The standard j pole antenna has about a 30 degree vertical angle of radiation while the modified j pole called the slim jims angle of radiation dips down towards the horizon an additional 910 degrees, giving the slim jim additional apparent gain over the j pole. A slim jim antenna is basically similar to a jpole design, but it exhibits a lower radiation angle in the range of 810 degrees on the horizon, compared to 12 wave jpole which exhibits a 2030 degree angle on the horizon. Slim jim, by his definition, is any halfwave dipole antenna fed with a quarterwave stub with the feedline across a portion of the stub to find an optimal impedance this includes the traditional jpole, zepp, etc. They work great for amateur radio, public safety, scanner listening, business band, and gmrs purposes. As with all folded dipoles, the currents in each leg are in phase, but in the matching stub they in phase opposition, so little or no radiation occurs from the matching section. This makes them a good choice as an antenna for low to moderate elevation levels and would be a great choice as a remote base or receive antenna on a repeater system. Apr 30, 2017 the national film board of canada for the canadian air forces great explanation of propagation. The slim jim antenna has a higher resistance of irradiation, and can give better performance for it.
The slim jim version of the jpole arose after amateurs discovered that they could construct the antenna from a single length of common tv parallel transmission line or ribbon cable. There is also an analysis of radiation pattern, gain of the antenna, directivity of the antenna, electric far field. Pdf comparative analysis of slim jim antenna for ham. Can anyone recommend a 2m 70cm to use in an apartment. The introduction of slim jim antenna doesnt help those issues. The slim jim vertical angle of radiation is almost parallel to ground so maximum radiation is where it is needed. The slim jim, designed by the late fred judd, g2bcx, can be a great portable roll up antenna, if made out of 300. Jpoles will certainly work well as a repeater antenna. The main category is antennas for 2 meters band that is about antenna projects for 144 mhz. The superj variation of the jpole antenna adds another collinear halfwave radiator above the conventional j and connects the two with a phase stub to ensure both vertical halfwave sections radiate in current phase.
Judd found the slim jim produces a lower takeoff angle and better electrical performance. The slim jim retains the same difficulttocure common mode problems, and has the same pattern unpredictability, as a jpole. For example, the ubiquiti sector antenna am5g19120 has its antenna properties defined as seen in this link. It has two electric poles charged positive and negative. The following instructions may help you if you decide to try the slim jim antenna with aluminum tubing.
The included diagram illustrates that the vertical angle from the sj is 8 degrees, while the common 58th wave ground plane antenna is about 32 degrees. The slim jim is functionally just a jpole with one difference. The top section is altered by having a very closespaced conductor in the top element. Jpole antennas including the slim jim have very poor decoupling from the antenna to the coax and its recommended to use an effective choke near the feedpoint.
I currently have a 14 wave antenna up in a tree 22 feet high, it works great, but im still unable to reach some local repeaters or reach certain areas home to car around my area. Qantenna is able to show antennas in a 3d plot, and calculate its radiattion pattern. It uses a matching system similar to jpole antenna. Plus the antenna also have the great low noise floor and wide bandwidth typical of our other antennas. This link is listed in our web site directory since wednesday feb 23 2011, and till today 2 meter slim jim antenna from ordinary wires has been followed for a total of 4978 times. On my site you can find both the all copper 2 meter jpole antenna and an all copper 2 meter slim jim antenna. Refer to the slim jim antenna project for more details if needed. Liveagent boasts the fastest chat widget on the market and has over 150m endusers worldwide. Frequency mhz velocity factor see text vf actual wavelength inches wavelength considering velocity factor inches a.
The program provides ability for changing the language of signs and messages of the program. Slim jim antenna vs 14 wave ground plane results posted in technical discussion. Moreover, the radiation patterns are almost omnidirectional in the. Let me start by saying that since discovering the slim jim antenna design i have. It has a folded dipole design that gives it more gain and a lower angle of rf radiation, 7 degrees, vs 20. The dimensions quoted in the diagram have been used successfully by some constructors, whilst others have found it to be offfrequency by a few megahertz. Is there any software that enables me view antenna radiation patterns in 3d by simply using the information in say the. These two features of the antenna gives you about twice the gain as a standard jpole. Pdf ham radio applications demand antenna design with an aim of achieving. They have an omnidirectional doughnut shaped radiation pattern.
Vortex antenna systems radio communication antenna. Slim jim is a special wire antenna which has impedance selectivity of 50. Slim jim and j pole calculator american version m0ukd. For hello spiceheads is there any software that enables me view antenna radiation patterns in 3d by simply using the information in say the. As we will see below, the slimjim antenna performs admirably in both simulations and chamber measurements. My antennas have a low noise floor and a beautiful omnidirectional radiation pattern. The best yagi uda antenna modelling software today i want to share with you a great yagi uda antenna modeling software for amateur radio operator and enthusiast. The fact of the matter is this antenna design will function like a jpole, no better, no worse.
Both are great antennas, i dont have a problem recommending either of them as the foundation for a amateur radio base station. Enhanced machine controllerbased antenna range emcar emcar employs linuxcnc based machine control coupled with open source software to implement a measurement system for antenna radiation pattern data i. A slim jim antenna is basically similar to a jpole design, but it is supposed to exhibit a lower radiation angle in the range of 8 degrees on the horizon, compared to 12 wave jpole which exhibits a 20 degree angle on the horizon. I have used this antenna made by nelson antennas on ebay on many occasions over the past 2 years. In any illustration, the sketch drawn to represent the radiation of an antenna is its radiation pattern. Construction details are available for registered users. Measurements for the target frequency 145mhz and 50. My workshop under the garage needed to have a separate antenna, preferably hung from a nearby tree. Describe your experience with the slim jim portable 2 meter antenna by n9tax and tell us why you give it the rating you did required. See the pattern and antenna currents on the same color 3d display as the antenna. The vertical angle from the slim jim is about 8 degrees, while the common 58th wave ground plane antenna is about 32 degrees. Minimum swr on 70 cm is very low and the 70cm elevation radiation pattern shows a strong low angle pattern much like the regular 2m slim jim or a jpole, directing much of the energy toward the horizon and is virtually omni directional.
This makes the 2 meter slim jim antenna a great solution for repeater sites, data and packet stations, aprs, and even every day. The omnidirectional radiation pattern and higher takeoff angle makes it easier to get a signal out if you are surrounded by buildings or rough. So i have been looking at high gain base antennas but they are all to tall, so i decided to make a slim jim and do some testing with. Its called a slim jim, and is made out of a length of twin lead wire. Keywords microstrip, patch, antenna, slit directivity of the antenna, electric far field 1. This antenna is made from a length of 300ohm ribbon cable, which makes it easily portable, but you have to devise some method of suspending it.
Apr 07, 2014 download antenna radiation diagram plotter for free. Notes on the original slim jim antenna by dave coomber, m0uxb. Because jpole and slim jim antenna designs share virtually identical common mode and repeatability issues, either one can beat the other. One can simply understand the function and directivity of an antenna by. Radiation is the term used to represent the emission or reception of wave front at the antenna, specifying its strength. The slim jim has a lower takeoff angle and more compressed radiation pattern. Pdf comparative analysis of slim jim antenna for ham radio. The resource is currently listed in in 2 categories. Ive been producing these antennas professionally for nearly a decade now and have sold over 15000 units. The azimuth radiation pattern is essentially omni directional. As with all folded dipoles, the currents in each leg are in phase, whereas in the matching stub they in phase opposition, so little or no radiation occurs from the matching section.
Three source files plain text can be loaded and plotted at the same time. The simulations results are obtained by using electromagnetic simulation software called feko software are presented and discussed. Aug 19, 2015 these agree well with the real jpole and 2bcx antennas measured in a real antenna test chamber in figure 2. A little more gain will make up for some of the feedline losses youll receive at vhf frequencies. Jpole and slim jim antenna frequently asked questions faq. Making a basic slim jim 2m antenna the slim jim is probably one of the cheapest and easiest antennas to make, and its a very handy one too. The great thing about jpole antennas is their simple design and excellent performance. For best results, to say nothing of the radiation angle, it is best fed balanced. The elevation radiation pattern is at a maximum at a very low angle, with most of the energy below 45 degrees and a calculated gain maximum of 5. My main shack location has a commercial 2m jpole dual band mounted on a short mast. My slim jim antenna is a perfect choice for a repeater. Slim jim style jpole antenna s have an omnidirectional radiation pattern and a low angle of radiation when vertically polarized. I used half inch od junk aluminum tubing cut to these final lengths. The n9tax slim jim antenna is the highest quality roll up antenna available today.
I decided that to simulate a typical 2 meter setup i would run the model with an antenna height of about 3 wavelengths above the ground, a typical height for a 2 meter set up. Slim jim antenna category is a curation of 25 web resources on, 2 meter slim jim antenna, slim jim vs jpole, dual band slim jim. Many users of the slimjim participate in the bewilderment as well. The most interesting part of the software is, it can help you to improve your design by projecting the antenna radiation pattern and estimating the radiation resistance. Eplane gain measurements of j antenna with respect to reference dipole.
The slim jim, similar to the jpole, is in fact a half wave end fed dipole, in the slim jim s case, an end fed folded dipole. This in itself says something about the dedication i have to creating a quality product. Its radiation pattern is close to that of an ideal vertical dipole because it is endfed. The slim jim afaik is just a jpole made of twin lead. Slim jim antennas have two very desirable characteristics. Other useful information would include your experience with similar products, infomation on a product that you would purchase instead of this one, and so on. Made with care, the slim jim is capable of a performance superior to the jpole and the radiation angle is reduced to about ten degrees which is often enough for a couple of s points at times. At this point its pretty crystal clear fred judds 2bcx slim jim antenna doesnt offer anything special compared to a traditional jpole antenna. Most people make these for 2m use, but you can make them for 70cm use if required. Most of the slim jim antennas i have seen have been built for 2 meters, the jpole example from mmanagal is for 28. Real measurements of a slim jim antenna and traditional jpole antenna reveal the truth about their respective gain and pattern. Various internet claims the slim jim has significant gain over other similar function antennas.
I was able to contact a few repeaters, that are around 45. The antenna is end fed and generally has an omnidirectional radiation pattern although there is a slight bias in directivity towards the stub side of the array as shown on the eznec simulation. Comparative analysis of slim jim antenna for ham radio applications. The result is that more of your signal gets out lower vs the other antenna types that sends more of it up into the clouds. With all ground planes, including those with radials a wavelength long, the vertical angle radiation is tilted upwards at an angle of 30 degrees or more. The halfwave section is then folded back on itself towards the stub at a distance of approx 0. Thats the reason slim jim antennas are usually described as having more gain. Aug 26, 2015 the slim jim, similar to the jpole, is in fact a half wave end fed dipole, in the slim jims case, an end fed folded dipole. Using an example model from the eznec files with 45degree radials elevated 5 wavelengths, the dipole was compared to the slim jim model. The slim jim antenna the slim jim is a vertically polarized omnidirectional endfed antenna having considerable gain and this is concentrated almost parallel to ground toward the horizon rather than skyward making it more efficient than a ground plane type antenna by about 50 percent better. The basic difference between a standard j pole antenna and the slim jim j pole antenna is the radiation pattern and the vertical angle of radiation. Judd found the slim jim produces a lower takeoff angle and better electrical performance than a.
Antenna design calculators category is a curation of 83 web resources on, magnetic loop excel sheet, parallel square conductor transmission line calculator, analysis of antenna mast strength and bending stress. Since the vertical angle of radiation is so narrow, about 8 degrees toward the horizon, it usually out. It has a radiation pattern peaking between 5 and 8 degrees above the horizon. Initially, builders cut one wire at the top of the matching section and stripped away the wire.
Searching the internet turned up the slim jim design, described by fc judd. Some notes on the slim jim antenna dave coomber m0uxb, uk introduction. D needs to be fine adjusted for the 50 the given value is accurate in theory, however, since we cannot build a perfect antenna, the. The standard of comparison vertical antenna is a vertical 14 wave dipole with a ground plane. I note that the plots of the radiation pattern in the article have no marked scale. The slim is an endfed folded dipole antenna that has a gain of 6 dbi and a nice low rf take off angle. The slim jim variation of the jpole antenna has characteristics and performance similar to a simple or folded halfwave antenna and identical to the conventional jpole construction. The double wave and inphase signal pulls the angle of the radiation pattern downwards towards the horizon with a slight elongation, hence the claimed horizontal gain of 6db over the jpole. It was described by the late fred judd, g2bcx, in the uk magazine practical wireless and subsequently in other journals and books.
Our uhf slim jim antenna delivers up to 6dbi of gain on the 440 470 mhz uhf bands, which is almost twice the gain of a jpole and 5 times the gain of a 14 wave groundplane antenna. Contact attempts to a certain copper pipe 6 db slimjim maker remain unanswered. Understanding why slimjim antenna aficionados hype the gain in their marketing. Nov 10, 2014 most of the slim jim antennas i have seen have been built for 2 meters, the jpole example from mmanagal is for 28. Why is the slim jim so much more efficient than the popular 58 wave or other ground plane antennas, despite the latters claimed 3db. The vortex slim jim antenna consists of a single element, one half wavelength long radiator with a quarter wave parallel feedline tuning stub. It is this and this alone that makes this one of the best terrestrial communications antennas i have ever seen for the price. It is estimated that the slim jim appears to have about 6db gain over a 58 wave antenna due to the extreme low angle of radiation. It is the most effective antenna when compared to other ground plane antennas. The bruteforce allcopper or brass, or aluminum, or whatever is also a really silly antenna, as it takes up another 14wavelength vertically as a matching section which does nothing to provide radiation or performance. Solved software for viewing 3d antenna radiation pattern. The farfield pattern of an antenna may be determined experimentally at an antenna range, or alternatively, the nearfield pattern may be found using a nearfield scanner, and the radiation pattern deduced from it by computation. Slim jim antenna vs 14 wave ground plane results technical.
A slim jim has a different radiation pattern than a quarter wave, half wave or jpole antenna, with a lower takeoff angle. This morning i try out a new antenna for the 2 meter ham radio band. Slim jim j pole 2 meter 440 vhf uhf ham radio antenna 24ft. Authentic n9tax vhf slim jim jpole 2 meter antenna roll up jpole use with baofeng. The 2 meter slim jim copper tubing antenna project by richard ke5fxu sk updated 1162012 credit for the original design goes to f. Mar 31, 20 a slim jim antenna is basically similar to a jpole design, but it is supposed to exhibit a lower radiation angle in the range of 8 degrees on the horizon, compared to 12 wave jpole which exhibits a 20 degree angle on the horizon. Antenna radiation diagram plotter polar plots of measured em emission, with a proper radial axis scaling and span. Since its publication in 1978, the slim jim aerial has been built by many uk amateurs. Aug 20, 2014 with twice the gain of a standard jpole antenna, the 2 meter slim jim antenna is a jpole on steroids. Judd, g2bcx get that signal lower to the ground for better performance. A vertical wideband antenna for the 27mhz 11m band. If you decide to make a 2m antenna, youll end up with 1.
Multiple patterns can be superimposed on a single graph for comparison. Save slim jim antenna to get email alerts and updates on your ebay feed. The vertical radiation pattern of the slim jim compared to the jpole is shown in fig. The approximate gain in the hplane of the slim jim is from 1. Antenna descriptions and pattern plots are easily saved and recalled for future analysis. With a good choke at the feedpoint the antenna will be fairly immune to grounding anywhere below the choke. Some modelling of the jpole antenna using mmanagal was the next step. As i was setting up my amateur radio station, one requirement was for 2m and 70cm antennas in two locations.
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