Just the bare 80m wire is shown in red. 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. Lowest frequency = 7.000 MHz. A design by VK3JEG is only 66-ft. long, about the size of a 40m dipole. I am currently working on measurements of an EFHW antenna. By using traps, the antenna works on all three bands with no operator interaction. After doing some research on the internet I eventually came across something about rattling radiating elements in Diamond vertical ant, For several years the EF-10/20/40 MKII EndFedz has been my main station antenna for HF. Yes, indeed EFHW antennas are very useful for SOTA or other field operation. 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. If you want to minimize leakage inductance, the way to do that is to keep the two windings very close to one another. A ktelez mezket * karakterrel jelltk. I got the, http://pa-11019.blogspot.com/2012/04/149-transformer-for-endfed-antennas-35.html, End Fed Half Wave (EFHW) Antenna Upgrade Part 2 - The Loading Coil. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. From that we can find Mismatch Loss. 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 other end, attached to the transformer and antenna analyzer, is about 1 meter above the ground. Even at 15W the voltage at the ends may reach 100-200V. This will also be handling 100W. We use cookies to optimize our website and our service. To further improve the flux linkage, I wound the primary on top of the secondary. Below about 7 MHz, transmission losses increase as the core temperature increases. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 80 meter and higher bands. 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. To calculate the impedance ratio, use the following equation: A completed tuner is shown here, which depicts the inductance assembly. The previous table already contains these measurements. 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 Best regards and thanks again for your comment. 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. 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. application of Kirchhoff's current Law on a typical EFHW antenna configuration. Your calculation is correct, the result I get is also .000000000258, which is clearly wrong (it is Farads instead of pF). I ran WSPR at 10mW for about 2 hours and got the results below. Once that's done, the instructions say "adjust the coil as necessary" to bring the other bands into resonance. This is perhaps one of the most hotly debated rookie topics in. The SWR for the 20 meter EFHW antenna was < 1.2:1 The above illustration displays a typical set of Azimuth and Elevation sections of the radiation patterns that one might expect from a horizontally configured EFHW Wire Antenna deployed at an average height of 40 ft. above ground level (AGL). Interpretation of S-Meter Noise Floor in HF Radio Receivers. I place a 2 inch coil of the antenna wire with 3 turns (green) or 6 turns (brown) close to the box. Wideband RF components ultimately succumb to the non-ideal behavior of materials and assembly methods. If you stare at the above frequency sweeps you will discover a few things. One of the many confusing terms used in Workers' Compensation, "IME" stands for Independent Medical Evaluation or Independent Medical Examination. Tuning the antenna to its resonance will result in 50 seen at the output of the SWR circuit. Above my old grey-haired head to be certain BUT well written enough to guide the neophyte through it all. 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. 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. We would like to try to fly a kite with a halfway antenna wire and see what miracle we achieve. 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. 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. I used the 14g enameled wire and wound it on the FT240-43. Nevertheless, this is a rather curious result that might have derating implications for the 160 and 80 meter bands. Above 7MHz, there is very little temperature dependence at all. I then added two 220pf capacitors in series between the center conductor and ground. Let me review the salient observations from the previous work. 2 0 obj A Brief Synopsis of the Antenna Features & characteristics, EFHW Antenna Geometry versus Center-Fed Dipole. RC = 2500 x 1.0e-12 = 2.5 nS Now consider the period of a 30 MHz wave. Ismerje meg a hozzszls adatainak feldolgozst . 73 I use shock cord to connect the insulator at the end of the wire to my fence. A graphical presentation of the mathematical analysis of EFHW antenna SWR variations on account of variations in counterpoise length as well as the Unun impedance transformer at the feed-point. End Fed Half Wave Antennas: Is a Primary Capacitor Really Needed? Two layers of 1mil Kapton tape are placed over the winding. Low SSN Why do most Hams find HF Radio so difficult? Hi Ajai, On top of the first wire, wrap a second one around the toroid three times (I used a red wire for this). The radiation pattern of this antenna on most bands produces multiple lobes. It does not need any special components; in fact, most of us may have them in our shack drawers already. You cant really see the antenna wire, but the red line shows the antenna path. 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. Wow, Gary! 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. 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. 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. Thanks in advance, good health for you in these times, An EFHW antenna has a very high impedance at the end point and you need a matching transformer to feed power to it. Very interesting design. This article will describe a 40/30/20m band end-fed half wave antenna, focusing on its matching unit. See the table above. If not a lightning strike, I will write an article about the experience as well. Consider the RC time for a source with 2500 impedance into a 1pF capacitor. Transmitting on 15 meters was impossible because of RF into the radio. 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. I tossed the line as far up as I could in a tree. (30 votes, Rating: 5.00) - Please vote the article with your valuable star rating. : I see you were able to post your comment now, so I just copied my email answer here for others to see. The next important parameter is the parallel resonant circuits resonant frequency. 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. 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??). Consequently, this is how the capacitance values are determined. The permeability rapidly goes away above the Curie temperature, about 160 C on the data sheet. Now I just need to build or acquire a decent radio to utilize this new antenna. (LogOut/ The antenna is effective and the materials and construction are of a very high quality. . I checked the wall brackets and mast, but all the fixings were nice and tight. My favorite SOTA antenna is the End-Fed Half Wave Antenna. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. 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). Scaling the small core to higher power levels would mean that the flux level in the ferrite core would increase. Basu Bhattacharya (VU2NSB). We will return to that shortly, but first let us look at the VSWR associated with such added capacitance when driving the 2450 load resistor. Real end fed antennas operated harmonically do not present a constant impedance, not even in harmonically related bands. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. Apply for the Job in Software Engineer - EDI at St. Louis, MO. Looking at several builds and discussions, such as commercial antennas (e.g. 73! There is lot of controversy around the EFHW antennas. Then we find Bmax = 0.076 T. The Type 43 data sheets show us what we have to look out for. As I reexamined my formula, you pointed it out correctly, there is an error in it. My design objectives were: 1. 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. And of course, a counterpoise with various lengths. 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 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. Can you give me an idea for your 100 W version, you built for 80/60/40 m. It is quite possible that designing more than three or four bands into a tuner will lead to a failure. 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. The Counterpoise is a short, typically one twentieth (0.05 * ) of the wavelength. Hello, a wonderful approach for the problems.. 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. I needed to add an additional coil (approx 12.5 uH) about . The End Fed Half Wave antenna or the popularly known EFHW antenna has been around almost ever since the inception of HF radio. Is it any good? Therefore, I picked a momentary push button to switch the operational mode to tuning mode while tuning up. For the last step, I put together a RF choke to use between the radio and the feedline. Above, 3t on the primary delivers Gcore<0.002S. Workers' Comp. 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. The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. I tried to operate from a hotel, and learned the hard way that this type of antenna is not suitable for such location. Zin=46.52+j6.72. I went with a 49:1 unun to match the unbalanced antenna to the unbalanced feed line. My concern with the KN5L design is mostly about voltage breakdown through the enamel insulation where the secondary crosses the primary ground. We have been in the middle of Storm Arwen and Strom Barra here, so I had the pole down for a few days. I cut 2.5m of 16AWG wire, added a connector, and hooked this up to one end of the inductor. The wire as I strung it up seemed to resist having a good SWR for the 20m band. 5) It is very hard to avoid stray capacitance on the output. 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. I also built one that is heavy-duty handling easily up to 100W for 80/60/40m bands. That is an end-fed, but very different then the half wave construction. Note: If we change the primary number of turns, the impedance ratios will considerable change also. Note that the resonances do not necessarily line up harmonically, there is commonly some enharmonic effect. A method for estimating the impedance of a ferrite cored toroidal inductor at RF. The model results show the need for a not entirely insignificant counterpoise. The band compensating inductor placed on the wire is another story. Basu (VU2NSB), Antenna Bearings Geodesic Map We present automatically rendered Antenna Bearings with Geodesic Paths projected on a Rectangular Map. Three EFHW single band antennas were prepared for 20, 30, and 40 meter bands. So I built myself an improved replacement matching transformer. I was a little long on 80m not surprisingly, so folded back about 40cm of wire leaving about 2.1m beyond the coil. I installed an eyebolt on one end as a pull-point, and a BNC connector on the other. Payment: If you are eligible, Crosswalk CAA will make the appropriate payment to your energy provider (s) on your behalf. The toroid with its many taps may be soldered directly on a multi-position switch. Hence, we need to move along and start to include the antenna with our testing. It will present its parameters, so anybody with basic home-brew skills will be able to build it. This will allow good matching of the half-wave radiating antenna wire to the 50 coaxial cable at virtually any location. Above is a sweep of the uncompensated prototype with a 3220+50 load. 0 7t8An. }pKumm" t7Vb55nx S;/E}*+RS'|(q&wA;n";&.'KDff9H0^SF7 O0~{h9*QX\Mwk> u)Y h&kvDc%=(]F_$?6!:\EsM4"+>R%;93|"Jn\j+1 z}?>xBaR3 c +U+WLX`\Ld.Q2.VDHh']o.)k;a6*~s" With very little counterpoise, the antenna is being fed at a high impedance point so a rather large impedance step-up is employed. With the coil and its wire attached I fired up my AA-35 Zoom analyzer from RigExpert and had a look. Cmzett: Weince joseph How can we help? Inverted V Antenna A popular Dipole variant, EMI-RFI and Noise related HF Radio Station performance loss. What seemed to work best was to concentrate the turns on the tap-side of the secondary winding, using several (#28) wires in parallel for the primary turns such that they covered about half of the underlying secondary winding. There are many good descriptions on the net about this type of antenna. I've been using a 1:8 ratio transformer successfully in other EFHW antennas, so I planned the same for this one. A lot of radio amateurs have made similar antennas to this with larger transformers for higher power handling.