERFECT antenna that is small, easy to build and is super efficient. You may be that designer. If not, you will still have the satisfaction of working that DX with a homebrew antenna.
To get you started, I have made up programs that cover the most common types of antennas and a few experimental designs. Click on the icons to download. The programs do not write to the Windows registry so just delete the files when you no longer wish to keep them. THEY DO REQUIRE THAT THE DLLS ARE UP TO DATE, SO IF YOU GET AN ERROR OR THE PROGRAMS WILL NOT RUN, DOWNLOAD THE FULL VERSION OF HF QUAD 2002 AND IT WILL INSTALL THE PROPER DLLS SO ALL THE PROGRAMS WILL RUN. Also some European machines use a comma instead of the decimal point. The program will give an error 13 when you try to compute. They require numbers like 14. 255 (14dot255) to be put in as 14,255 (14comma255). Most programs have inch and metric calculations. MOST ARE AVAILABLE ON THE 2003 AMATEUR FUNK ( German Ham Radio magazine) CD. There are few construction details here. I am a builder not a writer. If you are new to building, check out other sites for construction details. There are lots of good websites out there. Originally I started writing the programs for my own use but I decided to make them available for the amateur community. They are continually evolving as I gather new information. If you discover anything that would make a program better or more accurate, please forward the info to me. THX ahead of time.
Quads are my specialty. The Standard quad is designed from the textbook equations and is compliments of Roger Clement KC5LCA. It is designed for 50 ohms and is the tried and true method.
The HF version is my program taken from research done by W3GNR who must have spent many hours of field research to develop his formulae.
He discovered that odd number of elements perform better than even and developed the wire size scaling. No other quad program uses this information. I find this best for HF or VHF with few elements.
My version 3 ( 50 ohm error corrected Dec16/03 ) was developed from the original HF version but was optimized using two different computer modelling programs. This allowed me to tweak the original formulae for maximum gain. I also developed 50, 75 and 125 ohm feeding. See WHY QUADS for information on feeding and choice of a quad. I just replaced my original version quad with a new V3 version that is 30% smaller and almost as much gain. Gain is roughly 9.4 db for a 3 element and .9 more for each element. The gain per element reduces with large numbers. The gain is always less than a yagi with equivalent numbers but other factors still make it the better choice in my opinion..
The coaxial dipole or bazooka is the best keep secret. Made out of coax, it matches closely to 50 ohms and can be set up horizontally or in an inverted V. It is very broadband for a dipole and makes a great field day antenna.
The loaded dipole (V2) is not as good as a full size antenna but it can be used in limited spaces and even indoors.
The yagi-uda antenna is the most recognized antenna. It produces maximum gain but requires tweaking for the number of elements. This program uses different formulae for 2, 3 or multi-element designs and includes element tapering.
Verticals covers all the common types with a coil calculator built in for the antennas that require them.
.The quagi may be the best of two worlds. It has the yagis gain and the quads direct feed and signal capture. I could not find any published formula for them but only sample antennas. From these samples, and computer modelling, I developed the program. I have only built a 440mhz version which works very well but would like to hear about your results. Modelling has shown the formulae to be out a bit at the higher frequencies. For 900mhz or higher, the center frequency shifts up to 1% higher. I will upgrade the program to reflect this as soon as actual built versions verify it. Until then design the antenna for a 1% lower frequency and inform me of the results.(Updated to fix bug in metric conversion of element spacings after director number six)
The discone is most seen as a receive antenna but is under-rated. It can cover multiple bands and has more gain than verticals. This also is true of transmitting. It does have a variance across its range that can't be easily predicted so if the match is not what you want, just increase or decrease the starting range to shift the "nulls". HF versions have been built that cover many bands.
The J-POLE antenna is a quick and easy plumbers delight. Some swear by it but I am sorry , I have never heard one that worked that well. The correct method of attaching the coax is the live to the stub except for some super designs which are really dipoles next to the radiator. Here come the arguments as about half the designs attach to the radiator. This is correct for mobile j-poles. If you want to get technical, a real j-pole is feed with 200 to 600 ohms.You make the choice.The program is here if you want it. NEWS I have been informed by a local ham that the problem with bad j-poles is the fault of the builder. An old 1938 US army mil specs recommends choking the coax to prevent rf on the shield. Try coiling the coax into a 6 turn ,4 to 6 inch coil just below the attachment point. I have not tried this, but it makes sense as the coax is connected to the tuning stub and the main radiator is connected to the braid. The rf on the shield would also give builders wrong swr readings and improper tuning for the attachment points. I have heard back from enough builders that state that the choking does help whether you are attached to the radiator or the stub.
The Skyhopper was named after the first one was compared to a grasshopper . The antenna is basically a quad opened up on the bottom. This up and over, over and down design had been used in HF wire antennas. The antenna acts like a stacked pair on the vertical and a standard yagi on horizontal. The prototype for 2 meters made its first contact of over 200 miles while lying upside down on a picnic table. This lead to the discovery that it can be used very low to the ground by inverting it. This method can also be used when there is match problems due to nearby objects. A 440 version with suction cups allowed an apartment dweller to have a beam antenna stuck to his ceiling. The antenna is very forgiving of dimensions. The prototype had screws in the end of the elements for adjusting but at 2 meters, 1/4 inch changes did not affect performance. I highly recommend this for new builders. The only problem is that it fires off to the corner opposite the feed. Over the years I have seen the design renamed and modified by others, and posted on other web sites. This is the original.
Parabolic antennas are the most directional of all antennas and have the most gain. Because of their size, they are usually used for UHF and up. They are much easier to built than you think. Any long bar will bend to a parabolic arc when stressed on the end. If you mount 1 X 1 inch wood strips solidly to a center hub, a wire can be strung through loops on the outer ends. When the wire is drawn tight, the ends will curl up forming the dish.
FOR THE EXPERIMENTER
Homebrew capacitors for antennas, matchers or whatever.
If you don't have the means for measuring reactance, resistance and capactance on your antenna, the gamma program will give you a STARTING POINT for designing the gamma match.
Single line next to the tower, twin ladder line, 4 wire line and even HOMEBREW HARD LINE can be designed with theFeedline program.
Baluns are very complicated with poor designs giving very poor results. If you have some knowledge, this program will assist you in designing rf transformers and antenna baluns and ununs.
Back in the days when CB was at its height, with CBers in the millions, the antenna companies strived to build the best. Two interesting designs emerged. Avanti Antennas produced a quad called the PDL-II. This quad ,fed by 2 coax lines, was able to work both vertical and horizontal. Its "co-inductive" secret was that it used a folded dipole to feed the quad. This gave the antenna more gain than a simple quad. I modelled the program to find out how it worked. The loops of folded antenna have been replaced by V shaped elements without any changes and easier matching. This antenna is worth experimenting with . Co-inductive and PDL-II are trademarks and this antenna is most certainly covered by patents. You are allowed to build a not for monetary gain, experimental version for yourself.
The other antenna was made by Antenna Specialist who are still in business and may still produce the Super Scanner. This antenna beams into three quadrants without the use of a rotator. By using relays, a single feed line could be switched to 1 of 3 elements or to all for an omni position.The coax jumpers made the other 2 unactive elements appear to be longer and act as reflectors. Later versions grounded the inactive elements through a tuned capacitance/inductance circuit. I found that the jumpers work better at times when made of 75 ohm coax. This antenna is recommended for advanced antenna builders only as it is VERY sensitive to element length and spacing changes. Some adjusting will probably be required. This antenna and the name SuperScanner have patents and trademark restrictions.
As soon as I saw QUAD in Quadrifilar Helicoildal Antenna, I had to investigate it. Used for weather satellite reception, this omni directional antenna has everything you want. It is small in size, has a very low angle of radiation and up to twice the normal verticals gain. The program has 6 variations of the design, ( SEE PATTERNS HERE) with different formulae for each. There is no construction or matching details in the program yet, so check out qha sites on the net for this info. I built a 2 meter desk top version out of foam disks and 20 awg wire. Wrapping the coax around the 3/8 fiberglass pole about ten times was good enough to reduce the match to 1.5 over a mhz. It measures at 5.1 db gain and I can work all the local repeaters and about 15 miles simplex with the antenna sitting on the BASEMENT floor. It also appears to work like a discone on receive. Receive is good outside the band both above and below the 2 meters.
It easily hears from 137 to 174 mhz. All except the RCA version are designed to be made out of 3/8 inch tubing which is easier to work with. The dimensions are NOT designed for use with elbows or bent radius corners. Cut the tubing 1 diameter longer than the required length , flatten the ends in a vise and drill bolt holes at the correct dimensions. After assembly you may still solder the joints. Using an A/D converter hooked up between the receiver and a computer plotted out the receive pattern of the 1/2 turn .3 ratio Wxsat Qha mounted 20 feet up on the rooftop. The pattern was almost identical to the modelling results shown on the patterns page. The signal is solid from horizon to horizon ,being out only seconds from predicted passes. NEW Matching calculator for low impedance QHA ...HERE
While researching the qha, I wanted something easier for checking out circular polarization. I discovered that 70% of all commercial FM radio stations run circular polarization. Home receivers are usually horizontal while mobiles are vertical. After looking up the types of antennas they use, I came up with two designs. The first has as much gain as a QHA but is much easier to build. I recommend this to new builders as small errors will not greatly affect performance. The QHA can be rendered useless by errors of only a few millimeters. The FM station antennas use a round horizontal element which is difficult to scale and build. By changing the elements to square, the antenna scales from 500 mhz to 1 mhz and is easy to build.
The second antenna is even simpler, consisting of only two bowed elements. While not as good as the first , it still shows promise and anybody could build it. Although originally designed for 137.5 wefax reception, circular polarized antennas can make nice standby omni antennas to monitor band openings, both horizontal base, vertical mobile communications or even for a beacon xmitter.
The omniquad (V2 corrected) is a very simple but excellent standby vertical antenna. I've built many over the years but just got around to making up a program. The main advantage is the extreme bandwidth. Make all the dimensional errors you want, and it will still work. You can use wire or tubing. A broom handle ,some 1/4 dowels and under 10 feet of wire will make a 2 meter antenna. There is very little gain or pattern difference between the 3 and 4 sided versions but the 4 sided version does give a better match. It can even be used as a desk top antenna.
The log periodic antenna is the ultimate broadband beam. It can provide high gain on a single band or moderate gain on multiple bands. On vhf you can easily design a single feed 2 and 6 meter antenna. On hf the size and element diameters are usually a drawback .Wire versions are usually the answer. Although 4 bands is usually stretching it, don't be afraid to try more. I had an inverted 'T' loaded 13 element designed for 160 to 6 meters and it worked. It covered an acre ,was 120 feet wide ( 40 meters), 350 feet long (105 meters) and was suspended from 3 towers. The 1/2 mile of wire looked like a suspension bridge. The neighbours are still cautious to talk to me and the XYL doesn't want to discuss it.
Why doesn't the computer modeled antenna work as expected? It could be that the antenna is designed in free space, and you had to mount the elements to a boom to make it. The boom adds negative reactance to the elements. This not a problem on hf, a minor problem on 2 meters , very noticeable on 440 mhz and can destroy a 1.2 ghz design. Ever scale an antenna up from a lower band and have it work poorly? Same problem. This program will give element correction factors for top insulated elements and elements going thru the boom and still insulated. A second page will give correction for elements that are mechanically and electrically attached to the boom. This extra precision is adjusted for each element based on research by VK2KU and works to an element/boom diameter ratio of .08 where the standard is good only to .055. This is a bonus to SHF antenna builders where the boom is usually large compared to the wavelength.
For the Amateur Radio Astronomer, here is a planetarium chart of the 4C catalog of radio sources. Use real time or for planing a run or identifying sources you have charted.
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