Build a double bazooka antenna k3dav version by david k3dav. An interesting point is to compare the lengths specified by john against the formula for a 14 wave element at 52 mhz 70 mm long 30052 x 0. To help secure the coax put another wire tie an inch or two below the. The center lead of the coax forms one half of the dipole and the braid forms the other. These coaxial dipole antenna are sturdy, rugged all weather model, enclosed in a abs radome, uses 6063t6 ultra corrosion resistant architectural aluminum alloy and does not require any field tuning or adjustments. Electrically it is very different to a conventional dipole. The dipole antenna is said by many to be the perfect antenna for a specific frequency. Aug 2001 qst copyright 2009 american radio relay league. The balun, operating for a frequency range of 180 to 400mhz, is made using a pair of rg58cu coaxial cables and is integrated with a simple dipole antenna. Antenna geeks rejoice you have another great antenna web site to visit during your next armchair browsing session. But to be strictly correct, that antenna is a dipole only at the lowest frequency of use. Nov 05, 20 dipole antenna made from the rtlsdr stock antenna cable. The loaded dipole v2 is not as good as a full size antenna but it can be used in limited spaces and even indoors.
While it is difficult to estimate the actual coaxial cable trap ratings, i. Centerfed dipole antennas range from 29 to 47 inches in height and. The thin wire runs through the center and of course. If you want to use a dipole for a band of frequencies, you cut it to the center frequency on that band, and hope it has a low enough swr at each end of the band.
But if youve never done it, you probably have a few questions. Feeding dipole antennas androscoggin amateur radio club. Walt maxwell, w2du, put it succinctly10 when he said that a baluns primary func tion is to provide proper current paths. Note that the dipole element pointing up should be connected to the center conductor of the coaxial cable. I came across the website of derek hilleard, g4cqm, containing a wonderful assortment of details to help make your next yagiuda project antenna a success. Since we tend to feed the dipole with coaxial cable, we are concerned with the antenna length and resonance. Since its original conception as a uhf 460mhz antenna for unmarked police vehicles, this planar and transparent. It is always good practice to use a one to one current balun on a single band dipole connected to coaxial cable. Just what is a dipole antenna, and why are they so popular. A more practical dipole is the halfwave dipole referring to the fact that it is 2 long. The doublebazooka antenna broadband dipole using coaxial construction by charles c. Pdf this paper presents the design of a calculable standard dipole antenna with a hybrid balun in. Pdf the antenna is a key component for reaching the maximum. The above versions need some sort of matching to enable use at 50 ohms.
Antenna broadband dipole using coaxial construction by charles c. Material 34 inch pvc pipe cut dimension a to b 23 or more. An improved multiband trap dipole antenna hamradio. Bonnie crystal was granted the us patent 7,151,497 coaxial antenna system on december 19, 2006 after filing in 2003 for new types of coaxial antennas with reduced size providing efficient broadband, wideband and controlled bandwidths, using radiation by the outside of the coaxial elements. Vhf uhf coaxial dipole antenna resource detail the. Pdf development and analysis of coaxial slot antenna in. A more robust construction can be achieved using tubing for the elements and moulded dipole centre boxes, available from a number of amateur radio antenna manufacturers and at radio rallies. You will need a center insulator for connection of the two quarter wave elements and the coaxial cable. Multiband antenna design parallelresonant circuits called traps are widely used to isolate parts of multiband antennas to make the antenna resonant on different fre. Coaxial antennas are easy to construct, naturally adapted to a coaxial in put connection, thus. Many antennas are based on halfwave dipoles fabricated from wire or tubing.
Abstracta small sleeve dipole antenna sda for a suppressing leakage current on a coaxial cable is presented in this letter. To achieve these design considerations, i concluded my 6 m dipole antenna shall be be made from rigid aluminum elements, supported at its center on a single mast, utilizing a strong, light. Gets its name from its two halves one leg on each side of center each leg is the same length its a balanced antenna the voltages and currents are balanced across each leg does not need a counterpoise or ground radials at resonance, the total antenna length is onehalf design frequency wavelength. An attic coaxial cable trap dipole for 10, 20, 30, 40, and 80 meters john deg00d nu3e nu3e a abstract 15, a coaxial cable trap dipole antenna installed in the attic provides a surprisingly effective solution to iif. An endcenterfed vertical dipole behaves like a centerfed vertical dipole zo 70 ohms, so 75 ohm coax is the best match top half is. The vhf dipole antenna at vhf and uhf, most antenna systems are derived from the dipole or its complement, the slot antenna. This antenna is for vertical polarization via ground wave and longhaul ionospheric propagation, and requires just one point of suspension. The original version 19992003 used a tconnector instead of a power combiner and did. Simplicity and effectiveness for a wide range of communications needs are. Pdf the design of calculable standard dipole antennas in the. About vhf uhf coaxial dipole antenna the resource is currently listed in in a single category. The bottom folded over coax shield is 34cm and the upper part of the antenna is currently 55cm.
A more practical dipole is the halfwave dipole referring to the fact that it. Antenna here is a dipole youve probably heard this phrase in many qsos. A good design can provide bandwidths of 10 to 1 whereas coil coaxial baluns can provide bandwidths of 2 or 3 to 1. Uhf coaxial dipole the laser clear transparent antenna is an innovation bought about by the need for discreet and high performance antennas used on wireless communication systems. The dipole coaxial line has the jacket removed from a central portion thereof to expose the outer conductor which is there severed and spread apart to form a gap exposing the dielectric layer, the lengths of coaxial line on each side of the gap comprising dipole elements. Extended double zepp longer than a dipole 58 wave or longer. Endfeeding a horizontal dipole this feed method also works to centerfeed a horizontal dipole from one end for example, a dipole suspended near the window of an upper floor shack in a house, apartment building, or hotel, with the other end suspended in a tree resonant z of this antenna would be the same as.
Coaxial traps for multiband antennas, the true equivalent circuit. Endfeeding a centerfed vertical dipole jim brown k9yc. The dipoles are electromagnetically fed by planar slots, formed on a 50. 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. While it is difficult to estimate the actual coaxial cable trap ratings, i have tested notes appear on page 17. You will note the bottom half braid section of the coaxial dipole antenna is considerably shorter than a 14 wave length most likely due the velocity factor of the cable. The antenna is designed to be fed with 50 or 75 ohm coax cable of most any length with a balun. An improved multiband trap dipole antenna you need thistraps with lower loss, higher q, increased powerhandling capability and fourband coverage. The broadband doublebazooka antenna how broad is it. The sleeve dipole is simply a dipole antenna where one leg is a tube so that the feed line reaches the feed point through the tubular element, instead of at right angles to the elements. One of the more interesting features is the braid itself. The g5rv antenna is a dipole antenna fed indirectly, through a carefully chosen length of 300.
Tuning help for a 2m coaxial dipole antenna radioreference. The original ed fong dual band vhfuhf 70cm2m jpole pvc pipe antenna. An antenna balun blocks undesirable currents on the outside of a cable. Since coaxial antennas extend along a straight line. A truly broadband, efficient low band dipole 2 w7zz and n6ry, c. Analysis of coaxial stub type balun fed dipole antenna ieee xplore. The desired operating frequency of the antenna was 220 225 mhz, and the desired input impedance was 50. The coaxial dipole or bazooka is the best keep secret. The dipole antenna can be erected in different ways, in. Making a coaxial dipole if you start with a common half wave. Sota 6m 52 mhz coaxial dipole antenna get out of the. For a more complete list, see the advertisements in this and other issues of qst. The antenna shall be reasonably inexpensive compared to the cost of a similar size wire dipole antenna.
The measurements below are for building a simple dipole antenna. One side of the antenna element consists of a hollow conducting tube through which a coaxial cable passes. Antenna here is a dipole american radio relay league. Development and analysis of coaxial slot antenna in comparision with coaxial dipole antenna for interstitial microwave ablation. By al buxton, w8nx this improved multiband trap dipole introduces a new trap design and a change in trap location. Complete text article will be published soon in the pdf format that will include background and a bit of theory how i came to idea to design this simple to build antenna. Feb 21, 2018 i am trying to tune a coaxial dipole antenna that i built from some rg58a as a portable 2m antenna for my ht. If a dipole antenna is fed with a coaxial cable from the transceiver, it is always necassarry to use a balun. Building a resonant feed line dipole for 2 meters by n5boy. Sleeve dipole antenna design and build in compliance. The dipole is a balanced antenna and the coaxial cable is an unbalanced feed line connected to an unbalanced transimitter output at least in modern rigs. Both these facts are a result of the electrically small nature of the antenna.
More than this length, much of the signal almost half is lost in the cable. Build a double bazooka antenna k3dav version by david. The main category is antennas for vhf uhf bands that is about antennas for vhf and uhf radio bands. Coaxial antennas with properties similar to those of a twowire dipole antenna are presented and analyzed. The sloper antenna is a slanted vertical dipole antenna attached to the top of a single tower. The resulting antenna has a low radiation pattern and an impedance of 55 60 ohms. Wire antennas for the beginner every ham knows how to make and install wire antennas.
Diy 7 mhz wx sat vdipole antenna this is a short version, the final of the article describing how to build the weather satellite 7 mhz vdipole antenna. Ver2calwireantenna actuallyaver2callyorientated resonate12wavedipolewith theearthbeingthe return half duetopoorground conduc2vitya. For example, an 80 meter dipole cut according to the formula, hung at 80 feet and. Apr 16, 2019 coaxial dipole driver for yagiuda antennas. A dipole antenna and a feedline therefor both formed from coaxial line.
Coaxial traps for multiband antennas, the true equivalent circuit by karlotto muller, dg1mft a new perspective on the analysis and design of this popular antenna element. Cd series coaxial dipole antennas are omnidirectional antennas for vertically polarized waves. Signal is also lost in the coaxial cables used to connect the antenna to the transmitter or to the receiver, and this. The values of the equivalent parallelcircuit components of the dipole impedance at 3. An attic coaxialcable trap dipole for 10, 15, 20, 30, 40. Many would be familiar with the traditional folded dipole made from tubing or wire, and possibly the. Ive never made an antenna before so i started with an upper length of 66cm and the. I am trying to tune a coaxial dipole antenna that i built from some rg58a as a portable 2m antenna for my ht. Homebuilt ve3sqb coaxial dipole antenna aka double bazooka the first hf antenna i put up was a coaxial dipole, the concept was developed by mit. Antenna, ve3sqb ham radio antenna design software programs. A coaxial antenna is a variant of the dipole antenna, designed for use with an unbalanced feed line. The shield of the cable is connected to the end of the tube at the center of the radiating element.
By folding an electrical quarter wavelength of braid back over the insulated coax we are forming both a dipole and a bazooka sleeve balun, a coaxial 1. Eznec models of dipoles from the standard formula, fed directly with 50 ohm coax blue line or series matched purple line. The antenna itself is an offcenter fed vertical dipole made by flipping a quarter wavelength of braid back over the outside of the coax. To put a loop on your antenna first tune it to the lower end of the band, lowest swr at about 144. A coaxial dipole antenna includes a first radiator which is approximately one quarter wavelength long.
A second radiator exhibits length less than one quarter wave length and is coupled to the feed port by a reactive element which has an electrical reactance which is insufficient to increase the electrical length of the second radiator to one quarter of the wavelength. Dipole antenna made from the rtlsdr stock antenna cable. Pdf design of a 600 mhz dipole antenna researchgate. The antenna wire and coaxial cable parts of the jove antenna system are the same. Why you need a current balun 15 dec 2014 3 va7jw antenna impedance matching coaxial cables typically have a 50 ohm characteristic impedance, which turns out to be close to the radiation resistance at the feed point of a dipole antenna. Us4504834a coaxial dipole antenna with extended effective. If a dipole antenna is fed with a coaxial cable from the transceiver, it is always a good idea to use a balun. Many would be familiar with the traditional folded dipole made from tubing or wire, and possibly the lightweight version made from 300 ohm ribbon cable. One of the members commented to me that i should write an article about collinear arrays so that we could all build our own. Volume 7 antennas and wave propagation navedtra 14092. It is made of two pieces of lucite bolted together to form a mechan ical support and protect the joint from the weather. Build a 9 db, 70cm, collinear antenna from coax by n1hfx recently the rason technical committee was hard at work at the repeater site repairing our 2 meter repeater antenna. This enables us to adapt an unbalanced fed system coaxial cable to a balanced antenna system dipole antenna.
The antenna has been previously described as an easily trans ported portable antenna when made from a piece of coax cable. A novel high gain printed dipole array antenna for omni directional coverage is presented. Halfwave dipole page 1 halfwave dipole the dipole we have studied so far is not terribly useful, since it is not very e ciency and di cult to impedancematch to. The coaxial dipole antenna is designed for use in the uhf range, with an rf. Bus healy, nj2l assistant technical editor ipole antennas have been widely used since the early days of radio. Bending the loop effectively shortens the antenna and should bring the point of best swr up to something close to 146.