. Ismerje meg a hozzszls adatainak feldolgozst . However, from the measurements we made on the self resonance frequency, we know that most of this capacitance is right at the output of the transformer and not internal to the windings. Tuning the antenna to its resonance will result in 50 seen at the output of the SWR circuit. (30 votes, Rating: 5.00) - Please vote the article with your valuable star rating. So I built myself an improved replacement matching transformer. Therefore, I picked a momentary push button to switch the operational mode to tuning mode while tuning up. It is worth experimenting with its length also. Disclaimer | Privacy Policy | Cookie Policy | Terms of Use. is the initial disequilibrium temperature, is the equilibration time constant, and is the heat capacity. Essentially, the matching is done with a tank circuit, which represents the highest impedance when it is tuned to resonance. The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes. Nevertheless, this is a rather curious result that might have derating implications for the 160 and 80 meter bands. It is not necessary to calculate the above; the results are sown in the following table. 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! % Well, in ham radio, everything works. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. 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. AC Coil Replacement Cost 2023 - Forbes Home I mounted the transformer on a tree for testing. (Tvir s tvbeszl gpek s kszlkek) Ksznm. The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. Above my old grey-haired head to be certain BUT well written enough to guide the neophyte through it all. It uses a coil as a compensation unit, and no counterpoise. We have been in the middle of Storm Arwen and Strom Barra here, so I had the pole down for a few days. This provides proper insulation from the relatively high voltages on the seconder winding. The above data from K1RF shows that the SWR for 20 meters (my dark red markings - SWR scales differ in each graph) is about the same with or without a capacitor in the transformer primary. It should be no surprise that 80pF is close to optimal. As is often the case, packaging was determined by what boxes I had laying around. 5 Band EFHW Antenna 80m-10m | 49:1 End Fed Half Wave Ham Radio DX 27.1K subscribers 19K views 7 months ago #HamRadio #AmateurRadio #EFHW Here are my experiments and modifications with an EFHW. Some hams swear by them, yet some completely demean it. Could it be something to do with the new vertical aerial I had recently installed? I have been searching the internet for a very long time (AA5TB, VK3YE, SOTA Reflector, among MANY others), and your posting finally made clear for me the many questions I have had. On the transformer, I added a few wingnuts to tighten down the antenna wire. Below about 7 MHz, transmission losses increase as the core temperature increases. But systems that work better increase the prospects of contacts. Contact Commercial Coils A design by VK3JEG is only 66-ft. long, about the size of a 40m dipole. coil inductance calculator at 66pacific.com. I was a little long on 80m not surprisingly, so folded back about 40cm of wire leaving about 2.1m beyond the coil. I am already seeing interesting things with it, but not enough measurements to make any conclusions yet. I swept the antenna with a nano vna from 2 to 30MHz and there were nice dips at each band. A 100pF silvered mica was connected in shunt with the transformer primary. 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'. We also need to know what are the frequencies or bands for which we plant to use this antenna. 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. . Note: If we change the primary number of turns, the impedance ratios will considerable change also. 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. Not the ideal antenna, but convenient! I found that sometimes the multimeter that was measuring the temperature would give unreliable information when RF was present, so the off periods provided regular intervals for measuring the temperature. As the length of the antenna is around 2/3 of the span of a half-wave dipole on 80m, there are two compromises. The resistance (real) component of the impedance is right where we want it near 50 ohms. Ive spent some time on digital modes over the last week and and my signal reports seem very similar to the pre-80m-extension period, which is good, and I am getting out well past 1000 miles on 20, 40m and 80m digital. End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer . That is an end-fed, but very different then the half wave construction. And not all hf antenna installation are same, with most requiring bit of tinkering. 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. Zin=46.52+j6.72. PDF MANUAL: ENDFEDZ ALLBAND-KW 80-10 EFHW 1KW ICAS ANTENNA - DX Engineering However, in reality, the term Omnidirectional needs to be taken in the context of the communication. View the job description, responsibilities and qualifications for this position. 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 Trapped five band EFHW SOTA antenna | VK3IL Blog Looking at several builds and discussions, such as commercial antennas (e.g. I will publish my findings, but I cannot not promise to complete it until early fall. It may be one or even five kilo-ohms. used with a load such that the input impedance Zin is approximately 50+j0, Gin=0.02S; Duffy, O. 2. It is common to use compensation coils of a few turns of the antenna wire to improve the alignment of the bands. With very little counterpoise, the antenna is being fed at a high impedance point so a rather large impedance step-up is employed. Low SSN Why do most Hams find HF Radio so difficult? Is it any good? I am building an EFHW antenna for my new MTR3b, but do I need to include the capacitor for 20, 30 and 40 meters? y73s de Michael DL9SKY, Visszajelzs: The End-Fed Half Wave Antenna a bit Differently Coventry Amateur Radio Society, Az e-mail cmet nem tesszk kzz. 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. In that case, expected efficiency (meaning PowerOut/PowerIn) of the transformer was less than 65% at 3.6MHz. I have seen and read quite a few reports of making this antenna, and some got away no problem with the 110uH when they came to set up and adjust the antenna, others needed to tweak their coil turns. By using traps, the antenna works on all three bands with no operator interaction. With such a switch, it is impossible to forget to switch back to operational mode. The SWR figures were as follows: FT240-43 132ft/100pF capacitor There is much more that can be written about this antenna and its matching, but that was not my aim. My favorite SOTA antenna is the End-Fed Half Wave Antenna. Your article was well written and very informative, thanks. Ambient temperature is 20, and the core temperature increased by 5 over 120s @ 20W continuous input. 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. My design objectives were: 1. Select components with good insolating materials and properly chosen, relatively high voltage rated parts. 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. I also will ask, why didnt it work for you. This article will describe a 40/30/20m band end-fed half wave antenna, focusing on its matching unit. PDF shortened multi-band End-Fed Half Wave (EFHW) antenna for 80-10m Since it is a EFHW and not a non-resonant end fed, the wire length for 40m is about 67 feet. An end fed half wave antenna, or efhw, is a variation of a half wave dipole, but it is fed from one end. Basu Bhattacharya (VU2NSB). 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. We would like to try to fly a kite with a halfway antenna wire and see what miracle we achieve. A few comments have been made about why the capacitor is needed: 'Improves higher frequency UNUN performance' and 'Compensates for UNUN primary leakage' - K1RF A/l for the chosen core is 3.5 times that of a FT82-43 yet it is only 1.6 times the mass. There are many resources online that explain the details better than I can, so Id suggest doing your own research if youd like to build one for yourself. Increasing the drive impedance tends to move the resonances to slightly higher frequencies. Jos van den Helm's (PA1ZP) article published in Radcom: 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. Another design by KB0ZZ is a little longer, but resonates on both 40m and 80m. It is important to consider the voltages on this tank circuit. With a very short counterpoise it is difficult to resonate the fundamental with any drive impedance. IIRC they call it a "compensator". Consequently, this is how the capacitance values are determined. 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. However, let me write about it from a slightly different perspective that was not very obvious from the articles I read. Basu (VU2NSB), Antenna Bearings Geodesic Map We present automatically rendered Antenna Bearings with Geodesic Paths projected on a Rectangular Map. A short 80m antenna for my lot - KB6NU's Ham Radio Blog The SWR for the 20 meter EFHW antenna was < 1.2:1 How to tune a multi-band EFHW antenna using a loading coil (LogOut/ There's seemingly conflicting information out there, such as on QRZ the consensus seems to be to either use no choke on the coax, or choke it some ways away from the feedpoint - WA7ARK recommends .07 wavelength, which is about 9' on 40M. A method for estimating the impedance of a ferrite cored toroidal inductor at RF. I tossed the line as far up as I could in a tree. The usual problems of having the multiple band resonances all line up appear here with the end-fed design, similar to the same issue with off-center-fed designs. Thanks again Jim. So the differences I see in the data sheets hysteresis curves are not the correct explanation. Klubunknl folyamatos a tagfelvtel. No capacitor was installed. Subscribe to our newsletter and receive regular updates on new posts and articles. xZ Wxi@@=\A,Y1I0E~?)JdWfe.z/|iqLI?>BPo>Pf*w~]WZu.VZZZM5zjO=?`yC^l_-H{q|m|U]21xgS6~ltFGZH}(6FE4n0D9Klx`T/;! As I reexamined my formula, you pointed it out correctly, there is an error in it. A krdsem az, hogy a knyv elrhet esetleg pdf-ben is? Replacing your AC evaporator or condenser coil might, on average, cost around $1,200, with the typical cost range between $800 and $2,400 depending on the brand, your region and other factors . Consider the RC time for a source with 2500 impedance into a 1pF capacitor. Above, 3t on the primary delivers Gcore<0.002S. 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. The overlaid VSWR plots are shown below. I then added two 220pf capacitors in series between the center conductor and ground. Consequently, lets pick the lowest frequency 7,000MHz that we need to be able to tune the inductance to, for each of the taps on the inductance. If not a lightning strike, I will write an article about the experience as well. Three EFHW single band antennas were prepared for 20, 30, and 40 meter bands. How badly can high Local Ambient QRM affect HF Radio? ON7EQ EFHW Antenna - qsl.net At this point, I'm leaning towards the EFHW, but any of these antennas seem . : I see you were able to post your comment now, so I just copied my email answer here for others to see. 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. Hi Ajai, After acquiring a MTR3b for SOTA activations I decided I needed a different antenna than the End Fed Random Wire (EFRW) or the speaker cable 20 meter dipole I use with my KX2. 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. End Fed Half Wave Antennas: Is a Primary Capacitor Really Needed? With the entire winding length short, the flux from the primary need not travel all the way around the core to link all of the secondary turns. The biggest uncertainty in these measurements was the actual power level used. Being conservative, assume we are just 90% efficient, then the average power level we could support would be about 140W. I needed to add an additional coil (approx 12.5 uH) about . Most informative and appreciated. Some of my research showed that a small compensation coil can be added about 2 meters from the transformer to pull down the SWR on the higher bands. There is lot of controversy around the EFHW antennas. I settled on a compact secondary using #28 wire. 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. 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. Because of the turns ratio N, the secondary capacitance will appear N2 larger at the primary and will resonate with the primary magnetizing inductance. Just the bare 80m wire is shown in red. 2 0 obj The highest frequency could be14.350MHz. Look at the compensation coil slide. Winding the wire manually was a bit tedious but once done I temporarily held the wire with cable ties and checked the inductance. Wideband RF components ultimately succumb to the non-ideal behavior of materials and assembly methods. i liked it a lot, you give good ideas, many thanks. The finished tran, End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer. 2006. The final turns ratio turned out to be 3:29. Thanks! The technical storage or access that is used exclusively for anonymous statistical purposes. For Jackson County, please call Western Egyptian Economic Opportunity Council, in Steeleville, at (618) 965-9031. The capacitor makes very little difference to the low frequency behavior, but it reduces the input VSWR significantly at the high end. 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 checked the inductance again to make sure this hadnt been overly affected, and it remained unchanged at 109.8H, good enough! I dont have an amplifier, so only need to be able to handle 100W. Tackling both of these issues at once led to a much smaller, lighter, and less costly transformer with better loss characteristics than previous designs. %PDF-1.4 Independent Medical Evaluation - IME | Cynthia Hennessey The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. After cleaning it up and testing it, I installed it on the side of my house on top of a straight pole. clear. But I would caution its usage for higher power than 10-15W. 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. This is typically a weak spot. Also find news related to Efhw Compensation Coil Experiment which is trending today. End Fed Half Wave Antenna Coupler Schematic - 7-30MHz. This can then, fed with coaxial cable, in many cases be . The effect of the capacitor is very apparent for 17 meters and above, flattening and lowering the SWR curve through 10 meters. (The antenna wire could also be tuned for the lower end of 80 meters without the coil but the . I designed and built a few EFHW tuners already (calculating them from scratch, I only optimized the formula for the article). of the wavelength. Firstly, bandwidth on 80m is restricted to about 80 kHz at . Then record the change in temperature recorded at the core from the probe, and the elapsed time so I could corrected for not reaching perfect equilibrium. I found it very useful to label the tuner with switch and capacitance positions. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. Transmitting on 15 meters was impossible because of RF into the radio. I have an EFHW and the SWR is acceptable on all the bands with the exception of the WARC bands which is to be expected since the harmonic relationship is different. But Ill find the error of my ways.and there are various on-line calculators to help me ensure I get the decimals and (H, mH, uH, pH, etc.) I have been using a 40m End-Fed Half Wave (EFHW) antenna very successfully for the last few months and I wanted to extend the design to multi-band whilst avoiding the need to take a . I used the 14g enameled wire and wound it on the FT240-43. This suggests an inductive reactance. It not a loading coil. 100W on a Wire Antenna - How far would it reach? In fact, this was the second one I had built, as I had also made one for a 30m/15m end fed antenna. 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. application of Kirchhoff's current Law on a typical EFHW antenna configuration. 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. One point of my small-core, compact winding design was to be able to cool the core. 73 In comparison to the EFHW antenna, a simple dipole offers a far better prospect. To compensate for the antenna connector capacitance, the solution might be to add the appropriate inductance on the wire right near the box. Since the tuners location is best if it is handy for the operator, one end of the end-fed antenna is also close to the operator. This gave the RF some place else to go, trapped by the coil and capacitively shunted to ground, rather than on to the transceiver. Taking the time derivative of the above equation you get the power dissipation. 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. Ha elolvasod alapszablyunkat s a benne lertakat elfogadod, akkor nincs ms teendd, mint a ha5kdr@ha5kdr.hu email-cmen, vagy egy klubnapon jelentkezni nlunk! There are two aspects, however that we need to consider: Lets begin with the transformer. (LogOut/ I ran WSPR at 10mW for about 2 hours and got the results below. Finally the tank circuits specification is complete, which is sown below. 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. The wire as I strung it up seemed to resist having a good SWR for the 20m band. Scaling the small core to higher power levels would mean that the flux level in the ferrite core would increase. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. It is worth experimenting with its length also. Thirty turns #28 are wound on the two FT114-43 cores. For fun, I attached an 18 clip lead to the secondary output and observed 7.2 pF due to the dangling clip lead. The other end, attached to the transformer and antenna analyzer, is about 1 meter above the ground. In this case, it looks important. RC = 2500 x 1.0e-12 = 2.5 nS Now consider the period of a 30 MHz wave. Very interesting design. Above 7MHz, there is very little temperature dependence at all. If you really want to get the heat out, add some fins to the aluminum box. In the problematic upper bands, the resonant wire significantly improved the in-band SWR compared to the resistively terminate box (purple). The next important parameter is the parallel resonant circuits resonant frequency. = 1/30.e6 = 33 nS. I used four parallel #28 wires (not twisted) for the primary. Engineering the EFHW 49:1 Transformer and Antenna 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. stream end fed half wave antenna - awsh.org Efhw Compensation Coil Experiment - Local Search Denver Post And of course, a counterpoise with various lengths. In his article, I will try to bust some of the myths associated with Inverted. Multiband End-fed Half-wave EFHW Antenna - VU2NSB.com The previous table already contains these measurements. 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. I started with a small piece of PVC pipe and drilled a few holes in it to run the wire through. I am building an EFHW antenna for my new. Although it is simple to build and is a multiband antenna, it has several attributes that . Two layers of 1mil Kapton tape are placed over the winding. I installed an eyebolt on one end as a pull-point, and a BNC connector on the other. This animated illustration shows the harmonically related current conditions that exist on the EFHW antenna wire on various HF bands. There is no BIG secret about the EFHW-8010 antenna, it is just a wideband low loss transformer and a piece of wire. Nevertheless, I will also describe, how it is designed, if one decides to embark on building it for different bands. Why had I not noticed this before? I thought to test this hypothesis by measuring the losses as an oven-heated transformer box cools down. The permeability rapidly goes away above the Curie temperature, about 160 C on the data sheet. Don't sweat the digits to the right of the decimal point too much, the SWR readings changed as the feed height and droop of the antenna changed. Above is a thermograph of the transformer at 20W input at 3.6MHz. Adding an additional 2 meters to the counterpoise did very little to affect the resonant frequencies, much less than adding that length to the main wire would accomplish. From that we can find Mismatch Loss. Now I just need to build or acquire a decent radio to utilize this new antenna. 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. This totally un-rigorous calculation just gives a quick idea of how much you have to be careful. Ez az oldal az Akismet szolgltatst hasznlja a spam cskkentsre. I use my MFJ-939Y AMU regularly anyway, and it has zero trouble with this setup. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Enter your email address to subscribe to this blog and receive notifications of new posts by email. The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. 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. 3) Total losses are approximately independent of core volume. 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. The cooling curve I measured is shown below. You can start with the links below. 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. The SWR results are as follows: Feeling brave, I decided to tape my coil up and solder connectors on and hope I would be one of the lucky ones who wouldnt need much coil adjustment (will I be right??). I particularly want to know how counterpoise affects the common mode currents on the coax. The total lenght is about 15mtr only and using 2 coils and a little stub (s) on the 80m coil or/and the 40m coil. 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. In my research on End Fed Half Wave (EFHW) antennas I found that nearly all have a capacitor in the primary (rig) side of the transformer. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 80 meter and higher bands. 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. VK1OD.net (offline). 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. Radio amateurs using this antenna might remain oblivious to the presence of many active DX traffic originating from the direction of the shadow regions in the nulls. EFHW-8010-Is this the ultimate 'magic' antenna? - MyAntennas.com