Ham Radio 2000 #2

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* * * * * * * * * * * * * * * * * * * A N T E N N A M A K E R * * * * Antenna Design Programs * * * * * * * * * * * * * * * * * * * Copyright 1994, ALC Electronics By: John K. Agrelius, KM6HG Protected by Federal Copyright Laws Permission granted for non-commercial use and distribution. A N T E N N A M A K E R ========================= The programs in this package are intended to assist the average Amateur Radio Operator with the design and construction of some of the most common antennas in use today. Several antennas have been built using these programs and excellent results have been reported. Just read all the documentation thoroughly and follow the instructions and you'll have the personal satisfaction of building your own antennas. We do recommend that you use other sources of information such as the ARRL Handbook for Radio Amateurs, the ARRL Antenna Book, the VHF Handbook for Radio Amateurs and All About Cubical Quads, just to mention a few. Disclaimer ---------- ALC Electronics distributes freeware and shareware programs and data files without charging a fee. In no case do we intentionally violate any copyright request or convention. We remind the purchaser that in the case of shareware, author's rights are important. If you continue to use a program you must abide by an author's request for registration and fee payment. This supports and encourages the author to improve existing software and develop new software products. ALC Electronics and it's distributors cannot assume liability or responsibility for any loss or damage arising from the use of these programs. This product is used with this understanding by user. Warranty and Liability ---------------------- ALC Electronics does not warrant that the functions contained in these programs will meet your requirements or that the operation of these programs will be uninterrupted or error free. In no case will ALC Electronics be held liable for damages direct, indirect or incidental resulting from any defect or omission in the Users Manual, the Disk, or any other related items and processes, including, but not limited to, any loss of income, anticipated profit or other consequential damages. This statement of limited liability replaces all other warranties or guarantees, expressed or implied, including warranties of merchantability and fitness for any purpose. ALC Electronics neither assumes any other warranty or liability nor authorizes any other person to assume any other warranty or liability for it, in connection with the use of this product. CONTENTS ======== Inverted Vee Antennas ...................... Page 1 Cubical Quad Antennas ...................... Page 3 Coax Antenna Traps ......................... Page 7 Inverted Vee Diagrams ...................... Page 9 Cubical Quad Diagrams ...................... Page 10 Coax Trap Diagrams ......................... Page 13 Other Shareware Programs ................... Page 14 I N V E R T E D V E E A N T E N N A S ========================================= By: John K. Agrelius, KM6HG The Inverted Vee Antenna (sometimes called a Drooping Dipole) is basically a center fed dipole with the ends lower than the feed point. The characteristic impedance of this antenna at the feed point will vary with the height above ground, the apex angle and surrounding objects. It will generally be close enough to 50 ohms that it can be fed directly with 50 ohm coax. The apex angle (at the feed point) should be somewhere between 90 degrees and 120 degrees with 110 degrees as a good starting point. It's not too critical, just don't make it less than 90 degrees. Also, don't be afraid to use dog legs near the ends of the antenna if you don't have enough real estate. Just try to keep the feed point in the clear and as high as possible. This will improve your radiation pattern and your radiation angle. Running the Program ------------------- The program is quite simple to use. Just enter the Design Frequency and the Height above ground. The Frequency will be used to calculate the dimensions and the Height will be used to determine the approximate feed point impedance for your antenna. When the calculations are done and the dimensions are displayed you'll have 4 Choices: #1 - This will Restart the Program. #2 - This will Recalculate with a New Antenna Height. #3 - This will Print the Design Specifications of your Antenna. #4 - This will Quit the Program and Return to the Main Menu. Building Your Antenna --------------------- The support for the antenna should be made of wood, fiberglass, PVC or some other non-metallic material. A 3 or 4 foot piece of PVC pipe on top of a metal mast works OK. An all wooden mast would be better but isn't very practical for high antennas. You can use a small piece of plexiglass, maybe 3" X 5" X 1/4", at the feed point, attached to the PVC pipe for the antenna connections. Just drill a 1/4" hole near each corner, at one end of the plexiglass. This will be used for the legs of the antenna. You should also drill a couple of holes in the middle of the plexiglass near the other end to be used for mounting it to the mast. Strip the insulation off the end of one leg of the enameled copper wire for about 6 inches. Run about 4 inches of this end of the wire through one of the corner holes and making a loop, wrap it back on itself and solder the connection. Do the same with the other leg of the antenna. Refer to FIGURE 1. Connections between the antenna and the coax are made at the solder joint of each leg. Separate the shield from the center conductor of the 50 ohm coax for about 4 inches. Use some silicone glue to weather proof the coax where the shield and center conductor separate. Solder the shield to Page 1 one leg of the antenna and solder the center conductor to the other leg. Refer to FIGURE 1. NOTE - A good quality current balun could be used in place of the plexiglass to reduce feedline radiation. One thing you need to keep in mind is that the 4 inches of coax and shield become part of the antenna. This extra length was lost when you looped each leg through the plexiglass so it should balance out. BUT be sure that in the beginning you cut the legs about a foot or two LONGER than they need to be. You'll need to adjust the length of the legs for the lowest VSWR. You can always cut off the extra length when you're done. When adjusting the antenna, be sure to add or subtract equal amounts from each leg. Also, you'll need insulators for the ends of the antenna and to support any dog legs. You can use plexiglass or some PVC pipe with a hole drilled in each end. One final note - A good quality Current Balun is the best way to connect the antenna to your coaxial cable. It will improve the radiation pattern and cut down on RF radiated by the feedline. Antenna Adjustment ------------------ With the antenna in position, check the VSWR with your SRW Meter. First take a reading at the Design Frequency and write it down. Now check the reading above and below the Design Frequency. If the VSWR is Higher at the Higher frequency then it's obviously resonant at a lower frequency, so you need to shorten the ends of the antenna. When the antenna is shortened, the resonant frequency will go up. Remember, you must shorten the antenna by the same amount on each leg. If the VSWR is Higher at the Lower frequency then you'll have to lengthen the antenna. Continue to adjust the antenna until the VSWR is at it's lowest reading at the Design Frequency. The Approximate VSWR on the printout is exactly that, so don't rely on it to much. The antenna is influenced by Height above ground (and who knows where that is), the Apex Angle, any Surrounding objects and probably other things we don't even know about yet. If the VSWR is less than 2:1 across the entire band then it should work fine. Page 2 C U B I C A L Q U A D A N T E N N A S ========================================= By: John K. Agrelius, KM6HG The Cubical Quad Antenna is basically a directional beam antenna made out of wire loops. The loops are usually square and are approximately one wavelength long, with the reflector slightly larger and the director(s) slightly smaller. It has more gain per element than a Yagi, it is less susceptible to static noise and best of all the characteristic impedance is close enough to 50 ohms that it can be feed directly with 50 ohm coax. The major disadvantage is that it's pretty bulky for HF and quite a chore to build. But, it's ideal for VHF. In fact, I'm using a 5 element Quad on 2 meters at my QTH. It has great gain, a good front to back ratio, it covers the entire band and the VSWR is flat at the Design Frequency. Running the Program ------------------- The program is quite simple to use. Just enter the Design Frequency and the Number of Elements. The Frequency will be used to calculate the dimensions and the Number of Elements will be used to determine the Theoretical Gain. When the calculations are done and the dimensions are displayed you'll have 4 Choices: #1 - This will Restart the Program. #2 - This will Recalculate with a New Number of Elements. #3 - This will Print the Design Specifications of your Antenna. #4 - This will Quit the Program and Return to the Main Menu. In the next few paragraphs I'll go through the process of building a vertically polarized 4 element, 2 meter (146 MHz) Cubical Quad. It's not difficult but the dimensions are critical and you need to take your time. The same basic techniques apply to the other bands, the only difference would be that the size of almost everything would change proportionally. Building Your Antenna --------------------- The support for the antenna should be made of wood, fiberglass, PVC or some other non-metallic material. I used 2" X 2" pine for the boom and 1/2" wood dowel for the spreaders. The wire loops were made of number 18 enameled copper wire (for HF I would use number 12 copperweld). You'll also need a couple of pieces of 1/8" plexiglass about 1" X 2", a couple of muffler clamps that will fit your mast and a piece of aluminum tubing or PVC pipe about 18" long. That's it.. Take the 2" X 2" pine and using the dimensions from the printout, cut the boom. CAUTION - The dimensions are the MINIMUM length of the boom, you'll have to add a little just to be safe. I added an additional 24" because I mounted the boom to the mast behind the reflector so the antenna Page 3 was not affected by the mast. This makes the total boom length about 64" (40.2" + 24"). Now, take the wood dowel and using the dimensions from the printout, cut two wood dowels per element. CAUTION - Again, the dimensions are the MINIMUM length necessary to make the wire loops. I added an additional 2" to each spreader. This makes the Reflector spreaders 32.7" (30.7" + 2"), the Driven Element spreaders 31.2" (29.2" + 2") and the Director spreaders 29.7" (27.7" + 2"). Using a drill press, drill a small hole 1" from the end of each spreader. These holes will be used to run the wire through, making the square loops. Take one of the 32.7" spreaders and one of the 31.2" spreaders and using a saw, cut a slit on one end of each spreader up to the hole you just drilled. Using care, make the slits wide enough to slide the plexiglass into them. Drill an 1/8" hole near each end of both pieces of plexiglass. Press the plexiglass into the slits, center it and drill another 1/8" hole through the wood dowel and the plexiglass 1/2" from the end of the dowel. Refer to FIGURE 3. Attach the plexiglass to the wood dowel with a small screw and some Elmers glue. Now, using the drill press, drill a 1/2" hole 1" from the front end of the boom. With the dimensions from the printout, drill a second hole 12.4" from the first hole, and so on, until all four holes are drilled. These will be the holes for the horizontal spreaders. Rotate the boom 90 degrees on the drill press and measure 1/2" back from the middle of each hole and mark it. Drill the other four holes for the vertical spreaders. You'll also want to drill a couple of holes for mounting the antenna to the mast. I used a muffler clamp and it seemed to work OK. You may have a better way, especially if it's a horizontally polarized antenna. Drill the two holes for the clamp about one foot from the rear end of the boom. Remember, if the beam is vertically polarized then the holes for the clamp must be drilled horizontally through the boom. You'll also need to drill a small hole near the end of the boom to attach the support arm. You can now insert the spreaders in the holes on the boom. I hung the boom from the ceiling with some wire to keep it in the clear. Starting at the rear of the boom, insert the long 32.7" spreader (with the plexiglass insulator) into the hole. Moving toward the front of the boom, insert the 31.2" spreader (with the plexiglass insulator) into the next hole. Make sure the plexiglass insulators are both on the same side of the boom. Continuing toward the front of the boom, insert two of the 29.7" spreaders in the next two holes. You should now have 4 horizontal spreaders lined up with the two shortest in the front of the boom and the longest at the rear. Both plexiglass insulators should be on the same side. Using plenty of Elmers glue, center each spreader and glue them in place. Be sure to align the spreaders so that they are all parallel and make sure the holes for the square wire loops are aligned properly. After the glue dries, do the same for the vertical spreaders. Let the glue dry and put at least 2 coats of spar varnish on everything and let it dry over night. You're now ready to string the wire loops through the cross-bars. Using the dimensions from the printout, measure and cut the enameled wire to length. CAUTION - Again the dimensions are for the exact length needed, so you should add a little extra. I cut the directors one inch longer (78.4" + 1") for a total of 79.4 inches. The Driven Element and the Reflector need to be cut 4 inches longer. The extra length will be needed for adjustment of the antenna. So, the Driven Element should be 86.5" (82.5" + 4") and the Reflector should be 90.7" (86.7" + 4"). Now strip off about 2 inches of enamel from each end of the Director wires and about 6" of enamel from the Driven Element wire and Reflector wire. Feed one of the Director wires through the holes on the end of each spreader at the front Page 4 of the boom. Pull the wire tight making a square loop, overlap the two ends by 1" and solder the connection. Do the same for the next Director. Now take the Driven Element wire and feed it through each of the spreaders with the ends of the wire terminating at the plexiglass insulator. Run equal amounts of wire through the holes in the insulator, fold the wires back and wrap each one around itself a couple of times. Point the ends of the wires toward the front of the boom and solder the connection. Do the same for the Reflector. You're going to need a shorting stub on the Reflector to adjust the antenna. This can be made from a short piece of copper wire. Cut a 2 1/2" piece of number 12 copper wire and bend the ends over, making a small loop in each end. This will slide over the two ends of the Reflector wires at the insulator. Push it all the way down to the insulator for now, making the Reflector loop as short as possible. Refer to FIGURE 4. Antenna Adjustment ------------------ We're now ready to hook up the feedline, mount the antenna and make some adjustments. The hard part is over. For VHF you should use low loss cable like RG-213, for short runs you can get away with RG-8X. Separate the center conductor from the shield for about 1 1/2". Twist the length of exposed shield and tin the wire. Strip back 1/2" of insulation from the center conductor and tin the wire. Bend a small loop in the end of both the shield and center conductor. Connect the center conductor to one of the ends of the Driven Element loop close to the insulator and the shield to the other end of the loop the same distance from the insulator and solder the connections. Using electrical tape, attach the coax to the spreader and the boom, routing the coax down the boom through the Reflector loop and out the rear of the antenna. You can now mount the antenna to the mast but be careful, it's pretty bulky and fragile. This is a good time to call on one of your Ham friends, they're always eager to help with antennas. Refer to FIGURE 6 so you can understand the mounting method using the Antenna Support Arm. With the antenna mounted in position, hopefully well away from surrounding objects, you can hook up the other end of the coax cable to your SWR meter and check the VSWR. First take a reading at the Design Frequency and write it down. If the VSWR is below 1.5 : 1 at the Design Frequency you might want to leave it alone and get some signal reports from a few friends. Rotate the antenna while listening to a weak station. You should see a big difference as you point the beam in different directions. If the VSWR is too high, first recheck all the dimensions, especially the Driven Element. The total length of the Driven Element should be very close to the dimensions on the printout. For our antenna, at 146 MHz., it should be about 82.5". That includes the length of coax that was stripped back. Measure from where the coax shield separates from the center conductor, all the way around the spreaders and back to where the center conductor and shield separate. That is the total length of the Driven Element. If that measures OK, then you need to adjust the stub on the Reflector for the lowest VSWR. As a last resort, you may need to move the coax connection at the feed point. If the VSWR is Higher at a Lower frequency then you need to make the Driven Element Longer. Keep the Feed Point the same distance from the insulator for each connection to the coax. Remember, the antenna is influenced by the Height above ground and Surrounding Objects, so keep it as high as possible. Remember to solder the Reflector Shorting Stub when finished. One final note - When building a Cubical Quad with only two elements, Page 5 the characteristic impedance of the antenna will be well above 50 ohms. Their are several ways to compensate for this. Two of the easiest ways are to either decrease the spacing between the Driven Element and the Reflector (about one half of what the printout recommends) or to use a 1/4 wavelength piece of 75 ohm coax as a linear transformer to feed the antenna with. The rest of the feedline would still be 50 ohm coax. Remember, we're talking about an electrical 1/4 wavelength (246 divided by the Frequency times the Velocity Factor). For HF, the best way is to use a Balun. In fact, you should always use a good Current Balun with any HF antenna that uses coaxial cable as feedline. Page 6 C O A X T R A P S =================== By: John K. Agrelius, KM6HG Coaxial Antenna Traps are antenna traps made from coaxial cable. It's a great way to make traps. They are inexpensive to make and work quite well. With the inherent capacitance in coax all you have to do is wind it around a form to create some inductance and Bingo.. you have a resonant circuit. The trick is to make it resonant at the Design Frequency. That's what the Coaxial Trap Design Program does. Running the Program ------------------- The program is quite simple to use. Just select your Coax Type and enter the Form Diameter and the Design Frequency. When the calculations are done and the dimensions are displayed you'll have 5 Choices: #1 - This will Restart the Program. #2 - This will Recalculate with a New Form Diameter & Frequency. #3 - This will Recalculate with a New Frequency. #4 - This will Print the Design Specifications of your Trap. #5 - This will Quit the Program and Return to the Main Menu. Building Your Traps ------------------- The Form for your traps should be some type of round non-metallic material. When I made my 40/75 meter Trap Dipole I used 3" ABS, which has an outer diameter of 3.5". My Trap Design Frequency was 7.2 MHz. and my 75 meter frequency was 3.9 MHz. If you choose a Trap Design Frequency that's a little on the low side, then the coax will be a little longer than you actually need, so you'll have a safety margin. Let's go through it step by step and build a 40/75 meter Trap Dipole like mine. You'll need to make printouts for a 40 meter Dipole (Inverted Vee), a 75 meter Dipole and a Trap for 40 meters. The first thing you need to do is to build your antenna for the Highest frequency (40 meters), let's say 7.2 MHz. Using the Inverted Vee Program, the antenna would be 32.45 feet on each leg. Get your 40 meter antenna adjusted for the lowest VSWR. Now you can build your traps. I used RG-58C which was 5 Turns around my 3.5" Form and had to be 59.5" long (for 7.2 MHz). The width of the 5 Turns would be .97 inches, so I made my Form 4 inches long. That gave me an extra 1.5" on each end of the Form. I drilled a 1/4" hole about 1/2" from each end of the two Forms. The holes were used to connect the Form to the antenna. Remember, the 59.5 inches of coax is the length of the shield. It's no longer coaxial cable where the center conductor and shield are separated. I added 2 inches and cut the coax to 61.5 inches. Separate the shield from the center conductor for 1 inch at each end of the 2 pieces of coax and tin the shield and the center conductor. Wrap the coax around the Form (not too tight) and tape it off neatly with electrical tape. You can run the tape in through the form and Page 7 back over the coax. Don't cover up the ends of the coax. Now, take the shield from one end and the center conductor from the other end and solder them together. Refer to FIGURE 7. You may need some extra wire, I used copper braid. Do the same with the other Trap. You can now hook the Traps to the ends of the 40 meter antenna. Replace the insulators at the end of each leg with the Traps. Any extra wire, including the ends of the coax, that will be used to make the connection, will become part of the antenna and must be subtracted from the total length of the 40 meter antenna. I connected the center conductor to the 40 meter side of the antenna and the shield to the 75 meter side. Now you need to add the wire to the 75 meter side of the Trap to make your 75 meter antenna. This is the tricky part. There's no way to determine precisely just how much wire you'll need. That's because the amount of inductance in the Trap will be different at different frequencies, it will change with the Form diameter, the type of coax used, etc. Besides, the length of the ends of the antenna will also be affected by it's proximity to ground. All we know for sure, is that the overall length of the antenna will be shorter than a full length dipole for 75 meters. If you subtract the length of the coax (59.5") from the length of one leg of the 75 meter antenna (718.8"), this will give you 659.3". We also have to subtract the length of the 40 meter leg to get our starting point. So, 659.3" - 389.4" = 269.9" or about 22.5 feet. That's what we'll start with, and maybe a little extra to be safe. Remember, it's easier to cut off extra antenna wire than it is to stretch it, so always make it longer than you need. Hook the 22.5 feet of wire to the 75 meter end of the Trap and solder the connections on the Trap. Do the same for the other leg. Refer to FIGURE 8. Antenna Trap Adjustment ----------------------- With your SWR meter connected, check the VSWR at 7.2 MHz. The VSWR should be very close to what it was as a 40 meter dipole (before the Traps were added). Check the SWR Above and Below the Trap Design Frequency. If the VSWR is better at a Lower frequency then you'll have to shorten the coax on the Trap. It doesn't take much to make a difference. I only had to take off 1/2" from each Trap. Just take a sharp knife and cut a slit down through the shield and separate the center conductor from the shield a little at a time and recheck the VSWR. If cutting the coax shorter makes the VSWR worse, then there's a problem. Check all the dimensions, if everything seems OK then you'll have to try again with a longer piece of coax. This shouldn't happen but something could cause a problem, like the Form material, weird coax or something else we're not aware of. Once you've got a reasonable VSWR on 40 meters, you can check the antenna on 75 meters. You'll probably have to shorten the ends to get it resonant at 3.9 MHz. My antenna only needed a little less than 16 feet added to each Trap to work on 75 meters but every installation is different. Don't forget to seal the ends of the coax with some RTV. Have Fun and Good DX, John. Page 8 Inverted Vee Diagrams --------------------- _______________ | 1/4" v | *|*O<- Holes ->O*|* Wire Loop ------->* | * | * | * * |* | *| * * *| | |* * Solder Joint ---->X | V | X * s | O | c * * s| |c * Antenna Leg --->* |s c| * * | s O c | * * | s c | * * Shield ------->s c<------- Center * * | |X| | Conductor * * Plexiglass ---->| |X| | * * |______|X|______| * |X| 50 Ohm Coax ---->|X| |X| |X| |X| FIGURE 1 - Inverted Vee Connections _________________________________________________________________________ _ Plexiglass ---->|_|* * | | * * | | * PVC Pipe ---------->| | * * |-| * * |X| * Left Leg --->* |X| *<--- Right Leg * |X| * * |X| * * Metal Mast --->|X| * * |X| * Insulator --->O |X| O x |X| x String -->x |X| x + |X| + | |X| | Pole -->| |X| | | |X| | ------------------- Ground ----------------------- Ground --------------- FIGURE 2 - Typical Inverted Vee Installation Page 9 Cubical Quad Diagrams --------------------- _______ | | 1/8" Hole ------>O | | | ---------------------------------------- ( O<--- 1/8" Hole Wood Dowel ---------------------------------------- | | 1/8" Hole ------>O |<---- Plexiglass |_______| FIGURE 3 - Insulators _________________________________________________________________________ * * * * * * *<------- Reflector Loop ------->* * * X<---------- Solder Joint ---------->X* * X * * * * * * * * * * ____*__ * * _ * * | * |* *| |* * Hole ------>O* *| |*| * | | | | * ---------------------- /| |\ * Reflector ( O <------ Wood Dowel ------->( | | ) *<-- Shorting ---------------------- \| |/ * Stub | |<------------ Plexiglass ------------>| | * Hole ------>O* *| |*| * |___*___|* *|_|* * * * * * * * * * * * X<--------- Solder Joint ----------->X* * X * * * * * * * *<------ Reflector Loop -------->* * * * * Front View Side View FIGURE 4 - Reflector Shorting Stub Page 10 Cubical Quads (continued) ------------------------- .\\ . . \\ ' . . \\ ' . . \ __ ' . _._______________________| |_______________________'_ - -----------------------|\\|-----------------------.- ' . | \\ . ' ' . | \\ . ' ' |. |\\ . '<---- 2nd Director | | \\. ' Loop .\\ .| | . \\ | |' . . \\| | ' . . \| | ' . _._______________________| |_______________________'_ - -----------------------|\\|-----------------------.- ' . | \\ . ' ' . | \\ . ' ' |. |\\ . '<---- 1st Director | | \\. ' Loop .\\ .| | . \\ | |' . Driven . \\| | ' . Element | . \| | ' . Feed ---> ||.________________________| |________________________'_ Point ---> |-------------------------|\\|------------------------.- ' . | \\ . ' ' . | \\ . ' ' . | |\\ . '<---- Driven Element '| . \\. ' Loop . \\. | | . \\ | | ' . . \\| | ' . Reflector | . \| | ' . Shorting ||._________________________| |_________________________'_ Stub ---> \|--------------------------|\\|-------------------------.- ' . | \\ . ' ' . | \\ . ' ' . | |\\ . '<---- Reflector ' | . \\. ' Loop | | | | | | *| || \ <------- Muffler Clamp *| || / | | Muffler Clamp ------> *--| \ | | *\\| / | | \\ | |<------ Boom \\ | | \\ | | Antenna Support Arm ------> \\| | \|__|* FIGURE 5 - Top View of 4 El. Quad Page 11 Cubical Quads (continued) ------------------------- || || || || __ Reflector /----->|| | | / ______||_______________|__|__________________ / Muffler _|__|_ __ | Cross /-------->() Clamp -->(O_ __ _O) /O/ |<---- Boom / ______ _______________|__|_____________/ /__| / || | | / / Bar /----------->|| | | / / || | | / / || | | / / || | | / / || Mast ------>| | / /<----- Support Arm | | / / | | / / | | / / | | / / | | / / _|__|_/ / Muffler Clamp -------->(O_|__|/O/ | / / | /_/ | | | | | | | | FIGURE 6 - Support Arm Page 12 Coax Trap Diagrams ------------------ | Coax | |<----------->| | Width | ____________(X)(X)(X)(X)_______________ | |X||X||X||X| | | |X||X||X||X| | | |X||X||X||X|<--- Coax | | |X||X||X||X| | | |X||X||X||X| | | sc |X||X||X| c<------ Center Conductor | s c |X||X||X| c | (to 40 M Side) 1/4" Hole ---->O s cc***********ss c O | | s |X||X||X| s c | Coax Shield ----->s |X||X||X|sc | (to 75 M Side) | |X||X||X||X| |<---- Coil Form | |X||X||X||X| | | |X||X||X||X| | | |X||X||X||X| | |_______________|X||X||X||X|____________| (X)(X)(X)(X) FIGURE 7 - Coax Trap _________________________________________________________________________ _ Plexiglass ---->|_|* * | | * * | | * PVC Pipe ---------->| | * * |-| *<---- 40 M Side * |X| * * |X| * 40 M Trap ---># |X| #<--- 40 M Trap * |X| * * Metal Mast --->|X| *<---75 M Side * |X| * Insulator --->O |X| O x |X| x String -->x |X| x + |X| + | |X| | Pole -->| |X| | | |X| | ------------------- Ground ----------------------- Ground --------------- FIGURE 8 - Typical Trap Dipole Page 13 O T H E R S H A R E W A R E P R O G R A M S =============================================== Included in this software package are some of the best Public Domain programs related to Amateur Radio that are available today. Following is a brief description of these programs. Antenna Programs ---------------- The HF Antenna Design program in the Sub Menu is Ariel Vers. 1.7 by J. Scott Hedspeth, WB4YZA. It's an excellent program that will design a wide variety of HF antennas, T-Matches for the antennas and has some other handy utilities. The UHF/VHF Yagi Design program is ANTDL6WU by K1DPP, W1JOT and WA2TIF. It's also an excellent program and will design Yagis with up to 48 elements. The J-Pole Antenna Design program is by Marv Hayes, NF6G. It's a handy little program that will design a J-Pole antenna. The Gamma Match Design program is by N6BV and will let you design Gamma Matches for antennas. All of these guys are in the Callbook and would appreciate any support you could give them. They've done a great job, so let's encourage them to develop some more software for Amateur Radio. Page 14