efhw compensation coil

It was difficult to work out where it was coming from but I found that it was more noticeable when it was windy outside. This article will describe a 40/30/20m band end-fed half wave antenna, focusing on its matching unit. 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. 73! The computation method is also touched on. The in-band SWR improved significantly with this localized inductance to compensate for the boxs capacitance. Low SSN Why do most Hams find HF Radio so difficult? After doing the ferrite transformer scaling experiments last time, and learning a bit more about what matters in these transformers, it was time to make a stab at designing one. It not a loading coil. Thirty turns #28 are wound on the two FT114-43 cores. The biggest uncertainty in these measurements was the actual power level used. They will be adjusted for resonance at or close to the CW portion of the bands. I checked the wall brackets and mast, but all the fixings were nice and tight. It is hard to wait an infinitely long time for the box to equilibrate to a given power level. It matches the impedance fairly well to the half-wave antennas high impedance at one of its ends. One end may even be close to the ground, not yielding the best radiation efficiency, but much activation proved it still operational. 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. It is not necessary to calculate the above; the results are sown in the following table. For . Firstly, bandwidth on 80m is restricted to about 80 kHz at . Can you give me an idea for your 100 W version, you built for 80/60/40 m. Yes, there is a coil a few feet from the box but it is NOT TRAP, it is no secret as well, actually, everything in this antenna was published and patented by few people a long ago. It is important that resonance may be achieved at each tap of the inductance. Then we find Bmax = 0.076 T. The Type 43 data sheets show us what we have to look out for. How big and where to place it is likely best determined empirically. I wanted to test the hypothesis that an inductance near the box would compensate for the output capacitance and further improve match on those bands. However, let me write about it from a slightly different perspective that was not very obvious from the articles I read. Elnzst krnk, de elsikkadt az zenete. EFHW Compensation Coil Experiment - YouTube It is worth experimenting with its length also. . 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. 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. A short 80m antenna for my lot - KB6NU's Ham Radio Blog It performed well on both the 2m and 70cm bands. Even at 15W the voltage at the ends may reach 100-200V. : I see you were able to post your comment now, so I just copied my email answer here for others to see. Csatlakozz csapatunkhoz! On the transformer, I added a few wingnuts to tighten down the antenna wire. Simulating the end-fed half-wave (EFHW) dipole antenna 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. The equation in the article is corrected now. 2) Winding capacitance and leakage inductance, especially present as you increase the number of turns, limit the high frequency performance. 100W on a Wire Antenna - How far would it reach? Because of the turns ratio N, the secondary capacitance will appear N2 larger at the primary and will resonate with the primary magnetizing inductance. This article will not address that antenna type. I look at the end-fed as just an extreme example of an off-center-fed 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. Do your own experiments with your own set up, 2019 - 2022 by Dan Koellen AI6XG. I started with a small piece of PVC pipe and drilled a few holes in it to run the wire through. 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. Winding the wire manually was a bit tedious but once done I temporarily held the wire with cable ties and checked the inductance. See the table above. At 5W input the connector at the end of the antenna wire may be up to 160V, and at 15W it may be 270V. 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. And since I am interested in building EFHW antennas for a single band or a few bands, how will that impact my design? So, how to construct an end-fed half wave antenna? I will go back and have the article corrected. It depends on the selection of the inductance and the capacitor values. We do not know what the actual impedance will be at the end of the antenna radiator. Looking at several builds and discussions, such as commercial antennas (e.g. Note that the resonances do not necessarily line up harmonically, there is commonly some enharmonic effect. Connected to the packaged transformer, I ran some SWR sweeps with just the bare wire and various configurations of small coils to act as band-tuning compensation. Although the original loading coil is very well engineered, I thought I could make a more efficient version given that I did not need to make it 'trail friendly'. The comparison is done on 4 bands - 10m, 20m, 40, and 80m. However, it has its idiosyncrasies. Commercial Coils, Inc. 213 Chesterfield Industrial Blvd Chesterfield, Missouri 63005. End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer I am testing it with the tuned tank circuit and a coax to the tuner with and without a common mode rejection choke. Since it is a EFHW and not a non-resonant end fed, the wire length for 40m is about 67 feet. The SWR results are as follows: The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. uBITX HF Transceiver Build - My Adventures in Engineering Regards VE9HAM. Basu Bhattacharya (VU2NSB). Most of the time 5 to 20W will be adequate for activation anyway. I used my IC-751As power meter and an in-line Siliconix power meter as well as a voltage probe on the feed cable. The solution was to make a small coil of the coax feed line, thrown on the ground, before connecting it to the radio. The EFHW transformer box from outside. I was a little long on 80m not surprisingly, so folded back about 40cm of wire leaving about 2.1m beyond the coil. Performance of 49:1 Ferrite CoreTransformers, 24 Hour Animated PSK Reporter ReceptionReports. Understanding Antennas The Good, the Bad, and the Ugly. Klubunknl folyamatos a tagfelvtel. 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). It uses a coil as a compensation unit, and no counterpoise. Typical EFHW Antenna Characteristics & Performance, Influence on Performance due to Deployment Environment, Construction Variables and Transmission Line Interface, Optimum Counterpoise length and Coupling Transformer, Influence of EFHW wire orientation on performance, Good Antenna for any Radio Station is vital The importance of antennas for radio communications can never be over-emphasized. I used a section of 40mm external diameter PVC waste pipe and 1mm diameter enameled magnet wire to make the coil. is the initial disequilibrium temperature, is the equilibration time constant, and is the heat capacity. PDF MANUAL: ENDFEDZ ALLBAND-KW 80-10 EFHW 1KW ICAS ANTENNA - DX Engineering I ran WSPR at 10mW for about 2 hours and got the results below. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. I can give a link if you need. Do I count the six loops around the pvc in the measurement? Start by wrapping the wire around the toroid. 2006. Ez az oldal az Akismet szolgltatst hasznlja a spam cskkentsre. The equation should have a 10^6 and not 10^-6 in the nominator. 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? And not all hf antenna installation are same, with most requiring bit of tinkering. 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. The coil came out at 89mm in length rather than the theoretical 83mm not surprisingly, but the inductance was bang on at just over 109H. Change), You are commenting using your Twitter account. Nevertheless, this is a rather curious result that might have derating implications for the 160 and 80 meter bands. Ive been thinking about getting an antenna up for 80m, and Ive come across a number of options that interest me and would suit the space I have available realistically no matter what I go for it will be a very compromised antenna, but still much better than none. My End-Fed Half-Wave (EFHW) AmateurRadio.com Be aware counterpoise or ground radials are required for all hf antennas for better performance. A transformer was wound on a FT50-43 toroid with 3 bifilar turns followed by another 31 turns of #26 enameled magnetic wire. Taking the time derivative of the above equation you get the power dissipation. 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 Calculate the capacity for the resonance at the lowest frequency to be covered with the lowest inductivity taken in consideration. Scaling the small core to higher power levels would mean that the flux level in the ferrite core would increase. IIRC they call it a "compensator". By using traps, the antenna works on all three bands with no operator interaction. Note: More extensive experiments including operation at HF frequencies higher than 20 meters, harmonic versus fundamental operation and transformer efficiency is posted in this blog. 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. 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. Refurbishing aluminium antenna parts affected by weather / corrosion. = .000001 / 3868.88 The orientation of these lobes varies with the frequency band of operation thus resulting in directional inconsistencies between bands. At FT82-43 matching transformer for an EFHW I wrote about the likely losses at 3.6MHz of a common design using a FT82-43 ferrite core with a 3t primary. 5) It is very hard to avoid stray capacitance on the output. 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. It should be no surprise that 80pF is close to optimal. This gave me an effective coil diameter of 40.5mm. Zin=46.52+j6.72. Thank you for an interesting and informative read. It requires a set distance to hang both ends of the antenna, and that is not always given. % 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. The overlaid VSWR plots are shown below. It may be one or even five kilo-ohms. Independent Medical Evaluation - IME | Cynthia Hennessey 5 Band EFHW Antenna 80m-10m | 49:1 End Fed Half Wave - YouTube (LogOut/ End Fed Half Wave Antenna Coupler (EFHW) - M0UKD Based on a 2014 survey, the most popular antennas for SOTA (Summit On The Air) activation are the following (see sotabeams.co.uk/blog/5-most-popular-hf-portable-antennas for details): Let us not confuse the End-Fed Half Wave antenna with the Random Length End Fed wire. In that case, expected efficiency (meaning PowerOut/PowerIn) of the transformer was less than 65% at 3.6MHz. Fig.1 - Withdraw the radiating element carefully to avoid damaging the matching components A few years ago I bought a secondhand Diamond X50 dual band (144/430) antenna at a radio car boot sale. The difference here is that the target bands are low frequency. It is quite possible that designing more than three or four bands into a tuner will lead to a failure. There is no substitute for playing with the analyzer, trimming the wire, adjusting the compensation coils, etc., and going through the process for a few iterations to get the multiband antenna to work well for you as you have it installed. I am planning to use this latest one at the Field Day next year. Typically the IC-751A would read about 60W on its power bridge, the Siliconix would show >50W on the 50W scale and 45W on the 500W scale, so there is ~20% uncertainty. Many people use an inductor placed at the near end to make things level out on the higher bands. Generally a loading coil has far more inductance and shortens the length of the antenna significantly. But before we do, let us look at the insertion and transmission loss that the VNA is reporting. PDF MANUAL: ENDFEDZ ALLBAND-KW 80-10 EFHW 1KW ICAS ANTENNA - Vibroplex One way or another there is always a counterpoise involved if the antenna is tuned correctly. I swept the antenna with a nano vna from 2 to 30MHz and there were nice dips at each band. Newtons Law of Cooling tells us that heat flow is proportional to the temperature difference. First, note that the transformer has low transmission loss up to nearly 50MHz. I am building an EFHW antenna for my new MTR3b, but do I need to include the capacitor for 20, 30 and 40 meters? A 100pF silvered mica was connected in shunt with the transformer primary. 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. I wish I had a simple answer, but really this is where some experimentation can pay off. I wish you lots of productive experimentations and successful portable operations. Show more. My goal was to describe the parameters of an antenna that can be easily build, yet show enough theory for someone to design his or her own antenna and antenna tuner. In his article, I will try to bust some of the myths associated with Inverted. http://www.hamuniverse.com/randomwireantennalengths.html, https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/. An EFHW antenna has a very high impedance at the end point and you need a matching transformer to feed power to it. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 80 meter and higher 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. Wrap the first wire around the toroid 27 times (I used a black wire for this). . You can start with the links below. HA5CBM Mikls, Finally the tank circuits specification is complete, which is sown below. Gut feeling says that should be possible with just a couple of FT114-43 cores, similar to the design by John Oppenheimer, KN5L. Thanks again Jim. Ive been wanting to get back into radio stuff for a while now, but the only antenna that I have up now is a 40 meter dipole. 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. Cmzett: Weince joseph How can we help? From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. Im not interested in trialing coil-loaded dipoles at the minute (from my limited reading bandwidth can be a real issue) so the options I like include: The G0KYA/PD7MAA/IK0IXI EFHW extension to cover 80m calls for a 110uH coil placed at the end of the EFHW, with a further 2-2.5m of wire beyond this. The point is to get the characteristic time constant for the cooling, which is the reciprocal of the exponent coefficient that Excel shows for the fitting equation. The original coil is designed for low power portable applications. It is quite difficult to satisfy both requirements of achieving proper impedance ratio and resonance of the tank circuit at each tap of the inductance. A radio station is as good or as bad as the antenna it has. With very little counterpoise, the antenna is being fed at a high impedance point so a rather large impedance step-up is employed. I also built one that is heavy-duty handling easily up to 100W for 80/60/40m bands. Current Balun 1. <> For the transformer, a T130-2 toroid will be sufficient, on which we wind the seconder with multiple taps, as shown in the below table. AC Coil Replacement Cost 2023 - Forbes Home The photos above show a method that works fairly well. Transmitting on 15 meters was impossible because of RF into the radio. However, I think I made a good choice with a Hammond 1590A diecast aluminum box. 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. Or transmitting about 50% of the time, the peak power you would want to run with would be about 300W. (Tvir s tvbeszl gpek s kszlkek) Ksznm. Ive been wanting to put together a decent multi-band antenna for a long time and finally settled on an end fed half wave antenna. How to get started on ISS Cross band Repeater? Increasing the drive impedance tends to move the resonances to slightly higher frequencies. In practice, exactly how you wind the primary turns can drastically affect the high frequency behavior of the transformer when measured into a 2450 load. With no counterpoise wire it will be the coaxs shield providing it. That does not seem inconsistent with the expectation calculated above of about 10% core loss at 3.6MHz. There is lot of controversy around the EFHW antennas. Assuming, most of us use the 40/30/20m band for HF SOTA activation, so the following table shows the SOTA frequencies, and the calculated half wave radiator wire of the antenna. RC = 2500 x 1.0e-12 = 2.5 nS Now consider the period of a 30 MHz wave. An end fed half wave antenna, or efhw, is a variation of a half wave dipole, but it is fed from one end. I was pleasantly surprised that the dips were so perfect across all of the bands and the SWR was low enough to not really need a tuner. The original coil is designed for low power portable applications. (30 votes, Rating: 5.00) - Please vote the article with your valuable star rating. Finally the tank circuits specification is complete, which is sown below. 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. Each geodesic great circle path displayed on the map originates from your location that is derived Read More, The Great Circle Map GCM We present an automatically rendered Great Circle Map GCM based on your location derived from your Internet IP address. How to tune a multi-band EFHW antenna using a loading coil The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. A tutorial on estimating the impedance of a toroidal ferrite cored inductor for radio frequencies, Pulse test of a Hantek 6204BD 4 channel 200MHz USB DSO and supplied probe. 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. Above is a sweep of the uncompensated prototype with a 3220+50 load. If you want to minimize leakage inductance, the way to do that is to keep the two windings very close to one another. It performed well on both the 2m and 70cm bands. Hello, a wonderful approach for the problems.. Other observations along the way: 4) Tight windings or backwinding over the primary can significantly reduce leakage inductance. From that we can find Mismatch Loss. If you need to change it, is necessary to recalculate the secondary turns, and the resonance frequency needs to be adjusted also. Lowest frequency = 7.000 MHz. Be cautious, such voltages may cause a quite painful skin scorch. Thanks in advance, good health for you in these times, Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you. The highest voltages as well as radiation are also at the end of the antenna wire. Efhw Compensation Coil Experiment - Local Search Denver Post The 2 coils are 35uh and 90uh. A 100pF silvered mica was connected in shunt with the transformer . Why does antenna radiation occur? Let's find out! With the coil and its wire attached I fired up my AA-35 Zoom analyzer from RigExpert and had a look. The bridge than will measure zero voltage across the bridge, and the LED will turn off. In this case C~5pF and Z~2450 suggests that the inductance needed should be about 30 H. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. A method for estimating the impedance of a ferrite cored toroidal inductor at RF. Steps to improve the heat transfer over the present design could make this small transformer work at even higher power levels. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 40 meter and higher bands. The SWR for the 20 meter EFHW antenna was < 1.2:1 I used four parallel #28 wires (not twisted) for the primary. This will yield the minimal capacitance of the variable capacitor. To calculate the impedance ratio, use the following equation: A completed tuner is shown here, which depicts the inductance assembly. 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. The final turns ratio turned out to be 3:29. I installed a QRP SWR meter into the tuner that makes tuning very handy. Disclaimer | Privacy Policy | Cookie Policy | Terms of Use. Engineering the EFHW 49:1 Transformer and Antenna I particularly want to know how counterpoise affects the common mode currents on the coax. The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user. The Truth, ,and Nothing But The Truth (as I've experienced it) Therefore, installation is quite easy, and its tuner circuit is rather simple as well. 1) More primary turns and primary inductance improve the transformer efficiency and low end performance. A ktelez mezket * karakterrel jelltk. Subscribe to our newsletter and receive regular updates on new posts and articles. How does this SWR meter works? Look at the compensation coil slide. 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. 100W on a Wire antenna! How badly can high Local Ambient QRM affect HF Radio? Ambient temperature is 20, and the core temperature increased by 5 over 120s @ 20W continuous input. I have also had SSB QSOs in Europe, USA and Canada on 20m so havent seen any degradation in performance on that band. This happens to place the coil near the peak of a current maximum for the 20m band, which coincidentally appears to have significantly improved the match on that band. 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. A method for estimating the impedance of a ferrite cored toroidal inductor at RF. Note: Crosswalk CAA administers the LIHEAP in Franklin, Jefferson, and Williamson Counties. End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 80 meter and higher bands. As you stated early in your posting, I also have found 99.99% of all posting on the internet tell you WHAT they did.not HOW they determined the specific design criteria. From experience, I found that with this tuner my SWR was better by simply disconnecting the counterpoise at lower bands. Im a hundred watt guy, so do not have a lot of experience with high voltage RF, but I know that ~5kV peak-to-peak RF voltage that you would expect at the 2450 output at kilowatt power levels could begin to cause you some trouble. These inductances are required in determining the right capacitance values, of which two values are important: the minimal and the maximum capacitance values. used with a load such that the input impedance Zin is approximately 50+j0, Gin=0.02S; Duffy, O. The aluminum box is the logical heatsink, so I cut a few scraps of aluminum to make a thermal connection to the bottom of the box and to the lid, adjusting with aluminum shims so that when the box lid is screw down, the entire thermal assembly, with the cores in the middle, is under a little compression. I assume you know the GNARC source for EFHW antennas. However, the insertion loss of the packaged transformer would be intolerable on the 10 meter band if it appeared the same way with an antenna wire connected. EFHW-8010-Is this the ultimate 'magic' antenna? - MyAntennas.com This can then, fed with coaxial cable, in many cases be . EFHW Antenna Frequency Compensation Lead - YouTube 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. These four data points are plotted on the Transmission Losses chart shown below as the yellow squares, all but the 80 meter point coming in a bit lower than expected losses based on the VNA measurements. I needed to add an additional coil (approx 12.5 uH) about . 40M EFHW & 3D printing - Member Projects & Builds - Parker Radio It was difficult to work out where it was coming from but I found that it was more noticeable when it was windy outside. In the problematic upper bands, the resonant wire significantly improved the in-band SWR compared to the resistively terminate box (purple). View the job description, responsibilities and qualifications for this position. PDF VK4YE Compact End-Fed 5 Band HF Antenna - SARC

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