Even if outdated, is still a good program to calculate and desing yagi antennas elements dimensions, sizing and spacing.
I’ve used it to verify some antenna plans I’ve found on the net.
It’s particularity is that you at first need to tell the program the size of your antenna and then, you can calculate resonating frequency, expected SWR and optimize the design.
About the project
It’s a portable dual-band antenna working principally on 10 meters but also close to the 30 meter band. It’s compact, light, economical and doesn’t need any radial.
If you would like to repeat my experiment you will first need a big plastic flower pot (around 70cm high, 60 top diameter and 30 cm base diameter).
Wind an electrical lambda (10m) (start with more than 7-8m, the length finally will be around 6.5 m) of rg58 cable uniformly around the pot and fix it with hadesive tape.
At the end of the cable (close to the mouth of the pot) solder the inner conductor to the shield; at the base of the pot solder the shield of the winded cable to the inner conductor of the rig cable. Make at the base of the pot an LC net.(C around 0-200pF,’ L around 10 coils, diameter: 5cm wire diameter: 2mm).
Insert the LC net between the inner conductor of the winded cable and the shield of the rig cable.
See the figure and the pictures.
Analyze antenna
Now you need an antenna analyser.
Adjust the cable length to obtain the best impedance on 10 meter band.? In order to tune the system better especially in the 10 meter band, tune the? variable capacitor .
Please note that this flowerpot works quite well if you install it horizontally.
by IZ0FYL
Article by VE3GK
I was assembling a HY/GAIN, TH6DXX, a 10 – 15 and 20 meter beam the other day and thought there might be some interest in the function of the traps. I have also included some practical information on how
to build traps for a multi-band, 10-15-20 meter antenna.
RESONATE PARALLEL NETWORKS REVIEWED:
When a certain amount of capacitance is connected in parallel with a certain amount of inductance it results in a very high resistance at a certain frequency. In other words this combination of inductance and capacitance results in a special high resistance resistor designed to work at a narrow band of frequencies. Other frequencies above and below this frequency exhibit the opposite condition, a very low resistance.
TRI-BAND ANTENNA ELEMENT TRAP EXAMPLE: EXAMPLE:
When a Tri-band 10, 15 and 20 meter beam is excited with 21 MHZ energy only the length of element to the 21 MHZ trap is used.
The trap is situated 1/4 wave length from the boom of a yagi and is similar to that of an open switch.
The same electric circuit is present on 10 meters. Conversely, the 14 MHZ signal perceives the 21 and 28 MHZ traps as a closed switches at 14 MHZ. The 20 meter signal and uses the whole length of the element.
TYPICAL TRAP FOR 20–15–10–METER BEAM
Please refer to the following drawings for the practical application of the parallel tuned traps that are used in multi band beams and wire dipoles. The capacitor is made by inserting one aluminum tube inside another with an insulating sleeve in between serving as the dielectric.
The capacitance should be around 25 pf. for the 15 and 10 meter bands when the tubes over lap about 5 inches.
The dimensions of the coil determine the frequency of operation. The coil is air wound from one tube to the other.
The diameter and length of the coil should be about 3 inches. Allow 7 turns for 15 meters and 5 turns for 10 meters.
Approximately number 8 aluminum wire should be used.
The final tuning should be done on both networks with a grid dip meter. Adjustments should made to the coil and capacitor to resonate the network at the lower edge of the designated band.
TYPICAL TRAP FOR 20–15–10–METER WIRE DIPOLE
The same values of inductance and capacitance apply. It is important that the voltage rating of the capacitor be in the 2 to 3 KV range. Several lower voltage capacitors could be assembled in series to make up the required voltage rating. The higher the power the higher the KV rating should be.
Remember when identical capacitors are installed in series you have to divide the value of one of them by the total number of capacitors in the string to get the total value of capacitance.
RECEIVING ANTENNAS
The K9FD Receiving Loop
The Answer To Suburban DXing On the Low Bands – by K9FD
Editor’s note: Merv Schweigert, K9FD, has been working jusl about everything on the 40, 80 and 160 meter band” this season. In this article he shares some of his experiences with receiving antennas. lf you live on a typica! suburban lot you might want to read this article carefully as you won’t need forty acres to use this antenna. A few months ago I lost access to my faim neighbor’s corn field that I used to utilize for Beverage antennas in the winter months. In the past I would erect a few terminated Beverage antennas towards the east and south to enhance my receiving capability on the low frequency bands. After losing this superior receiving capability, I set out to find some kind of replacement system that would again allow me to be viable on the low bands.
Early Receiving Antenna Trials – My first attempt at improved reception was a low dipole for 160 meters. This antenna was installed at the 8′ level. After trying it for a few months, I abandoned it as copy was typically better on my transmit antenna, an inverted L at 75′. The search for Q5 copy continued.
My next receiving antenna project was a 2 wire Beverage that is described in the Beverage Antenna Handbook, written by Victor Misek, W1WCR. This antenna is 238′ long with the wires about 6′ off the ground and utilizes a tuning network that changes the phase angle to null the noise off the rear. This antenna worked fairly well, to the south, but because of some power line noise to the north that always seemed to surface as I was trying to make a DX contact this system was also setaside.
The third attempt at improving my receiving capability was to try a
receiving loop. My information said that the loop has a terrific null off of the side and if shielded can be quite effective. The first receiving loop I tried
was made with RG-59 coax, as recommended and it did work rather well. You could rotate the loop and null the noise down to zero and still hear signals. The problem that I encountered with loop #l was that the signal strength was low and a preamp would be required to correct this condition. When you run a kilowatt in close proximity to a loop you can imagine what will happen to the preamp unless switching considerations are taken. This switching concept is certainly possible, but a more elegant solution with less complexity was tried.
The next loop I constructed was similar to the RG-59 loop except that I
used 3/4″ 75 ohm TV hardline in the construction. This cable has a much larger center conductor. I am very much impressed with the results. The signal gain is much better than the RG-59 loop and no preamp is required. This loop works well on nulling powerline noise and can also help you null out the noise produced by approaching thunder storms.
Constructing the Loop – This receiving loop is constructed from a 20′
long length if 3/4″ diameter 75 obm cable TV hardline. Form the length into a circle and using a pipe cutter, cut through the shield at the top center of the loop in two places about 1″ apart. Then, using a hacksaw, careftilly split the 1″ section from the hardline and peel it off. To strengthen this gap, place a 6″ long piece of (split) 1″ PVC pipe over the gap and secure it to the cable using a couple of hose clamps.
You can house the trimmer capacitor in either a metal or plastic enclosure. Use a grid dip meter to tune the loop for resonance on the band of your choice. I used a 400 pf. fixed mica capacitor with a 400 pf trimmer in parallel for the system at K9FD. Conclusion – In using this loop I sometimes see some directive properties on DX signals. Some publications say that the loop is omnidirectional to sky wave and only has directional properties to local noise.
I have no answer to this as it is not apparent on every DX signal. What I do
know is that the use of the 3/4″ diameter 75 ohm cable TV hardline for
constructing the loop receiving antennamakes a huge difference.
You will also find that the hardline loop will require less of a support
structure. When placing your loop in your yard try to locate it as far away from your transmit antenna and other structures as much as possible.
This antenna is not a substitute for an 80 acre Beverage farm, but if
you are on a small lot and are plagued by power line or other man made noise this receiving loop will improve your receiving capability on the low frequency bands. You won’t work all of the DX, but you will get a much bigger share than before.
THE LOW BAND MONITOR – NOVEMBER 1994
This antenna has several advantages, not least being only 1 metre diameter! This loop relies on being horizontally polarised and receives only the magnetic wave, thus as most noise in the domestic environment is vertically polarised and electrical wave, it delivers low noise to your transeiver/receiver, which makes for nice clean listening. In addition any signal arriving in the direction of the loop end on will be nulled out, this can be useful to get rid of an interfering signal by simply rotating the loop leaving the desired signal in the clear. It can be used indoors with ease and works well at ground level which is not the case for long wire/dipole antennas at shortwave wavelengths.
So what are its disadvantages? Well its tuning is critical, such that for a small change in frequency the antenna will need to be retuned at the loop end. This is even more important for transmitting where a high reflected wave (swr) due to not being tuned correctly will damage the output stage of your transmitter! In addition due to the very high “Q” of the loop, very high voltages can build up on the loop tuning capacitor even with low amounts of power from your transmitter. It is for this reason I recommend this loop is used with a transmitter of no more than 8 watts, any more and the ordinary broadcast tuning cap will arc over with spectacular results. Of course should you wish, a higher spec/bigger air spaced tuning cap would allow higher power output transmitters to be used. Also I consider the use of remote tuning using a fairly high geared motor and insulated coupling on the tuning cap essential. For shortwave listeners manual tuning would suffice.
In setting up the tuning of the loop, connect to a receiver and tune to 14 mhz. Now tune the loop which as it nears peak tuning will cause a whooshing sound. Stop the tuning you should now hear good strength signals in your receiver. For tuning for a transmitter, 1st use receive method then apply low power and fine tune loop tuning and tweak gamma match for lowest swr.
Magnetic loop dimension details
Construction Tips
Article by Bill Orr W3SAI on solving problems on 160 meters band antennas
A 2.4 GHz 10 elements Yagi antenna hombrewed.
Download the PDF files for full instructions.
Full sized images and detailed instructions are listed here
Introduction
A rotating quad for 80 meters are you crazy? well i did it and it worked well. now i’m not saying that i think anyone else be as nuts as me but it seemed to fun be idea at the time. i remember calling into a local 80 meter net on 3.755 mhz asking for a front to back check – they thought i was bananas.
General specifications:
200 ft of wire in each element with 25 foot tuning stubs, 40 ft front to back spacing, top of diamond at 135 ft, 85 ft boom as main support structure, front to back 25 db, front to side 40 db, reflector tuned to 3.6 mhz, operated as a reflector on phone and as a director on cw.
The 2 element QUAD for 80 meters with 40-ft front to back spacing and the top of the diamond at 117-feet. Note: Because the tower is telescopic the top height may vary from project to project.
The photo below, shows the quad on it’s way up to 125 ft. Note the wires drooping with the tower about half way up. The end elements at each end will be pulled up with the antenna wire when it reaches full height..
The 2 element QUAD for 80 meters with 40-ft front to back spacing and the top of the diamond at 117-ft.
Copy rights, original project and pictures by Gerry King VE3GK
Dear Fellow Hams
Here are the numbers for the Copper Cactus J-Pole antenna!
I hope you are already familiar with the construction of the standard J-Pole antenna, so I won’t go into any unnecessary detail.
The antenna may be built as a MonoBander, DuoBander, TriBander, QuadBander or whatever with great success.
You can either feed it with separate coax’s for each band or a single coax, however, separate coax’s make it much easier to tune.
Theres no trick to building them, just remember the overall length is for the lowest frequency of operation. In other words, a MonoBander, DualBander and TriBander are all exactly the same length overall 58.09″ on 2mtrs.
Feed the coax up the center of the pipes. Use T-Fittings at the proper distance below the top of the antenna for the desired frequency. The only problem is that the more bands you try to incorporate into the antenna, the harder it is to get the SWR flat on all bands.
Here are the numbers you are looking for:
Frequency 52MHz 146MHz 223.5MHz 435MHz 912MHz 1265MHZ
Pipe Dia. 1" 3/4" 1/2" 1/2" 3/8" 3/8"
Stub 54.70" 19.36" 12.65" 6.46" 3.02" 2.16"
Overall Length 163.92" 58.09" 37.94" 19.39" 9.07" 6.49"
Separation 5" 2" 1-1/4" 3/4" 1/2" 1/4"
Connect at 6" 2-1/4" 1-1/2" 1" 3/4" 1/2"
For best results, build the highest band first, for eg. the 435MHz antenna, If you really want it to look neat, use 3/8″ copper for the vertical and 1/4″ copper for the transformer section (stub). Naturally the finished product will be in the shape of a “J”.
Now build the next band, for eg. the 223.5MHz antenna, by adding pipe to the T-connector that is the base (mast mount) of the 435MHz antenna, I use 1/2″ for the vertical and 3/8″ for the stub of this section.
Now build the 146MHz antenna, don’t forget the overall length of the antenna is the lowest frequency you will be using. I use 3/4″ for the vertical and 1/2 for the stub.
The stub must be parallel to the vertical, however you can point the base of each stub in any direction you like. I prefer 3 equal distant points, but you can make them all on the same side if you wish. I feel the three points make it look like a cactus.
My measurements on overall length, and stub length are from the centerline of the separation pipe (horizontal) to the top of the antenna. The Separation distance is technically from centerline to centerline, but inside measurements are fine and visually look better.
Some of the measurements are less than physically possible, in this case just push the T-Fitting and elbow as close together as you can get them, no need to trim the fittings.
The Connect at measurement is from the top of the horizontal member to the point of connection.
Final Note: If you use 1/2″ pipe for all the construction, on the 2-meter stub, add 1/4″ to its length, or use pipe-caps and adjust them up or down to get the 1/4″ additional length.
The antenna should be in perfect tune, SWR less than 1.2 – 1 on all bands, using separate coax for each band.
Solder all the joints before installing the coax, any pipe you have left over can be used as the mast.
To install the coax, drill a 1/4″ hole in the top of the horizontal part of each T-fitting closest to the vertical, then tilt the drill at an angle, so that the drill bit is sorta heading down the vertical.
Enjoy Building: If you have any questions just ask, or further instructions, just send me a message and I will promptly respond.
PS Until you are familiar with the construction techniques of the J-Pole, I wouldn’t attempt any more than three bands the first time out. In fact, A dual-bander, using the above dimensions will be perfect every time.
73s de Gary – KGØZP
Document Revision Date 2/26/98 Applicable To This Page Only