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. I was able to contact a few repeaters, that are around 45. Aug 19, 2015 these agree well with the real jpole and 2bcx antennas measured in a real antenna test chamber in figure 2. This makes the 2 meter slim jim antenna a great solution for repeater sites, data and packet stations, aprs, and even every day. Since its publication in 1978, the slim jim aerial has been built by many uk amateurs. Some notes on the slim jim antenna dave coomber m0uxb, uk introduction. Ive been producing these antennas professionally for nearly a decade now and have sold over 15000 units. Traditional jpole antenna february 8, 2018 august 19, 2015 real measurements of a slim jim antenna and traditional jpole antenna reveal the truth about their respective gain and pattern. 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. My workshop under the garage needed to have a separate antenna, preferably hung from a nearby tree. Slim jim style jpole antenna s have an omnidirectional radiation pattern and a low angle of radiation when vertically polarized. The 2 meter slim jim copper tubing antenna project by richard ke5fxu sk updated 1162012 credit for the original design goes to f. 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. Jpoles will certainly work well as a repeater antenna.
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. This morning i try out a new antenna for the 2 meter ham radio band. 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. One can simply understand the function and directivity of an antenna by. It has a folded dipole design that gives it more gain and a lower angle of rf radiation, 7 degrees, vs 20. 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.
Slim jim j pole 2 meter 440 vhf uhf ham radio antenna 24ft. 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. My antennas have a low noise floor and a beautiful omnidirectional radiation pattern. Both are great antennas, i dont have a problem recommending either of them as the foundation for a amateur radio base station.
It is the most effective antenna when compared to other ground plane antennas. 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. 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. Vortex antenna systems radio communication antenna. Some modelling of the jpole antenna using mmanagal was the next step. 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. 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. The vertical radiation pattern of the slim jim compared to the jpole is shown in fig. Plus the antenna also have the great low noise floor and wide bandwidth typical of our other antennas. Real measurements of a slim jim antenna and traditional jpole antenna reveal the truth about their respective gain and pattern. Apr 07, 2014 download antenna radiation diagram plotter for free. The great thing about jpole antennas is their simple design and excellent performance. Measurements for the target frequency 145mhz and 50. Slim jim is a special wire antenna which has impedance selectivity of 50.
It was described by the late fred judd, g2bcx, in the uk magazine practical wireless and subsequently in other journals and books. 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. 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. For hello spiceheads is there any software that enables me view antenna radiation patterns in 3d by simply using the information in say the. 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.
Understanding why slimjim antenna aficionados hype the gain in their marketing. Searching the internet turned up the slim jim design, described by fc judd. The slim is an endfed folded dipole antenna that has a gain of 6 dbi and a nice low rf take off angle. 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. The fact of the matter is this antenna design will function like a jpole, no better, no worse.
The vortex slim jim antenna consists of a single element, one half wavelength long radiator with a quarter wave parallel feedline tuning stub. Three source files plain text can be loaded and plotted at the same time. With a good choke at the feedpoint the antenna will be fairly immune to grounding anywhere below the choke. 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.
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. Since the vertical angle of radiation is so narrow, about 8 degrees toward the horizon, it usually out. The azimuth radiation pattern is essentially omni directional. Judd found the slim jim produces a lower takeoff angle and better electrical performance. At this point its pretty crystal clear fred judds 2bcx slim jim antenna doesnt offer anything special compared to a traditional jpole antenna. Contact attempts to a certain copper pipe 6 db slimjim maker remain unanswered. The main category is antennas for 2 meters band that is about antenna projects for 144 mhz. If you decide to make a 2m antenna, youll end up with 1. On my site you can find both the all copper 2 meter jpole antenna and an all copper 2 meter slim jim antenna. My slim jim antenna is a perfect choice for a repeater. Its called a slim jim, and is made out of a length of twin lead wire.
Using an example model from the eznec files with 45degree radials elevated 5 wavelengths, the dipole was compared to the slim jim model. 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. Thats the reason slim jim antennas are usually described as having more gain. Can anyone recommend a 2m 70cm to use in an apartment. 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. The standard of comparison vertical antenna is a vertical 14 wave dipole with a ground plane. The slim jim vertical angle of radiation is almost parallel to ground so maximum radiation is where it is needed. This calculator can be used to design a slim jim or a j pole antenna. 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. Keywords microstrip, patch, antenna, slit directivity of the antenna, electric far field 1. The program provides ability for changing the language of signs and messages of the program.
It has a radiation pattern peaking between 5 and 8 degrees above the horizon. 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. Eplane gain measurements of j antenna with respect to reference dipole. 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. These two features of the antenna gives you about twice the gain as a standard jpole. Initially, builders cut one wire at the top of the matching section and stripped away the wire. 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.
Various internet claims the slim jim has significant gain over other similar function antennas. A slim jim has a different radiation pattern than a quarter wave, half wave or jpole antenna, with a lower takeoff angle. I note that the plots of the radiation pattern in the article have no marked scale. Pdf ham radio applications demand antenna design with an aim of achieving. Notes on the original slim jim antenna by dave coomber, m0uxb. 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. The slim jim has a lower takeoff angle and more compressed radiation pattern. Aug 20, 2014 with twice the gain of a standard jpole antenna, the 2 meter slim jim antenna is a jpole on steroids. 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. For best results, to say nothing of the radiation angle, it is best fed balanced.
Most people make these for 2m use, but you can make them for 70cm use if required. The simulations results are obtained by using electromagnetic simulation software called feko software are presented and discussed. Pdf comparative analysis of slim jim antenna for ham. 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. Liveagent boasts the fastest chat widget on the market and has over 150m endusers worldwide. 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. See the pattern and antenna currents on the same color 3d display as the antenna. Judd found the slim jim produces a lower takeoff angle and better electrical performance than a. Slim jim antennas have two very desirable characteristics. The resource is currently listed in in 2 categories. They work great for amateur radio, public safety, scanner listening, business band, and gmrs purposes. 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. The introduction of slim jim antenna doesnt help those issues. The slim jim antenna has a higher resistance of irradiation, and can give better performance for it.
The halfwave section is then folded back on itself towards the stub at a distance of approx 0. Save slim jim antenna to get email alerts and updates on your ebay feed. For example, the ubiquiti sector antenna am5g19120 has its antenna properties defined as seen in this link. Construction details are available for registered users. In any illustration, the sketch drawn to represent the radiation of an antenna is its radiation pattern. I used half inch od junk aluminum tubing cut to these final lengths. 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. Comparative analysis of slim jim antenna for ham radio applications.
Many users of the slimjim participate in the bewilderment as well. 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. Moreover, the radiation patterns are almost omnidirectional in the. 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. As we will see below, the slimjim antenna performs admirably in both simulations and chamber measurements. Authentic n9tax vhf slim jim jpole 2 meter antenna roll up jpole use with baofeng.
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. Multiple patterns can be superimposed on a single graph for comparison. Slim jim and j pole calculator american version m0ukd. The vertical angle from the slim jim is about 8 degrees, while the common 58th wave ground plane antenna is about 32 degrees. The following instructions may help you if you decide to try the slim jim antenna with aluminum tubing. The approximate gain in the hplane of the slim jim is from 1.
I have used this antenna made by nelson antennas on ebay on many occasions over the past 2 years. A little more gain will make up for some of the feedline losses youll receive at vhf frequencies. Because jpole and slim jim antenna designs share virtually identical common mode and repeatability issues, either one can beat the other. Jpole and slim jim antenna frequently asked questions faq. Pdf comparative analysis of slim jim antenna for ham radio. Discussion in amateur radio antennas started by masel, apr. 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. Its radiation pattern is close to that of an ideal vertical dipole because it is endfed. It uses a matching system similar to jpole antenna. 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. They have an omnidirectional doughnut shaped radiation pattern. 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. 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.
It has two electric poles charged positive and negative. The farfield radiation pattern can also be calculated from the antenna shape by computer programs such as nec. 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. It is this and this alone that makes this one of the best terrestrial communications antennas i have ever seen for the price. The omnidirectional radiation pattern and higher takeoff angle makes it easier to get a signal out if you are surrounded by buildings or rough. Slim jim antenna vs 14 wave ground plane results technical. The top section is altered by having a very closespaced conductor in the top element. Let me start by saying that since discovering the slim jim antenna design i have. 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 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. 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.
Frequency mhz velocity factor see text vf actual wavelength inches wavelength considering velocity factor inches a. This in itself says something about the dedication i have to creating a quality product. There is also an analysis of radiation pattern, gain of the antenna, directivity of the antenna, electric far field. Most of the slim jim antennas i have seen have been built for 2 meters, the jpole example from mmanagal is for 28.
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. The slim jim afaik is just a jpole made of twin lead. The slim jim retains the same difficulttocure common mode problems, and has the same pattern unpredictability, as a jpole. The slim jim, designed by the late fred judd, g2bcx, can be a great portable roll up antenna, if made out of 300. Radiation is the term used to represent the emission or reception of wave front at the antenna, specifying its strength. As i was setting up my amateur radio station, one requirement was for 2m and 70cm antennas in two locations. Antenna radiation diagram plotter polar plots of measured em emission, with a proper radial axis scaling and span.
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 n9tax slim jim antenna is the highest quality roll up antenna available today. The slim jim is functionally just a jpole with one difference. Apr 30, 2017 the national film board of canada for the canadian air forces great explanation of propagation. Judd, g2bcx get that signal lower to the ground for better performance. Solved software for viewing 3d antenna radiation pattern. 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. My main shack location has a commercial 2m jpole dual band mounted on a short mast. Qantenna is able to show antennas in a 3d plot, and calculate its radiattion pattern. 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.
774 509 1277 366 1306 535 123 1300 99 1636 865 504 1603 1327 797 115 892 320 1526 687 1164 251 623 261 947 247 694 1484 1194