efhw compensation coil

Trapped five band EFHW SOTA antenna. I used four parallel #28 wires (not twisted) for the primary. We have been in the middle of Storm Arwen and Strom Barra here, so I had the pole down for a few days. I installed an eyebolt on one end as a pull-point, and a BNC connector on the other. Graphed with a log scale, it makes a nice straight line. I think the idea is to begin by tuning 40m operation, adjusting the wire length as needed. No wire counterpoise is used to reproduce the SOTA setup. After doing some research on the internet I eventually came across something about rattling radiating elements in Diamond vertical ant, Once I had upgraded the matching transformer for my EF-10/20/40 MKII "EndFedz" (see Part 1) my thoughts turned to the loading coil. This was a little bit of a compromise as the last 20ft of the antenna had to run down a fence to fit it into the garden. %PDF-1.4 In the problematic upper bands, the resonant wire significantly improved the in-band SWR compared to the resistively terminate box (purple). Hence, there is no optimum single-fit solution. Measurements were made on the unmounted transformer with just a ~2 inch length of lead from the secondary to the 2450 load and sampling resistor (jig connections as shown in the photo above). The Counterpoise is a short, typically one twentieth (0.05 *. ) 2015. This antenna is working for 80,40,20,10 and 6m bands. Cmzett: Weince joseph How can we help? This illustration provides a graphical view of approximate comparative difference in expected Common-Mode-Current (CMC) that could flow on the transmission line to undermine the overall performance of the antenna system. If we wish to limit the ferrite temperature to 130 C, then assuming ambient temperature of 30 C, we can tolerate a 100 C temperature rise. How to get started on ISS Cross band Repeater? Wideband RF components ultimately succumb to the non-ideal behavior of materials and assembly methods. He was afraid that being, Inverted V Antenna - A popular Dipole variant, The Center-fed Half-Wave Dipole Inverted V Antenna An Inverted V antenna is a very popular variant of the standard horizontal dipole. Note that building loss into antenna system components is a legitimate and common method of taming VSWR excursions, eg TTFD, CHA250, many EFHW transformers, but in some applications, users may prioritise radiated power over VSWR. With most operations you only transmit for 50% of the time, and since a small transformer with four or more primary turns can achieve >90% efficiency, that implies that I really only need to dissipate ~5W. Or transmitting about 50% of the time, the peak power you would want to run with would be about 300W. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. The overlaid VSWR plots are shown below. The final turns ratio turned out to be 3:29. The other end, attached to the transformer and antenna analyzer, is about 1 meter above the ground. Once completed and tape-wrapped, I applied a layer of liquid electrical tape over the surface and the interior wire connections, ready to go outdoors. It was difficult to work out where it was coming from but I found that it was more noticeable when it was windy outside. Thirty turns #28 are wound on the two FT114-43 cores. EFHW coil and 80m extension in place (coil visible at tip of red arrow) With the coil and its wire attached I fired up my AA-35 Zoom analyzer from RigExpert and had a look. Although it is simple to build and is a multiband antenna, it has several attributes that . Intro EFHW Compensation Coil Experiment Steve Ellington 10.3K subscribers Subscribe 29K views 4 years ago The little coil helps place the EFHW resonance points where we want them. The high frequency performance was extraordinarily sensitive to anything that could add capacitance to the output lead. I did struggle with the C in pF calculation..I seem to be getting hung up on the correct decimal placement..for example, for the 40-meter Capacitor requirement, I get .000000000258: C pF = .000001 / [ ( 2 * 3.14 * 7 MHz) ^2 ] * 2 uH This will yield the minimal capacitance of the variable capacitor. From experience, I found that with this tuner my SWR was better by simply disconnecting the counterpoise at lower bands. Therefore, installation is quite easy, and its tuner circuit is rather simple as well. PDF MANUAL: ENDFEDZ 40-10-KW EFHW 1KW ICAS ANTENNA - Vibroplex It depends on the selection of the inductance and the capacitor values. Very interesting design. Let me review the salient observations from the previous work. The basic question before us is how does an antenna work? The SWR for the 20 meter EFHW antenna was < 1.2:1, The SWR for the 40 meter EFHW was ~1.4:1 for 40 meters and 1.2:1 for 20 meters (full wavelength), For my 20, 30 and 40 meter EFHW antennas I will not use a capacitor in the primary. This is based on random lengths of the antenna, which is transformed with the un-un into a medium-ohmic impedance range with reactive components. I use shock cord to connect the insulator at the end of the wire to my fence. I suspect that a small coil near the transformer is generally a good idea, whether it is my transformer design or others, since it is very difficult to get the antenna wire out of the box without incurring some excess capacitance. Hence after about 3pF of output capacitance, the source will have a hard time charging up that capacitance before it is time to start discharging it. If the antenna is not tuned properly, and it represents other than 50, the diode will rectify the current flowing across the bridge and the LED will light up. The toroid with its many taps may be soldered directly on a multi-position switch. application of Kirchhoff's current Law on a typical EFHW antenna configuration. Functioning as an, HF Wire Antennas - A Primer When we speak about wire antennas, the first and foremost thought that comes to mind is the 1/2 Dipole antenna. On the ends of each winding I slip the end under the last turn and pull tight to lock the winding in place. Yes, indeed EFHW antennas are very useful for SOTA or other field operation. In the case of the EFHW 49:1 transformer, the major shortcomings of the most popular current designs are excessive leakage inductance and poor heat transfer from the ferrite material to the environment. Firstly, bandwidth on 80m is restricted to about 80 kHz at . It is common to use compensation coils of a few turns of the antenna wire to improve the alignment of the bands. Do your own experiments with your own set up, 2019 - 2022 by Dan Koellen AI6XG. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. A krdsem az, hogy a knyv elrhet esetleg pdf-ben is? Even at only 100W, the RF voltage on the high Z output of the transformer can easily be >1300 Vpp, so this is not an idle concern. End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer. The blue trace above shows the results of adding a 6-turn 2 coil about 6.5 ft. from the box. Let us touch on some necessary theory to begin with. Proudly created withWix.com. Note: If we change the primary number of turns, the impedance ratios will considerable change also. Next, I started winding the transformer. This antenna is only 15m long using 2 loading coils. The original coil is designed for low power portable applications. Im very pleased with that indeed. This is why we need the impedance transformer from the 50 coaxial feed-line to the several kilo-ohm antenna connections. 1) More primary turns and primary inductance improve the transformer efficiency and low end performance. Therefore the Great Circle Map generated below should be Read More, Multiband End-Fed Half-Wave EFHW Antenna The End Fed Half Wave antenna or the popularly known EFHW antenna has been around almost ever since the inception of HF radio. Above, the magenta curve is measurement of a real transformer from 1-11MHz with nominal resistance load and three compensation options: cyan: 0pF, too little compensation; magenta: 80pF, optimal compensation; and. So far so good. 100W on a Wire Antenna - Is it good enough for DX? MyAntennas.com Group | When I'm measuring the half way point on my EFHW At equilibrium, the heat leaving the box due to cooling will exactly equal the heating power input. It was difficult to work out where it was coming from but I found that it was more noticeable when it was windy outside. Lowest measured inductivity = 2.0 H. The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. Can a diode be used to rectify signals smaller than its threshold voltage? A design by VK3JEG is only 66-ft. long, about the size of a 40m dipole. However, a key restriction is its 25W power rating, due to the small matching transformer. With tension on the antenna wire, you can just roll the coil up/down the wire to try different positions as you are optimizing for a particular band. point to the loading coil is 20.2m and this sets the 40m resonance at 7.1MHz, which in turn dictates the responses of the harmonically related bands 14MHz, 21MHz and 28MHz. Do I count the six loops around the pvc in the measurement? Can you give me an idea for your 100 W version, you built for 80/60/40 m. The above factors often also lead to unacceptably high CMC on the coaxial cable transmission line thus rendering a rather poor antenna system. You cant really see the antenna wire, but the red line shows the antenna path. blue: 250pF, to much compensation. Nevertheless, the EFHW antenna had in the Read More, SSN, SFI, Solar Data for HF Radio Propagation Here are some of the important Solar activity parametric data that are responsible for influencing the behavior of the Ionosphere on earth. Lets do a quick calculation to see how much an issue is this output capacitance. There could be any number of reasons for that, where I put the bends in the wire, the location of tree branches, etc. There are many good descriptions on the net about this type of antenna. I also built one that is heavy-duty handling easily up to 100W for 80/60/40m bands. The resistance (real) component of the impedance is right where we want it near 50 ohms. It turns out that we can easily measure the effective parallel secondary capacitance by looking at the primary self resonance when the secondary is open. Generally a loading coil has far more inductance and shortens the length of the antenna significantly. When the transformer was mounted in its box and the output connected to an antenna connector feedthrough, the observed capacitance increased dramatically to about 6.0 pF. The latest news about Efhw Compensation Coil Experiment. Nevertheless, this is a rather curious result that might have derating implications for the 160 and 80 meter bands. So, I embarked on testing it for myself. ENDFED/EFHW Antenna & Choke - F5NPV - V85NPV The bottomline, your putting the relationships of 1) Toroid windings and to measure their inductance together with 2) the required capacitance calculation is exactly what I needed to move forward with my specific design plans. The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. Not the ideal antenna, but convenient! end fed half wave antenna - awsh.org An end fed half wave antenna, or efhw, is a variation of a half wave dipole, but it is fed from one end. I chose to use FT8 transmissions for this test since they generate 100% duty cycle during the transmission period with an average duty cycle of 12.6 sec / 30 sec = 42% overall when including the listening periods. Another design by KB0ZZ is a little longer, but resonates on both 40m and 80m. No capacitor was installed. Once that's done, the instructions say "adjust the coil as necessary" to bring the other bands into resonance. Inverted V Antenna A popular Dipole variant, EMI-RFI and Noise related HF Radio Station performance loss. With the coil and its wire attached I fired up my AA-35 Zoom analyzer from RigExpert and had a look. PART - 1 : The EFHW antenna as a radiating and receiving element is a decent multi-band antenna with good efficiency on all bands, provided it is driven at its feed-point using a well configured and well-matched driving source. The SWR for 30 meters, 1.05:1, was the lowest of all three antennas since the transformer was tuned for impedance match at 30 meters. Saturation of a warm core happens near 0.2 T (2000 g) and if you dont want to deal with significantly reduced permeability, then better to limit to 0.1T. End-Fed antennas are useful in many ways, includes easier mounting of cable at one end (freeing the antenna from unnecessary weight of cable) & antenna maintenance in future. A half-wave at the lowest band of interest will also work well on all harmonically-related bands which has become particularly attractive to those wanting a quick portable wire antenna. Since I wont be connecting a counterpoise, the antenna will use the coax shield as the counterpoise, so the RF choke will keep any unwanted RF from feeding back through the coax. Evaluating it at a we get: which gives the power dissipation simply in terms of the heat capacity, cooling time constant and the temperature difference from ambient. I placed the box in a cool oven and let it get up to about 200 F, soak for a while, and then I took it out, hung it in still air and measured the temperature as time passed and the box cooled. With the cooling curve and a good estimate for the heat capacity of the box, now it is just a matter of running some power through the transformer and measuring the the temperature rise from ambient to be able to determine the power that turns to heat in the transformer. Experiments with 160m antennas | VK3IL Blog First, note that the transformer has low transmission loss up to nearly 50MHz. 73! In fact, this was the second one I had built, as I had also made one for a 30m/15m end fed antenna. I checked the wall brackets and mast, but all the fixings were nice and tight. We do not know what the actual impedance will be at the end of the antenna radiator. Thanks for your comments. Lowest frequency = 7.000 MHz. The antenna is effective and the materials and construction are of a very high quality. Be aware counterpoise or ground radials are required for all hf antennas for better performance. I drilled a couple of holes at each end of the former, a small one for the wire to pass through and a larger one for a bolt and wingnut for wire attachment as I wanted the end result to be portable across different antenna projects. As you look to use this transformer at higher power levels, I can imagine that the bottleneck might be voltage breakdown or corona in the windings. The conjugate impedance matching arrangement of this nature is far from perfect resulting in considerable reactive currents on some of the bands. Does your station desperately need a good RF ground to behave properly? It performed well on both the 2m and 70cm bands. Why does a wire carrying RF current radiates to produce EM waves which travel through, Beware of Skip Zone while working HF radio A good radio amateur friend of mine from Poland sounded quite anxious when he told me that his new antenna was behaving peculiarly. uBITX HF Transceiver Build - My Adventures in Engineering However, a key restriction is its 25W power rating, due to the small matching transformer. End Fed Half Wave (EFHW) Antenna Upgrade Part 2 - The Loading Coil This totally un-rigorous calculation just gives a quick idea of how much you have to be careful. Commercial Coils, Inc. 213 Chesterfield Industrial Blvd Chesterfield, Missouri 63005. View the job description, responsibilities and qualifications for this position. For our transformer at 100W (==> 71 Vrms into 50 ) , the core cross section for the two FT114s is 0.74 cm2 , consider the lowest frequency as 3.5 MHz and our 5-turn primary, then plugging in the numbers we find Bmax = 0.012 T. Lets consider a much more challenging extreme: 1000W and the 160m band. The SWR was measured for each of the three antennas across the CW portion of the bands. The transformer is wound as an autotransformer, 3+21 turns, ie 1:8 turns ratio. End Fed Half Wave Antenna Coupler (EFHW) - M0UKD The antenna is up. The antennas are set up as a sloper as in my SOTA outings. Thermal gasketing between the cores and the aluminum heat sinks could help a lot, as would a single piece of aluminum rather than the stack up of thin sections I used. On the transformer, I added a few wingnuts to tighten down the antenna wire. I used the 14g enameled wire and wound it on the FT240-43. I was a little long on 80m not surprisingly, so folded back about 40cm of wire leaving about 2.1m beyond the coil. Therefore, I picked a momentary push button to switch the operational mode to tuning mode while tuning up. My favorite SOTA antenna is the End-Fed Half Wave Antenna. I settled on a compact secondary using #28 wire. Most of the time 5 to 20W will be adequate for activation anyway. On one end, I added a ring terminal to connect it to the transformer and on the other end, I connected an electric fence insulator. The SWR for the 20 meter EFHW antenna was < 1.2:1 Dutch radio amateurs in particular have been active in this area: John, PD7MAA's blog - http://pa-11019.blogspot.com/2012/04/149-transformer-for-endfed-antennas-35.html Jos van den Helm's (PA1ZP) article published in Radcom: "A 3- or 5-Band End Fed Antenna", February 2016, Radcom, published by the RSGB in the UK. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. I then added two 220pf capacitors in series between the center conductor and ground. Having recently built a MTR2 3-band CW transceiver, I was keen to make band switching on a mountain top as simple as possible. This is indeed a classic antenna that is not only, Introduction to Omnidirectional Antennas In the literal sense, an Omnidirectional antenna is an antenna that radiates uniformly in all directions. The purpose of the transformer is to step down the high impedance of a resonant EFHW, not as a resonant circuit or tank itself. The band compensating inductor placed on the wire is another story. One end may even be close to the ground, not yielding the best radiation efficiency, but much activation proved it still operational. The results are shown below. For . I've always had issues with 10m loading up properly so I'll also be adding a compensation coil 78 inches from the feed point on the wire. The End-Fed Half Wave Antenna a bit Differently, The End-Fed Half Wave Antenna a bit Differently Coventry Amateur Radio Society, Ismerje meg a hozzszls adatainak feldolgozst, 40 M R/7E azaz a kirlyi ejternysk rdillomsa, jra megy az SSTV tjtsz 144,500 MHz-en. (LogOut/ Update: Full size 132ft EFHW For one month I replaced the 66ft wire and loading coil and replaced it with a full 132ft of wire, connected to the FT240-43 balun. After some internet research, I settled on making the former from a paint roller. Ha elolvasod alapszablyunkat s a benne lertakat elfogadod, akkor nincs ms teendd, mint a ha5kdr@ha5kdr.hu email-cmen, vagy egy klubnapon jelentkezni nlunk! The goal of the temperature characterization is to determine how much temperature difference (core to ambient) there will be for a given level of power dissipation. I thought to test this hypothesis by measuring the losses as an oven-heated transformer box cools down. 2006. You can achieve this inductance with half a dozen turns of the antenna wire tied in a small coil. From this article one may build a 40, 30, 20m end fed half wave antenna, with no special parts needed, or no special skills required. In comparison to the EFHW antenna, a simple dipole offers a far better prospect. Ambient temperature is 20, and the core temperature increased by 5 over 120s @ 20W continuous input. I came up with a very simple way to build these coils on the antenna wire that proved quick and easy to change and test, involving small piece of PVC pipe and a piece of Velcro shown below. The transformer was attached to the 30 meter EFHW antenna and turns were removed for best match to 50 ohms. I first mounted the SO239 connector to the box. Trapped five band EFHW SOTA antenna | VK3IL Blog Toll Free 800-532-2645 636-532-1523 Fax: 636-532-8259. I would mention first its ease of installation. It performed well on both the 2m and 70cm bands. I added some Christmas colored zip ties to hold everything in place. Then I covered the coil in kapton tape to hold it together. EFHW Antenna Frequency Compensation Lead 5,144 views Jan 20, 2019 188 Dislike Share Save Steve Ellington 9.92K subscribers 8 inches of wire attached to the antenna post can lower the frequency. Your article was well written and very informative, thanks. My design objectives were: 1. Most informative and appreciated. The blue trace above shows the results of adding a 6-turn 2 coil about 6.5 ft. from the box. The low end of the secondary, which will be the tap, is bent back over to the center of the winding and covered with a small piece of Kapton tape, and then the primary is wound over the tape (and the secondary tap wire). When I'm measuring the half way point on my EFHW, looking for 67', how do I factor in the compensation coil on the MyAntennas wire? CG K/ J/ S/ B to 4-20mA 0-1800 Celsius Thermocouple Converter TC Input 4-20mA Output Head-mounted Temperature Transducer first impressions, Some wisdom that shapes articles on this site, Designing high performance VHF/UHF receive systems, A new impedance calculator for RF inductors on ferrite cores, Calculate ferrite cored inductor (from Al), Calculate VSWR and Return Loss from Zload (or Yload) and Zo, https://owenduffy.net/files/EstimateZFerriteToroidInductor.pdf. Check your inbox or spam folder to confirm your subscription. An End Fed Half Wave (EFHW) antenna for operation on 20, 30 and 40 meters was built for SOTA operation. Radio Transceiver S-Meter Pitfalls to avoid, Atmospheric impact on VHF Radio Propagation, Terrestrial VHF Radio Signal Coverage LOS, Terrestrial VHF Radio Signal Coverage BLOS, HF Surface Wave Propagation (Ground Wave). Refurbishing aluminium antenna parts affected by weather / corrosion. . These dimensions were derived from modelling the antenna in EZNEC. stream . 3) Total losses are approximately independent of core volume. We also need to know what are the frequencies or bands for which we plant to use this antenna. It is basically an end fed half wave dipole on 20m/40m and an end fed full wave dipole on 10m. It requires a set distance to hang both ends of the antenna, and that is not always given. For calculating the length of a half wave in metres, I use 141 (MHz) for wire elements. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. For the antenna wire itself, I used 119 feet of 22g stranded hookup wire. Software Engineer - EDI - salary.com More designs can be found by Googling "80m loaded dipole.". Below is the schematic of the final build. To this end, I weighed the main components of the box and looked up the specific heat capacities to get an approximate overall heat capacity for the entire box. We use cookies to optimize our website and our service. Un-Uns for Endfed-Antennas (EFHW) by DK7ZB. Csatlakozz csapatunkhoz! I made one quite similar to it but 3T Primary with #16 speaker wire (2 parallel wires) and 15T Secondary close wound just using about one-third of the circumference of the 2 inch toroid. Z8Vq9_@x C\Agv#. I strung up a nominal 80m half-wave antenna wire into the trees, snaking it through the open screen door to the work bench where I was doing the tests. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. I mounted the transformer on a tree for testing. The smallest number I measured was 1.6 pF, derived from the self-resonance at 41 MHz with the leakage inductance (measured at 198 nH) when the secondary was shorted. Note that there is some uncertainty in the measurements, but we can be confident that the loss is no where near the figure estimated for the FT82-43 design. Above 7MHz, there is very little temperature dependence at all. 101: The Independent Medical Evaluation - "IME" By: Cynthia M. Hennessey Attorney. Highest frequency = 14.350 MHz. The computation method is also touched on. In that case, expected efficiency (meaning PowerOut/PowerIn) of the transformer was less than 65% at 3.6MHz. Change), You are commenting using your Facebook account. It is very hard to know what will be the best solution for a given antenna installation if you want to hit all of the bands exactly. Your calculation is correct, the result I get is also .000000000258, which is clearly wrong (it is Farads instead of pF). I wish you lots of productive experimentations and successful portable operations. The overall lenght is only 15m. Is it any good? High Q, hence low loss. (LogOut/ However, I think I made a good choice with a Hammond 1590A diecast aluminum box. I hope to do more experiments with single and multi band EFHW antennas above 20 meters - stay tuned -- The experiments have been performed, check it out! I may try to bring down the 20, 15 and 10m bands at some point, either with a small coil 2m from the feed point or with a short section of wire as a compensation lead added at the feed point as shown in the video below from Steve Ellington. Basu (VU2NSB), Antenna Bearings Geodesic Map We present automatically rendered Antenna Bearings with Geodesic Paths projected on a Rectangular Map. Moreover, this antenna produces several inter-lobe nulls creating multiple band dependant shadow regions in its coverage. VK1OD.net (offline). Consequently, this is how the capacitance values are determined. Independent Medical Evaluation - IME | Cynthia Hennessey

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